Thursday, June 02, 2011

Firefighters & MRSA Revisited



# 5593




Last November (see Firefighters & Paramedics At Greater Risk Of MRSA) I wrote about a study by researchers from the University of Washington that looked for – and found – MRSA (Methicillin-resistant Staphylococcus aureus) contaminated surfaces at fire houses in Snohomish county.


In addition to finding MRSA in 4% of samples taken from places such as kitchens, bathrooms, and rescue vehicles – researchers also found 20% of firefighters who volunteered to be tested were colonized with MRSA and an additional 10% carried S. aureus in their noses.


MRSA rates that are far higher than usually found in the general population.


Lead researcher Professor Marilyn Roberts found that the MRSA strains carried by fire personnel were related to the strains found on environmental surfaces – suggesting transmission between personnel and the environmental surfaces.


You can read more about this initial study in MRSA exposure for firefighters, medics greater than for general public: UW study  from the University of Washington’s School of Public Health.


Yesterday a follow up to that study appeared in APIC’s American Journal Of Infection Control. 


A second sampling of these fire stations was conducted several months later - after more stringent infection control procedures were put in place - but once again environmental surface contamination and personal carriage of MRSA was found.


Follow the link to read the entire abstract.


Isolation and characterization of methicillin-resistant Staphylococcus aureus from fire stations in two northwest fire districts

Marilyn C. Roberts, PhD, Olusegun O. Soge, PhD, David No, BS, Nicola K. Beck, MS, John S. Meschke, PhD 


MRSA was isolated from 44 of 1,064 samples examined (4.1%) and included USA300 isolates. The same strains of MRSA were found in both the garage (ie, medic and fire trucks and protective clothing) and the living quarters. Nasal carriage of MRSA from one fire district was 22.5%.


Community-like and hospital-like MRSA were isolated from the environmental samples. The majority of the nasal MRSA/S aureus isolates were genetically related to the environmental MRSA strains, suggesting possible transmission between personnel and the environmental surfaces. Further research is needed to verify this hypothesis.



More details on this study can be found in  journal publisher Elsevier’s press release - Study Finds Fire Stations Contaminated with MRSA including the results of the second sampling (excerpted below).


At the second sampling, 18 (3.9%) of the 464 surface samples were MRSA positive, with MRSA positive samples again found in all nine areas sampled. The kitchen and outer gear both had 4 (22%) MRSA positive samples, while the medic truck had 3 (16.6%), other areas had 1-2 MRSA positive samples each. Two samples contained a strain of MRSA (MRSA SCCmec type II), which is commonly found in hospitals, and were isolated from the fire truck/engine and garage areas.


Thirty percent of the nasal cultures were positive for MRSA (9 samples) or S. aureus (3 samples). The majority (58%) of the nasal MRSA and S. aureus were genetically related to environmental surface isolates suggesting transmission between personnel and the environmental surfaces may be occurring.



Carriage of MRSA in the nares isn’t the same thing as being infected. About 95% of those who have been found to be colonized are asymptomatic.


The concern is that those who carry these resistant organisms could later develop an infection, or potentially pass bacteria on to others.


Exactly how big a risk colonization might be hasn’t been well quantified.


According to the CDC’s  MRSA AND THE WORKPLACE  webpage:


While 25% to 30% of the population is colonized with staph (meaning that bacteria are present, but not causing an infection with staph), approximately 1% is colonized with MRSA.


Staph infections, including MRSA, occur most frequently among persons in hospitals and healthcare facilities (such as nursing homes and dialysis centers) who have weakened immune systems. These healthcare-associated staph infections include surgical wound infections, urinary tract infections, bloodstream infections, and pneumonia.


Colonization among HCWs (Health Care Workers) has been found to run higher than in the general population, with a 2008 Lancet Infectious Diseases study coming up with an HCW colonization rate of just under 5% (surveys conducted between 1980-2006).


The CDC in Precautions to Prevent the Spread of MRSA in Healthcare Settings states that standard precautions (Hand Hygiene, gloving, PPEs, etc.) should control the spread of MRSA in most instances.


But a huge debate continues over just how aggressive hospitals and other health care providers should be in the testing for MRSA colonization in patients and in staff – and exactly what should be done when it is detected.



In Should healthcare workers be screened routinely for meticillin-resistant Staphylococcus aureus? A review of the evidence J Hosp Infect. 2011 Apr;77(4):285-9 NHS researchers in Scotland point out that:


`The role of HCW carriage in the transmission of MRSA is not well understood’  and `There are no published controlled trials examining the impact of routine HCW screening as an intervention in the prevention and control of MRSA infections in the endemic hospital setting.’


They concluded that more research was needed before a recommendation could be made to introduce routine MRSA screening of HCWs in the NHS in Scotland.


Similarly, the researchers from the University of Washington are now calling for more study to see if their findings in Snohomish county are representative of MRSA rates in fire stations and personnel throughout the country.

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