Selection of multi-drug resistant bacteria from water treatment plants

Water disinfection using chlorine is an important step in purification that prevents dissemination of pathogens in drinking water. However, water treatment has become a challenging operation these days as persistence of pathogens after final step of chlorination was evident in many cases. The mechanism of chlorine tolerance is not yet clear. The occurrence may be due to cellular modification of the pathogens. In the present study sensitivity of microorganisms towards chlorine and various antibiotics were determined to find whether chlorine resistance supports pathogen to attain antibiotics resistance or not. Staph. aureus, Micrococcus, Enterobacter, Morganella morganii, Hafnia alvei, Rahnella aquatilis, Klebsiella and Pseudomonas aeruginosa were isolated from chlorine treated water (p > 0.05) using Membrane Filter technique. In- vitro chlorine resistance and antibiotic resistance study reveals that chlorination at sub- optimal dosage (0.5 ≤ 1.5 ppm) greatly enhances survival ability of Pseudomonas aeruginosa and Enterobacter. Bacteria from chlorine treated water were found to be more resistant to residual free chlorine and to most of the antibiotics compared to isolates obtained from the un-chlorinated pond water, leading to a conclusion that chlorination might have induced some changes in bacterial cell that ended in acquisition of chlorine tolerance and antibiotics resistance.