The Association of Biofilm Formation with Antibiotic Resistance in Lactic Acid Bacteria from Fermented Foods

Abstract

AbstractFifty‐three lactic acid bacteria (LAB) strains from five species of bacteria were isolated and identified from yogurt and Chinese pickled vegetables. Susceptibility of all the isolates to five antibiotics (ampicillin, erythromycin, tetracycline, vancomycin, streptomycin) was tested with disc diffusion methods. All LAB were resistant to streptomycin. Thirty‐seven strains were resistant to vancomycin, seven strains were resistant to tetracycline and erythromycin, and six strains were resistant to ampicillin. The corresponding genetic determinants were characterized by polymerase chain reaction. No antibiotic resistant gene was detected among all resistant strains. Biofilm‐forming ability was monitored by a modified crystal violet staining method. Among the 53 strains, 32 strains showed different levels of biofilm‐forming ability, while 21 strains did not form biofilms. The minimal inhibitory concentration of antibiotics (MIC) and the biofilm inhibitory concentration (BIC) were determined in the 32 strains which can form biofilms. There are significance correlations between biofilm formation and BIC/MIC for all antibiotics (P < 0.05) except vancomycin. Biofilms exhibited increased antimicrobial resistance compared with planktonic isolates, but the extent of enhanced antibiotic resistance in biofilms is different with different antibiotics.Practical ApplicationRecently, there are increasing researches focusing on the safety of LAB, due to their antibiotic resistance. However, effects of antibiotic resistance in LAB were different in different application fields. So it is necessary to understand the mechanism of resistance all sidedly. In this study, we found those LAB isolates, which exhibiting antibiotics resistance in the susceptive tests, carried no transferable antibiotic resistance determinant, while there was a significant positive correlation between four antibiotics resistance and biofilm‐forming ability. Data derived from this study can be used as a basis for assessing the safety of LAB applied in fermented food.