Using real time PCR to detect shigellosis: ipaH detection in Kaeng-Khoi District, Saraburi Province, Thailand

To get a real number of the disease burden caused by Shigella in Kaeng-Khoi District, Saraburi Province, Thailand, real time-PCR was used to detect Shigella-associated DNA. Randomly selected rectal swabs from 20 Shigella culture-positive and from 300 Shigella culture-negative patients detected in population-based surveillance of patients seeking care for diarrhea were processed using real time PCR. The target of the primer pair is the invasion plasmid antigen H gene sequence (ipalI) carried by all 4 Shigella species and enteroinvasive Escherichia coli. IpaHwas detected in l9 out of 20 (95%) Shigella culture-positive specimens compared to 48 out of 300 (16%) culture-negative patients free of dysentery @<0.001). The data from real time PCR amplification indicate that the culture-proven prevalence of Shigella among diarrheal patients may underestimate the true prevalence of shigellosis by an order of magnitude.