Epidemiology of Invasive Group B Streptococcal Disease in Alberta, Canada, from 2003 to 2013

Abstract

bGroup B streptococci (GBS) cause severe invasive disease in both neonates and adults. Understanding the epidemiology of GBS provides information that can include determining disease prevalence rates in defined populations and geographic regions, documenting the success of GBS screening programs, and understanding antimicrobial susceptibility patterns. In Alberta, only neonatal invasive GBS (iGBS) disease is notifiable to health authorities. We performed a surveillance study of iGBS in Alberta, Canada, from 2003 to 2013. Over the 11-year period, the disease incidence rate increased from a low of 3.92 cases/100,000 population to a high of 5.99 cases/100,000 population. Clindamycin resistance also increased, from 12.2% to 32.5%. In summary, Alberta, Canada, has experienced an increase in GBS disease; the increase includes both neonatal and adult disease. CPS IV cases also notably increased during the surveillance period, as did resistance to erythromycin and clindamycin.

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

“…However, all of the colonizing ST17 serotype III isolates that we identified possessed the hvgA gene. Interestingly, this gene has recently been described among serotype IV ST459 invasive GBS isolates from Alberta, Canada (31). The emergence of serotype IV GBS as an agent of invasive disease, particularly among adults, was first reported in the United States (27,46) and later in Canada (31,34).…”

“…Interestingly, this gene has recently been described among serotype IV ST459 invasive GBS isolates from Alberta, Canada (31). The emergence of serotype IV GBS as an agent of invasive disease, particularly among adults, was first reported in the United States (27,46) and later in Canada (31,34). Frequencies of less than 1% were common in the 1990s (46) but have increased to 6 to 12% in populations studied between 2008 and 2015 (27,29,30,47).…”

“…For example, earlier reports from Minnesota described the isolation of serotype IV GBS strains belonging to different STs among isolates of both colonizing and neonatal invasive GBS in the United States (27,28). We and others recently described an increase in the frequency of isolation of serotype IV strains among invasive GBS infections in Canada (29)(30)(31). In addition, as exemplified by polyvalent conjugate pneumococcal vaccination schemes (32), vaccinating with the GBS trivalent formulation may select for vaccine escape recombinants through capsular switching.…”

Identification of Group B Streptococcus Capsule Type by Use of a Dual Phenotypic/Genotypic Assay

“…No CPS type VII except for the reference strain was present in our collection; therefore, no clinical CPS VII isolates were assayed (15). We compared the CPS typing by the duplex RT-PCR assay against serotyping by the immunodiffusion assay for CPS types Ia, Ib, and II to VIII or a previously described PCR assay (40) for CPS type IX.…”

“…An important virulence factor of GBS is a capsular polysaccharide (CPS); there are ten antigenic CPS variants designated Ia, Ib, and II to IX (8)(9)(10)(11). In North America and a number of European countries, five CPS types (Ia, Ib, II, III, and V) cause the bulk of invasive disease cases, with CPS III causing a higher rate of disease among neonates and CPS types Ia and V causing higher rates among adult patients (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Interestingly, recent studies have noted the emergence and circulation of CPS IV, a previously uncommon serotype, as an important cause of both neonatal and adult infections (14,19,(24)(25)(26)(27)(28).…”