Evaluation the Impact of Chlorination on Development of Chlorine and Antibiotic Resistant Bacterial Isolates in Public Swimming Pools

Water is essential for daily life activities; it also serves as a medium for transporting numerous waterborne diseases. This study investigated the bacteriological safety of water in swimming pools in Sulaymaniyah city, Iraq. For this purpose, during summer time (August to September, 2021), sixty-seven water samples were collected from eight indoor public swimming pools. The physicochemical parameters were determined and a bacteriological assessment was done using Most Probable Number test. Then, the diversity of microbial communities was determined using Vitek 2 compact and 16S rRNA. In addition, chlorine resistance test and biofilm formation were quantified using microdilution technique and crystal violet staining method, respectively. Moreover, Kirby- Bauer disk diffusion technique was used to test antimicrobial susceptibility. Variable results of physicochemical analysis were recorded for each of the temperature, pH, and free chlorine ranged between (25.81±1.16 to 28.69±1.03 °C), (7.02±0.24 to 7.46±0.31), (0.12±0.05 to 1.38±1.24 mg L -1 ), respectively. MPN negative results showed that 80% of water samples was contaminated by non-lactose fermenter bacteria, including Enterobacter cloacae 57.61%, Pseudomonas spp. 16.96% and other major opportunistic pathogens 25.43%. The rate of contamination was strongly correlated with the sources of water used for swimming pool and free chlorine concentrations in the pools. Results of chlorine resistance test revealed variation among all isolated bacteria (1.25 to 5 mg L -1 ). Moreover, the correlation between different chlorine concentrations with the growth and biofilm formation was exhibited linear negative correlation. Most importantly, strong positive linear correlation was found between bacterial growth and the degree of biofilm formation (r=0.90 to 0.98), also variation in antibiogram profiles were recorded against 15 antibiotics used in this study. It can be concluded that most of the studied swimming pools are heavily contaminated by chlorine and antibiotic resistance waterborne pathogens. Therefore, continuous monitoring and use of maximum permissible chlorine disinfectant is highly recommended.