Multiplex PCR for identification of Campylobacter coli and Campylobacter jejuni from pure cultures and directly on stool samples

Abstract

A multiplex-PCR method, specifically designed for application in routine diagnostic laboratories, was developed for the detection ofCampylobacter coliandCampylobacter jejuni. Primers were directed towards the following loci: the hippuricase gene (hipO) characteristic ofC. jejuni, a sequence partly covering an aspartokinase gene characteristic ofC. coli, and a universal 16S rDNA gene sequence serving as an internal positive control for the PCR. The method was tested on 47C. colistrains and 88C. jejunistrains, and found to be almost 100 % in concordance with biochemical analyses (all except for oneC. colistrain), regardless of whether the DNA was prepared from colonies by a simple boiling procedure or by DNeasy Tissue Kit. Pure cultures ofC. coliandC. jejuniwere identified at 10–100 cells per PCR. When the multiplex-PCR method was used on spiked human stool samples, both strains were identified at 105cells per ml stool. This sensitivity limit was the same whether the DNA was purified by the method of KingFisher mL or QIAamp DNA Stool Kit. When the same spiked stools were grown on modified charcoal cefoperazone deoxycholate agar (mCCDA) plates before PCR, the sensitivity was 100 cells per ml stool, indicating that culturing of campylobacters on mCCDA plates is superior to direct DNA extraction at least when fresh stool samples are analysed by PCR.