Characteristics of multi-antibiotic resistance of Enterobacteriaceae isolated from Ornamental carp (koi fish)

Abstract

Ornamental fish culture is rapidly expanding in Ho Chi Minh City. However, the increased use of antibiotics to prevent and cure aquatic animal disease, in general and ornamental fish disease, in particular recently has resulted in the emergence of bacteria resisting to multi-antibiotics. In this study, the
Enterobacteriaceae isolated from the diseased Ornamental carp (koi fish) were assessed for multi-antibiotic resistance characteristics and guessing the position of resistant genes (ARGs) by using a plasmid curing test. Based on 16s rRNA sequencing data, the bacterial isolates with the ß-hemolysis phenotype (5/27) were identified, such as: Vibrio cholerae (B2), Citrobacter freundii (B4), Klebsiella aerogenes (M6), Escherichia coli (M7), and Klebsiella pneumonia (M8). The indicator of multi-resistance (MAR) of bacterial
strains with 15 groups and 30 investigated antibiotics was 0.2 - 0.3. Especially, six antibiotics used in the farm including ampicillin, erythromycin, ciprofloxacin, doxycycline, sulfamethoxazole/trimethoprim, and tetracycline were resisted by at least one bacterial strain. After plasmid curing, the bacterial strains continue showing multi- resistance ability with antibiotics used in the fish farm, and three out of fiveisolates exhibited the reduction of antibiotic resistance. Our findings revealed that Enterobacteriaceae
isolated from the Ornamental carp may carry antibiotic resistance mechanism through chromosomes and plasmids. Further study is needed to examine the environmental factors affecting to the moving ability of
plasmids and ARGs into genome, as well as among the species in the same ecosystem in order to have the important understandings on antibiotic resistance trend of the pathogens.