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

Abstract

Introduction: Shigellosis 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.

Methods: Rectal 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.

Results: ipaH 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).

Conclusion: The 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.