Put this fire out: Culture studies running amuck

January 12th, 2015

We seemed to have reached critical mass regarding studies finding MRSA or some other pathogen on cell phones, key boards, ties, stethoscopes, lab coats, uncooked retail meats, ad nauseam. While the role of the environment is taking on a justified renewed focus in health care, searching for bugs on various and sundry objects at a considerable distance from the bedside of the immune compromised patient is a dubious use of infection prevention resources.

Ok, long term care may be the exception that proves the rule, but a fire station manned by healthy firefighters? A recent study and accompanying press release implies MRSA “transmission” may be occurring in fire stations. The study’s conclusion that finding a genetic link between some environmental and nasal isolates suggests “transmission between [fire] personnel and the environmental surfaces” is misleading -- particularly since many news sites will pick this up and circulate it without the slightest scrutiny.

On the contrary, no transmission of infection – or any infection period -- occurred in the study, nor were there any MRSA infections of firefighters cited in the references. All props to these heroes, and I know they do EMT work and everything else. However, the rare but real risk of community-acquired MRSA has been clearly established, particularly in communal settings in the absence of basic hygiene and environmental cleaning. Hand hygiene and basic prevention measures are required, not endless bug hunts.

In the study, a total of 1,064 samples were collected from various surfaces, locations, vehicles at fire stations. At the first round of sampling, 26 (4.3%) of the 600 surface samples were MRSA positive, with MRSA positive samples found in all nine areas sampled. Nasal samples were obtained from 40 healthy fire personnel from 13 stations to evaluate MRSA carriage. Nine MRSA-positive nasal cultures (22.5%) were recovered, along with MRSA and three for drug susceptible S. aureus. Reporting the latter finding was dutiful science, but it is well to mention here that roughly a third of the entire U.S. population is carrying some form of staph in their noses.

That said, the findings – though based on small numbers – suggest that firefighters may be at some elevated risk for MRSA colonization, which is found in some 4 million people or 1.5% of the population.

But to reiterate, since no MRSA infection developed nor was transmitted between firefighters, what we have here is a failure to communicate the basic conditions necessary to complete the time-honored “chain of infection.” These factors typically are cited as an infectious agent, a reservoir, a portal of exit, a mode of transmission, a portal of entry, and host susceptibility. It’s important to remember that if any one of these links is broken we have no transmission of infection to an actual human as opposed to a coffee pot.

If hand hygiene is the take-home, fine with me and more power to the message that firefighters should wash their hands and keep their station clean. That said, the epidemiological benefit of detecting MRSA on environmental surfaces in such settings is questionable, as is culturing healthy people for colonization with MRSA unless they are being admitted to a hospital or slated for elective surgery.