Alpha Omega Alpha Honor Medical Society

2011 Research Abstract

Are Bacterial Agents of Community-Acquired Gastroenteritis Under-Diagnosed? Impact of Stool Antigen Tests for Campylobacter and Enterohemorrhagic E. coli

Investigator: Claire Detweiler, University of Texas Medical Branch School of Medicine
Mentor: Mike Loeffelholz, PhD, ABMM, University of Texas Medical Branch School of Medicine

Campylobacter and Enterohemorrhagic Escherichia coli (EHEC) are two of the most common food- or waterborne causes of bacterial gastroenteritis. Campylobacter and EHEC are commonly detected by culture of a stool specimen. Culture can only identify E. coli serotype O157:H7. Recently, non-culture-based methods for detection of Campylobacter antigen and EHEC shiga toxins (ST) have been developed, such as rapid antigen tests, ELISA, and PCR. The ImmunoCard STAT! (ICS) CAMPY and EHEC ST1 and ST2 tests (Meridian Bioscience, Cincinnati, OH) are rapid, lateral flow immunochromatographic tests that detect antigens in stool specimens. This study compared ICS CAMPY and EHEC tests to culture in 175 patient specimens. Discordant results were arbitrated by performing Loop-Mediated Isothermal Amplification (LAMP) assays and by patient chart review. In this set of consecutive patient specimens, culture detected a single Campylobacter infection, which was also positive by ICS CAMPY and LAMP. 16 specimens were positive by ICS CAMPY tests that were negative by culture, and only one was positive by LAMP. Culture detected no E. coli O157:H7 infections. All of the 8 discordant EHEC specimens (ICS EHEC positive and culture negative) were negative by LAMP. In this low prevalence setting, the ICS CAMPY and EHEC assays appear to have a high false positive rate (poor positive predictive value). We recommend ICS CAMPY should not be used to detect Campylobacter. We recommend routine culture for E. coli O157:H7 on all feces samples from patients with acute community-acquired diarrhea. However, ICS EHEC should not be used for routine screening of EHEC.

Updated on January 10, 2012.

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