mBio: MRSA – Making A House A Biome

MRSA - Photo Credit CDC

 

# 9804

 

From the Open Access journal mBio this morning, a report that suggests that MRSA can hang around a household, bounce repeatedly between family members, and evolve into a unique `family’ strain, over a period of several years.

Previously we’ve looked at MRSA colonization, where the CDC quantified colonization by stating:

 

While 25% to 30% of people are colonized* in the nose with staph, less than 2% are colonized with MRSA (Gorwitz RJ et al. Journal of Infectious Diseases. 2008:197:1226-34.).

*Colonized:
When a person carries the organism/bacteria but shows no clinical signs or symptoms of infection. For Staph aureus the most common body site colonized is the nose.

 

However, in  Firefighters & Paramedics At Greater Risk Of MRSA and Firefighters & MRSA Revisited we looked at research showing a 10x’s greater incidence of MRSA colonization (20%) among a sampling of firefighters tested in Washington State.

 

As we learn from an American Society of Microbiology press release today (see MRSA can linger in homes, spreading among its inhabitants), a 2012 study found up to 50% of family contacts in households with one SSTI (Skin or soft Tissue Infection) with MRSA were colonized with the resistant bacteria.

They describe the findings of today’s study as:

 

Households can serve as a reservoir for transmitting methicillin-resistant Staphylococcus aureus (MRSA), according to a study published this week in mBio®, the online open-access journal of the American Society for Microbiology. Once the bacteria enters a home, it can linger for years, spreading from person to person and evolving genetically to become unique to that household.

<SNIP>

he researchers found that isolates within households clustered into closely related groups, suggesting a single common USA300 ancestral strain was introduced to and transmitted within each household. Researchers also determined from a technique called Bayesian evolutionary reconstruction that USA300 MRSA persisted within households from 2.3 to 8.3 years before their samples were collected, and that in the course of a year, USA300 strains had a 1 in a million chance of having a random genetic change, estimating the speed of evolution in these strains. Researchers also found evidence that USA300 clones, when persisting in households, continued to acquire extraneous DNA.

"We found that USA300 MRSA strains within households were more similar to each other than those from different households," said senior study author Michael Z. David, MD, PhD, an assistant professor of edicine at the University of Chicago. Although MRSA is introduced into households rarely, he said, once it gets in, "it can hang out there for years, ping-ponging around from person to person. Our findings strongly suggest that unique USA300 MRSA isolates are transmitted within households that contain an individual with a skin infection."

(Continue . . .)

A link, and the abstract to the entire mBio report can be accessed below:

 

 

 

Transmission and Microevolution of USA300 MRSA in U.S. Households: Evidence from Whole-Genome Sequencing

Md Tauqeer Alam^a, Timothy D. Read^a,b, Robert A. Petit III^a, Susan Boyle-Vavra^c, Loren G. Miller^d, Samantha J. Eells^d, Robert S. Daum^c, Michael Z. David^c,e

ABSTRACT

Methicillin-resistant Staphylococcus aureus (MRSA) USA300 is a successful S. aureus clone in the United States and a common cause of skin and soft tissue infections (SSTIs). We performed whole-genome sequencing (WGS) of 146 USA300 MRSA isolates from SSTIs and colonization cultures obtained from an investigation conducted from 2008 to 2010 in Chicago and Los Angeles households that included an index case with an S. aureus SSTI.

Identifying unique single nucleotide polymorphisms (SNPs) and analyzing whole-genome phylogeny, we characterized isolates to understand transmission dynamics, genetic relatedness, and microevolution of USA300 MRSA within the households. We also compared the 146 USA300 MRSA isolates from our study with the previously published genome sequences of the USA300 MRSA isolates from San Diego (n = 35) and New York City (n = 277). We found little genetic variation within the USA300 MRSA household isolates from Los Angeles (mean number of SNPs ± standard deviation, 17.6 ± 35; π nucleotide diversity, 3.1 × 10⁻⁵) or from Chicago (mean number of SNPs ± standard deviation, 12 ± 19; π nucleotide diversity, 3.1 × 10⁻⁵).

The isolates within a household clustered into closely related monophyletic groups, suggesting the introduction into and transmission within each household of a single common USA300 ancestral strain. From a Bayesian evolutionary reconstruction, we inferred that USA300 persisted within households for 2.33 to 8.35 years prior to sampling. We also noted that fluoroquinolone-resistant USA300 clones emerged around 1995 and were more widespread in Los Angeles and New York City than in Chicago. Our findings strongly suggest that unique USA300 MRSA isolates are transmitted within households that contain an individual with an SSTI. Decolonization of household members may be a critical component of prevention programs to control USA300 MRSA spread in the United States.

IMPORTANCE USA300, a virulent and easily transmissible strain of methicillin-resistant Staphylococcus aureus (MRSA), is the predominant community-associated MRSA clone in the United States. It most commonly causes skin infections but also causes necrotizing pneumonia and endocarditis. Strategies to limit the spread of MRSA in the community can only be effective if we understand the most common sources of transmission and the microevolutionary processes that provide a fitness advantage to MRSA.

We performed a whole-genome sequence comparison of 146 USA300 MRSA isolates from Chicago and Los Angeles. We show that households represent a frequent site of transmission and a long-term reservoir of USA300 strains; individuals within households transmit the same USA300 strain among themselves. Our study also reveals that a large proportion of the USA300 isolates sequenced are resistant to fluoroquinolone antibiotics. The significance of this study is that if households serve as long-term reservoirs of USA300, household MRSA eradication programs may result in a uniquely effective control method.

(Continue . . . )

 

NEJM: Targeted vs Universal Decolonization For ICU Patients

 

UPDATED:   Maryn Mckenna – who is Flublogia’s resident expert in all things antimicrobial – has just posted a blog post on this important story on her Superbug Blog.

To Prevent MRSA In Hospitals, Don’t Prevent Only MRSA

• By Maryn McKenna
• 05.30.13 10:54 AM

 

# 7341

 

HCAIs (Health care associated Infections) or HAIs (Hospital acquired infections) constitute a major threat to life, health, and the cost of medical care in this country, and around the world.

 

This oft quoted assessment from the CDC on the burden of Hospital Acquired Infections in the United States is from 2010.

 

A new report from CDC updates previous estimates of healthcare-associated infections. In American hospitals alone, healthcare-associated infections account for an estimated 1.7 million infections and 99,000 associated deaths each year. Of these infections:

• 32 percent of all healthcare-associated infection are urinary tract infections
• 22 percent are surgical site infections
• 15 percent are pneumonia (lung infections)
• 14 percent are bloodstream infections

 

Since 2008 the Centers for Medicare & Medicaid Services (CMS) have adopted a `no pay’ rule for `preventable infections’, or medical mistakes associated with hospital stays in order to encourage facilities to improve procedures and patient safety.

 

The problem is that many people entering hospitals are colonized – but not necessarily infected – with bacteria like MRSA. When hospitalized, invasive procedures (needle sticks, catheterization, PICC lines, etc) can turn a benign colonization into a life threatening infection.

 

And their bacteria can be transferred to other patients, staff, or visitors as well.

 

We’ve covered HAIs often in this blog, including:

 

HPA: Healthcare-Associated Infection (HCAI) Survey

A Barrier To Good Hand Hygiene

Study: Hospital Uniforms And Bacteria

Study: HAIs, Universal Surveillance, & MRSA

 

Today, a look at a large study -involving 74 adult ICUs and 74,256 patients between 2009-2011 – published yesterday in the  NEJM - that compared three HAI prevention strategies for ICU patients.

 

1. MRSA screening and isolation of colonized patients;
2. Targeted decolonization (screening, isolation, & 5 day decolonization regimen of MRSA carriers)
3. Universal decolonization (decolonization of all patients without screening - ie. twice-daily intranasal mupirocin x 5 days, daily bathing with chlorhexidine-impregnated cloths for the entire stay)

 

The results showed that bloodstream infections were cut by more than 40% with universal decolonization. The CDC – which was a participant in this study – has the press release below, after which I have a link to the NEJM study itself.

 

MRSA study: simple steps slash deadly infections in sickest hospital patients

Bloodstream infections cut by more than 40 percent in study of more than 74,000 patients

 

A new study on antibiotic-resistant bacteria in hospitals shows that using germ-killing soap and ointment on all intensive-care unit (ICU) patients can reduce bloodstream infections by up to 44 percent and significantly reduce the presence of methicillin-resistant Staphylococcus aureus (MRSA).  Patients who have MRSA present on their bodies are at increased risk of developing a MRSA infection and can spread the germ to other patients.

 

Researchers evaluated the effectiveness of three MRSA prevention practices: routine care, providing germ-killing soap and ointment only to patients with MRSA , and providing germ-killing soap and ointment to all ICU patients.   The study found:

• Routine care did not significantly reduce MRSA or bloodstream infections.
• Providing germ-killing soap and ointment only to patients with MRSA reduced bloodstream infections by any germ by 23 percent.
• Providing germ-killing soap and ointment to all ICU patients reduced MRSA by 37 percent and bloodstream infections by any germ by 44 percent.

The study, REDUCE MRSA trial, was published in the New England Journal of Medicine and took place in two stages from 2009-2011. A multidisciplinary team from the University of California, Irvine, Harvard Pilgrim Health Care Institute, Hospital Corporation of America (HCA) and the Centers for Disease Control and Prevention (CDC) carried out the study.  A total of 74 adult ICUs and 74,256 patients were part of the study, making it the largest study on this topic to date.

 

You can read the NEJM Editorial on REDUCE MRSA Trial, and the study at the link below.

Targeted versus Universal Decolonization to Prevent ICU Infection

Susan S. Huang, M.D., M.P.H., Edward Septimus, M.D., Ken Kleinman, Sc.D., Julia Moody, M.S., Jason Hickok, M.B.A., R.N., Taliser R. Avery, M.S., Julie Lankiewicz, M.P.H., Adrijana Gombosev, B.S., Leah Terpstra, B.A., Fallon Hartford, M.S., Mary K. Hayden, M.D., John A. Jernigan, M.D., Robert A. Weinstein, M.D., Victoria J. Fraser, M.D., Katherine Haffenreffer, B.S., Eric Cui, B.S., Rebecca E. Kaganov, B.A., Karen Lolans, B.S., Jonathan B. Perlin, M.D., Ph.D., and Richard Platt, M.D. for the CDC Prevention Epicenters Programthe AHRQ DECIDE Network and Healthcare-Associated Infections Program

May 29, 2013DOI: 10.1056/NEJMoa1207290

Full Text of Results...

Conclusions

In routine ICU practice, universal decolonization was more effective than targeted decolonization or screening and isolation in reducing rates of MRSA clinical isolates and bloodstream infection from any pathogen. (Funded by the Agency for Healthcare Research and the Centers for Disease Control and Prevention; REDUCE MRSA ClinicalTrials.gov number, NCT00980980.)

 

It is an impressive result, and reduced not only MRSA, but bloodstream infections by any pathogen. It may very well affect the way ICU admissions are handled in the future.

 

One caveat from the authors was that extensive use of these antimicrobials could eventually lead to bacteria developing resistance to mupirocin and chlorhexidine.

 

The authors conclude by writing:

 

In conclusion, we found that universal decolonization prevented infection, obviated the need for surveillance testing, and reduced contact isolation. If this practice is widely implemented, vigilance for emerging resistance will be required.

Revisiting The Seasonality Of MRSA

 

Credit CDC PHIL

 

# 6976

 

 

Just shy of two years ago, in MRSA: It’s Got Seasonality, we looked at a PLoS One study that found a significant spike in CA-MRSA infections reported by Rhode Island Emergency rooms during the 3rd & 4th quarters of the year.

 

Seasonality of MRSA Infections

Mermel LA, Machan JT, Parenteau S (2011) Seasonality of MRSA Infections. PLoS ONE 6(3): e17925. doi:10.1371/journal.pone.0017925

 

The authors reported that pediatric patients saw roughly 1.85 times as many community-associated CA-MRSA infections and 2.94 times as many hospital-associated HA-MRSA infections in the second two quarters of the year as opposed to the first two quarters.

 

 

While a similar pattern was observed for adults, it was less pronounced, with 1.14 times as many CA-MRSA infections in the 3rd & 4th quarters, but no detectable increase in adult HA-MRSA infections.

 

The authors suggested that factors such as excessive hydration of the skin (sweating), summer insect bites, and warm, humid environments conducive to bacterial survival and spread may partially account for the rise, but summer conditions alone cannot not account for the increases.

 

Temperatures in the 2nd quarter of the year in Rhode Island are normally much higher than during the 4th quarter. 

 

Fast forward a couple of years, and a new study in the American Journal of Epidemiology finds a similar - but not quite identical – pattern across the United States between 2005 and 2009.

 

 

The Changing Epidemiology of Methicillin-Resistant Staphylococcus aureus in the United States: A National Observational Study

Eili Y. Klein, Lova Sun, David L. Smith and Ramanan Laxminarayan*

 

While the abstract is free, the complete study is behind a subscription/pay wall. Luckily, the following press release from Johns Hopkins Medicine gives us a pretty good overview.

 

 

Strains of antibiotic-resistant 'Staph' bacteria show seasonal preference; children at higher risk in summer

Strains of potentially deadly, antibiotic-resistant Staphylococcus aureus bacteria show seasonal infection preferences, putting children at greater risk in summer and seniors at greater risk in winter, according to results of a new nationwide study led by a Johns Hopkins researcher.

 

It's unclear why these seasonal and age preferences for infection with methicillin-resistant Staph aureus (MRSA) occur, says Eili Klein, Ph.D., lead author on the study and a researcher at the Johns Hopkins Center for Advanced Modeling in the Social, Behavioral and Health Sciences.

 

But he says that increased use of antibiotics in the winter may be one of the reasons. The winter strain that infects seniors at a greater rate is generally acquired in the hospital and resistant to more antibiotics. On the other hand, the summer strain of MRSA, which is seen with growing frequency in children, is largely a community-transmitted strain that is resistant to fewer antibiotics.

 

"Overprescribing antibiotics is not harmless," Klein notes. "Inappropriate use of these drugs to treat influenza and other respiratory infections is driving resistance throughout the community, increasing the probability that children will contract untreatable infections."

 

In fact, the study found that while MRSA strains exhibit a seasonal pattern, overall MRSA infections have not decreased over the last five years, despite efforts to control their spread.

 

A report on the study, which used sophisticated statistical models to analyze national data for 2005-2009, appears today in the online issue of the American Journal of Epidemiology.

 

As the researchers report, hospitalizations from infections tied to MRSA doubled in the United States between 1999 and 2005. The ballooning infection numbers were propelled by MRSA acquired in community settings, not hospital or other health care settings, as had been the case prior to 1999.

 

Specifically, the study found that a strain of MRSA typically seen in community settings is more likely to cause infection during the summer months, peaking around July/August. The authors' data analysis showed children were most at risk of becoming infected with this strain, typically from a skin or soft tissue wound or ailment.

 

In fact, in examining data for one year — 2008 — the research team found that 74 percent of those under the age of 20 who developed an infection with MRSA had a community-associated MRSA infection.

 

Meanwhile, the health care-associated MRSA strain, which is typically seen in hospitals, nursing homes and other health care settings, was found to be most prevalent in the winter months, peaking in February/March. Patients aged 65 or older are more likely to acquire a MRSA infection from this strain.

 

"Our analysis ... shows significant seasonality of MRSA infections and the rate at which they affect different age groups," write the authors of the report titled "The changing epidemiology of methicillin-resistant Staphylococcus aureus in the United States: A national observational study."

 

Klein said additional research on seasonal patterns of MRSA infections and drug resistance may help with developing new treatment guidelines, prescription practices and infection control programs.

 

 

Unlike with the smaller Rhode Island study, these researchers found an increase in HA-MRSA among adults (particularly over the age of 65) that peaked during the 1st quarter. A trend, the authors suggest, that may be linked to the increased use of antibiotics during the winter.

 

From the Abstract, the authors sum up:

 

We observed significant differences in infection type by age, with HA-MRSA–related hospitalizations being more common in older individuals. We also noted significant seasonality in incidence, particularly in children, with CA-MRSA peaking in the late summer and HA-MRSA peaking in the winter, which may be caused by seasonal shifts in antibiotic prescribing patterns.

HPA: Unusual Number Of PVL Pneumonia Cases In the UK

Credit CDC

 

# 6892

 

In an article called Warning over killer pneumonia linked to flu, Rebecca Smith, Medical Editor for The Telegraph writes today that a rare type of bacterial pneumonia – one that usually only accounts for 30 to 40 cases each year in the UK - has been identified in 18 cases of community acquired pneumonia between December 6th and January 7th.

 

The culprit is a strain of Staphylococcus aureus that carries a gene for PVL (Panton-Valentine leukocidin) – which is a potent cytotoxin that can destroy human neutrophils (white blood cells), spark severe infections, and cause necrotizing pneumonia.

 

PVL producing genes have been detected in at least 14 different strains of S. aureus (cite BMJ), but are found in less than 2% of all S. aureus bacteria. It is most commonly associated with aggressive skin and soft tissue infections (SSTIs), but it is also the cause of a small number of severe (usually community-acquired) pneumonia cases each year. 

 

S. aureus is a very common bacteria that is carried asymptomatically by as much as 30% of the population  – including some strains with the PVL gene – as part of the normal bacterial flora of their skin and mucus membranes (see Coffee, Tea, or MRSA?).

 

The HPA website describes PVL (updated July 2012) this way:

 

PVL-associated Staphylococcus aureus

Panton-Valentine Leukocidin (PVL) is a toxic substance produced by some strains of Staphylococcus aureus which is associated with an increased ability to cause disease.

 

Although several other countries have encountered widespread problems with PVL-related disease, infections caused by PVL remain uncommon in the UK and, to date, most have been caused by bacteria which are sensitive to a range of antibiotics.

 

PVL has been seen in the UK since the 1950s and 60s but cases continue to be seen here only in small numbers. There is currently no UK-based evidence to suggest that children are more vulnerable than other groups to PVL-related infections or that these infections are acquired or spread through playgrounds.

 

The risk to the UK general public of becoming infected with PVL Staphylococcus aureus is small but the Agency is actively working alongside healthcare colleagues to raise awareness of this infection, as well as ensuring appropriate research continues to monitor trends in infection.

 

PVL genes can be found in  both methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains.  According to today’s article in The Telegraph.

 

The 18 cases have all needed intensive care and several required sophisticated life-support known as ECMO, where oxygen is pumped into the blood outside the body because the lungs are overwhelmed with infection.

 

The patients ranged in age from four to 63 years with a median age of 41 and most have flu-like symptoms before developing pneumonia. In five cases the bug had spread between family members.

 

The Telegraph article refers to an HPA bulletin on these cases, but I’ve been unable to locate it as of this writing.  I’ll update this post with a link when it becomes available.

 

From the Annals of Intensive Care in 2011, we get some interesting research on PVL pneumonia, that looked at 32 case reports, with an overall mortality rate of 41%. 

 

They describe the infection:

 

Community-acquired necrotizing pneumonia due to S. aureus-secreting PLV toxin is a highly lethal infection, affecting a young and healthy population group [5]. The hallmarks are an influenza-like prodrome, leukopenia, rapid progression to septic shock, and respiratory distress, with multilobar necrosis and haemoptysis [5,6,14].

 

The Open Access article is available at:

Community-acquired necrotizing pneumonia due to methicillin-sensitive Staphylococcus aureus secreting Panton-Valentine leukocidin: a review of case reports

Lukas Kreienbuehl^1*, Emmanuel Charbonney² and Philippe Eggimann

 

In examining the records of 32 patients, they concluded:

 

Conclusions

Necrotizing pneumonia due to PVL-secreting S. aureus mandates prompt recognition and specific treatment to prevent premature death in immunocompetent patients.

 

Early suspicion should be triggered by the presence of influenza-like prodrome, leucopenia, rapid progression to septic shock, respiratory distress with multilobar necrosis, and hemoptysis.

 

For PVL-secreting MSSA-necrotizing pneumonia, influenza-like prodrome may be associated with fatal outcome, whereas previous SSTI may reduce mortality. Further studies based on a larger patient number are necessary to confirm this finding.

 

Today’s story from the UK mention 5 cases of family transmission, which is somewhat reminiscent of a story we followed last spring at the end of what was an otherwise lackluster 2011-12 flu season.

 

Our attention was briefly directed towards three members of a family (out of five who fell ill) that died from a respiratory infection in Calvert County, Maryland (see Calvert County: Update On Fatal Cluster Of Respiratory Illness).

 

While these deaths made national headlines and spurred considerable speculation as to the viral cause, in the end we learned that it was seasonal H3N2 influenza, exacerbated by a MRSA (or necrotizing) pneumonia co-infection.

 

According to The Telegraph article, the HPA is not worried this will to turn into an epidemic, but since early diagnosis is crucial, they are urging that, “Healthcare personnel should remain vigilant for such cases, especially during the influenza/ respiratory virus season.”

 

The HPA provides the following HCP guidance for the treatment of PVL pneumonia on their website.

 

Steering Group on Healthcare Associated Infection; Guidance on the diagnosis and management of PVL-associated Staphylococcus aureus infections (PVL-SA) in England, 2nd Edition. 2008

 

Management of PVL-Staphylococcus aureus, Health Protection Agency, Local and Regional Services; Recommendations for Practice 2010

 

Staphylococcus aureus, Health Protection Agency (HPA)

Study: Weighing The Risks Of MRSA Colonization

MRSA - Photo Credit CDC

# 6807

 

The CDC tells us, in their Definition of MRSA page, that:

 

While 25% to 30% of people are colonized* in the nose with staph, less than 2% are colonized with MRSA (Gorwitz RJ et al. Journal of Infectious Diseases. 2008:197:1226-34.).

*Colonized:
When a person carries the organism/bacteria but shows no clinical signs or symptoms of infection. For Staph aureus the most common body site colonized is the nose.

 

 

Although 2% doesn’t sound like a lot, there are signs that number may be increasing. Once considered primarily a hospital acquired infection, CA-MRSA (community acquired) is growing in incidence.

 

As an example, in Firefighters & Paramedics At Greater Risk Of MRSA and Firefighters & MRSA Revisited we looked at research showing a 10x’s greater incidence of MRSA colonization (20%) among a sampling of firefighters tested in Washington State.

 

Since one person’s colonization can become another person’s infection, topics of debate have included:

 

1. What risks are there to the individual from long-term colonization?
2. What risks are there to others In the Community or a household?
3. What risks are there to others in a hospital or long-term care environment?
4. What (if any) steps should be taken to decolonize carriers, and in what setting (hospital admission? Outpatient?) is decolonization desirable and effective?

 

There are, it seems, few easy answers. 

 

Mary McKenna, editor of the terrific Superbug Blog, took a look at the problems inherent with the decolonization of MRSA carriers in 2009 with:

 

Decolonization: disappointing news 

The upshot was that while studies have shown that decolonization procedures on hospitalized patients about to undergo surgery can reduce infections, the value to other patients is far less clear.

 

And as Maryn points out, overuse of mupirocin – the primary antibiotic used to decolonize patients –can lead to increased resistance over time.

 

And Mary also tells of a paper published in Infection Control and Hospital Epidemiology, that evaluated the success of decolonization protocols in 3 major Illinois hospitals, that less than reassuring results: a temporary reduction in patients’ being colonized with MRSA, but no success in preventing infection.

 

In 2011, the Infectious Diseases Society of America published their clinical practice guidelines for treating MRSA in adults and children, where they endorse `decolonization’, but only under select scenarios (note SSTI = Skin & Soft Tissue Infection):

 

14. Decolonization may be considered in selected cases if:

• i. A patient develops a recurrent SSTI despite optimizing wound care and hygiene measures (C-III).

• ii. Ongoing transmission is occurring among household members or other close contacts despite optimizing wound care and hygiene measures (C-III).

 

• ii. Contacts should be evaluated for evidence of S. aureus infection:
• a. Symptomatic contacts should be evaluated and treated (A-III); nasal and topical body decolonization strategies may be considered following treatment of active infection (C-III).
• b. Nasal and topical body decolonization of asymptomatic household contacts may be considered (C-III)

 

But what, if anything, to do about asymptomatic carriers who are colonized, but not infected with MRSA remains up in the air.

 

Hospital strategies to contain and control MRSA range from passive surveillance to aggressive `search & destroy’ policies – with variations in between.

 

Passive surveillance – which is the most commonly used protocol in the United States – involves  testing only those who have clinical signs or symptoms of
MRSA.

Since patients may be colonized without exhibiting outward signs, this will fail to detect a great many carriers of the bacteria.

Active Surveillance – requires the testing of high risk admissions (ie.  Hx of MRSA, Antibiotic Use, Admission to Hospital in past year, Resident of Long-term care facility, etc.) for the bacteria.

Patients testing positive may be isolated and decolonized or treated, with strict infection control precautions enforced.

Universal Surveillance – takes the above steps to a higher level, where all admissions and personnel are routinely swabbed and tested for MRSA.

“Search & Destroy” – which is the most intensive protocol, has been used successfully in countries like Finland, Denmark and the Netherlands.

It combines Active or Universal Surveillance with testing of patients in high-risk wards at intervals and prior to discharge.

 

The reluctance to adopt the more aggressive of these measures have been the costs, the inconvenience to patients and their visitors, and quite frankly, objections by some hospital staff over being repeatedly tested.

A recent study appearing in Critical Care Medicine, looked at the effects of a strict S&D policy instituted at a rural trauma center, and found an immediate reduction specific types of HAIs (Hospital Acquired Infections) after implementation.

 

Search & Destroy (S&D): Eradication of Mrsa Colonization Is Associated With Decreased Mrsa Infections in Trauma Patients

Borst, Gregory; Waibel, Brett; Toschlog, Eric; Coogan, Michael; Skarupa, David; Rotondo, Michael; Ramsey, Keith

Conclusions: Search and destroy is associated with significant decreases in the incidence of MRSA VAP and CLABSI in trauma patients. Decreases in MRSA CAUTI and wound infections were also seen after the implementation of this program. Pre-emptive strategies to identify and eradicate MRSA are worthwhile endeavors in terms of preventing nosocomial infection.

 

Despite its critics, S&D policies have often shown reductions in HAIs. 

 

Which brings us to another study, published last week in the journal Antimicrobial Agents and Chemotherapy, that finds (among a relatively small cohort of patients) that colonization with MRSA posed a substantial risk of MRSA infection, increased mortality, or readmission to the hospital, compared to patients without MRSA colonization.

 

 

Long-Term Risk for Readmission, Methicillin-resistant Staphylococcus aureus (MRSA) Infection, and Death among MRSA-Colonized Veterans.

Quezada Joaquin NM, Diekema DJ, Perencevich EN, Bailey G, Winokur PL, Schweizer ML.

Source

Division of Infectious Diseases.

Abstract

Background: While numerous studies assessed outcomes of MRSA colonization over the short term, little is known about longer-term outcomes after discharge. An assessment of long-term outcomes could inform the utility of various MRSA prevention approaches.

Methods: A matched cohort study was performed among Veterans Affairs (VA) patients screened for MRSA colonization between the years 2007 and 2009 and followed to evaluate outcomes until 2010. Cox proportional hazard models were used to evaluate the association between MRSA colonization and long-term outcomes such as infection-related readmission, and crude mortality.

Results: 404 veterans were included, 206 of whom were MRSA carriers and 198 who were non-carriers. There were no culture-proven MRSA infections on readmission among the non-carriers, but 13% of MRSA-carriers were readmitted with culture proven MRSA infections on readmission (P<0.01).

MRSA carriers were significantly more likely to be readmitted, be readmitted more than once due to proven or probable MRSA infections, and be readmitted within 90 days of discharge compared to non-carriers (p<0.05). Infection-related readmission (adjusted hazard ratio [AHR] =4.07; 95% confidence interval [CI]: 2.16, 7.67) and mortality (AHR=2.71; 95% CI: 1.87, 3.91) were significantly higher among MRSA carriers compared to non-carriers, after statistically adjusting for potential confounders.

Conclusions: Among a cohort of VA patients, MRSA carriers are at high risk of infection-related readmission, MRSA infection and mortality compared to non-carriers. Non- carriers are at very low risk of subsequent MRSA infection. Future studies should address whether interventions such as nasal or skin decolonization could result in improved outcomes for MRSA carriers.

Although based on a small cohort, this study suggests that being colonized (but not infected) with MRSA is a significant risk factor for future infection, and if these findings can be confirmed by others, may influence how MRSA colonization is viewed in the future.

 

Despite some recent improvements in MRSA rates among hospitalized patients in the United States, HAIs (which include many other pathogens) continue to exact a heavy toll. This oft quoted assessment from the CDC on the burden of Hospital Acquired Infections in the United States is from 2010.

 

A new report from CDC updates previous estimates of healthcare-associated infections. In American hospitals alone, healthcare-associated infections account for an estimated 1.7 million infections and 99,000 associated deaths each year. Of these infections:

• 32 percent of all healthcare-associated infection are urinary tract infections
• 22 percent are surgical site infections
• 15 percent are pneumonia (lung infections)
• 14 percent are bloodstream infection

For more on MRSA, and many other antibiotic-resistant threats, you can do no better than to visit Maryn McKenna’s terrific Superbug Blog, and to read her book Superbug: The Fatal Menace of MRSA . . . which won last year’s  NASW Science in Society Journalism Award.

You’ll find my review of her book HERE

Study: MRSA In Waste Water Treatment Plants

 

Photo Credit USGS – Wastewater: The Primary Treatment Process

1. Screening 2. Pumping 3. Aerating 4. Removing sludge 5. Removing Scum 6. killing bacteria

 

 

# 6699

 

While it may not seem (or even be) glamorous, there are scientists who spend considerable time examining the input and output of wastewater (sewage) treatment plants. Given the potential environmental impact of the discharges from these facilities, it is important work.

 

The subject of wastewater treatment plants - and the substances that their processes can fail to remove during treatment - has come up before in this blog.

 

In 2007, with governments around the world stockpiling large quantities of Tamiflu (Oseltamivir) in anticipation of a pandemic, concerns turned to what would happen if millions of doses were dispensed, consumed, and excrete by humans into the waste water system in a short period of time.

 

In The Law of Unintended Consequences we looked at a report in Environmental Health Perspectives (EHP) called Potential Risks Associated with the Proposed Widespread Use of Tamiflu that found enough of excreted oseltamivir carboxylate (OC) would survive treatment, and be ejected into the environment, to raise concerns.

 

In October of 2009 and we saw another report (see Everything Old Is News Again), based on studies done the previous year in Kyoto, Japan – that showed elevated levels of the OC Metabolite in wastewater discharge. 

 

In 2011, in Pandemics & The Law Of Unintended Consequences we saw yet another study that looked at potential problems inherent in the massive distribution and consumption of antibiotics and antivirals during a pandemic.

 

WWTPs (Wastewater Treatment Plants) depend upon microbial activity in order to breakdown or `digest’ sewage.

 

Antibiotics in the sewage – at elevated levels such as might be seen during a pandemic – could inhibit microbial activity, resulting in the failure of WWTPs and the discharge of under-treated wastewater into the environment.

 

Today, a new study, this time on MRSA (methicillin-resistant Staphylococcus aureus) and how it fares in the wastewater treatment process. As many WWTPs provide reclaimed water for irrigation use, the concern is that MRSA shed in feces might make it through the plant and into the environment.

 

The University of Maryland-led study study appears as an open access article that appears in Environmental Health Perspectives. 

Methicillin-Resistant Staphylococcus aureus (MRSA) Detected at Four U.S. Wastewater Treatment Plants

November 1, 2012 Research 

Rachel E. Rosenberg Goldstein, Shirley A. Micallef, Shawn G. Gibbs, Johnnie A. Davis, Xin He, Ashish George, Lara M. Kleinfelter, Nicole A. Schreiber, Sampa Mukherjee, Amir Sapkota, Sam W. Joseph, and Amy R. Sapkota

Abstract

Background: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal waste­water could be a reservoir of this micro­organism. To date, no U.S. studies have evaluated the occurrence of MRSA in waste­water.

 

Objective: We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. waste­water treatment plants.

 

Methods: We collected waste­water samples from two Mid-Atlantic and two Midwest waste­water treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® micro­broth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.

 

Results: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) waste­water samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multi­drug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.

 

Conclusions: Our findings raise potential public health concerns for waste­water treatment plant workers and individuals exposed to reclaimed waste­water. Because of increasing use of reclaimed waste­water, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated waste­water.

 

Environ Health Perspect 120:1551–1558 (2012). http://dx.doi.org/10.1289/ehp.1205436 [Online 6 September 2012]

Full PDF FILE

 

 

The full report runs 8 pages, and can be download here.

A summation of this research is available from the University of Maryland’s School of Public Health. I’ve cut to the chase with the excerpts  posted below, so follow the link to read the full story.

 

The School of Public Health News

November 5, 2012
NEWS RELEASE
Contact: Kelly Blake, kellyb@umd.edu, 301-405-9418

Superbug MRSA Identified in U.S. Wastewater Treatment Plants

University of Maryland-led study is first to document environmental source of the antibiotic-resistant bacteria in the United States

<SNIP>

They found that MRSA, as well as a related pathogen, methicillin-susceptible Staphylococcus aureus (MSSA),were present at all four WWTPs, with MRSA in half of all samples and MSSA in 55 percent.MRSA was present in 83 percent of the influent-- the raw sewage--at all plants, butthe percentage of MRSA- and MSSA-positive samples decreased as treatment progressed. Only one WWTP had the bacteria in the treated water leaving the plant, and this was at a plant that does not regularly use chlorination, a tertiary step in wastewater treatment.

 

Ninety-three percent of the MRSA strains that were isolated from the wastewater and 29 percent of MSSA strains were resistant to two or more classes of antibiotics, including several that the U.S. Food and Drug Administration has specifically approved for treating MRSA infections. At two WWTPs, MRSA strains showed resistance to more antibiotics and greater prevalence of a gene associated with virulence at subsequent treatment stages, until tertiary chlorination treatment appeared to eliminate all MRSA. This suggests that while WWTPs effectively reduce MRSA and MSSA from influent to effluent, they may select for increased antibiotic resistance and virulence, particularly at those facilities that do not employ tertiary treatment (via chlorination).

 

“Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater,” says Rachel Rosenberg Goldstein, environmental health doctoral student in the School of Public Health and the study’s first author. “Because of increasing use of reclaimed wastewater, further research is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.”

(Continue . . . )

 

Most WWTPs are designed to efficiently remove solids and to disinfect discharge water, but do less well when it comes to removing chemicals.

 

Although only four plants were studied in this project, the results suggest that plants that fail to chlorinate routinely may be at greater risk of letting antibiotic resistant bacteria back into the environment. 

 

Whether it is antiviral or antibiotic metabolites, remnants from  illicit drug use, or resistant organisms themselves, what comes out of these treatment plants can affect our environment, and our population.

 

On a planet with 7 billion people, figuring out how to safely dispose of, recycle, or treat human waste has become a major challenge.

 

Shortcomings in WWTP systems – even seemingly small ones - can pose serious public health risks, including potentially creating and spreading resistant bacterial organisms.

 

As the authors of this study concluded, more research is now needed to evaluate and quantify the risk.

The Flight Of The Bacterial Intruder

Credit CDC PHIL

 

 

# 6625

 

HCAIs (Health care associated Infections) or HAIs (Hospital acquired infections) constitute a major threat to life, health, and the cost of medical care in this country, and around the world. This oft quoted assessment from the CDC on the burden of Hospital Acquired Infections in the United States is from 2010.

 

A new report from CDC updates previous estimates of healthcare-associated infections. In American hospitals alone, healthcare-associated infections account for an estimated 1.7 million infections and 99,000 associated deaths each year. Of these infections:

• 32 percent of all healthcare-associated infection are urinary tract infections
• 22 percent are surgical site infections
• 15 percent are pneumonia (lung infections)
• 14 percent are bloodstream infections

 

A 2009 report The Direct Medical Costs of Healthcare-associated Infections in U.S. Hospitals and the Benefits of Prevention finds:

 

Applying two different Consumer Price Index
(CPI) adjustments to account for the rate of inflation in hospital resource prices, the overall annual direct medical costs of HAI to U.S. hospitals ranges from $28.4 to $33.8 billion (after adjusting to 2007 dollars using the CPI for all urban consumers) and $35.7 billion to $45 billion (after adjusting to 2007 dollars using the CPI for inpatient hospital services).

 

 

As you can imagine, hospitals are engaged in a perpetual battle against the spread of infection - and while progress is being made - many pathogens continue to slip past the infection control safeguards.

 

A study from the University of Leeds recently published in the Journal Building and Environment may provide a clue as to why the infection control measures being used today have failed to curb the spread of bacteria in the hospital setting.

 

 

Bioaerosol Deposition in Single and Two-Bed Hospital Rooms: A Numerical and Experimental Study

M.F. King, C.J. Noakes, P.A. Sleigh, M.A. Camargo-Valero

 

You’ll find the abstract, along with figures and tables from this article, at the link above. But the full paper is behind a pay wall. The University of Leeds website, however, has a synopsis of this research project, which is excerpted below:.

 

 

Superbugs ride air currents around hospital wards

Published Thursday 11th October 12

Hospital superbugs can float on air currents and contaminate surfaces far from infected patients’ beds, according to University of Leeds researchers.

 

The results of the study, which was funded by the Engineering and Physical Sciences Research Council (EPSRC), may explain why, despite strict cleaning regimes and hygiene controls, some hospitals still struggle to prevent bacteria moving from patient to patient.

 

It is already recognised that hospital superbugs, such as MRSA and C-difficile, can be spread through contact. Patients, visitors or even hospital staff can inadvertently touch surfaces contaminated with bacteria and then pass the infection on to others, resulting in a great stress in hospitals on keeping hands and surfaces clean.

 

But the University of Leeds research showed that coughing, sneezing or simply shaking the bedclothes can send superbugs into flight, allowing them to contaminate recently-cleaned surfaces.

 

PhD student Marco-Felipe King used a biological aerosol chamber, one of a handful in the world, to replicate conditions in one- and two-bedded hospital rooms. He released tiny aerosol droplets containing Staphyloccus aureus, a bacteria related to MRSA, from a heated mannequin simulating the heat emitted by a human body. He placed open Petri dishes where other patients’ beds, bedside tables, chairs and washbasins might be and then checked where the bacteria landed and grew.

 

The results confirmed that contamination can spread to surfaces across a ward. “The level of contamination immediately around the patient’s bed was high but you would expect that. Hospitals keep beds clean and disinfect the tables and surfaces next to beds,” said Dr Cath Noakes, from the University’s School of Civil Engineering, who supervised the work. “However, we also captured significant quantities of bacteria right across the room, up to 3.5 metres away and especially along the route of the airflows in the room.”

 

“We now need to find out whether this airborne dispersion is an important route of spreading infection,” added co-supervisor Dr Andy Sleigh.

(Continue . . .)

 

 

While we often think first of viruses when it comes to airborne transmission of illness, some types of bacteria (e.g. Legionella, Mycoplasma pneumonia, Tuberculosis) are easily aerosolized and transmitted.

 

This study is not the first to identify the airborne spread of Staphylococcus aureus, but they have developed an ingenious way to quantify it.

 

Regarding MRSA and C. Difficile the Journal of The Royal Society published a review in 2009 called:

 

Airborne transmission of disease in hospitals

I. Eames, J. W. Tang,Y. Li and P. Wilson

(EXCERPT)

MRSA can survive on surfaces or skin scales for up to 80 days and spores of Clostridium difficile may last even longer. MRSA can be transmitted in aerosol from the respiratory tract but commonly attaches to skin scales of various sizes. The distance of travel depends on the size of the scale, the larger falling to the floor within 1–2 m, the smaller travelling the entire length of the ward.

<SNIP>

Clostridium difficile spores are thought to spread in the air and can be found near a patient carrying the organism (Roberts et al. 2008). However, unlike MRSA, they are rarely isolated from air samples.

 

 

Not surprisingly, in 2010, we saw a study published in the AJIC: American Journal of Infection Control that found that the more roommates you have during a hospital stay, the greater chance you will have of contracting an HAI like MRSA or C. Diff.

 

Exposure to hospital roommates as a risk factor for health care–associated infection

Meghan Hamel, MSc, Dick Zoutman, MD, FRCPC, Chris O'Callaghan, DVM, MSc, PhD

 

The authors used this study to promote the idea  of making private (or at least, semi-private) rooms the norm in Canadian hospitals. While acknowledging that it would involve considerable up-front costs, they believe the long-term savings would be considerable.

 

All of this highlights the great challenges involved in substantially reducing the incidence of HAIs in our health care facilities.

 

Solutions must not only include stringent hand hygiene and improved cleaning methods, but engineering solutions as well.

 

For more on the prevention of Hospital Acquired Infections you may wish to visit the CDC’s HAI PAGE.

 

 

Or revisit some of these earlier blogs on hospital acquired infections.

 

HPA: Healthcare-Associated Infection (HCAI) Survey

A Barrier To Good Hand Hygiene

Study: Hospital Uniforms And Bacteria

Study: HAIs, Universal Surveillance, & MRSA

 

And finally, the subject of HAIs is often addressed by Maryn McKenna on her excellent Superbug Blog, and was a major focus of her book SUPERBUG: The Fatal Menace Of MRSA.

 

Both are highly recommended.

McKenna On MRSA Pneumonia Cluster In Maryland

 

 

Clumps of methicillin-resistant Staphylococcus aureus Magnified 2390x. – Credit CDC PHIL

# 6211

 

Author, journalist, and blogger Maryn McKenna is Flublogia’s resident expert on everything antimicrobial resistant, and is the author of Superbug: The Fatal Menace of MRSA.

 

This morning she has written about the cluster of flu-related deaths in Calvert County Maryland that has captured out attention this week.

 

Yesterday, new details emerged that suggest that a form of MRSA (or necrotizing) pneumonia served as a deadly co-infection in these deaths (see CIDRAP: MRSA Pneumonia Suspected In Calvert County Flu Cluster).

 

While we await further lab and autopsy results on this unusual and tragic story, Maryn gives us the short course in this emerging, and often lethal, complication of flu.

 

 

 

Flu Infections And MRSA Deaths In Maryland

• By Maryn McKenna March 9, 2012 | 

CIDRAP: MRSA Pneumonia Suspected In Calvert County Flu Cluster

 

Clumps of methicillin-resistant Staphylococcus aureus – Credit CDC PHIL

# 6210

 

 

Although we haven’t seen any official updates since late yesterday afternoon, reports have been trickling in through various media outlets suggesting that the fatal flu cluster in Lusby, Md.  involved the seasonal H3N2 virus and an aggressive form of MRSA pneumonia.

 

Lisa Schnirring of CIDRAP News  brings us up to date this evening with this report.  Follow the link to read her report in its entirety.

 

 

MRSA pneumonia suspected in fatal flu cluster

Lisa Schnirring Staff Writer

Mar 8, 2012 (CIDRAP News) – Another family member linked to a fatal flu cluster in Calvert County, Md., has been hospitalized, as suspicion grew that an aggressive drug-resistant form of pneumonia may have played a role in the severe illnesses, according to media reports.

 

Maryland and Calvert County health officials didn't report any new details about the cases, but the Washington Post reported yesterday that the sister of the 81-year-old woman who died has been hospitalized at MedStar Washington Hospital Center with fever but no other flu symptoms.

(Continue . . . )

 

 

Tissues taken during autopsies from two of the victims have reportedly been sent to the CDC for further analysis, which can take a day or two to complete.

McKenna: Man Vs. MRSA

 

 

# 6115

 

Among the many fascinating topics Maryn McKenna covered in her book Superbug: The Fatal Menace of MRSA was the possibility that a vaccine might someday be developed against this growing epidemic of antibiotic resistant staph.

 

 

 

 

Today, Maryn follows up with a terrific feature that appears in the prestigious Journal Nature, which focuses on Robert Daum, the founder of the University of Chicago's MRSA Research Center, and others who are in search of this as-yet elusive goal.

 

Follow the link to read:

 

Vaccine development: Man vs MRSA

For decades, Robert Daum has studied the havoc wreaked by methicillin-resistant Staphylococcus aureus. Now he thinks he can stop it for good.

• Maryn McKenna

01 February 2012

The Passing Parade Of 2011 – Pt. 2

 

 

 

# 6036

 

Over the past year I’ve posted more than 900 blogs, dozens of which looked at some of the latest research into influenza and other emerging infectious diseases.

 

Since these studies oft times make an initial splash only to get lost in the passing parade of new reports, today I’ve some brief summaries (with links back to the original blogs) on some of the research of 2011 I believe is deserving of a second look.

 

This is the second such roundup, the first one may be accessed at this link.

 

 

Last April in Lancet Study: NDM-1 In New Delhi Water Supply, we saw a report authored by Timothy Walsh, Janis Weeks , David M Livermore, and Mark A Toleman that looked for – and found – bacteria carrying the NDM-1 enzyme in New Delhi's drinking water supply.

 

We’ve a press release on this study, issued by Cardiff University, that gives the highlights of the research, but the `money quote’ (emphasis mine) buried about halfway down is:

 

Resistant bacteria were found in 4 per cent of the water supplies and 30 per cent of the seepage sites. The researchers identified 11 new species of bacteria carrying the NDM-1 gene, including strains which cause cholera and dysentery.

 

Below is a link to the Lancet study, which you can read in its entirety (a free registration is required).

 

 

The Lancet Infectious Diseases, Early Online Publication, 7 April 2011

doi:10.1016/S1473-3099(11)70059-7

Dissemination of NDM-1 positive bacteria in the New Delhi environment and its implications for human health: an environmental point prevalence study

Prof Timothy R Walsh PhD , Janis Weeks BS, David M Livermore PhD , Mark A Toleman PhD

 

Again in April, we saw research seeking to answer the question over why there was such a wide variance in death rates around the world with the 1918 Spanish influenza. 

 

In 2006, in a Lancet journal (doi:10.1016/S0140- 6736(06) 69895-4) article cited as much as a 30-fold difference in mortality rates around the world:

 

Estimation of potential global pandemic influenza mortality on the basis of vital registry data from the 1918—20 pandemic: a quantitative analysis

Christopher JL Murray , Alan D Lopez , Brian Chin , Dennis Feehan , Kenneth H Hill

Excess mortality ranged from 0·2% in Denmark to 4·4% in India. Since there was some under-registration of mortality in India, total pandemic mortality could have been even higher.

 

 

This wide disparity in mortality rates – much of it based on anecdotal accounts – has long intrigued researchers.  This new study from the Norwegian Institute of Public Health that attempts to answer some of these questions.

 

What they found was that the mortality rate varied nearly 100 fold between remote, rural regions and urban populations, and that in the more remote areas, older persons were just as susceptible to the virus as those who were younger.

 

This study appears in the Journal Epidemics.

Geography May Explain Adult Mortality from the 1918–20 Influenza Pandemic

Original Research Article
Pages 46-60
Svenn-Erik Mamelund

 

The theory that a similar H1 virus circulated prior to 1890 – and that provided some immunity to those over the age of 30 – is bolstered by this study.

 

 

Given the current flap over the H5N1 experiments conducted by Ron Fouchier in the Netherlands and Yoshihiro Kawaoka  at the University of Wisconsin (see The Biosecurity Debate On H5N1 Research) the next two studies deserve a second look as well.

 

 

Simplified Illustration of a Serial Passage Experiment. 

 

In H5N1: A Rite Of Passage we looked at how serial passage studies are conducted, and at one in particular that appeared in the Journal of Animal and Veterinary Advances that looked at increases in pathogenicity (in mice) of two H5N1 viruses after six serial passages in quail.

 

The study is called:

 

The Pathogenicity Variation of Two Quail-Origin H5N1 HPAV to BALB/c Mice after Six Passages in Quail

Hailiang Sun, Peirong Jiao, Yuqiang Cheng, Runyu Yuan, Pengfei Cui, Liming Jin, Chaoan Xin and Ming Liao

 

Another study, profiled in PNAS: Reassortment Potential Of Avian H9N2, looked at the reassortment potential of the avian H9N2 virus and H1N1. Research was done using ferrets whose respiratory physiology is considered relatively close to humans.

 

Compatibility of H9N2 avian influenza surface genes and 2009 pandemic H1N1 internal genes for transmission in the ferret model

J. Brian Kimble, Erin Sorrell,  Hongxia Shao,  Philip L. Martin, and Daniel Roberto Perez

 

(Excerpt from the abstract)

Four reassortant viruses were generated, with three of them showing efficient respiratory droplet transmission. Differences in replication efficiency were observed for these viruses; however, the results clearly indicate that H9N2 avian influenza viruses and pH1N1 viruses, both of which have occasionally infected pigs, have the potential to reassort and generate novel viruses with respiratory transmission potential in mammals.

 

 

The entire study is available online, and open access.

 

 

And in Study: Prior Antibiotic Use & MRSA In Children Canadian researchers, examining 13 years worth of data from the UK’s General Practice Research Database (GPRD), came up with what they called  a `robust association’ between a prior history of antibiotic use and rates of CA-MRSA (Community Acquired Methicillin Resistant Staph Aureus) infection in children.

The study appeared Aug. 1st  in the Archives of Pediatrics & Adolescent Medicine.

 

Antibacterial Drugs and the Risk of Community-Associated Methicillin-Resistant Staphylococcus aureus in Children

Verena Schneider-Lindner, MD, MSc; Caroline Quach, MD, MSc; James A Hanley, PhD; Samy Suissa, PhD

Arch Pediatr Adolesc Med. Published online August 1, 2011. doi:10.1001/archpediatrics.2011.143

 

What these researchers found was that while nearly half of children with MRSA in this study had no recent history of antibiotic use, the adjusted relative risk (RR) of developing MRSA was 3.5 times higher among children who had received antibiotic treatment in the previous 30-180 days before infection.

 

And that relative risk increased substantially among children who received more than one course of antibiotics.

 

To find more blogs specific to research you can use the RESEARCH quick link on my sidebar.

 

As news is often slow during the holiday season, over the next couple of weeks I plan to post one or two more retrospectives on the news and research of the year that was.