Improved Detection of <i>Shigella</i> Species in Diarrheic Children in Ghana Using Invasion Plasmid Antigen H-based Polymerase Chain Reaction Technique

Shigella species play an important role in the morbidity and mortality of children <5 years of age in low and middle-income countries. Previous surveillance studies to evaluate the burden of Shigella disease in Ghana involved conventional culture method which most probably resulted in underestimated prevalence. As efforts are being made globally to introduce vaccines against Shigella and Enterotoxigenic Escherichia coli (ETEC), this study sought to establish Shigella burden of disease in children <5 years of age for the implementation of appropriate public health measures to control diarrheal disease in Ghana. The study reports data of a collaborative research between Noguchi Memorial Institute for Medical Research (NMIMR), University of Ghana and Tel Aviv University (TAU), Israel, under the STOPENTERICS FP7 programme. STOPENTERICS FP7 programme aims to provide novel prophylactic solutions by imposing a two-fold paradigm switch in the development of vaccine candidates against Shigella and ETEC. Bloody diarrheal stool samples were collected from children (cases) (n=269) and from healthy children (controls) (n=38) aged <5 years and tested by traditional culture method in the department of Bacteriology, NMIMR. Samples were shipped and tested using invasion plasmid antigen H-based (ipaH-based) molecular method in TAU. All cases and controls tended Shigella culture-negative at NMIMR. Retesting by ipaH PCR assay in TAU identified Shigella in 31.2% (n=84) of 269 cases and 2.6% (n=1) of 38 controls. The males represented 63.1% (n=53) whilst females represented 36.9% (n=32) of cases (p=0.009). The single asymptomatic carrier (n=1) of the 38 controls, was a 3-month old male child. The asymptomatic carrier in the control group may be regarded as a potential transmitter of disease to vulnerable children of the household. Sanger sequencing confirmed ipaH in 10% of the positive samples. The prevalence of >30% of shigellosis indicates a substantial contribution of Shigella to diarrheal burden in children <5 years in Ghana. The most appropriate diagnosis of shigellosis should be PCR which is capable of detecting small amounts of nucleic acid. Furthermore, molecular screening for the detection of Shigella must be carried out in conjunction with the traditional culture method since isolation alone, may underestimate the prevalence of Shigella. Continuous surveillance will be useful in making evidence-based decisions on the introduction of vaccines against Shigella and ETEC in Ghana.