Antibiotic resistance is a fight we will never win

Antibiotic resistant E. coli (left), sensitive (right)

One of the most significant issues facing health care workers today is the unavoidable fact that our primary means of treating infectious diseases are rapidly losing their efficacy. Penicillin was the first commonly used antibiotic available to medicine, and became widely used through the 1940’s. The first report however of a bacterial enzyme capable of degrading penicillin was report even before the widespread use of penicillin was achieved. Indeed, the capability of microorganisms to resist many common antibiotics currently in use is a property that existed prior to recorded history, as indicated by the presence of antibiotic resistance genes in permafrost soil samples. The emergence of resistance of any antibiotic we have available should therefore not be viewed as “a possibility,” but instead should be viewed as “a certainty.”

A piece published recently in the Atlantic Monthly offers a chilling reminder of exactly how scary this scenario is. Doctors in India have reported that over 50% of the infections treated in local hospitals are resistant to one or more antibiotics, and this rate is increasing annually. Teams of scientists from South East Asia and the United Kingdom found in 2009 that almost one quarter of these patient isolates were in fact resistant to the most cutting edge antibiotics, a class of antibiotics known as carbapenems.  A news report that a friend pointed me to indicated that there are many cases of tuberculosis in India that continue to increase in resistance, but what is more alarming is that this new report indicates that resistance to antibiotics is appearing in a broad class of microorganisms, not just in a single species.

Molecular examination of these resistant bacterial isolates has identified the NDM-1 gene, which encodes a beta-lactamase enzyme that is able to break down many forms of related antibiotics. Examination of the DNA database at the National Institutes of Health shows that the NDM-1 gene has been found in 8 different bacterial species; comparison of their protein coding sequences shows that they are very highly related. This high degree of sequence conservation in turn suggests that the sequences have been exchanged between the different bacterial species via a process known as horizontal gene transfer. The ability to exchange DNA sequences like this means that a huge number of pathogens can potentially acquire resistance to these antibiotics, simply by acquiring the DNA sequence in question from a bacterium that has the gene.

The Atlantic Monthly article also describes a measure of controversy over the naming of the NDM-1 gene. An article in the journal Antimicrobial Agents and Chemotherapy, and followed up in a review article in The Lancet, presents the initial molecular characterization of the gene, and named it NDM-1 from the city New Delhi, where it had been found in bacteria isolated from a patient who had been hospitalized there. Further epidemiological analysis had identified cases throughout several Indian and Pakistan cities, as well as in the United Kingdom in 2009. To date, isolates have been identified from a number of countries, indicating that the resistance gene is spreading globally, and presents a health risk not just in India, but everywhere. An apology by Richard Horton, editor of The Lancet, argues that the geographic naming and the implications of that naming do a disservice to this global risk.

That said, I am not convinced that there is inherent bad-context territorialism in the geographic naming of pathogens. It is bias neutral information related to an important public health issue. A quick search in Genbank shows that infectious agents such as smallpox are tagged with where the outbreak occurred. This is what epidemiology does: it characterizes who is sick, when they were sick, and where the outbreak occurred. It is through assembling and understanding these criteria that we can predict and prevent further outbreaks, and that helps all concerned.

But that’s just my opinion–what do you think?

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About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on February 3, 2012, in Danger danger danger!, Microbes in the News. Bookmark the permalink. Comments Off on Antibiotic resistance is a fight we will never win.

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