Value of a commercial multiplex molecular panel for the diagnosis of cholera in an outbreak setting in Hammanskraal, Tshwane, South Africa

Abstract

Cholera is not endemic in South Africa. However, between February and July 2023, 1073 suspected cholera cases, and 198 laboratory-confirmed cases were reported nationally. This is the first report of the use of a commercial, rapid diagnostic assay in an outbreak setting. This method evaluation study was conducted at the National Health Laboratories Service (NHLS) Tshwane Microbiology laboratory in Pretoria, South Africa, during the outbreak period. Eighteen retrospective stored culture-positive Vibrio cholerae isolates and 102 prospective clinical specimens were processed on the EntericBio® Dx panel (Serosep, Limerick, Ireland) as well as the gold standard of culture. For the EntericBio® processing, stools were processed according to the manufacturer's instructions. Real time polymerase chain reaction (PCR) was performed on the Roche LightCycler®. The diagnostic performance was compared between culture and the EntericBio® Dx assay. All discrepant results were resolved at a referral laboratory using an in-house PCR assay. The mean time to results using EntericBio® was 48 h earlier than culture results. Overall, the EntericBio® Dx panel demonstrated a sensitivity of 100 % for the detection of Vibrio species when compared to culture. Although the EntericBio® platform reported the results as Vibrio species, the pre-test probability was high for V. cholerae in an outbreak setting. Further serotyping methods have confirmed this. The quick turnaround time and excellent sensitivity of the EntericBio® platform expedites patient treatment and institution of appropriate infection control practices and has potential to rapidly control such outbreaks.

Keywords: Laboratory evaluation; Molecular testing; Multiplex PCR; Outbreak; Vibrio cholerae.