The role of weather, season and climate in HAI

The recent attention given to climate change served as a backdrop to this talk (slides posted below) that I just gave at ICPIC in Geneva. ICPIC has been a wonderful conference and it was a nice forum for discussing the larger, international issues hindering HAI control. I look forward to seeing everyone again in two years.

Climate change and hospital pathogens

Do hospital pathogens like living in a Greenhouse?

Nothing should dare threaten your coffee.  So when Starbucks announced today that global climate change is threatening coffee supplies, you knew it would get media attention. What's a journalist without their coffee and cigarettes? (aaaack) What about hospital pathogens? Could climate change impact hospital infection rates. We thought it might. (Note: by we, I mean my colleague from Maryland Judy Johnson - She's now in Gainesville).

Back in 2006, Judy and I were sitting on a park bench (it was a nice day) discussing the upcoming ICAAC abstract deadline and pondering what we should submit, when she suggested we look for seasonal variation in Gram-negative pathogens.  Judy mentioned some data suggesting Gram-negative infections were more common in tropical countries and we also discussed the high incidence of Acinetobacter infections in troops returning from Iraq. Sure, we also knew that others had noticed summer peaks in certain pathogens, but the prior research didn't control for meteorologic factors and also combined summer data from across the entire US (hint: Maine ≠ Texas). Thus, we felt there was room for further exploration.

In our initial analysis, published in ICHE (2008), we reported that summer season (vs. winter) was associated with 28% more P. aeruginosa, 46% more E. cloacae, 12% more E. coli and 21% more A. baumannii clinical cultures over 8 years. Importantly, we found that for each 10°F increase in temp, there was a 17% increase in the monthly rates of infection caused by P. aeruginosa and also A. baumanii. Of course, this was a single center study, so we needed more proof.

Mike Eber and our group have just published a follow-up study in PLoS One looking at BSI data from 132 hospitals over 8 years. Using 211,697 inpatient blood isolates, we again found that Gram-negative organisms were more frequent in summer months ranging from 12.2% higher rates for E. coli to 51.8% higher for Acinetobacter spp. And more interestingly, we reported that independent of season, monthly humidity, monthly precipitation, and long-term trends, each 10°F rise in mean monthly temperature was associated with higher Gram-negative bacterial BSI frequencies ranging between 3.5% for E. coli to 10.8% for Acinetobacter spp.  Thus, warm temps = more Gram-negative bacteremias; that is, even a warm winter is a bad thing.  Lots more work to do to figure out why this might be, but I think it's an interesting first (or second) step. Cheers.

Note: Special thanks to Ramanan Laxminarayan and Extending the Cure for supporting this project.

Bacteria can walk?---Whoa, Nellie!---Bacteria can walk!

Image Credit: Gerard Wong, UCLA

Well, I knew there had to be an explanation.  It couldn't be that bacteria spread from patient to patient because hand hygiene compliance is only 60%.  No, it can't be our fault.  Now, there is finally data for surgeons to use when they say they're too busy to wash their hands.  They can just say that the bacteria will just walk to the next patient room anyway, so why bother.  Well, maybe not exactly...

There is a new study out in Science from scientists at UCLA, Houston, Illinois and Notre Dame that identified a new surface motility mechanism in Pseudomonas aeruginosa whereby they were able to stand upright and "walk" in a verticle orientation. This was thought to allow for surface exploration, improve surface detachment and perhaps enhance biofilm formation.

So maybe washing our hands makes them too slippery for bacteria to walk on and they just trip?  OK, I just made that up. Anyway, it probably remains a good idea to perform proper hand hygiene.

Gibiansky et al. Science 8 October 2010

h/t: ars technica, Nobel Intent post