METHODS: The Foodborne Diseases Active Surveillance Network (FoodNet) conducts sentinel, population-based surveillance for foodborne infections diagnosed by culture or CIDT and clinical laboratory surveys. We describe Campylobacter, Salmonella, and Shigella infections during 2012-2014, according to diagnostic method, and the testing practices of clinical laboratories serving surveillance catchment area residents in 2015.
RESULTS:
The percentage of infections diagnosed only by CIDT without culture confirmation varied by pathogen-- Campylobacter (11% to 15%), Salmonella (1.3% to 1.5%), and Shigella (2.1% to 4.5%). The majority of Campylobacter CIDT reports were based on commercial antigen-based tests; all Salmonella and Shigella CIDT reports were based on laboratory-developed PCR tests. Compared with patients with culture-confirmed Salmonella and Shigella infections, patients with infection detected by CIDT were younger, more likely to be white, and less likely to be hospitalized, while patients with Campylobacter detected by CIDT were older, more likely to be hospitalized, and less likely to have severe symptoms. In 2015, the percentage of laboratories that used CIDT to detect Campylobacter was 18%, Salmonella was 5%, and Shigella was 5%.
CONCLUSIONS: The percentage of bacterial enteric infections diagnosed by CIDTs is increasing. Differences in the demographics and clinical characteristics of patients diagnosed by culture and by CIDT may reflect differences in test performance or in testing practices. Continued collection of CIDT information is important to quantify the impact on measured trends.