Field Evaluation of a Transport Medium and Enrichment Broth for Isolation of Campylobacter Species from Human Diarrheal Stool Samples

Abstract

Campylobacter continues to be a major cause of bacteria-mediated diarrheal diseases, both for Thai citizens and travel- ers to Thailand. For field epidemiological studies, appropriate methods for storage, intra-laboratory transport of patients specimens and use of enrichment culture to isolate this organism is critical. Study A, represents patient stool specimens collected in Bangkok and processed for Campylobacter culture within three hours after collection. Study B, represents stool specimens collected from patients in northeast and Southern regions of Thailand in modified Cary-Blair transport medium. These specimens were transported and processed for Campylobacter in Bangkok at varying intervals ranging from 1 to 7 days. Of 900 diarrheal samples examined in study A, a total of 158 were Campylobacter positive through culture. Of these, 145 and 141 isolates were cultured by direct plating and enrichment plating respectively (P = 0.5839). From 1,168 diarrheal stool samples examined in study B, 184 were positive for Campylobacter. Direct and enrichment plating resulted in 139 and 168 culture isolates; respectively (P = 0.0003). Samples from study B delayed in processing for 1 to 3 days, resulted in 46 and 50 isolated by direct and enrichment plating; respectively (P = 0.4545). However, among samples delayed in processing for 4 to 7 days, a total of 128 Campylobacter isolates were cultured, having cul- tured 93 and 118 isolates through direct and enrichment plating; respectively (P = 0.0003). At present these studies demonstrate that enrichment culture has no benefit when stool specimen collection and immediate processing occur and when there is a processing delay period of 1 - 3 days. However, enrichment culture was beneficial in instances where transport and processing was delayed 4 - 7 days.