Abstract:

Background: Streptococcus agalactiae or Group B Streptococcus (GBS) is part of the gastrointestinal tract and vaginal microbiota, and one of the commonest pathogen affecting pregnant women. Its rate of colonization varies widely globally due to differences in laboratory investigation methods, socio-cultural, epidemiological and clinical factors among pregnant women. Limited information exists on the burden of GBS among pregnant women in Tanzania resulting in lack of screening, management and vaccination recommendations.

Objective: To determine maternal vaginorectal Streptococcus agalactiae colonization and its associated factors among HIV infected and uninfected pregnant women in Mwanza, Tanzania.

Methods: We conducted a cross-sectional study from February to June 2021 including women attending to primary health care to tertiary level hospitals. A total of 872 pregnant women were enrolled during routine antenatal clinic visits. Demographics, obstetric and other clinical information was collected using a structured questionnaire. Two swabs (vaginal and rectal) were taken from each participant and cultured on conventional blood agar and CHROmagarTMStrepB, followed by antimicrobial susceptibility testing using disk diffusion.

Results: The overall proportion of S. agalactiae colonization was 24.5% (214/872), and colonization was significantly more prevalent in the rectal compared to vaginal samples [21.1% (184/872) versus 8.83% (77/872), respectively; p-value <0.001)]. S. agalactiae recovery was significantly better on CHROMagarTM Strep B agar compared to blood agar [24.4% (213/872) versus 18.8% (164/872)], respectively, p-value = 0.004. S. agalactiae colonization was significantly higher in HIV positive compared to HIV negative women [63.1% (70/111) versus 18.9% 144/761, respectively; OR (95% CI) = 7.33 (4.77 – 11.29, p-value <0.001). S. agalactiae isolates were highly sensitive to ampicillin (100%), erythromycin (76.3%, clindamycin (84.4%) and vancomycin (98.1%). No association could be found be found between GBS colonization and health care facility levels or pregnancy trimesters.

Conclusions and recommendation: This was the first larger scale assessment of GBS colonization in pregnant women residing in Mwanza. HIV positive pregnant women shoe higher rates of colonization and routine screening of GBS is recommended during routine antenatal clinical visits. Ampicillin is suitable for prophylaxis and treatment of GBS following international guidelines. Serotyping and genotyping of these isolates should be carried out to guide preventive and vaccination strategies.