Pseudomonas aeruginosa (PA) is a leading pathogen in intensive care units (ICUs). Surveillance for PA may improve empiric antimicrobial therapy, since colonizing strains may subsequently cause infections. The source of colonization may be 'endogenous' or 'exogenous' (from the environment or other patients). The PA source determines the measures needed for infection control. In this prospective study we aimed to investigate the sources of PA and to correlate colonizing and infecting strains.
ICU patients were screened on admission and weekly from the pharynx, endotracheal aspirate (EA), rectum and urine. Molecular typing of screening and clinical cultures isolates was performed using Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR.
Between Nov2014-Jan2015, 34 patients were included in the study. Thirteen (38%) were colonized with PA upon admission. The rectum was the most common site for PA colonization (identifying 77% of the colonized patients upon admission, and 91% after 1 week of ICU stay).
Twenty ERIC-PCR types were identified among 18 patients. Generally, most types were unique to patients and sites (mainly in the rectum), but cross-overs between sites and types occurred (figure 1). First-time detection of a PA-ERIC type was most common in the rectum (70%), followed by the pharynx (43%), EA (39%) and urine (9%). Weekly screening of all 3 sites (rectum, EA and pharynx) identified 96% of PA-types.
Patients colonized with PA upon admission were at a higher risk for PA-related clinical infection, compared with negative patients upon admission (8/13 (61%) vs. 1/25 (4%), OR=38.4, CI (3.8-379), p=0.0002). In 13 out of the 14 (93%) PA-related infections, the same type was found in at least one screening culture from the same patient. Ventilator-associated pneumonia (VAP)-related PA-ERIC-type was best predicted by the EA and pharynx screening types (75-87% of cases). No clinical case of PA was found among the 22 patients with repeated negative screening.
PA origin in this non-outbreak setting was mainly 'endogenous' and PA-types were generally patient- and site-specific, especially in the GI tract. While prediction of VAP-related PA-types by screening (mainly of pharynx and AE) was fair, the negative predictive value of screening was very high.
Z. Shimoni, None
S. Cohen, None
M. Afraimov, None
M. Shapiro, None
M. Uda, None
A. Adler, None
S. Paikin, None