Untargeted Phylogenetic Group III of Multi-drug-Resistant Bacillus cereus Isolated Using Fraser Medium from Retail Chickens in Ho Chi Minh City.

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.

Antimicrobial resistance profiles and molecular characterization of Escherichia coli strains isolated from healthy adults in Ho Chi Minh City, Vietnam.

In this study, we attempted to isolate Escherichia coli from healthy adults in Ho Chi Minh City, Vietnam, and characterized its antimicrobial resistance profile, extended-spectrum ß-lactamase (ESBL) genotype, phylogenetic grouping and virulence gene profile. A total of 103 E. coli isolates were obtained, and most of them were antimicrobial resistant such to streptomycin (80.6%), tetracycline (67.0%), ampicillin (65.0%), sulfamethoxsazole/trimethoprim (48.5%), nalidixic acid (43.7%), chloramphenicol (34.0%), cefotaxime (15.5%), ciprofloxacin (15.5%), kanamycin (12.6%), ceftazidime (10.7%), fosfomycin (4.9%) and gentamicin (2.9%). However, all these E. coli strains were susceptible to imipenem. Surprisingly, of 103 strains, 74 (71.8%) and 43 (41.7%) strains showed resistance to more than 3 and 5 classes of antimicrobials, respectively. Furthermore, 10 E. coli strains were ESBL-producers and positive for blaCTX-M genes (7 for blaCTX-M-9 and 3 for blaCTX-M-1), while five were additionally positive for blaTEM genes. S1-nuclease pulsed-field gel electrophoresis analysis revealed that 7 and 3 strains of E. coli carry blaCTX-M genes on their large plasmid and chromosome, respectively. Phylogenetic analysis exhibited that majority of the E. coli strains was grouped into A (44.7%), followed by B1 (23.3%), B2 (18.4%) and D (13.6%). Virulence genes associated with diarrheagenic E. coli, such as astA, EAF, eaeA, elt and eagg were also detected in ESBL-producing E. coli as well as antimicrobial resistant strains. These data suggest that commensal E. coli of healthy human could be a reservoir for antimicrobial resistance determinants and some of them might be harmful to human.

Monitoring of Antibiotic Residues in Aquatic Products in Urban and Rural Areas of Vietnam.

Antibiotic residues in aquatic products in Vietnam were investigated. A total of 511 fish and shrimp samples were collected from markets in Ho Chi Minh City (HCMC), Thai Binh (TB), and Nha Trang (NT) from July 2013 to October 2015. The samples were extracted with 2% formic acid in acetonitrile and washed with dispersive C18 sorbent. Thirty-two antibiotics were analyzed by LC-MS/MS. Of the 362 samples from HCMC, antibiotic residues were found in 53 samples. Enrofloxacin was commonly detected, at a rate of 10.8%. In contrast, samples from TB and NT were less contaminated: only 1 of 118 analyzed samples showed residues in TB and only 1 of 31 showed residues in NT. These differences were attributed to the local manufacturing/distribution systems. To understand the current status of antibiotic use and prevent adverse effects that may be caused by their overuse, continual monitoring is required.