One of the reasons I’ve not been blogging as much over the past 2 years or so is that it’s been just insane in the lab. As I was still living off start-up funds and pilot grants, I didn’t have anyone full-time to take care of everything, so all the work has been done by myself and a handful of excellent graduate & undergrad students. Happily, some of the initial projects are wrapping up, and publications are starting to come out (I’ll be blogging about others in the coming days/weeks). One of them was published yesterday in Emerging Infectious Diseases: Livestock-associated Staphylococcus aureus in Childcare Worker. More after the jump.
As part of a project by PhD student Erin Moritiz (now Dr. Moritz), we sampled for S. aureus in daycares in the state, taking samples from kids and the workers. We did molecular typing on all of these; the main manuscript is still in draft. However, we noticed that one isolate from a worker was spa type t571. (“spa typing is one way to analyze Staph, based on variability within the gene encoding a surface protein called Protein A). t571 is one of more than 2 dozen spa types that are associated with ST398, the strain of S. aureus that’s been found in swine in Canada, the in the US, as well as many countries in Europe. The t571 type has been found in at least 6 different studies (reviewed here) as well as in the European study noted above, and has been found in Manhattan and the Dominican Republic. It was also responsible for the death of a 14-year-old in France.
What’s been unique about some of these t571 isolates–including ours–is that many of these individuals had no documented contact with live swine. We had questionnaire data from this individual and specifically asked about animal contact, and none was reported. However, as we note in the paper, this was a very large facility (60 employees and 168 children at the time that we sampled) and only a small fraction of the kids and employees participated. Therefore, it’s quite possible that someone else in the facility was colonized via contact with animals, and transmitted it to the employee where we found it. We’ve also found this type on raw meat products. This is an emerging area of study, and no one really knows how likely it is to pick up S. aureus from meat and end up becoming colonized with it.
I should emphasize also that the strain we found wasn’t MRSA–methicillin-resistant S. aureus. It was susceptible to this drug (methicillin-susceptible S. aureus, or MSSA), as were those found in Manhattan and France. Does that mean there are distinct MSSA ST398 strains circulating? Absolutely–not all ST398 are MRSA. The isolate in France also contained the pvl gene, which has been associated (anecdotally, at least–the jury is still out on many aspects regarding pvl) with increased virulence. Ours was pvl negative. Bottom line: we still have a long way to go toward understanding the epidemiology and ecology of ST398 (and S. aureus in general), both in humans and animals.