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 Yersinia enterocolitica by direct plating onto routine laboratory media. These stools were also inoculated into phosphate-buffered saline and subcultured to the same media after 1 day or 3 weeks of incubation at 4 degrees C. Y. enterocolitica was isolated from 174 index cases and 34 household contacts. One hundred eighty-one isolates were of serotype O:3, and the remaining 21 belonged to other serotypes. Eighty-one percent (147/181) of O:3 isolates were recovered by direct plating, and 6.1% (11/181) and 13% (23/181) were recovered by 1-day and 3-week 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-week cold enrichment, respectively. The efficacy of the cold enrichment for the 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. These results indicate that the cold enrichment methods increase the sensitivity of Y. entercolitica culture methods considerably in convalescent and asymptomatic subjects but only minimally in patients with diarrhea caused by serotype O:3.