Antibiogram and beta-lactamase genes among cefotaxime resistant E. coli from wastewater treatment plant

Antimicrob Resist Infect Control. 2020 Mar 12;9(1):46. doi: 10.1186/s13756-020-0702-4.

Abstract

Background: The World Health Organization (WHO) recently classified Enterobacteriaceae resistance to third-generation cephalosporin into the group of pathogens with critical criteria for future research.

Methods: A study to assess the antibiogram and beta-lactamase genes among the cefotaxime resistant E. coli (CREc) from a South African wastewater treatment plant (WWTP) was conducted using standard phenotypic and molecular biology characterization methods.

Results: Approximate total E. coli (TEc) concentration (log10 CFU/mL) ranged between 5.7 and 6.8 among which cefotaxime resistant E. coli were between 1.8 and 4.8 (log10 CFU/mL) for cefotaxime antibiotic concentration of 4 and 8 mg/L in the influent samples. Effluent samples, heavily influenced by the chlorination had only 0.3 log10 CFU/mL of TEc. Fifty-one cefotaxime resistant isolates were selected out of an overall of 75 isolates, and subjected to a new round of testing, with a follow up of 36 and 48 isolates for both colistin and gentamicin, respectively as guided by initial results. Selected CREc exhibited resistance to amoxicillin-clavulanic acid (35.3%; n = 51), colistin sulphate (76.5%; n = 36), ciprofloxacin (47.1%; n = 51), gentamicin (87.5%; n = 48) and intermediate-resistance to meropenem (11.8%; n = 51). Extended spectrum-beta-lactamase genes detected, viz.: blaCTX-M (52.6%; n = 38) and blaTEM (84.2%; n = 38) and concurrent blaCTX-M + blaTEM (36.8%; n = 38), but no blaSHV was detected. Carbapenem resistance genes, blaKPC-2 (15.8%; n = 38), blaOXA-1 (57.9%; n = 38), blaNDM-1 (15.8%; n = 38) were also detected. Approximately, 10.5 - 36.8% (n = 38) co-occurrence of two or more beta-lactamase genes was detected in some isolates. Out of the selected number (n = 30), 7(23.3%) were enterotoxigenic E. coli (ETEC), 14 (46.7%) were Enteroaggregative E. coli (EAEC), but no enteropathogenic E. coli (EPEC) was detected.

Conclusion: Resistance to cefotaxime and the presence of a wide range of beta-lactamase genes exposed the potential risks associated with these pathogens via occupational and domestic exposure during the reuse of treated wastewater.

Keywords: Beta-lactamase genes; Carbapenem; Cefotaxime; Ciprofloxacin; Wastewater; bla CTX; bla OXA-1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amoxicillin-Potassium Clavulanate Combination / pharmacology
  • Cefotaxime / pharmacology*
  • Chlorine / adverse effects
  • Ciprofloxacin / pharmacology
  • Colistin / pharmacology
  • Drug Resistance, Multiple, Bacterial*
  • Escherichia coli / drug effects*
  • Escherichia coli / genetics
  • Escherichia coli Proteins / genetics
  • Gentamicins / pharmacology
  • Microbial Sensitivity Tests
  • Phenotype
  • South Africa
  • Wastewater / microbiology*
  • Water Purification
  • beta-Lactamases / genetics*

Substances

  • Escherichia coli Proteins
  • Gentamicins
  • Waste Water
  • Chlorine
  • Ciprofloxacin
  • Amoxicillin-Potassium Clavulanate Combination
  • beta-Lactamases
  • Cefotaxime
  • Colistin