Predictive parameters of heterotroph plate count bacteria amplification in hospital water lines

Introduction: This research illustrates microbial instability in hospital water line from point of heterotroph bacteria (HPC) amplification in accordance with residual chlorine, pH, temperature, dissolved oxygen (DO) and alkalinity (Alk).Methods: Hundred-fifty samples were collected from hot and cold tap water systems of three selected hospitals. Resid-ual chlorine, pH and temperature were determined promptly in place; HPC was cultured on R2Aculture media by spread plate method. Dissolved oxygen (DO) and alkalinity (Alk) was determined by Winkler and photometric meth-ods, respectively.Results: HPC was detected in 96% of the samples and fifty-two percent had higher bacteria than the recommended standards and HPC density in samples was 947±998 CFU/ml. The highest contamination was detected in cooling sys-tems, gynecological, NICU and sonography ward (1500-2000 CFU/ml) and the lowest was inendoscopy, medical labor-atory and drug store (125-175 CFU/ml). Spearman correlation and multivariate linear regression revealed that HPC density in cold water had negative correlation with Cl2, temperature and DO and positive correlation with pH and Alk. In warm water, HPC density had negative correlation with temperature, pH, and DO and positive correlation with Cl2 and Alk. Chi2 test revealed that higher densities (>500 CFU/ml) in cold water was more frequent than warm water (OR: 2.3).Conclusion: HPC has unexpected distribution in water. Occurrence of high densities of HPC can affect the presence of hazardous bacteria; therefore, it is advised to implement the routine test of HPC monitoring with indicator bacteria and remark the effective efforts for hospitals’ water disinfection for quality assurance.

کلیدواژه ها:

Heterotroph Bacteria ، Residual chlorine ، Water ، Dissolved Oxygen ، Alkalinity ، Hospital