Efficacy of cold enrichment techniques for recovery of Yersinia enterocolitica from human stools

Abstract

Stool specimens from children with gastroenteritis and their household contacts were cultured for Y. enterocolitica by direct plating onto routine laboratory media. These stools were inoculated into phosphate-buffered saline and subcultured to the same media after 1 day or 3 wk of incubation at 4.degree. C. Y. enterocolitica was isolated from 174 index cases and 34 household contacts. Of the isolates, 181 were of serotype O:3 and 21 belonged to other serotypes. Of O:3 isolates, 81% (147/181) were recovered by direct plating and 6.1% (11/181) and 13% (23/181) were recovered by 1 day and 3 wk cold enrichment, respectively. For other serotypes, 26% (7/27), 0% and 74% (20/27) were isolated by direct plating, 1 day cold enrichment, and 3 wk cold enrichment, respectively. The efficacy of the cold enrichment for the recovery of serotype O:3 varied according to the patient''s clinical condition. When patients were still symptomatic, 94 and 6% of Y. enterocolitica were identified by direct plating and cold enrichment, respectively. Isolation rates were 66% by direct plating and 34% by cold enrichment when stools were obtained from asymptomatic carriers or from those convalescing from Y. enterocolitica gastroenteritis. The cold enrichment methods may increase the sensitivity of Y. enterocolitica culture methods considerably in convalescent and asymptomatic subjects but only minimally in patients with diarrhea caused by serotype O:3.