Genotypic and Phenotypic Methods for the Investigation of a Nosocomial Legionella pneumophila Outbreak and Efficacy of Control Measures

Abstract

To determine the source of a nosocomial outbreak of Legionella pneumophila serogroup 1 infection and the efficacy of control measures, clinical and environmental isolates were characterized by molecular subtyping and disease surveillance was conducted. The outbreak involved 32 cases (relative risk, 4.0; P less than .001 vs. previous period). Water colonization with L. pneumophila serogroup 1 and patients' exposure to faucet use incriminated the water system as the environmental source. Monoclonal antibody typing showed that patient isolates belonged mainly to type Pontiac and water isolates mainly to type Bellingham (P less than .001). By four genotypic techniques, outbreak-related isolates from patients and the water system were found to be clonally related and distinct from control strains (P less than .001). Heat and UV light treatment of the water system showed a protective efficacy of 88% (95% confidence interval, 75%-94%). These findings indicate that phenotypic variation may interfere with monoclonal antibody typing of legionellae and that waterborne legionellosis can be controlled by physical disinfection.

Molecular typing of Legionella pneumophila serogroup 1 isolates from patients and the nosocomial environment by arbitrarily primed PCR and pulsed-field gel electrophoresis

“…Although many Legionella species are found in the natural environment, L. pneumuphila is responsible for >85% of cases of Legionnaires' disease [2]. Outbreaks of community-acquired and nosocomial L. pneumophila infection have been described [ 1,3]. During such outbreaks, epidemiological studies are required to identify the environmental source of the infection and a possible epidemiological link between the cases.…”

“…Serotyping of L. pneumuphila isolates with specific antibodies is used widely, but is of limited value as most L. pneumuphila infections involve serogroup 1 [2]. Other epidemiological markers used in the investigation of legionellosis include monoclonal antibody subtyping of serogroup 1 [4], analysis of allo-enzymes [5] and PCR la Ville de plasmids [6], and restriction endonuclease digestion of chromosomal DNA [3]. Restriction fragments of L. pneumuphila DNA have been used as probes for molecular typing of nosocomial isolates belonging to the same serogroup (serogroup 3) [7].…”

Legionella Pneumonia Associated with Adult Respiratory Distress Syndrome Caused by Legionella Pneumophila Serogroup 3

“…The culture was positive with recovery of 2.6×10 2 CFU/100 ml of Legionella pneumophila serogroup 3. In order to identify the source of infection, restriction enzyme analysis by pulse-field gel electrophoresis (PFGE) was performed as previously reported (6). Genomic DNA was extracted with a GenePath plug Kit 5 (Bio-Rad Laboratories, Hercules, CA, USA) according to the manufacturer's protocol.…”

Hot Spring Bath and Legionella Pneumonia: An Association Confirmed by Genomic Identification.

“…Pulsed-field gel elec trophoresis Pulsed-field gel electrophoresis (PFGE) was performed as previously described (9). Bacterial cultures were harvested and genomic DNAwas extracted with a GenePath plug Kit 5 (BioRad Laboratories, Hercules, CA, USA)according to the manufacturer's protocol.…”