Extraintestinal Pathogenic Escherichia coli and Antimicrobial Drug Resistance in a Maharashtrian Drinking Water System (original) (raw)

Although access to piped drinking water continues to increase globally, information on the prevalence and clonal composition of coliforms found in piped water systems in low-resource settings remains limited. From June to July 2016, we examined Escherichia coli isolates in domestic water from the distribution system in Alibag, a small town in India. We analyzed the isolates for drug resistance and genotyped them by multilocus sequence typing. Of 147 water samples, 51 contained coliforms, and 19 (37%) of the 51 were biochemically confirmed to contain E. coli. These samples contained 104 E. coli isolates-all resistant to ampicillin. Resistance to ceftazidime was observed in 52 (50%) isolates, cefotaxime in 59 (57%), sulfamethoxazole-trimethoprim in 46 (44%), ciprofloxacin in 30 (29%), and gentamicin in two (2%). Thirty-eight (36%) belonged to sequence types recognized as extraintestinal pathogenic E. coli (ExPEC); 19 (50%) of these 38 ExPEC belonged to known uropathogenic E. coli lineages. This exploratory field research shows the extent to which "improved" drinking water is a potential source of E. coli strains capable of causing extraintestinal infections. The prevalence of bacteria resistant to antimicrobial agents is a serious threat to global public health. Studies have shown that human activity is correlated with increased prevalence of genes conferring resistance to antimicrobial agents in the environment. 1 Specifically, this increase in resistance is correlated with the introduction of antimicrobial agents and bacteria resistant to antimicrobial agents into the environment through activities known to occur in low-resource settings, such as wastewater dumping. 2 When piped drinking water contains agents such as NDM-1, a metallo-beta-lactamase, even the highest rung of the Joint Monitoring Program's "im-proved" water ladder is not safe. 3,4 The risks are potentially high in small towns of the global South, where water treatment and water quality data are both limited. As Escherichia coli is easily eliminated from drinking water, researchers use it as an indicator bacterium to determine whether water has recently been exposed to feces and whether it is safe for consumption. Its presence in more than 5% of drinking water samples indicates that the water treatment (if any) is inadequate to eliminate more harmful bacteria such as Campylobacter or Salmonella. 5 Detection of E. coli can also indicate either treatment inadequacy or posttreat-ment contamination. When considering an intermittent system , the possibility of posttreatment contamination is high. Few researchers have conducted in-depth microbiological studies of drinking water distribution systems; their focus has largely been on general bacterial community analysis or calculating the number of colony-forming units of E. coli. 6-8 The use of E. coli solely as a fecal indicator bacterium prevents researchers from understanding the public health impact of its antimicrobial drug resistance and its potential to be a human pathogen. A subgroup of E. coli causes diarrhea and is responsible for foodborne diseases in both high-income and low-income countries. 9 Another group of E. coli causes extraintestinal infections, referred to as extraintestinal pathogenic E. coli (ExPEC). It is the leading cause of Gram-negative bacter-emia and the most common cause of urinary tract infections (UTI), an infection primarily affecting women; both are potentially lethal if left untreated. 10,11 This exploratory study in a "typical" small town in India sought to determine what proportion of E. coli strains used as an indicator bacterium in field drinking water tests are drug-resistant, and are potential human pathogens. Alibag, Maharashtra, is a coastal tourist city with a population of 20,743. 12 Its piped drinking water system is intermittently supplied with water by the Maharashtra Industrial Development Corporation (MIDC). The MIDC drinking water treatment plant sources drinking water from the Amba River and treats the raw water using liquid alum sul-fate, flash mixing, flocculation/settling, sand filtration, and chlorination with Cl 2 gas to 0.2 ppm. The treated water is then tested four times a day by an MIDC chemist for multiple contaminants. Water samples were collected from the water distribution system over an 8-week period from June to July 2016, which evenly captured the end of summer and the onset of the monsoon season. Samples were collected once a week from the treated water at the MIDC and from one of the three elevated storage reservoirs from which water is piped to households. Many households stored water in rooftop tanks connected to the distribution system to cope with its intermittent deliveries. Point-of-use samples were taken from households with in-home taps; for households collecting water from a public tap connected to the distribution system, points-of-collection samples were taken during their scheduled water allocations. Households were sampled such that the service area of the drinking water system was adequately covered. Water samples for quantification of bacteria were collected and processed with the compartment bag test (CBT) (Aqua-genx, Chapel Hill, NC), which uses a β-D-glucuronide E. coli indicator. 13 As per the CBT protocol, drinking water was collected in presterilized 100-mL pouches with a sodium thio-sulfate tablet to neutralize any residual chlorine-samples