A survey of extended-spectrum β-lactamase-producing Enterobacteriaceae in environmental water in Okinawa Prefecture of Japan and relationship with indicator organisms

Abstract

Surveys of extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-pE) in stream water and untreated wastewater were carried out in Okinawa Prefecture, Japan. Thirty-six samples of water were collected from 18 streams in Okinawa Prefecture, as well as ten samples of wastewater flowing into four wastewater treatment plants (WWTPs). We investigated bacterial species, Escherichia coli O antigen, ESBL phenotype, ESBL genotype, and pulsed-field gel electrophoresis (PFGE) type of isolates, and total viable count and fecal coliforms as indicator organisms. The relation between indicator organisms and ESBL-pE was also validated using the same samples. A total of 141 ESBL-pE including 107 E. coli, 15 Klebsiella pneumoniae, 2 Proteus mirabilis, and 17 other species was isolated from stream water and wastewater. Of the 141 ESBL-pE, 14.9% and 54.6% were found to be blaCTX-M-15 and blaCTX-M-14-like types, respectively, which have been found in hospital isolates in Okinawa. Two pairs of possibly related patterns according to PFGE criteria were isolated from stream water and wastewater in two districts. When ESBL-pE was significantly isolated, total viable count and fecal coliform boundaries were ≥ 6.0 × 10³ CFU/ml and ≥ 4.3 × 10² most probable number/100 ml, respectively. These results suggested that ESBL-pE isolated from stream water is human derived, and that total viable count and fecal coliforms will be useful as indicators for confirming the spread of ESBL-pE to the environment by means of simple hygiene surveys.

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