Effect of chlorination on antibiotic resistance profiles of sewage-related bacteria

Abstract

A total of 1,900 lactose-fermenting bacteria were isolated from raw sewage influent and chlorinated sewage effluent from a sewage treatment plant, as well as from chlorinated and neutralized dilute sewage, before and after a 24-h regrowth period in the laboratory. Of these isolates, 84% were resistant to one or more antibiotics. Chlorination of influent resulted in an increase in the proportion of bacteria resistant to ampicillin and cephalothin, the increase being most marked after regrowth occurred following chlorination. Of the other nine antibiotics tested, chlorination resulted in an increased proportion of bacteria resistant to some, but a decrease in the proportion resistant to the remainder. Multiple resistance was found for up to nine antibiotics, especially in regrowtb populations. Identification of about 5% of the isolates showed that the highest proportion of Escherichia coli fell in untreated sewage. Some rare and potentially pathogenic species were isolated from chlorinated and regrowth samples, including Yersinia enterocolitica, Yersinia pestis, Pasteurella multocida, and Hafnia alvei. Our results indicate that chlorination, while j01jally lowering the total number of bacteria in sewage, may substantially increase the proportions of antibiotic-resistant, potentially pathogenic organisms. The occurrence of multiply antibiotic-resistant (MAR) bacteria in both drinking water and wastewater has been demonstrated in many studies (2, 3, 22, 23, 25) and is considered an important potential health problem. Antibiotic resistance in pathogens causes difficulty in effectively treating human infections, but antibiotic resistance in organisms which are not considered primary pathogens is also important because of the ability of these organisms to transmit

Introduction of biocides into clinical practice and the impact on antibiotic-resistant bacteria

“…Of possible significance are the findings of Armstrong et al (1981Armstrong et al ( , 1982 who isolated multiple-antibiotic-resistant bacteria from drinking water, especially in view of the subsequent proposal (Murray et al 1984) that disinfection and purification of water may augment the occurrence of antibiotic-resistant bacteria. Chlorination was suggested as being responsible for selecting or inducing such changes.…”

Microbial Source Tracking of Escherichia coli in a Constructed Wetland

“…Previous studies have found evidence that chlorination of wastewater selects for multiple antibiotic-resistant bacteria, but with mixed results. Murray et al (1984) found that regrowth bacteria had a higher resistance to ampicillin (83%), cephalothin (75%), and tetracycline (18%), but a decreased resistance to kanamycin (2%). In another study, Staley et al (1988) found that chlorinated fecal-coliform isolates were more sensitive to kanamycin, streptomycin, and tetracycline, but more resistant to ampicillin.…”

“…Also, fecal coliforms have been shown to survive and regrow in wastewater effluent following chlorination (Heukelekian, 1951;Shuval et al, 1973). Some researchers have shown that regrowth bacterial populations consisted of a higher proportion of multiple antibiotic resistant (MAR) bacteria than the initial surviving population in chlorinated effluent (Murray et al, 1984;Rusin, 1989). Therefore, the microbial removal capability of these wetland systems may not be realized, resulting in counts exceeding acceptable levels for regulatory permitting.…”

Significance of biocide usage and antimicrobial resistance in domiciliary environments

“…The likelihood is further reduced by the fact that these agents are unstable or volatile and thus, do not persist in the environment in an active form. It is therefore perhaps surprising that Murray et al (1984) reported that chlorination of sewage produced an increase in the proportion of antibiotic-resistant isolates. A suggested explanation was that chlorination caused selection of stress-tolerant strains which were also antibiotic-resistant, or stimulated transfer of resistance plasmids, but these aspects were not investigated.…”