Detection and antibiotic susceptibility of pathogenic Escherichia coli isolated from the final effluent of two wastewater treatment plants in the Eastern Cape Province of South Africa

Abstract

Wastewater is an important reservoir for Escherichia coli and can present significant acute toxicity if released into receiving water sources without being adequately treated. To analyze whether pathogenic E. coli strains that cause infections are in treated effluent and to recognize antibiotic profile. 476 confirmed isolates from two treatment Plants were characterized for the presence of various E. coli pathotypes. A total of 8 pathotypes were screened and only four were confirmed. UPEC was about 5.7% followed by EAEC at 2.3%, NMEC at 1.1% and EPEC at 0.6%. Antibiotic susceptibility patterns of E. coli pathotypes such as UPEC showed low resistance to antibiotics like meropenem (100%), cefotaxime (100%) and gentamicin (88.9%). The pathotype also showed high degrees of resistance to tetracycline (74.1%), ampicillin (74.1%) and cephalothin (66.7%). Other E. coli pathotypes, EAEC, NMEC and EPEC, showed high sensitivity (100%) to meropenem, gentamicin and cefotaxime, and varying degree of resistances to ampicillin, tetracycline and cephalothin. The results of this study reveal that the two Plants discharge effluents with pathogenic E. coli and are reservoir for the bacteria into receiving water sources. In summary, this finding raises the possibility that at least some pathogenic E. coli pathotypes are getting into the environment through WWTPs and represent potential route for enteropathogenic infection. In addition, certain pathotypes may have acquired resistance properties, becoming a potential cause of drug resistance infection. This study reveals inadequacy of the plants studied to produce effluents of acceptable quality.