Laboratory Practices and Incidence of Non-O157 Shiga toxin–producingEscherichia coliInfections

Kathleen A Stigi,Kathryn H Lofy,J Kathryn Macdonald,Anthony A Tellez-Marfin

doi:10.3201/eid1803.111358

Abstract

Highlights

We surveyed laboratories in Washington State, USA, and found that increased use of Shiga toxin assays correlated with increased reported incidence of non-O157 Shiga toxin–producing Escherichia coli (STEC) infections during 2005–2010
Combining the number of processed specimens and testing protocol for each laboratory, we estimated that 40% of stool specimens in Washington State were cultured for O157 STEC and tested for Shiga toxin (Stx), 47% were cultured for O157 STEC exclusively, and 13% were tested for Stx exclusively (Figure 2, panel B)
During 2005 through 2010, the number of laboratories in Washington State that tested for Stx increased from 2 (4%) in 2005 to 19 (33%) in 2010, and the incidence of reported non-O157 STEC infections increased from 8 cases (0.13/100,000 population) in 2005 to 76 cases (1.13/100,000) in 2010

Summary

Introduction

We surveyed laboratories in Washington State, USA, and found that increased use of Shiga toxin assays correlated with increased reported incidence of non-O157 Shiga toxin–producing Escherichia coli (STEC) infections during 2005–2010. Only half of processed stool specimens underwent Shiga toxin testing during 2010, suggesting substantial underdetection of non-O157 STEC infections. The Centers for Disease Control and Prevention (CDC) published formal STEC testing recommendations for clinical laboratories in 2009, advocating that all stool specimens submitted for routine bacterial pathogen testing be simultaneously cultured for O157 STEC and tested with a nonculture assay to detect Stx. Use of this testing protocol ensures timely identification of all STEC infections [2,5].

Results

Conclusion