Improvement of Karmali Agar by Addition of Polymyxin B for the Detection of Campylobacter jejuni and C. coli in Whole‐Chicken Carcass Rinse

 The Karmali agar was modified by supplementation with a high concentration of polymyxin B. The goal of the study was to evaluate the effect of a high concentration of polymyxin B on the ability and selectivity of the modified Karmali agar to isolate Campylobacter jejuni and Campylobacter coli from whole chicken carcass rinse. A total of 80 whole chickens were rinsed with 400 mL of buffer peptone water. The rinsed samples were incubated with 2× blood‐free modified Bolton enrichment broth for 48 h, and then streaked onto unmodified Karmali agar and modified Karmali agar supplemented with 1 IU/L polymixin B (P‐Karmali agar). The suspected colonies were finally confirmed by colony PCR. The P‐Karmali agar exhibited a significantly better ( P < 0.05) isolation rate than the unmodified Karmali agar (P‐Karmali agar, 73.8%; unmodified Karmali agar, 33.8%). Moreover, the selectivity of the P‐Karmali agar was also better ( P < 0.05) than that of the other selective agar when comparing the number of contaminated plates (P‐Karmali agar, 68.8%; unmodified Karmali agar, 87.5%) and growth index of competing flora (P‐Karmali agar, 1.4; unmodified Karmali agar, 2.7). The improved selective agar excluded competing flora resistant to antibiotic agents in unmodified Karmali agar, increasing isolation rate and selectivity for C. jejuni and C. coli .