Studies On The Detection And Biofilm For Antibiotic Resistance Of Lactic Acid Bacteria From Fermented Food

Objective Lactic acid bacteria(LAB) were isolated and identified from fermented food. The investigation about the relation of phenotype resistance, genotype resistance and biofilm formation were done for LAB antibiotic resistance. The research work was significant for resistance mechanism and food security LAB involved of fermented foods.Methods physiology and biochemistry methods were used for strain screening and16SrDNA sequencing analysis for species identification. On one hand, susceptibility of all the isolates to the five antibiotics including ampicillin(AM), erythromycin(E), tetracycline(T), vancomycin(V) and streptomycin(S) were tested with disk diffusion method and plate dilution method. The corresponding resistance genetic determinants were characterized by polymerase chain reaction(PCR). On the other hand, biofilm-forming ability, the minimum inhibitory concentration(MIC) and the biofilm inhibitory concentration(BIC) were monitored by a modified microtiter plate crystal violet staining method. The statistical significance of associations between LAB biofilm formation abilities and antibiotic resistance was calculated using the independent-samples T test. All statistical analyses were performed using SPSS13.0for windows.Results Fifty three LAB strains from traditional fermented foods were isolated and identified in five species:Lactococcus lactis(12), Lactobacillus casei(21). Lactobacillus GG(10), Lactobacillus bulgaricns(1). Drugs susceptibility results showed that All LAB were resistant to streptomycin. Thirty seven strains were resistant to vancomycin, seven strains were resistant to tetracycline and erythromycin respectively, and six strains were resistant to ampicillin. LAB in different species showed different levels for five antibiotics resistance and some strains displayed multiple drugs resistant. No antibiotic resistant gene was found among all resistant strains. Thirty two strains performed different levels of biofilm-forming ability in biofilm formation ability detection. Fourteen isolates produced weak biofilm. eight isolates produced moderate biofilm and ten isolates produced strong biofilm. All the biofilm-forming isolates tested were highly resistant to vancomycin and streptomycin with MICs ranging from0.256mg/ml to4.096mg/ml while most isolates characterized were susceptible to ampicillin with MICs from0.004mg/ml to0.016mg/ml. The BICs were greater than the MICs for all antibiotics. The ratio of BIC/MIC of nineteen(59.3%,19/32) isolates were256to1024for ampicillin, eighteen (56.3%) isolates for erythromycin ranging from128yo512and seventeen (53.1%) isolates for tetracycline ranging from256to512, twenty(62.5%) isolates were from2to4for vancomycin, and nineteen (59.4%) isolates from7.8to15.6for streptomycin. This demonstrated that LAB formed biofilm to enhance the resistance ability for antibiotics and showed different strengthen resistance extents for different antibiotics. The statistical analysis suggested that resistances towards antimicrobial agents strongly correlated with biofilm formation ability, except for vanconmycin resistance.Conclusion we should drive attention to the idea that resistance of lactic acid bacteria isolated from fermented food for different antibiotics have the species characteristics to the sensitivity of different antibiotics. The resistance abilities to antibiotics were strengthened through lactic acid bacteria biofilm formation. However, different resistance abilities are closely related to different kinds of antibiotics.