How Super is MRSA?

 

 
 
 

Howard Rodenberg, MD, MPH, Dip(FM) | | Friday, January 18, 2008


I m sure there s a very good reason why sizes are no longer what they were, and I hope some bright spark will explain it to me some day. All I know is that when I was a kid, there were essentially three sizes: small, medium and large. As our society has grown literally we added extra large, then XXL and those that follow (I ll admit to being a traditionalist who would just as soon call men big and tall, and women well-rounded or curvaceous. It seems much more dignified.)

But the sizes I knew don t exist anymore, and I think that Starbucks is greatly at fault. Their small is a tall, their medium is a grande (because if it s in Spanish it s automatically larger) and their large is a venti -- which doesn t even mean molto grande in Italian, but instead means either 20 (like the number of ounces) or the plural of vento, or wind (which is presumably what you do when you cross a latte with lactose intolerance, which has nothing to do with sizes at all).

This notion of the artificial superlative (I just made that up ought to be good for an honorary doctorate somewhere) was brought to mind last week when I read a link on JEMS.com to an article talking about a superbug. This bacterial ninja was not only behind the death of a Virginia teen, but is also the cause of an alleged epidemic of massive proportions. The article went on to decry the lack of attention paid to this particular plague, and demand that it be regularly reported to health authorities. As the investigation and prevention of reportable disease is one of the reasons for being at a state health department, I wanted to try to set the record straight or at least slow it down from a 78 to a 33.

The superbug in question is known as Methicillin-Resistant Staphylococcus Aureus, or MRSA. The organism itself is a member of the gram-positive family of round bacteria, and the name is often shortened to staph (for those who may recall high school biology, gram-positives were the purple ones, and the gram-negatives were pink). The MR part of the name refers to a change in the chemical makeup of the bacteria that makes it resistant to methicillin and other related antibiotics, including virtually all penicillins.

Staphylococcus is commonly found on skin surfaces; more than 30% of fully asymptomatic people carry staph in their nasal passages. It s transmitted through direct contact with skin or other surfaces (such as used eating utensils and linens) which can harbor the bacteria. Infections with staph are usually caused by the entrance of bacteria through a break in the skin. The organisms most often cause skin infections, but can also infect the lungs, bones and bloodstream. Most of the time, the infections can be easily resolved with appropriate antibiotic therapy, although the resistant nature of MRSA makes it more difficult to treat than non-resistant strains. Within communities, staph infections are commonly seen in clusters, especially among people who live or work in close proximity to one another (like football teams or on fishing boats). Prevention of staph infections is relatively simple and is based on good hygiene practices. (This represents yet another plug for the use of universal precautions.)

MRSA is a product of natural selection. To say this is not to enter into the political debate about how biology is taught in the public schools, but simply a statement of fact of how nature works. Given that there are kazillions of staphylococci out there in the world, each of them trying to reproduce their little nuclei out the wazoo (two new scientific terms which should get me another honorary doctorate), it s not surprising that sometimes the complicated machinery behind the replication of DNA sometimes gets messed up. Most of the time the screw-up is minor and has no apparent effect; sometimes it s lethal to the organism; rarely, it may provide some kind of survival advantage. These differences occur more often than we know. All one has to do is recognize the natural occurrence of birth defects and inborn errors of metabolism in humans to know that these mutations are not uncommon.

(It s fair to wonder how often this happens, and it s hard to quantify. A change that infers a significant survival advantage in an organism is admittedly a rare thing. But it s much less rare than monkeys typing Shakespeare. According to Ask Dr. Math at The Math Forum@Drexel, if you had 5 x 10 monkeys working 24 hours a day, they would turn out one of The Bard s 14 line sonnets in a mere five years. The banana bill would be unfathomable.)

So if that s how MRSA came into the world, does that also explain its spread to epidemic proportions? Setting aside the question of what epidemic proportions are, it s true that MRSA has become ubiquitous in our society. Estimates are that up to 1% of us are routinely colonized with MRSA. But if you accept the fact that these kinds of mutations in bacteria occur far less than 1% of the time (and they clearly do, given the analysis above), why is the colonization rate so high? And why is it even higher in certain populations, such as hospitalized or institutionalized patients?

Most authorities pin a large share of the blame on the indiscriminate use of antibiotics. In many cases, antibiotic therapy for presumed infectious disease has become a fixed expectation on the part of patients regardless of the natural history of the proposed ailment. Physicians likely started the ball rolling in the wake of the first uses of these drugs, which had to be nothing short of miraculous. But despite abundant data that most infections (both viral and bacterial) are self-limited, and that antibiotics have a very narrow role in other aspects of care such as wound management, a lack of time for patient explanations and the fear of litigation over unmet expectations resulted in continued antibiotic overuse. So when antibiotics were used at every turn, the law of averages said that eventually you were going to start treating patients who had some of the resistant bacteria. As the antibiotic killed off all the susceptible bugs, the resistant ones were left to recolonize in the patient, and anyone else the patient subsequently came in contact with. It s not really surprising, then, to learn that in places where potent antibiotic use is most frequent, such as hospitals and nursing homes, MRSA rates are accordingly high.

(It s fair to wonder if there was a MRSA all along, or if it s strictly a creation of human activity. The truth is that nobody knows, but if these bugs have been floating around for eons their prevalence was certainly accelerated by indiscriminate antibiosis. I should also note that the emergence of MRSA and other resistant organisms has resulted in most practitioners reducing their dependence upon antibiotics. That s what professionals do.)

So is MRSA a superbug? It depends upon what you expect a superbug to do. It is, as you d infer from the name, resistant to antibiotics from the family of drugs that includes methicillin. It s transmitted, controlled and prevented just as any other staphylococcus might be. It does not fly through the air on gossamer wings. It has not developed fangs and pointy Vulcan ears. It will not, as depicted in a memorable episode of the legendary Britcom Blackadder Goes Forth, cause you to put underwear on your head, stick pencils in your nose, and end every sentence with the word wibble. It will not provide the Kansas City Chiefs with the explosive offense they lost when Al Saunders bolted for San Diego. Put simply, it does what you d expect it to do.

The news item that began this train of thought wondered why MRSA infections aren t reported to state and local health authorities. Diseases are usually reportable to health authorities when they are rare, easily transmitted between susceptible persons and have high rates of complications. Reportable diseases also mandate investigation to prevent further infection. In some ways, MRSA was a candidate to be a reportable disease a number of years ago, but now it s so common and well-known that the horse has left the barn, and not much can be gained from further review. And even if we want to begin reporting MRSA infections, Dr. Gail Hansen (the Kansas state epidemiologist) reminds me that part of the problem is deciding exactly what reporting actually means. Is it designed to detect outbreaks, study risk factors for infection, determine the prevalence of MRSA in the community, or provide accountability measures for hospitals and other health care facilities? Each of these goals requires different surveillance systems and different sets of data. The Council of State and Territorial Epidemiologists (CSTE) has issued a position paper supporting pilot research to outline what a surveillance and reporting system for MRSA might look like. Unfortunately, it seems that both legislators and the public want instant, rather than valid, information.

All this being said, are there in fact superbugs out there? Sadly, the answer is yes. You may have heard of the recent globetrotting lawyer from Atlanta with extensive drug-resistant tuberculosis (XDR), and there are rare cases of MRSA which are also resistant to the backup drug vancomycin. We ll work on developing new antibiotics, the bugs will come up with new means of resistance, and the never-ending dance will continue forever. That is, unless we happen upon some kryptonite.


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Related Topics: Industry News, PPE and Infection Control, Medical Emergencies, Humor

 
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