One Health approach to characterize antimicrobial resistance in Morganella morganii in humans, freshwater fish and pigs.

INTRODUCTION

Antimicrobial resistance to carbapenems in Morganella morganii is emerging globally.

MATERIALS AND

METHODS

Sixty isolates from freshwater fish, four from pig organs and 25 clinical patient isolates were included in the study. Freshwater fish and pork from wet markets in all districts in Hong Kong were obtained in April 2018 and January 2019. Food samples were inoculated to selective agars to look for Morganella morganii. Clinical isolates of M. morganii from three hospitals in Hong Kong were included in 2018-2022. Phenotypic antibiotic susceptibility testing was done by CLSI disc diffusion method. Whole-genome sequencing was performed to establish the antibiotic resistance gene (ARG) profile and phylogenetic relationship.

RESULTS

Phenotypic resistance to fluoroquinolones was significantly higher for animal isolates than human isolates whereas that of aminoglycosides was significantly higher in human isolates. There was no significant difference in other tested antibiotics. There was no significant difference in ARG distribution between human and non-human isolates. Phylogenetically, 12 clinical isolates were clustered with corresponding freshwater fish isolates.

CONCLUSION

M. morganii isolates that caused human infections were phylogenetically related to those found in freshwater fish in wet markets. There was significant overlap between antimicrobial resistance genes in major antibiotic classes across isolates from humans and isolates from fish.