In the latest edition of the medical journal Lancet: Infectious Diseases, an article details the detection of a new superbug. The culprit is a gram-negative Enterobacteriaceae which has shown resistance to most known antibiotics so far with the exception of tigecycline and colistin.
Enterobacteriaceae is not a single bacterium but a family of bacteria which includes some bugs that people are more familiar with like Salmonella and E.coli. Gram negative refers to the reaction of the bacteria to a staining procedure sometimes called Gram's method but most widely called Gram staining. Gram refers not to a unit of measurement but the name of the Danish scientist who developed the technique, Hans Gram.
Tigecycline was approved by the FDA in 2005 and was developed in response to antibiotic resistance bacterial strain prevalence. Colistin is an antibiotic and another drug targeted at resistant bacteria but is not approved for use in the U.S.
The bacteria apparently gained their resistance from a particular gene which was given the name New Delhi metallo-β-lactamase 1 or NDM-1. The researchers analyzed samples from areas in Southern and Northern India and cases referred to the U.K.'s national reference laboratory.
The researchers identified 44 isolates which carried the NDM-1 gene in India, the U.K. and Pakistan. The NDM-1 gene was found mostly in E. coli and K. pneumoniae. However, the really troubling part is that the gene was found in most of the isolates to be carried on plasmids. Why is this troubling? Let me explain.
Plasmids are "rings" of DNA found naturally within bacteria and a few other microorganisms. Plasmids can replicate independently in a viable host and are often transferred between bacteria. Since the NDM-1 gene is found mostly on plasmids this means the motility of that gene and the possibly of it spreading quickly is a great concern.
The CDC released a short statement about NDM-1 in their Morbidity and Mortality Weekly Report back during the last week of June warning of the detection of the NDM-1 gene here in the U.S.:
"Antimicrobial resistance in Gram-negative bacteria is a well-recognized problem, and a new resistance mechanism found in three U.S. Enterobacteriaceae could compound this challenge. This new mechanism, New Delhi Metalol-beta-lactamase (NDM-1), is linked to receipt of medical care in India or Pakistan, where it is common among enteric bacteria. NDM-1 is an enzyme that destroys many commonly used antibiotics, rendering them ineffective. It is carried on a mobile element that can readily spread to other bacteria. In order to prevent transmission of bacteria possessing NDM-1 in the U.S., CDC is alerting clinicians to be aware of NDM-1 in patients who have recently received medical care in India or Pakistan and requesting that carbapenem-resistant enteric bacteria from these patients be sent to CDC for further investigation. Also, CDC is reiterating the importance of implementing CDC recommendations to prevent the spread of these highly resistant organisms."
Just another thing to brighten the middle of everyone's week...
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