Posts Tagged MRSA

MRSA’s everywhere – ignore the MRSA

Ermahgerd! It’s MIRZAH!

MRSA, affectionately pronounced “mur-sah”, and the abbreviation for “methicillin resistant staphylococcus aureus”, has become the epidemic of our time.

Everyone thinks they know what it is. Few actually have a good handle on what it really means, especially with kids.

MRSA was first described back in good old Blighty in the 1960’s, not long after the drug methicillin was released in an attempt to combat the rise in penicillin-resistant staphylococcus aureus. In the modern era methicillin is no longer available, due to kidney toxicities that are much less in the current selection of anti-staph penicillins (nafcillin and oxacillin), but the MRSA tag remains in use.

In practical, and literal terms, it simply means that the organism in question is resistant to that particular antibiotic. Well, whoopdedoo. Lets just pick another. Except you can’t. The way in which staph becomes resistant to methicillin is through the production of an altered protein that renders the bug resistant to EVERY antibiotic in that entire FAMILY of antibiotics. Penicillin? Gone. Cephalosporins? Gone. Beta-lactamase inhibitors? Useless. Carbapenems? Fat chance.

So you go to another class – quinolones, aminoglycosides, tetracyclines, sulfonamides – but none of them are especially active against staph and…wait for it….MRSA is often resistant to these drugs too.

The first place in which MRSA was discovered was in healthcare settings – long-term care facilities and hospitals. The overuse and abuse of antibiotics selected for strains of bacteria that had acquired all sorts of resistance genes. In fact, the gene for hospital-acquired MRSA is a multi-segment behemoth that carries with it all sorts of additional genes, so the whole lot are inherited together. MRSA infections were associated with severe, invasive disease and death, usually in adults already weakened by other diseases. Due to delays in starting the right treatment, and being forced to use second-line, less effective drugs like vancomycin, MRSA infections add to hospital stays and healthcare costs. Like to the tune of $60,000 apiece.

Just as the world was getting used to dealing with MRSA in hospitals, we started hearing about it in the community. People were showing up with skin abscesses, boils and other infections that were, in about half of cases, growing out MRSA. Worse, they didn’t seem to have any link to the typical risk factors of diabetes, renal failure, cancer, prolonged hospital stay etc. And even more scarily, this was being seen in kids.

But they’re different from the old hospital-acquired MRSA cases. The community MRSA gene cassette is far smaller, lacking the resistance genes of the hospital MRSA. We have a small, but reliable list of antibiotics to use to treat it. Invasive disease is unusual, skin infections are the norm. I have not, yet, seen a real hospital-acquired strain of MRSA in a child. I have seen a few kids pick up MRSA while in the hospital, but it’s always been the “community” strain brought in by visitors, family or other patients.

Diagram of MRSA gene cassettes – hospital (top, types I thru III) versus community (bottom, types IV thru VI)

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Right now, I see a steady stream of kids with MRSA in my clinic and in the hospital. By far the vast majority are recurrent skin infections, often bouncing around various family members. Parents, reading up on MRSA online are understandably freaked out. Friends and relatives shun their kids, for fear of picking it up. Furnishings and furniture are steam-cleaned and thrown out, course after course of an antibiotic is given to treat each infection, but they never seem to go away. Even pets end up getting “swabbed” and tested in the lab, and yes, some are sent on their way as the presumed culprit.

None of this matters.

The truth of the matter is, while MRSA does indeed cause a good chunk of these kind of infections, it’s not got the hold on it. Just as many regular, sensitive staph (MSSA) cause these things. Fully one third of the population carries staph aureus on them – and clearly one third of the population is not suffering from recurrent skin infections. Carrying staph doesn’t mean you’ll get infections. And, annoyingly, you can test negative for staph from a swab (typically done from the nose) and still have infections elsewhere, such as the armpit, legs, or buttocks. We’re exposed to staph everywhere, all the time – and we mostly don’t even know it. That’s if we don’t have it already.

The reason why the skin infections keep happening is due to an entirely separate set of genes, related to immune evasion and skin invasion, which although more common in MRSA are also in some MSSA. (They are, interestingly, mostly absent in the hospital MRSA strains.) The way to get rid of it, if the levels are high enough for these infections to keep happening, is simply to decolonize the skin. That can be done with chlorhexidine washes and bactroban nasal ointment (a two week protocol), but you also have to prevent re-colonization, a more difficult proposition. Bathroom surfaces need to be bleached, towels washed daily (paper towels for hand washing) and EVERYONE in the household needs to have this done. There’s no point focusing on little Johnny with his butt abscesses if mommy and daddy, who are carriers, give him a hug and spread it back.

I never promise that with this approach staph will go away entirely. What we do know is that, if everything is done at once, you CAN eradicate staph at least temporarily from the skin. What we also know is that a third of the population carries staph….so wait long enough and you’ll get it again. I hope to merely reduce the frequency of outbreaks.

In my experience…this seems to work. Except in situations where kids have severe eczema or other skin issues, or where they’re not following EVERY step of the plan, I generally don’t see these kids back again.

So that’s prevention – what about cure? How should we treat these kinds of infections when they do show up? One drug that has seen a resurgence of late is bactrim – trimethoprim-sulfamethoxazole. A combination drug that is designed to inhibit the bacteria’s use of a chemical called folate which is a key component of DNA creation. It sounds good on paper, stop the bacteria from growing and it’ll die. In the lab, staph is often 99% sensitive or more (good odds when your risk of resistance to other staph drugs is around 50%!). The trouble is, in an abscess there is pus. And pus is basically dead and dying cells and bacteria. That’s a lot of DNA hanging around. Using bactrim in that setting is a lot like telling a farmer he can’t grow any more food, but putting him in a grocery store. He ain’t gonna starve any time soon. Bactrim also ignores the risk of strep, which are the other cause of skin infections and which are inherently resistant to bactrim. As such, deliberately targeting MRSA with this kind of approach actually results in MORE treatment failures than using a simple staph drug like cephalexin, even though that shouldn’t work with MRSA! You WILL get treatment failures with cephalexin too of course, and some with the other drugs like clindamycin, doxycycline etc. But it’s as if one should ignore the MRSA when planning your treatment. Drain abscesses (you usually don’t even need antibiotics if you do that) and then use a regular “skin infection” drug to minimize side effects and maximize your chances of success. These days we have NO ideal drug for empiric therapy of skin infections – but we certainly do worse if we panic about MRSA and try to tackle that first. Weird.

Of course sick patients are a different matter – even though the risk of severe invasive disease is low, the consequences are dire. You should ALWAYS cover a very sick patient with vancomycin or other MRSA drug until you know what you’re dealing with.

So I don’t panic about MRSA. I see it all the time. It’s annoying. It’s rarely dangerous. I know that if you focus on it to the detriment of the regular staph and strep you do worse. If someone is a carrier or has an active infection, good hand washing and covering any draining sites is enough to keep it at bay. No need to decontaminate entire schools just because a kid has been found to have MRSA. No need to put everyone on vancomycin if they’re not sick. And if they ARE sick, please don’t use vancomycin by itself, cos its a crappy drug and we only use it because we have to. Don’t bother swabbing just to check for carriage – positive results aren’t worth acting on unless the patient is sick (or, perhaps, due for surgery soon…that’s a whole other issue), and negative results are useless if the patient is actively infected. Deal with the infections, attempt decolonization, move on. Repeat if necessary.

MRSA – it’s a pain in the butt. And not just for the patients.

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