STOOL CULTURES FOR SHIGELLA SPP - IMPROVED SPECIFICITY BY USING MACCONKEY AGAR WITH XYLOSE

A fetal of 678 stool specimens were cultured on four different agars: on xylose-lysine-desoxycholate agar (XLD), MacConkey agar (Mac), MacCo nkey agar supplemented with xylose (Mac-X), and Hektoen enteric agar ( HE). Isolation rates for shigellae were 77% on HE, 86% on Mac and Mac- X, and 91% on XLD. The specificities of the media were 61% for Mac, 75 % for HE, and 78% for XLD and Mac-X. After overnight incubation, Mac-X is much easier to read than XLD, which requires incubation for at lea st 22 hours. Based on these results and also on the practical aspect t hat incubation for 22-21 hours does not fit well in our schedule, we n ow use Mac-X whenever shigellae need to be looked for (i.e. mainly pat ients with recent travel to tropical countries). As compared to our pr evious procedure the workload in the laboratory could be reduced by ab out 20%.