Mapping Presence of Group B Streptococcus: Study provides Insights from HIV-affected and HIV-unaffected Pregnant Women

Streptococcus agalactiae, commonly known as Group B Streptococcus (GBS), is a significant pathogen that can lead to serious infections in pregnant women and their infants. Given the varying global prevalence of GBS colonization, influenced by different laboratory methodologies and socio-cultural as well as epidemiological factors, recent study conducted in Tanzania determined the prevalence of GBS colonization among both HIV-infected and uninfected pregnant women and identify the associated risk factors.

The study utilized a cross-sectional analytical design, recruiting participants from multiple tiers of the healthcare system in Mwanza, Tanzania, ranging from primary to tertiary health facilities. A total of 872 pregnant women were enrolled, of which 111 were HIV-positive. The data collection involved a structured questionnaire capturing socio-demographic and clinical information, and GBS colonization was assessed through microbiological testing of vaginorectal swabs using both conventional blood agar and the more sensitive CHROMagar™ StrepB.

Prevalence of GBS Colonization

The overall GBS colonization rate found in this cohort was 24.5%, demonstrating a higher prevalence than previously reported in Tanzania's earlier studies, specifically noting significant differences between healthcare tiers without a clear association to trimester or demographic variables. Notably, the prevalence of GBS was significantly higher among HIV-infected women (63.1%) compared to their uninfected counterparts (18.9%), leading to an odds ratio of 7.3, indicating a strong association between HIV infection and GBS colonization.

Public Health Implications and Screening Recommendations

This highlights a critical public health implication, as GBS colonization poses risks of adverse outcomes for neonates, including sepsis and preterm births. The findings also emphasized the importance of enhanced GBS screening protocols for HIV-positive pregnant women due to their elevated colonization rates. The use of CHROMagar™ StrepB was found to substantially improve the detection rates of GBS compared to blood agar, supporting a recommendation for its adoption in clinical settings to optimize bacterial recovery.

Antimicrobial Susceptibility Profiles

Antimicrobial susceptibility profiles for GBS revealed high sensitivity to ampicillin (100%) and considerable susceptibility to erythromycin (76.3%) and clindamycin (84.4%), solidifying these as viable options for prophylactic treatment in cases of GBS colonization during labor. In contrast, very low susceptibility rates were observed for tetracycline and trimethoprim-sulfamethoxazole, necessitating careful consideration in treatment planning. While the findings provide critical insights into GBS colonization trends among pregnant women in Tanzania, they also underscore the need for further research to assess the evolving epidemiological landscape, including the influence of HIV-related immunosuppression and other underlying factors such as cultural practices and healthcare access. The study calls for routine GBS screening, particularly among HIV-infected women, and highlights the necessity for integrated strategies addressing both GBS and other sexually transmitted infections.

Study Limitations and Conclusion

Limitations included the cross-sectional nature of data collection, which precluded causal inferences, and the lack of comprehensive immunological data for HIV-infected participants, indicating the necessity for longitudinal studies to better understand the dynamics of GBS colonization among different populations. Overall, the results advocate for enhanced preventive measures and tailored screening programs to mitigate the risk of GBS-related complications in both mothers and newborns, marking an essential step forward in maternal and infant health in Tanzania.

Key Points

- -Prevalence Rates-: A prevalence rate of 24.5% for GBS colonization was identified among pregnant women in Tanzania, which is higher than that reported in previous studies. Notably, HIV-infected women exhibited a GBS prevalence of 63.1%, significantly higher than the 18.9% among HIV-uninfected women, revealing an odds ratio of 7.3.

- -Study Design-: The study utilized a cross-sectional analytical design, engaging 872 pregnant women from various healthcare facilities in Mwanza, Tanzania. Data was collected through structured questionnaires and microbiological testing of vaginorectal swabs using conventional blood agar and CHROMagar™ StrepB to assess GBS colonization.

- -Public Health Importance-: Highlighting the public health implications, GBS colonization increases risks of adverse neonatal outcomes, including sepsis and preterm births. The study emphasizes the need for improved GBS screening protocols, especially for HIV-positive pregnant women due to their higher colonization rates.

- -Antimicrobial Susceptibility-: Antimicrobial susceptibility testing showed 100% sensitivity of GBS to ampicillin and significant sensitivity to erythromycin (76.3%) and clindamycin (84.4%). However, low susceptibility rates for tetracycline and trimethoprim-sulfamethoxazole were noted, suggesting caution in treatment planning.

- -Recommendations for Clinical Practice-: The study supports the adoption of CHROMagar™ StrepB in clinical settings to enhance GBS detection rates compared to traditional blood agar methods, reinforcing the importance of accurate diagnosis in preventive healthcare.

- -Limitations and Future Research-: The cross-sectional design limits causal inferences, and a lack of extensive immunological data for HIV-positive participants indicates a need for longitudinal studies. Further research is required to understand the interplay of HIV-related immunosuppression and other socio-cultural factors influencing GBS colonization trends.

Reference –

Paul H Ngayomela et al. (2025). Streptococcus Agalactiae Colonization Is Common Among Pregnant Women With HIV Infection And Is Neither Predicted By Hospital Tier Nor Trimester In Mwanza, Tanzania. *BMC Pregnancy And Childbirth*, 25. https://doi.org/10.1186/s12884-025-07585