Formation of biofilm by strains of Listeria monocytogenes isolated from soft cheese 'wara' and its processing environment

Abstract

Quantification of biofilm formation by 40 Listeria monocytogenes strains from wara soft cheese and its processing environment was assessed on glass vials surfaces. Attachement to glass surface was quantified using a crystal violet binding assay. All the 40 strains produced biofilms after 48 and 72 h incubation at 37oC. No biofilms were formed at 24 h incubation but biofilm formation increased with incubation period in 20 out of the 40 strains. R2 values obtained were 0.0166 and 0.1193 respectively for biofilm formation between 24 and 48 h and 24 and 72 h incubation periods, respectively (P-values of 0.05*). L. monocytogenes strains isolated from wara cheese were generally sensitive to augmentin, streptomycin, claforan, erythromycin, gentamycin, septrin, tarivid, and rocephine and were highly resistant to nitrofuran, fortum, zinnat, and tetracycline. The enhancement of biofilm formation in L. monocytogenes strains from ‘wara’ in this study suggests a relationship with pathogenicity in foodborne isolates. The transfer of antibiotic resistant L. monocytogenes to human via the food chain is a significant health concern.