CLASSIFICATION OF PHYLOGENETIC GROUPS AND ANTIBIOTIC RESISTANCE OF ESCHERICHIA COLI ISOLATED FROM AKAGAWA RIVER SYSTEM, YAMAGATA, JAPAN

Abstract

 We investigated the distribution of E. coli in the Akagawa and Mogami Rivers, both of which flows through in the Shonai region in Yamagata Prefecture, Japan. The samples of river water were monthly collected through a year from April 2021 to March 2022 at six and one sites along the Akagawa River and Mogami River, respectively. The isolates of E. coli obtained from the water samples were classified into seven-phylogenetic group and evaluated for the antimicrobial susceptibility against 12 antibiotics.

 The concentration of E. coli in the two rivers ranged from <1 to 280 CFU/100 mL, demonstrating that all of the survey sites were satisfied with its criterion for Class A rivers set by Ministry of the Environment in Japan. The concentration of E. coli at the month of both rivers increased from October to January probably due to the dense population of migratory birds found in this season. Of a total of 653 isolates, which are identified E. coli based on uidA gene using PCR analysis collected in this study, 217 isolates (33.2 %) were classified into B2 group which is associated with a high pathogenicity. 175 isolates (26.8 %) of the isolates exhibited the resistance to one or more antibiotics, including the third-generation cephem antibiotics (Cefotaxime and Cefazolin) and carbapenem (Imipenem). This suggested the existence of the extended-spectrum beta-Lactamase (ESBL)-producing bacteria and carbapenem-resistant enterobacteriaceae (CRE) in the investigated rivers. Sixty-six isolates (10.1%) were multidrug-resistant (MDR) defined to show resistance to at least three different groups of antimicrobial agents, and an isolate was resistant to a total of seven antimicrobials. The fact that these antibiotic-resistant bacteria (ARB), which are clinically important, were found in the rivers with less fecal contamination motivates further investigations of ARB on the source and fate in the river environment.