Clinical Report: Epidemiology and Resistance of Invasive Group B Streptococcus in South Africa 2019-2020
Overview
This study characterized 658 invasive Group B Streptococcus (GBS) isolates from South Africa collected between 2019 and 2020, revealing predominant serotypes III and Ia and low penicillin resistance. Resistance to erythromycin, clindamycin, and tetracycline was noted, with specific resistance genes identified. The findings support continued use of β-lactam antibiotics and suggest good coverage potential for current vaccine candidates.
Background
Group B Streptococcus is a major cause of neonatal sepsis and meningitis and also affects adults, particularly those with comorbidities. Intrapartum antibiotic prophylaxis (IAP) reduces early-onset disease but is challenging to implement in resource-limited settings like South Africa. While penicillin remains the first-line treatment, emerging resistance to penicillin and other antibiotics has been reported globally. Vaccines targeting capsular polysaccharides and surface proteins are under development to address disease burden and antimicrobial resistance.
Data Highlights
Characteristic
Value
Total invasive GBS cases reported
1748
Isolates characterized
661
Isolates with phenotypic and genotypic results
658
Predominant serotypes (%)
III (42.8%), Ia (27.9%), V (11.9%), II (8.4%), Ib (6.7%), IV (2.3%)
ermTR (34.9%), mefA/E (30.1%) for erythromycin; ermB (32.0%) for clindamycin; tetM (95.8%) for tetracycline
Surface protein genes
All isolates had ≥1 pilus gene cluster; 98% had serine-rich repeat protein genes; hvgA exclusive to CC17
Key Findings
Five clonal complexes (CC1, CC8/10, CC17, CC19, CC23) and six serotypes were identified, with serotype III being most common.
Only one isolate showed reduced susceptibility to penicillin, confirming β-lactams remain effective for treatment.
Resistance to erythromycin (16.1%) and clindamycin (3.8%) was present, with ermTR, mefA/E, and ermB genes implicated.
Tetracycline resistance was very high (91.5%), predominantly mediated by the tetM gene.
All isolates carried key vaccine target surface proteins, including pilus gene clusters and alpha/Rib family determinants.
The hvgA gene, associated with hypervirulence, was found exclusively in CC17 isolates.
Clinical Implications
Penicillin and other β-lactam antibiotics remain appropriate for treating invasive GBS infections in South Africa. The presence of erythromycin and clindamycin resistance highlights the need for susceptibility testing when these agents are considered. Current polysaccharide and protein-based vaccines under development are likely to provide broad coverage against circulating serotypes and surface proteins in this setting.
Conclusion
This comprehensive molecular epidemiology study confirms the predominance of serotypes III and Ia in invasive GBS disease in South Africa and supports continued use of β-lactams for treatment. Vaccine candidates targeting prevalent serotypes and surface proteins show promise for effective prevention.
References
Group B Streptococcus Surveillance South Africa 2019-2020 -- Epidemiological Study
by Buhle Ntozini, Sibongile Walaza, Benjamin Metcalf, Scott Hazelhurst, Linda de Gouveia, Susan Meiring, Dineo Mogale, Senzo Mtshali, Arshad Ismail, Kedibone Ndlangisa, Mignon Du Plessis, Vanessa Quan, Sopio Chochua, Lesley McGee, Anne von Gottberg, Nicole Wolter
