Molecular epidemiology of group B streptococci in Ireland reveals a diverse population with evidence of capsular switching

Abstract

The molecular epidemiology of group B Streptococcus (GBS) in Ireland was investigated. Invasive (n = 132) and non-invasive (n = 45) isolates, collected in 2007-2011, were analysed by multilocus locus sequence typing, capsular polysaccharide (CPS) serotyping, profiling of surface proteins, pilus islands (PI), and antimicrobial susceptibility. Isolates grouped into 45 sequence types and five main clonal complexes (CC). CC1, CC17 and CC23 represented 67.2 % of isolates and the most prevalent serotypes Ia, III and V. Serotype and surface protein genes were largely predictive of CC. Accordingly, CPS V/alp3, CPS Ib/CPS II/bca + bac, and CPS Ia/eps predominated in CC1, CC12 and CC23, respectively, and CPS III/rib in CC17 and CC19. Supporting their vaccine potential, all isolates harboured at least one PI, of which the PI-1 + PI-2a combination was most prevalent. Macrolide resistance was found in 18.6 % of isolates. erm(B) and the globally disseminated CC1/CPS V were the most common resistance mechanism and CC/CPS type, respectively. CC17, significantly associated with neonatal disease, was also prevalent in pregnant adults, but was underrepresented among non-pregnant adults. Two of 46 CC17 isolates (typically CPS III) were CPS IV. Sequence analysis confirmed capsular switching and their relatedness to CC17/CPS IV strains recently characterized in France. CPS IV, detected only in invasive isolates (6.8 %), was most prevalent in adults (12 %) and showed an increase in prevalence to that reported (1.4 %) for invasive isolates in Ireland 1997-1999. Increases in serotype IV and evidence of capsular switching in CC17 highlights the importance of ongoing surveillance of GBS and may have implications for vaccine development strategies.

Association between capsular serotype V and macrolide resistance in group B Streptococcus

“…This is in line with previous findings in the Asia, Europe and the United States (Table 1 [ [6][7][8][9][10][11][12][13][14][15][16][17][18][19]). In the study by Morozumi et al [2], 7/32 (21·9%) serotype Ia and 24/88 (27·3%) serotype III GBS isolates showed ML resistance.…”

Molecular Characteristics of Group B Streptococci Isolated from Adults with Invasive Infections in Japan

“…Although relationships between serotypes and CCs have been reported in various countries (29)(30)(31)(32)(33), the prevalence was different among the studied population.…”

“…These hvgA-positive strains were obtained from adult patients. Almost all serotype IV strains were detected in invasive isolates from adults, and these have been reported to be increasing (29,37). Capsular switching may interfere with current efforts to develop GBS vaccines since serotype IV is not included (38).…”

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

“…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). The emergence of serotype IV GBS among colonizing isolates has also been noticed in the United States (28) and Europe (48).…”