Trouble at the Pittsburgh VA

The Pittsburgh VA has had a recent outbreak of nosocomial legionellosis. Based upon press reports, there have been at least five confirmed cases with one death. There are also references in the media to 24 additional cases reported beginning in January of 2011 (8 of which were felt to be community onset, and 16 unknown onset—likely in the “possible nosocomial” category). CDC personnel traveled there to assist in the investigation, and full details are likely to emerge eventually. 

There is a highly charged back-story here. Reading the press reports, one immediately notices some very pointed critical comments from two internationally recognized Legionella experts. In 2006, there was an acrimonious split between the Pittsburgh VA and Victor Yu and Janet Stout (you can read their side of that story here--click through to some of the e-mails to get a flavor for just how nasty this episode was). This public dispute ended with the destruction of a massive organism bank that included thousands of Legionella strains, leading to a letter and petition being published in Clinical Infectious Diseases. And now that the Pittsburgh VA is knee-deep in Legionella without them, these two colleagues are not holding back. 

We’ve had our own history with Legionella at Iowa, and this outbreak in Pittsburgh may reiterate several important lessons we learned long ago: (1) never assume that Legionella has been eradicated from a water system, it is only suppressed to levels that cannot be detected, and will re-emerge when given the opportunity, (2) copper-silver and chlorine dioxide suppression systems work, but only if they are carefully maintained and levels of the active agent(s) are monitored (not just centrally, but also at distal sites), (3) installing a suppression system doesn’t obviate the need for regular water testing in facility that has had nosocomial cases of legionellosis, (4) there is no way to definitively determine the source of a legionellosis case if cultures are not performed on patient samples (the urinary antigen test doesn’t provide an organism for typing), and (5) all legionellosis cases that fall into the “possible nosocomial” category (onset between 2-10 days after admission) should be assumed to be nosocomial, and an appropriate investigation begun to assess for a source in the hospital water supply.

MRSA in water treatment plants! Panic?!

There is a new study just published in Environmental Health Perspectives that is getting a lot of media attention (here and here and here). The (open-access) study by University of Maryland researchers identified MRSA (and MSSA) in water samples collected during 2009/2010 from two mid-atlantic and two mid-western water treatment plants. They found that 50% of samples contained MRSA and 55% contained MSSA. Among the MRSA strains, 83% were SCCmec type IV and 15% were SCCmec type II, while 68% were pvl gene positive. USA100, USA300 and USA700 PFGE strain types were identified.

Sounds pretty scary, and if you don't read carefully, you might conclude that you shouldn't drink municipal water. However, it appears that most of the MRSA/MSSA was detected in "influent" or pretreatment samples, which were 83% positive, while 17% of post-treatment "effluent" samples were positive and only 8% were MRSA positive. This suggests that water treatment is effective in eliminating S. aureus, so keep drinking the water.

Note:  The positive samples in the effluent were collected during periods when seasonal chlorination was not taking place. Thus, if your municipality uses chlorination, there is likely little S. aureus risk. Also, we should ask if we can generalize beyond this 4-facility sample.

Image Source: EPA via CDC