Hospital water distribution systems (HWDSs) are sources of Healthcare-associated legionellosis (HAL). National guidelines advocate surveillance Legionella (Lg) culturing as strategies to reduce the risk of HAL. Swab specimens (SS) are recommended to detect biofilm-associated Lg and liter water specimens (WS) planktonic Lg, but a strategy that involves both specimen types is expensive and laborious, and the threshold at which Lg detection should prompt corrective action is unclear. We sought to evaluate the ability to detect Lg in a HWDS using SS and liter WS.
Setting: University of Pittsburgh Medical Center (UPMC) Presbyterian Hospital is a complex 757-bed hospital whose patient care areas are supplied by 2 municipal water feeds. During Dec 2014 to May 2015, SS and WS were collected from 33 unique sink faucets. Additionally, WS were collected from the 2 water feeds. Lg disinfection consisted of copper-silver ionization (Dec-May) and monochloramine (Apr-May). HAL was tracked throughout the study period.
Microbial methods: SS were obtained from pre-moistened faucets. WS were collected in a non-sterile, sodium thiosulfate-containing plastic bag and contained 500mL each of cold and warm water. SS were directly plated onto selective solid media. WS were filtered through a 0.2 µM filter, re-suspended, and plated onto selective solid media. Plates were incubated at 360C for 7 days. Presumptive Lg colonies were quantified and confirmed via biochemical testing and matrix-assisted laser desorption/ionization (MALDI).
A total of 588 (294 pairs) SS and WS were collected from faucet sites. Lg was cultured a total of 13 times from 5 unique faucet sites, and on only 1 of these 13 occasions were SS and WS results congruent. Eleven positive WS were accompanied by negative SS, and 1 positive SS was accompanied by a negative WS. A total of 15 water feed specimens were collected, 6 of which grew Lg (3 from each feed). The median CFU for positive samples was 2 (range 1-63). Each water main grew L. pneumophila once; all other specimens grew Legionella anisa. No HAL was observed.
WS detected Lg more frequently than SS from the same sites. Despite the detection of Lg at faucet sites, we observed no HAL. The optimal strategy to preemptively detect clinically significant Lg requires further study.
L. Young, None
A. Sundermann, None
J. M. Tatar, None
S. Carrol, None
J. Crouse, None
A. Pasculle, None
C. Muto, None