An enhanced technique combining pre-enrichment and passive filtration increases the isolation efficiency of Campylobacter jejuni and Campylobacter coli from water and animal fecal samples

Abstract

Improved isolation techniques from environmental water and animal samples are vital to understanding Campylobacter epidemiology. In this study, the efficiency of selective enrichment in Bolton Broth (BB) followed by plating on charcoal cefoperazone deoxycholate agar (CCDA) (conventional method) was compared with an approach combining BB enrichment and passive filtration (membrane method) adapted from a method previously developed for testing of broiler meat, in the isolation of thermophilic campylobacters from surface water and animal fecal samples. The conventional method led to recoveries of Campylobacter from 36.7% of the water samples and 78.0% of the fecal samples and similar numbers, 38.3% and 76.0%, respectively, were obtained with the membrane method. To investigate the genetic diversity of Campylobacter jejuni and Campylobacter coli obtained by these two methods, isolates were analyzed using Comparative Genomic Fingerprinting, a high-resolution subtyping technique. The conventional and membrane methods yielded similar numbers of Campylobacter subtypes from water (25 and 28, respectively) and fecal (15 and 17, respectively) samples. Although there was no significant difference in recovery rates between the conventional and membrane methods, a significant improvement in isolation efficiency was obtained by using the membrane method, with a false-positive rate of 1.6% compared with 30.7% obtained using the conventional method. In conclusion, although the two methods are comparable in sensitivity, the membrane method had higher specificity, making it a cost-effective procedure for the enhanced isolation of C. jejuni and C. coli from water and animal fecal samples.