Introduction. Group B streptococci causing invasive infections (iGBS) represent a leading cause of sepsis and meningitis during the first 3 months of life. During the years 2020-2024, a total of 106 iGBS strains were received.
Materials and Methods. The iGBS strains were characterized for capsular type, phenotypic and genotypic susceptibility testing to erythromycin, clindamycin, tetracycline and high-level gentamicin resistance (HLGR), identification of the hypervirulent ST-17 lineage by hvgA gene-specific PCR and of the alpha-like surface protein genes.
Results. Overall, 38, 66 and 2 iGBS strains were from early-onset disease (EOD), late-onset disease (LOD) and stillbirth, respectively.
Serotype III was the most prevalent type (75.0%), followed by Ia (8.6%), V (5.8%), Ib (4.8%), II and IV (2.9% each). Among serotype III strains, the ST-17 lineage was responsible for 55.6% of GBS-EOD and caused the majority of GBS-LOD (87.7%).
Rib surface protein predominated (n=80, 76.9%) and specific serotype/alpha-like protein associations were found, such as III/rib, Ia/epsilon, Ib/alphaC, and II/alphaC.
Resistance rates to erythromycin, clindamycin, and tetracycline were 36.8%, 34.9%, and 87.4, respectively. HLGR was reported in 3 isolates. Overall, 89.5% macrolide-resistant isolates were constitutively resistant to both clindamycin and erythromycin, mediated by the ermB gene. The tetracycline resistance gene tetM predominated (61.5%). A total of 34 multidrug-resistant (MDR) iGBS isolates, mostly of serotype III-ST17 (n=27).
Conclusions. The distribution of serotypes differs between GBS-EOD and GBS-LOD. Our data show alarming high macrolide resistance rates with an increasing trend over time, partly due to the acquisition of MDR by the ST-17 lineage.