Abstract:The aim of this study was to evaluate the antibiotic sensitivity of Lactic acid bacteria isolated from commercially available yogurt in Guangzhou. The bacteria isolated from 31 commercially available yogurt samples (used before expiry date) were identified by physiological and biochemical reactions and 16s rDNA sequence analysis. The sensitivity of these strains to 18 different antibiotics was determined using Kirby-Bauer method. The minimum inhibitory concentration (MIC) of the drug-resistant strains in this study was determined by the Epsilometer test (E-test). In all, 48 isolates were identified, including 25 Streptococcus thermophilus strains, 20 Lactobacillus bulgaricus strains, and 3 Lactobacillus paracasei strains. All strains were found to be susceptible to ceftazidime, cefotaxime, and erythromycin; resistant to kanamycin and streptomycin; and showed different degrees of resistance to ciprofloxacin, gentamicin, and vancomycin. Moreover, multi-drug resistance (resistance to ≥3 antibiotics) was detected in 79.2% of isolates. The E-test results showed that MIC for all vancomycin-resistant strains was greater than 1024 μg/mL, except that for Lactobacillus bulgaricus MR10 (256 μg/mL). Strains from different yogurt samples showed resistance to different drugs, and multi-drug resistance was observed in lactic acid bacteria. Therefore, continuous monitoring of antibiotic resistance and safety evaluation of lactic acid bacteria is recommended.
