Legionelle pneumophila water contamination in three military hospitals of Tehran in 2013

Background: Identification of the water contaminated with Legionella is one of the most important steps to be taken for the control of infections associated with Legionella. This research investigated the water contaminated with Legionella in three selected military hospitals in Tehran.

Methods: One hundred and fifty samples with 4 Liters of cold and hot water were collected from the selected hospitals. After determining the residual chlorine, pH and temperature, the samples were transported to the laboratory for filtration. BCYE culture medium containing necessary ingredients was prepared based on the protocol and the interfering bacteria were eliminated by thermal treatment and GVPC supplement. Legionella colonies were identified via biochemical and morphological tests. Data were analyzed by Mann-Whitney and χ2 tests.

Results: Fifty-six samples (%37.33) were contaminated with Legionella pneumophila. The highest rate of contamination was observed in the air conditioning systems and endoscopy ward (100%) and the lowest rate of contamination was detected in hemodialysis, neuro-psychology, nuclear medicine ward and kitchen (%0), respectively. Air conditioning system had the highest bacterial density (122000 CFU/L) and orthopedic, pediatrics and sonography wards had the lowest bacterial density (1000 CFU/L). The mean values of chlorine residual, pH and temperature were not significantly different in the presence and absence of Legionella (P>0.05). The results of χ2 test revealed no significant difference between type of water system (hot and cold) and bacterial or lack of bacterial growth (P>0.05).

Conclusion: In spite of consuming treated water, 37.33% of the samples were contaminated with Legionella pneumophila. Since Legionella pneumophila is resistant to the conventional concentrations of chlorine residual, more effective disinfection procedures should be applied to eliminate Legionella contamination in hospitals’ water systems.