Antibiotic resistance and biofilm forming abilities of Listeria monocytogenes and effect of subMIC concentration of white vinegar on these virulence factors

In the present study, antibiotic resistance profiles and biofilm forming abilities of 9 Listeria monocytogenes isolates obtained from out of 30 retail meat samples were determined, and the effect of commercial white vinegar on these virulence factors in isolates exposed to subMIC concentrations were investigated. All isolates were found to be resistant to cefotixin and oxacillin, 8 isolates (26.6%) to clindamycin, 1 isolate (3.3%) to rifampicin, and 1 (3.3%) isolate was found to show intermediate resistance against clindamycin. Biofilm formation was determined for all the isolates at 22 °C and 37 °C (24 h, 48 h and 72 h). MIC values of white vinegar samples were determined at 3.12% for all isolates. MIC/2 and MIC/4 concentrations of white vinegar increased the biofilm forming capacity of the isolates by 21.2% and 17.1%, respectively. After exposure to MIC/2 concentration of white vinegar for seven days, the antibiotic resistance status of the isolates to tetracycline, rifampicin, and clindamycin changed, and the biofilm forming abilities significantly decreased at 4 °C and 37 °C for 48 h and at 37 °C for 72 h (P < 0.05). The results showed that the use of subMIC concentrations of white vinegar should be avoided in routine sanitation applications.