Continuous prevalence of VEB‐3 extended‐spectrum β‐lactamase‐producing Aeromonas hydrophila in a local river in gifu city, Japan

Abstract

Antimicrobial-resistant bacteria and resistance determinants are of great concern to human and veterinary medicine worldwide. Extended-spectrum β-lactamase (ESBL)-producing bacteria are resistant to broad-spectrum cephalosporins. ESBL-producing isolates, including those carrying blaCTX, blaPER, blaVEB, and blaGES, have been reported from rivers in several countries.1 In a study performed in 2018, using next-generation sequencing (NGS), we identified Aeromonas hydrophila K36 carrying both blaVEB-3 (accession number: LC570768) and blaCTX-M-14 (accession number: LC570769) in the surface water of the Ijira River flowing through Gifu City in central Japan. We conducted a longitudinal study between April and November 2019. ESBL producers were isolated from surface water collected at the same site (Table 1), as described in the supporting information (Methods for ESBL isolation). ESBL genes found in A. hydrophila included blaVEB-3, blaCTX-M-14, blaCTX-M-3, and blaGES-3. A. hydrophila harboring blaVEB-3 was consistently isolated from all samples, except those collected in July, August, and October 2019 (Table 1). Pulsed-field gel electrophoresis (PFGE) revealed seven clades (pulsotypes 1–7 [PT1–PT7]) having 90% pattern similarity; while most isolates in April were classified as PT3, divergent PTs were observed after May 2019 (Figure S1). VEB-type ESBL producers have been reported in several Asian countries.1 Although blaVEB has not been reported in Japan, VEB-3 ESBL producers were found to be consistently present in surface water. Additionally, A. hydrophila harboring both blaVEB-3 and blaCTX-M-14 was found. PFGE analysis classified A. hydrophila K36 isolated in April 2018 as PT1, which contained all the isolates harboring blaVEB-3 and blaCTX-M-14 obtained between April and May 2019 (Figure S1). Our results indicate the long-term presence of A. hydrophila harboring blaVEB-3, with or without blaCTX-M-14, in the surface water. CTX ESBL producers were isolated intermittently (Table 1). A. caviae harboring blaCTX-M-3 was isolated in August. CTX ESBL-producing Escherichia coli and Klebsiella pneumoniae were also isolated; E. coli (blaCTX-M-1, blaCTX-M-14, blaCTX-M-15, blaCTX-M-27, and blaCTX-M-55) was isolated in April, June, July, August, and October 2019, and K. pneumoniae (blaCTX-M-15) was isolated in August 2019. Sewage treatment facilities are located downstream (approximately 3.5 km) of the sampling point; therefore, the intermittent prevalence of CTX ESBL producers in the river water might be associated with domestic animals, such as companion and food-producing animals. In conclusion, this study showed a continuous prevalence of VEB-3 ESBL-producing A. hydrophila in a river in Japan. Additionally, multiple species of CTX ESBL-producing bacteria were found in the river. The persistence of ESBL-producing bacteria in the water environment poses a risk due to the transfer of bacteria via wild birds to other locations and via water supply to plants. The global action plan on antimicrobial resistance has been promoted in Japan. As has been proposed, we need to understand the relationship between trends and antimicrobial use in plants, the environment, humans, and animals.2-4 Our study could contribute to the development of this One Health approach. These findings require validation and research to clarify the source of resistant bacteria in the environment and to control their dissemination to humans and animals. The contig sequences of the A. hydrophila K36 strain were deposited in the DDBJ/EMBL/GenBank databases under the following accession numbers: LC570768 and LC570769. The sequences of ESBL genes, blaGES-3 (accession number: LC598227) and blaPER-3 (accession number: LC598226), in A. hydrophila and caviae, respectively, were also deposited in the DDBJ/EMBL/GenBank databases. This study was supported by JSPS KAKENHI (grant number 18H04073). We would like to thank Editage (www.editage.com) for English language editing. The authors declare that there are no conflicts of interest. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.