We tend to think of MRSA as a single organism that remains the same over time. But that’s far from the truth and it’s also dangerously misleading. The fact is, there are hundreds of different strains of MRSA – and counting. Which strains predominate will change over time and also over place – not just between hospitals and communities but also between countries. What’s more – and this is key – many of the newer strains are more drug resistant and virulent (toxic) than earlier strains thus making MRSA harder, or even impossible, to treat.
So says Dr. David Coleman at Trinity College, Dublin, whose research team studied a large sample of sporadically occurring MRSA in patients in hospitals over a decade.
There are 2 inter-related issues at work here. One is that society is literally on the move like never before and as we reported last month, bugs don’t have borders. As Professor Coleman puts it: “It is not a phenomenon unique to Ireland,” because “international travel increases the mixing of different community strains, helping to cause the very high level of [MRSA] diversity.”
The second issue has to do with how MRSA, like all microbes, respond to antibiotics, which literally are out to capture and kill them. So MRSA, like a bad guy on the run and to avoid being caught will not only change its identity it may change its “weaponry” too – knowing that the heat is on it will upgrade from a pistol to a machine gun.
And this is exactly what happened to a 35 year old male hospital patient in Brazil, where a new and highly resistant form of MRSA infected the man’s blood, killing him. (The case was reported in the New England Journal of Medicine last week but a more readable version can be found here.)
So why did he die? He became infected only after he was admitted to the hospital. The staff knew it was MRSA and so they began treating him timely with a number of drugs including the powerful MRSA antibiotic of last resort, vancomycin. So what happened? The patient developed resistant to the vancomycin while he was being treated with it – that’s how fast MRSA can change its identity. And it upgraded its “weaponry” too, changing into an aggressive and lethal bloodstream infection.
Which brings us back to the first issue of microbe mobility. “If the vancomycin-resistant superbug were to break out, it wouldn’t stay confined to one region or country,” says Dr. Cesar Arias, a professor of medicine at the University of Texas and one of the researchers of the study in the NEJM. “Bugs don’t have passports. They don’t respect borders. They can travel very easily. And, in fact, this has been shown for MRSA.”
And so the times, like MRSA, are a-changin’.