Multi-state study of Enterobacteriaceae harboring extended-spectrum beta-lactamase and carbapenemase genes in U.S. drinking water

Michelle Korando,Ramesh Goel ,Kathryn A. Seely,Adi V. Gundlapalli,Anderson G. Morris,Leslie A Chapman ,Windy Tanner ,Catherine M. Gurley,James Vanderslice ,Andrea Stadsholt,Pamela J. Higgins,Janice VanDeVelde,Ellen B. Braun-Howland ,Christine Minihane,Molly Leecaster ,Jeremy Olstadt,Kalifa-Amira Shabazz,Michelle Deras,Mark A. Fisher,Dee Jette,Othman Jaber

doi:10.1038/s41598-019-40420-0

Abstract

Community-associated acquisition of extended-spectrum beta-lactamase- (ESBL) and carbapenemase-producing Enterobacteriaceae has significantly increased in recent years, necessitating greater inquiry into potential exposure routes, including food and water sources. In high-income countries, drinking water is often neglected as a possible source of community exposure to antibiotic-resistant organisms. We screened coliform-positive tap water samples (n = 483) from public and private water systems in six states of the United States for blaCTX-M, blaSHV, blaTEM, blaKPC, blaNDM, and blaOXA-48-type genes by multiplex PCR. Positive samples were subcultured to isolate organisms harboring ESBL or carbapenemase genes. Thirty-one samples (6.4%) were positive for blaCTX-M, ESBL-type blaSHV or blaTEM, or blaOXA-48-type carbapenemase genes, including at least one positive sample from each state. ESBL and blaOXA-48-type Enterobacteriaceae isolates included E. coli, Kluyvera, Providencia, Klebsiella, and Citrobacter species. The blaOXA-48-type genes were also found in non-fermenting Gram-negative species, including Shewanella, Pseudomonas and Acinetobacter. Multiple isolates were phenotypically non-susceptible to third-generation cephalosporin or carbapenem antibiotics. These findings suggest that tap water in high income countries could serve as an important source of community exposure to ESBL and carbapenemase genes, and that these genes may be disseminated by non-Enterobacteriaceae that are not detected as part of standard microbiological water quality testing.

Highlights

Antibiotic-resistant infections are responsible for an estimated 2 million illnesses and 23,000 deaths in the United States each year[1]
The objectives of our study were (1) to determine whether extended-spectrum beta-lactamases (ESBLs)- and carbapenemase-producing genes are present in U.S drinking water samples that have tested positive for E. coli or total coliform bacteria, (2) to describe the sample and water system characteristics associated with samples testing positive for ESBL or carbapenemase genes, and (3) to determine if the ESBL and carbapenemase genes are present in viable bacteria isolated from the coliform-positive water samples
Sixty-four samples appeared to be positive for blaCTX-M by initial PCR and agarose gel screening; comparison of PCR amplicon sequences to the GenBank database revealed that the majority of the putative blaCTX-M positives were attributed to extended-spectrum beta-lactamase genes that are typically chromosomally-encoded in various Enterobacteriaceae species, including blaRAHN (Rahnella aquatilis), blaFONA (Serratia fonticola), blaOXY (Klebsiella oxytoca), blaSMO28, and Citrobacter amalonaticus class-A beta lactamase

Summary

Introduction

Antibiotic-resistant infections are responsible for an estimated 2 million illnesses and 23,000 deaths in the United States each year[1]. The rising prevalence of multidrug-resistant bacteria is especially alarming, as infections with these organisms have led to increasing use of broad spectrum antibiotics such as third and fourth generation cephalosporin and carbapenem antibiotics[1,2] Enzymes such as extended-spectrum beta-lactamases (ESBLs) and carbapenemases can render these antibiotics ineffective. ESBL and carbapenemase genes are frequently found in Enterobacteriaceae such as Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae, and Citrobacter species[4], but can be found in non-fermenting Gram-negative species[8] These bacteria are most commonly spread via fecal-oral transmission routes, including direct transmission (e.g. via hands) and indirect transmission (e.g. via the environment). Reports of ESBL- and carbapenemase-producing bacteria in drinking water have been limited to single-cases or intrinsic genes in nonpathogenic environmental bacterial species[10,13], but comprehensive studies are lacking. The objectives of our study were (1) to determine whether ESBL- and carbapenemase-producing genes are present in U.S drinking water samples that have tested positive for E. coli or total coliform bacteria, (2) to describe the sample and water system characteristics associated with samples testing positive for ESBL or carbapenemase genes, and (3) to determine if the ESBL and carbapenemase genes are present in viable bacteria isolated from the coliform-positive water samples

Objectives

Methods

Results

Conclusion