Thursday, November 15, 2012

CHP: Review Of NDM-1 In Hong Kong


Inoculated MacConkey agar culture plate cultivated colonial growth of Gram-negative, small rod-shaped and facultatively anaerobic Klebsiella pneumoniae bacteria. – CDC PHIL.


# 6719


The Centre for Health Protection publishes a weekly Communicable Disease Watch, where they highlight recent infectious disease events in and around Hong Kong.


Today, they include a review of the resistance enzyme NDM-1 (New Delhi metallo-ß-lactamase-1) which was first detected in a patient in Sweden (albeit with Indian origins) four years ago, but has subsequently spread to many countries around the world.


This enzyme confers resistance to certain gram negative bacteria like E.coli and Klebsiella against a class of antibiotics called carbapenems. Carbapenems are often our drug of last resort against a variety of bacterial infections.


Of particular concern, this enzyme is carried by a plasmid – a snippet of portable DNA  - that can be transferred to other types of bacteria (see Study: Adaptation Of Plasmids To New Bacterial Species).


The rise of antibiotic resistance - including this emerging NDM-1 enzyme - has long been linked to the overuse and misuse of antibiotics. A practice that is still widespread in many parts of the world, but is particularly rampant on the Indian sub-continent.


Citing a lack of doctors and low family incomes, the Indian government (see India: Still Looking For A Policy On Antibiotics) has been slow to stop the sale of antibiotics to the public without a doctor’s prescription.


It’s been more than 2 years since The Lancet published a study (see NDM-1: A New Acronym To Memorize)  by Walsh, Toleman, Livermore, et al. that sounded the alarm on the emergence and growing prevalence of the NDM-1 enzyme on the Indian sub-continent.


Since that time, we’ve seen a slow, but inexorable spread of NDM-1 carrying bacteria around the globe. A few of my past blogs on the subject include:


Carbapenemases Rising

NDM-1: One Year Later

WHO Unveils 6-Point Plan To Preserve Antibiotic Effectiveness

Eurosurveillance On Antimicrobial Resistance



Today’s report from the HPC indicates that they have identified 17 patients carrying the NDM-1 enzyme over the past four years, with one case each in 2009 and 2010, three cases in 2011, and 12 cases so far in 2012.


Many of these cases were colonized and detected through routine screening, but were asymptomatic. As this report indicates:


Infections varied from colonisation or mild to potentially life threatening or fatal. The level of risk depends upon which body part is infected and general health of the patient.


I’ve included some excerpts, but follow the link to read:



Source CHP Communicable Disease Watch

Among the 17 cases, 13 (76%) were male, and the median age was 64 years (ranged from 11 months to 94 years). Fourteen (82%) were Chinese, 2 Indian and 1 Burmese.


Among 16 imported cases, all except one had history of admission to hospitals while staying abroad. Twelve were hospitalised in Mainland China (8 in Guangdong province, 2 in Hunan province, 1 in Fujian province and 1 in Henan province), one in India, one in Myanmar and one in Thailand. Six (40%) of them had operations done during their hospitalisation.


The one without history of admission to hospital was a 66-year-old male patient of Indian ethnicity and he had travelled to India before onset of symptoms. Four cases had signs of infection (2 had chest infection, 1 urinary tract infection and 1 leg infection). 


Thirteen were asymptomatic colonisation detected by screening or contact tracing. One had the bacteria yielded from both sputum and rectal swab specimens. Two cases passed away due to underlying illness and aspiration pneumonia respectively.


In September 2012, CHP identified an import-related NDM-1 case affecting a 64-year-old man. A rectal swab was taken for this patient as part of the contact tracing exercise for another imported NDM-1 patient (78-year-old man) from Myanmar. They had stayed in the same cubicle of a hospital ward in Hong Kong.


The rectal swab was tested positive for NDM-1. Pulsed-field gel electrophoresis patterns of the two NDM-1 strains were subsequently found to be identical by the Public Health Laboratory Services Branch (PHLSB) of CHP.

This suggests that the 64-year-old case was epidemiologically linked to the 78-year-old imported case. Thirteen other patients stayed in the same cubicles as the case patients for more than 48 hours were screened by rectal swabs and all were tested negative.



This week is antibiotic awareness week (see A Health Crisis In Slow Motion) here in the United States, as it is in many places around the world. The erosion of the effectiveness of our antimicrobial arsenal increases with each year, and leads many doctors and scientists to worry that we’ll eventually lose the ability to treat even common infections.


For a far more complete discussion of antimicrobial resistance issues, I can think of no better primer than Maryn McKenna’s book SUPERBUG: The Fatal Menace of MRSA. And Maryn’s SUPERBUG Blog, part of Wired Science Blogs, continues to provide the best day-to-day coverage of these issues.

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