Microbiological Methods Used in the Enterics for Global Health Shigella Surveillance Study

Abstract

Background: Shigella is a major cause of diarrhea in young children worldwide. Multiple vaccines targeting Shigella are in development, and phase 3 clinical trials are imminent to determine efficacy against shigellosis.

Methods: The Enterics for Global Health (EFGH) Shigella surveillance study is designed to determine the incidence of medically attended shigellosis in 6- to 35-month-old children in 7 resource-limited settings. Here, we describe the microbiological methods used to isolate and identify Shigella. We developed a standardized laboratory protocol for isolation and identification of Shigella by culture. This protocol was implemented across all 7 sites, ensuring consistency and comparability of results. Secondary objectives of the study are to determine the antibiotic resistance profiles of Shigella, compare isolation of Shigella from rectal swabs versus whole stool, and compare isolation of Shigella following transport of rectal swabs in Cary-Blair versus a modified buffered glycerol saline transport medium.

Conclusions: Data generated from EFGH using culture methods described herein can potentially be used for microbiological endpoints in future phase 3 clinical trials to evaluate vaccines against shigellosis and for other clinical and public health studies focused on these organisms.

Keywords: Shigella; children; diarrhea; dysentery; microbiology.

Figure 1.

Isolation of Shigella spp. from rectal swabs and whole stool.

Figure 2.

Shigella agglutination flowchart using polyvalent and monovalent antisera. Abbreviations: CB, Cary-Blair medium; MAC, MacConkey agar; mBGS, modified buffered glycerol saline; XLD, xylose-lysine-deoxycholate agar.