Features of Streptococcus agalactiae strains recovered from pregnant women and newborns attending different hospitals in Ethiopia.

Background: Streptococcus agalactiae (Group B Streptococcus, GBS) serotypes, sequence types, and antimicrobial resistance profile vary across different geographic locations affecting disease patterns in newborns. These differences are important considerations for vaccine development efforts and data from large countries in Africa is limited. The aim of this study was to determine serotypes and genotypes of GBS isolates from pregnant women and their newborns in Ethiopia.
Methods: A hospital based cross-sectional study was conducted at three hospitals in Ethiopia from June 2014 to September 2015. Out of 225 GBS isolates, 121 GBS were recovered, confirmed and characterized at CDC's Streptococcus Laboratory using conventional microbiology methods and whole genome sequencing.
Results: Of the 121 isolates, 87 were from rectovaginal samples of pregnant women, 32 from different body parts of their newborns and 2 from blood of newborns with suspected sepsis. There were 25 mother-infant pairs and 24 pairs had concordant strains. The most prevalent serotypes among mothers and/or their babies were II, Ia and V (41.5, 20.6, 19.5 and 40.6%, 25 and 15.6%, respectively). Multilocus sequence typing (MLST) on 83 isolates showed ST10 (24; 28.9%) and ST2 (12; 14.5%) as most predominant sequence types. All GBS strains were susceptible to penicillin, cefotaxime and vancomycin, which correlated to the presence of wildtype PBP2x types and the lack of known vancomycin-resistance genes. Tetracycline resistance was high (73; 88%, associated primarily with tetM, but also tetO and tetL). Five isolates (6%) were resistant to erythromycin and clindamycin and 3 isolates were fluoroquinolone-resistant, containing associated mutations in gyrA and parC genes. All isolates were positive for one of four homologous Alpha/Rib family determinants and 1-2 of the three main pilus types.
Conclusions: Predominant serotypes were II, Ia, and V. A limited number of clonal types were identified with two STs accounting for about half of the isolates. All strains collected in this study were susceptible to beta-lactam antibiotics and vancomycin. Typical of most GBS, these isolates were positive for single alpha-like family protein, serine-rich repeat gene, as well as 1-2 pilus determinants.