Evaluation of the ‘HG Group B Streptococcus’ loop-mediated isothermal amplification assay for accurate identification of Streptococcus agalactiae

Abstract

This study evaluated the HiberGene Group B Streptococcus test, a CE-IVD-approved molecular assay for rapid detection of Streptococcus agalactiae [Group B Streptococcus (GBS)] in human clinical specimens. Performance of the assay in terms of specificity, sensitivity and genotype inclusivity was investigated using an extended specificity panel of 113 human and animal GBS isolates, and eight isolates from other streptococcal species, from the isolate collection of the German National Reference Center for Streptococci. Broth cultures were tested according to the manufacturer’s protocol, including lysis, heat denaturation and isothermal amplification. All 104/104 (100 %) human GBS isolates of nine serotypes (Ia, Ib, II, III, IV, V, VI, VII, VIII and non-typeable) were correctly identified by the assay as GBS. Additionally, 7/9 (78 %) GBS isolates from elephants were also correctly identified. Six isolates of other streptococcal species/subspecies ( Streptococcus anginosus , S. constellatus , S. castoreus , S. dysgalactiae and S. dysgalactiae equisimilis ) were correctly reported as negative. Two S. pyogenes (Group A Streptococcus) isolates gave invalid results. The HG Group B Streptococcus assay identified human GBS isolates in culture with 100 % sensitivity.