Background:
Invasive group B Streptococcus (GBS) is a worldwide healthcare concern among pregnant women and neonates, however, severe adult infections are a growing concern. GBS serotype VIII is rare having a low incidence and limited worldwide distribution. In Alberta (pop. 4.44 million), invasive infection due to serotype VIII is uncommon with 3 cases from 2003 to 2016 (14 years). From 2017 to 2021, invasive GBS cases due to serotype VIII increased. Here, we characterize 11 invasive serotype VIII isolated in Alberta from 2017–2021 (5 years).
Methods:
GBS serotype VIII were identified by multiplex PCR and sequenced. Genomes were subjected to molecular typing, virulence/antimicrobial resistance factor identification, and phylogenetic/pangenomic analysis. Trends in demographic and antimicrobial susceptibility data were evaluated.
Results:
Eleven cases of invasive serotype VIII were identified, with one case in 2017, two cases per year from 2018–2020, and four cases in 2021. Ten isolates were identified in individuals aged 50–80 years. The isolates comprised three sequence types (ST1, 2, 42), with ST42 being predominant (n=7). All isolates were susceptible to penicillin, erythromycin, clindamycin, chloramphenicol, and vancomycin, apart from a single isolate that exhibited erythromycin and inducible clindamycin resistance. Isolates carried resistance determinants implicated in peptide antibiotic (n=11), tetracycline (n=2), and macrolide/lincosamide/streptogramin resistance (n=1). All genomes carried multiple virulence factors, such as adherence and immune modulation factors, exoenzymes, and exotoxins.
Conclusions:
Invasive isolates of GBS serotype VIII have increased in Alberta. Infections were predominantly caused by ST42 and primarily affected older adults. Characterization and continued surveillance of this rare serotype can inform epidemiology and contribute to possible outbreak prevention.