Bacterial enteric infections detected by culture-independent diagnostic tests--FoodNet, United States, 2012-2014

Abstract

The increased availability and rapid adoption of culture-independent diagnostic tests (CIDTs) is moving clinical detection of bacterial enteric infections away from culture-based methods. These new tests do not yield isolates that are currently needed for further tests to distinguish among strains or subtypes of Salmonella, Campylobacter, Shiga toxin-producing Escherichia coli, and other organisms. Public health surveillance relies on this detailed characterization of isolates to monitor trends and rapidly detect outbreaks; consequently, the increased use of CIDTs makes prevention and control of these infections more difficult. During 2012-2013, the Foodborne Diseases Active Surveillance Network (FoodNet*) identified a total of 38,666 culture-confirmed cases and positive CIDT reports of Campylobacter, Salmonella, Shigella, Shiga toxin-producing E. coli, Vibrio, and Yersinia. Among the 5,614 positive CIDT reports, 2,595 (46%) were not confirmed by culture. In addition, a 2014 survey of clinical laboratories serving the FoodNet surveillance area indicated that use of CIDTs by the laboratories varied by pathogen; only CIDT methods were used most often for detection of Campylobacter (10%) and STEC (19%). Maintaining surveillance of bacterial enteric infections in this period of transition will require enhanced surveillance methods and strategies for obtaining bacterial isolates.

FIGURE 1

Incidence of culture-confirmed bacterial infections and positive CIDT reports, by selected pathogen — FoodNet, United States, 2012–2013 Abbreviations: CIDT = culture- independent diagnostic test; STEC: Shiga toxin–producing Escherichia coli.

FIGURE 2

Positive CIDT reports of Campylobacter and Shiga toxin–producing Escherichia coli, by test type and culture result — FoodNet, United States, 2012–2013 Abbreviations: CIDT = culture- independent diagnostic test; LDT = laboratory-developed test. * Excludes 274 Shiga toxin–positive reports from clinical laboratories that were Shiga toxin–negative at a public health laboratory and 53 reports of detection of O157 antigen without a test result for Shiga toxin. ^† For instances in which a positive result from a single specimen was reported from more than one laboratory (e.g., clinical laboratory and public health laboratory), test type was categorized according to the test type used for initial detection. ^§ Conducted at a clinical laboratory or public health laboratory.