Hoa T. K. Ho * , Nhi N. T. T. Nguyen , & Ngoc H. Le

* Correspondence: Ho Thi Kim Hoa (email: hoa.hothikim@hcmuaf.edu.vn)

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The aims of the study were to look into the quantities of live beneficial microorganisms and antibiotic resistance of bacterial strains in several probiotic products used for food animals in the market. Ten probiotic products that claim to contain beneficial bacteria and fungi were examined. Eight products are said on the label to contain Lactobacillus spp., nine contain Bacillus spp., five contain yeasts and two have molds. The results showed that eight products did not have the microbial quantities or/and composition of microorganisms as saying on their labels. Of eight products which claim to contain Lactobacillus spp., the bacteria were isolated from only four, of which three had Lactobacillus counts at least ten-fold as low as the numbers on the labels. Spore-forming bacilli were isolated from all nine Bacillus-containing products. However, two products had the bacterial counts at least 10-fold as low as the numbers printed on the labels. Among five products stated to contain yeasts, the organisms were recovered from samples of only one. Seven Lactobacillus and fifteen Bacillus isolates from all samples that had bacterial growth were tested for their susceptibility against seven common antibiotics using Kirby-Bauer disk diffusion method. The results revealed that all the Lactobacillus isolates showed susceptibility to the tested antibiotics except kanamycin. All 15 Bacillus isolates were susceptible to ampicillin, kanamycin, and ciprofloxacin; five isolates were intermediately resistant to tetracycline; one isolates resisted erythromycin, and one isolates was resistant to vancomycin. The results of this study would provide information for farm practice in choosing antibiotics used together with antibiotics to maintain or/and restore the gut microflora after antibiotic treatment.

Keywords: Antibiotic resistance, Bacillus, Lactobacillus, Probiotics

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