Identification of hippurate-negative thermophilic campylobacters

Twenty-eight thermophilic campylobacter isolates showing negative hippurate hydrolysis were further characterized. Using Campylobacter jejuni and coli specific primers for ceuE gene, five of the isolates with repeatedly negative results in rapid hippurate hydrolysis were positive in C. jejuni-specific polymerase chain reaction (PCR) and 13 isolates were shown to be C. coli. All except one isolate with positive results in C. jejuni PCR were negative in C. coli PCR including those with repeatedly negative hippurate hydrolysis results. One isolate was positive in both PCRs due to a mixed culture. In comparison with PCR, API Campy gave concordant results in only 20 of the 28 isolates tested. Hybridization with PCR probes for ceuE gene of known C. jejuni and coli strains confirmed PCR results in all 27 isolates tested. In contrast to hippurate hydrolysis, PCR seemed to be a more reliable method to identify C. coli.