Group B Streptococcus (GBS) invasive infections among non-pregnant adults in Belgium, 2018: bacteriological and clinical characteristics

Background
GBS increasingly causes significant morbidity and mortality among adults. We here provide an overview of bacteriological and clinical characteristics of GBS causing invasive diseases in adults in Belgium.
Methods
Overall 202 GBS strains isolated from invasive diseases among non-pregnant adults sent, on a voluntary-base, to the National Reference Centre (NRC) during the year 2018, were characterized: capsular polysaccharide (CPS)-typing by PCR, pili-typing by PCR, antimicrobial susceptibility testing, and detection of resistance genes by PCR. Clinical data were collected from short questionnaires.
Results
CPS-types V and Ia were predominant (25.2 and 24.7%) followed by III, Ib, II, IV, VI and IX (14.4%, 11.9%, 11.4%, 9.9%, 1.5% and 1%). All strains were susceptible to penicillin. Rate of resistance to macrolides/lincosamides was 33,6%. ErmB, ErmTr and MefA genes were detected respectively within 44,4%, 34,4% and 26,3% among the resistant strains. Two strains presenting the L phenotype harboured the LsaC gene. About pili-typing, the combined PI1, PI2a genes were predominant (54% of the cases), followed by PI2a alone, the combined PI1, PI2b and PI2b alone (35%, 5%, 4%). The median age at onset was 69 years old (range 20-101). Bacteremia without reported focus is the predominant manifestation (56,9%), followed by skin-and-soft tissue infections (20,8%), bone-and-join infections (7,4%), endocarditis (4,9%), meningitis (1.5%) and others (8,5%).
Conclusion
Among invasive adult diseases, GBS bacteriological characteristics were consistent with reported data among European countries. Macrolides/lincosamides resistance rate has slightly increased. Susceptibility of the elderly and the varied clinical manifestations were highlighted.