Selective Media for Campylobacter
Campylobacter species are known to be among the most common foodborne pathogens to cause diarrheal illness, with poultry being associated as the primary source of contamination. Detection and enumeration of low numbers of naturally occurring Campylobacter on poultry products have proven to be very difficult due to the presence of competing microbiota that are not eliminated by selective broths and direct plating agar media.
We did a study to compare the efficacy of various combinations of enrichment broths and plating media for detecting naturally occurring Campylobacter in broiler carcass rinses. Campy-Cefex Agar (CCA) and Campylobacter RF Chromogenic agar (RFA) were used as direct plating media for enumerating Campylobacter in buffered peptone water rinses from carcasses. These selective media were also used in combination with Bolton enrichment broth and Bolton broth supplemented with 1 µg/ml Triclosan (T-Bolton). Selection of these media was based on their ability to suppress background microbiota in the carcass rinses.
On average, recovery of Campylobacter from rinses on RFA was 3.38 log CFU/ml, with little interference by of background microbiota, while recovery on CCA was 3.17 log CFU/ml, with a significant amount of contamination by background microbiota. No significant difference (P > 0.05) was observed in the number of Campylobacter recovered on RFA and CCA. When analyzing Campylobacter-positive flocks (n=3), the use of T-Bolton enrichment broth in combination with CCA and RFA resulted in 18.1% and 1.39% higher recoveries, respectively. A combination of T-Bolton broth and RFA resulted in a 27.8% higher recovery compared with a combination of T-Bolton broth and CCA. Bolton broth and RFA gave a 44.4% higher recovery than Bolton broth and CCA.
When enriching or enumerating broiler rinses for naturally occurring Campylobacter, T-Bolton broth and RFA proved to be superior in eliminating background microbiota, thereby resulting in more accurate results. Because there was no significant difference in performance of CCA and RFA, it is suggested that both of these direct plating media be used to ensure maximum recovery of Campylobacter.