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The prevalence of food-borne bacteria in developing countries is less well understood than in developed countries. The ISO11290-1 isolation method is commonly used to study Listeria contamination in chicken; however, all isolates are identified as untargeted Bacillus cereus. This study aimed to determine the classification, antibiotic susceptibility, and virulence genes of B. cereus isolated from retail chickens in Vietnam. Bacterial isolation using the ISO11290-1 method yielded 12 strains of B. cereus from seven out of 60 chickens. For determining bacterial diversity, panC and multilocus sequence typing (MLST) analyses were performed. PanC analysis showed that all seven strains belong to the phylogenetic group III, to which the highest risk of foodborne illnesses was associated. MLST analysis showed that most strains contained a ST205 complex; further, all strains were found to be resistant to ampicillin, ciprofloxacin, and tetracycline. Virulence genes were also investigated. ces, a cereulide-related gene, was detected in 50% of the isolated strains, followed by cytK, nheA, and hblA enterotoxins in 41.7%, 16.7%, and 25% of the strains, respectively. In conclusion, B. cereus may be erroneously detected when attempting to detect Listeria in food using the ISO11290-1 method. Further study of the prevalence of B. cereus in Vietnamese food is needed to improve food safety. [ABSTRACT FROM AUTHOR]

The spread of antibiotic-resistant bacteria is a global problem that should be addressed through the perspective of the "one health" concept. The purpose of this study was to determine the contamination rate of antibiotic-resistant Aeromonas spp. in fresh water river fish purchased from a fish market in Vietnam. We then defined the pattern of antibiotic resistance to assess antibiotic-resistant contamination. Antibiotic-resistant Aeromonas spp. were detected in the intestinal contents of 32 of 80 fish. bla NDM-1 was detected in seven strains. Extended-spectrum β-lactamase and AmpC β-lactamase-related genes were detected in 28 strains, including bla CTX-M-55 , bla CTX-M-15 , bla CTX-M-1 , and bla DHA, bla FOX, and bla MOX. The bla NDM-1 detected in the seven Aeromonas spp. strains were found chromosomally. This finding suggests that the bla NDM gene is stable in the natural environment and may spread widely into animals and humans via Aeromonas spp. with a transposon. Our results suggest the importance of continuing to monitor carbapenemase genes in Aeromonas spp. to evaluate the possibility that they may spread in other Enterobacterales , and to elucidate the mechanism of spread. • bla NDM-1 -carrying Aeromonas spp. was isolated from the intestinal contents of fish. • Our results suggest the importance of continuing to monitor carbapenemase-related genes in Aeromonas spp. • bla NDM-1 of Aeromonas spp. was present on chromosome. [ABSTRACT FROM AUTHOR]