Assessment of Antibiotics Effect on Planktonic and Biofilm Forms of Campylobacter Isolates

Campylobacter spp. bacteria are one of the leading causes of food borne illness worldwide and has the ability to form biofilms. These biofilms have been reported to confer resistance against antibiotics. In this study, the effect of five different antibiotics has been compared on the planktonic and biofilm forms of Campylobacter isolates by determining their minimum inhibitory concentration (MICs). A total of 55 isolates (11 Campylobacter jejuni and 41 Campylobacter coli) were subjected to flaA typing and cluster analysis. On the basis of flaA typing, 23 isolates, comprising 17 C. coli and 6 C. jejuni representing each cluster were chosen and analyzed for their biofilm forming potential at two different temperatures (37°C and 42°C) under both aerobic and microaerobic conditions. The biofilm production was higher at 37°C in comparison to 42°C, and it was enhanced under aerobic conditions compared to microaerobic conditions at both temperatures. MICs of gentamicin, kanamycin, tetracycline, erythromycin and carbenicillin were determined for both planktonic and biofilm forms of campylobacter bacteria grown in 96 well microtitre plates containing Muller Hinton (MH) broth. All the isolates in the planktonic form showed absolute resistance against carbenicillin. The MIC values of gentamicin, kanamycin, tetracycline and erythromycin for planktonic form were found to be 0.032 µg/ml, 2 µg/ml, 0.1 µg/ml and 0.0125 µg/ml, respectively; while, for biofilm forms the same were found to be 1.025 µg/ml, 8 µg/ml, 0.8 µg/ml and 0.2 µg/ml, respectively. The findings revealed 32, 16, 8 and 4 fold higher resistance by biofilm associated campylobacter bacteria against gentamicin, erythromycin, tetracycline and kanamycin, respectively. ...