Serotype Distribution, Population Structure, and Antimicrobial Resistance of Group B Streptococcus Strains Recovered from Colonized Pregnant Women

Abstract

Using serotyping, multilocus sequence typing, and whole-genome sequencing (WGS) of selected strains, we studied the population structure of 102 group B Streptococcus (GBS) isolates prospectively sampled in 2014 from vaginal/ rectal swabs of healthy pregnant women in metropolitan Toronto, Canada. We also determined the susceptibilities of each of the colonizing isolates to penicillin, erythromycin, clindamycin, tetracycline, and other antimicrobial agents. Overall, we observed a high rate of tetracycline resistance (89%) among colonizing GBS isolates. We found resistance to erythromycin in 36% of the strains, and 33% were constitutively or inducibly resistant to clindamycin. The most frequently identified serotypes were III (25%), Ia (23%), and V (19%). Serotype IV accounted for 6% of the colonizing isolates, a rate consistent with that observed among patients with invasive GBS infections in metropolitan Toronto. The majority of serotype IV isolates belonged to sequence type (ST)459, a tetracycline-, erythromycin-, and clindamycinresistant ST first identified in Minnesota, which is considered to be the main driver of serotype IV GBS expansion in North America. WGS revealed that ST459 isolates from Canada are clonally related to colonizing and invasive ST459 organisms circulating in regions of the United States. We also used WGS to study recombination in selected colonizing strains from metropolitan Toronto, which revealed multiple episodes of capsular switching. Present and future circulating GBS organisms and their genetic diversity may influence GBS vaccine development.

Semina: Ciências Biológicas e da Saúde, Londrina, v. 39, n.1, jan./jun. 2018

“…(11,28) Data from North America reported rates of resistance to erythromycin and clindamycin ranging from 27.4% to 36% and 27.4% to 33%, respectively. (11,29) High rates of GBS resistance for both antimicrobials were reported in Italy (32.2% for erythromycin and 43.8% for clindamycin) (30) and China (78.6% for erythromycin and 64.3% for clindamycin) (WANG et al, 2015). (10) In contrast, lower rates of resistance were detected in Swiss (14.6% for erythromycin and 8.2% for clindamycin) (12) and Saudi Arabia (15.7% for erythromycin and 5.1% for clindamycin).…”

Within-Host Diversity and Vertical Transmission of Group B Streptococcus Among Mother-infant Dyads in The Gambia

“…In the remaining instances, GBS was first isolated from both mother and infant at the 18 third timepoint (dyad 6, week 2) or from the mother prior to isolation from the infant (dyad 19 20). 20 21 22 Figure 2A&B: Phylogenetic relationship between GBS isolates from mother-infant dyad 23 17 and three other genomes (2 mothers and two infants) 24 The genomes are labelled with the dyad number from which they were derived. Mother17 & 25…”

“…Several studies have associated ST196 with serotype IV [22]. We are aware of only one other study which reported one strain out of 102 prospectively collected strains to be ST196 with a serotype II capsular backbone [23].…”

A fatal case of pneumococcal sepsis years after splenectomy

“…6,9 Since the implementation of these recommendations, the rate of invasive pneumococcal disease in Canada has been stable, at about 9.6 cases per 100 000. 10 There has been a decrease in the incidence of pneumococcal serotypes covered by Pneu-C-13, but also a possible increase in serotypes not covered by the pneumococcal vaccines, specifically in the asplenic population. 10,11 The current Canadian vaccine guidelines can be found online at www.…”

“…10 There has been a decrease in the incidence of pneumococcal serotypes covered by Pneu-C-13, but also a possible increase in serotypes not covered by the pneumococcal vaccines, specifically in the asplenic population. 10,11 The current Canadian vaccine guidelines can be found online at www. phac-aspc.gc.ca/publicat/cig-gci/index-eng.php.…”