MULTIPLEX PCR FOR DIRECT IDENTIFICATION OF THERMOPHILIC CAMPYLOBACTER, C. JEJUNI, C. COLI, C. LARI AND C. UPSALIENSIS AND SIMULTANEOUS DETECTION OF CDTB GENE

Abstract

ABSTRACT A multiplex polymerase chain reaction (PCR) assay has been developed for the identification of the four thermophilic Campylobacter commonly associated with human gastroenteritis including C. jejuni, C. coli, C. lari and C. upsaliensis. The best combination of primers and the annealing temperature of multiplex PCR were examined. Detection limit was 2 × 105 cfu and 100 ng of DNA or whole‐cell suspension. The multiplex PCR was applied for the direct detection and differentiation of Campylobacter species in 33 human and 45 chicken caeca isolates. Of the 78 specimens evaluated by the multiplex PCR, 55 (70.5%) were identified as C. jejuni, 18 (23.0%) as C. coli and 5 (6.41%) as a mixed infection with both species. Comparison of hippurate test and multiplex PCR demonstrated five (6.41%) isolates with false‐positive hippurate enzymic activity and three (3.85%) with false‐negative activity. cdtB gene was detected in 100% and 38.9% of C. jejuni and C. coli, respectively. This multiplex PCR was found to be rapid, easy to perform and had a high sensitivity and specificity, even with mixed cultures. The system is useful for the detection of the presence of cdtB gene that is responsible for toxin activity in Campylobacter.PRACTICAL APPLICATIONSOur multiplex polymerase chain reaction (PCR) allows in a single tube PCR, the identification of the four clinically important Campylobacter species, with a simultaneous detection of the cdtB gene. The PCR works well in our hands with both purified genomic DNA and whole‐cell suspension. This should greatly speed up identification by replacing the current biochemical phenotypic schemes. In addition, the system can detect the presence of cdtB gene that encodes the cytolethal‐distending toxin activity.