Molecular characterization and antimicrobial susceptibility of hemolytic Streptococcus agalactiae from post-menopausal women

• The distribution of serotypes in postmenopausal women is similar to that of pregnant population.
• Reduced sequence type variability is observed in postmenopausal women than in pregnant population.
• The most common sequence types are ST-19 and ST-23, mainly related to colonization.
• Antimicrobial resistance percentages are somewhat higher in postmenopausal women.
• Characterization of strains in different populations is necessary for the development of candidate vaccines.

PurposeStreptococcus agalactiae (Group B streptococcus, GBS) is increasingly recognized as a pathogen in adult populations, including the elderly. Appropriate treatment involves antibiotics. An alternative to this strategy would be the administration of a polysaccharide vaccine therefore the capsular serotypes and molecular characterization of circulating strains needs to be known. Few studies have been conducted in this population.MethodsOne hundred and seven GBS isolates collected from vagino-rectal swabs from 600 post-menopausal women were analysed for their capsular type, antimicrobial resistance and genetic relatedness (multilocus sequence typing, MLST).ResultsThe colonization rate was 17.8%. Capsular type III was predominant (34.6%), followed by type V (22.4%). The most frequent sequence type (ST) was 19 (23.3%), followed by 23 (18.7%), 1 (16.8%) and 17 (12.1%). Isolates were assembled into three phylogenetic groups from ST-19, ST-23 and ST-17 founders. All isolates were susceptible to penicillin, whereas resistance to erythromycin and clindamycin was recorded in 23.4% and 20.6% of isolates, respectively.ConclusionsIn our setting, the GBS colonization rate in postmenopausal women is similar to that reported in others populations studied. The population structure of these isolates is highly diverse and contains different STs. These data can contribute to the future development of a polysaccharide vaccine for preventing GBS infection in older adults.