Surveillance of shigellosis by real-time PCR suggests underestimation of shigellosis prevalence by culture-based methods in a population of rural China

SummaryIntroductionShigellosis is a leading public health issue in China, especially in Children under 5 years of age. The disease burden of shigellosis is usually underestimated by conventional culture. In this study, real-time PCR was applied to detect Shigella infection in parallel with routine culture, to investigate the true burden of disease caused by Shigella spp.MethodsRectal swab specimens of 39 Shigella culture positive and 298 Shigella culture negative patients from a population-based surveillance study were selected randomly. Real-time PCR targeting the invasion plasmid antigen H gene sequence (ipaH) was used to detect DNA sequences characteristic for Shigella spp.ResultsipaH were detected in 174 of 298 (58%) randomly selected Shigella culture negative specimens and in 38 of 39 (97%) Shigella culture positive specimens (p < 0.001). Among 10 variables, culture results was the strongest predictive factor (OR = 15.5; 95% CI: 2.0–119.0), followed by a clinical presentation of diarrhea with fever (OR = 2.8; 95% CI: 1.2–6.2), epidemic season (OR = 2.4; 95% CI: 1.4–4.3), and female gender (OR = 1.8; 95% CI: 1.1–3.0).ConclusionThe high detection rate of ipaH in culture negative specimens through use of real-time PCR suggests that earlier estimates of shigellosis burden measured by conventional culture may have underestimated the true disease burden.