Reassessment of selective agars and filtration techniques for isolation of Campylobacter species from faeces

Abstract

Four different studies were conducted in order to re-evaluate conventional methods and assess the efficacy of new selective agars and a filtration method for the isolation of campylobacters. Skirrow's medium, Preston agar, modified CCD agar and Fennell's medium, incubated microaerobically at 37 degrees C for 48 h, gave similar Campylobacter isolation rates from 225 faecal samples, but the latter two media were more selective. Evaluation of modified CCD agar demonstrated that campylobacters could be isolated from that medium more successfully after incubation at 37 degrees C (173/177 positive samples) than at 42 degrees C (152/177 positive samples). In a larger study 1286 faecal specimens were cultured using modified CCD agar, Fennell's medium and a 0.45 micron membrane filtration technique, all incubated at 37 degrees C. Campylobacters were isolated from 89% (178), 86% (171) and 60% (130) of 199 positive samples respectively. Modified CCD agar was most successful in isolation of the majority of campylobacters, but Fennell's medium was essential for recovery of "Campylobacter cinaedi" and "Campylobacter fennelliae", whereas the 0.45 micron membrane technique was the only method to isolate all of the catalase-negative campylobacter strains. Further evaluation of the 0.45 micron and 0.65 micron pore size membranes showed that more strains of Campylobacter jejuni and Campylobacter coli were isolated using the larger pore size membranes.