title: Relationship between antibiotic- and disinfectant-resistance profiles in bacteria harvested from tap water.
abstract: Chlorination is commonly used to control levels of bacteria in drinking water; however, viable bacteria may remain due to chlorine resistance. What is concerning is that surviving bacteria, due to co-selection factors, may also have increased resistance to common antibiotics. This would pose a public health risk as it could link resistant bacteria in the natural environment to human population. Here, we investigated the relationship between chlorine- and antibiotic-resistances by harvesting 148 surviving bacteria from chlorinated drinking-water systems and compared their susceptibilities against chlorine disinfectants and antibiotics. Twenty-two genera were isolated, including members of Paenibacillus, Burkholderia, Escherichia, Sphingomonas and Dermacoccus species. Weak (but significant) correlations were found between chlorine-tolerance and minimum inhibitory concentrations against the antibiotics tetracycline, sulfamethoxazole and amoxicillin, but not against ciprofloxacin; this suggest that chlorine-tolerant bacteria are more likely to also be antibiotic resistant. Further, antibiotic-resistant bacteria survived longer than antibiotic-sensitive organisms when exposed to free chlorine in a contact-time assay; however, there were little differences in susceptibility when exposed to monochloramine. Irrespective of antibiotic-resistance, spore-forming bacteria had higher tolerance against disinfection compounds. The presence of chlorine-resistant bacteria surviving in drinking-water systems may carry additional risk of antibiotic resistance.
authors.affiliation: Department of Civil and Environmental Engineering, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ, UK; Department of Environmental Engineering, NED University of Engineering and Technology, University Road, Karachi 75270, Pakistan.
authors.forename: Sadia
authors.initials: S
authors.lastname: Khan
authors.affiliation: Department of Civil and Environmental Engineering, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ, UK.
authors.forename: Tara K
authors.initials: TK
authors.lastname: Beattie
authors.affiliation: Department of Civil and Environmental Engineering, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ, UK. Electronic address: charles.knapp@strath.ac.uk.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Knapp
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D002713:Chlorine / Q000737:chemistry / Q000494:pharmacology*; D004202:Disinfectants / Q000737:chemistry / Q000494:pharmacology*; D004203:Disinfection; D060766:Drinking Water / Q000382:microbiology*; D004352:Drug Resistance, Microbial; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D006801:Humans; D008826:Microbial Sensitivity Tests; D018508:Water Purification
chemical_list: D000900:Anti-Bacterial Agents; D004202:Disinfectants; D060766:Drinking Water; D002713:Chlorine
keywords: ARB; ARG; Antibiotic resistance genes; Antibiotic-resistant bacteria; Antimicrobial-resistant bacteria; DNA; DPD; Deoxyribonucleic acid; Disinfectant-resistance; Drinking-water; N,N-diethyl-p-phenylenediamine; PBS; PCR; Phosphate buffer saline; Polymerase chain reaction; Susceptibility