title: 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 clindamycin-resistant 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.
authors.affiliation: Public Health Ontario Laboratory, Toronto, Ontario, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Teatero
authors.affiliation: Departments of Laboratory Medicine and Pathology and Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Ferrieri
authors.affiliation: National Microbiology Laboratory, Winnipeg, Manitoba, Canada.
authors.forename: Irene
authors.initials: I
authors.lastname: Martin
authors.affiliation: National Microbiology Laboratory, Winnipeg, Manitoba, Canada.
authors.forename: Walter
authors.initials: W
authors.lastname: Demczuk
authors.affiliation: Mount Sinai Hospital, Toronto, Ontario, Canada.|Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Allison
authors.initials: A
authors.lastname: McGeer
authors.affiliation: Public Health Ontario Laboratory, Toronto, Ontario, Canada nahuel.fittipaldi@oahpp.ca.|Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nahuel
authors.initials: N
authors.lastname: Fittipaldi
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002170:Canada / Q000453:epidemiology; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology / Q000382:microbiology*; D011446:Prospective Studies; D012007:Rectum / Q000382:microbiology; D017422:Sequence Analysis, DNA; D065288:Serogroup; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000145:classification* / Q000187:drug effects; D014505:Urban Population; D014621:Vagina / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents
keywords: GBS vaccine; Streptococcus agalactiae; antibiotic resistance; colonizing GBS; group B Streptococcus; serotype IV; serotype switching