Clonal Analysis of Colonizing Group B Streptococcus , Serotype IV, an Emerging Pathogen in the United States

Abstract

Colonizing group B Streptococcus (GBS) capsular polysaccharide (CPS) type IV isolates were recovered from vaginal and rectal samples obtained from 97 (8.4%) nonpregnant women of 1,160 women enrolled in a U.S. multicenter GBS vaccine study from 2004 to 2008. Since this rate was much higher than the rate of prevalence of 0.4 to 0.6% that we found in previous studies, the isolates were analyzed by using surface protein profile identification, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) to characterize them and identify trends in DNA clonality and divergence. Of the 101 type IV isolates studied, 53 expressed ␣ and group B protective surface (BPS) proteins, 27 expressed BPS only, 20 expressed ␣ only, and 1 had no detectable surface proteins. The isolates spanned three PFGE macrorestriction profile groups, groups 37, 38, and 39, of which group 37 was predominant. The isolates in group 37 expressed the ␣ and BPS proteins, while those in groups 38 and 39 expressed the ␣ protein only, with two exceptions. MLST studies of selective isolates from the four protein profile groups showed that isolates expressing ␣,BPS or BPS only were of a new sequence type, sequence type 452, while those expressing ␣ only or no proteins were mainly of a new sequence type, sequence type 459. Overall, our study revealed a limited diversity in surface proteins, MLST types, and DNA macrorestriction profiles for type IV GBS. There appeared to be an association between the MLST types and protein expression profiles. The increased prevalence of type IV GBS colonization suggested the possibility that this serotype may emerge as a GBS pathogen.

Epidemiological surveillance of colonising group B Streptococcus epidemiology in the Lisbon and Tagus Valley regions, Portugal (2005 to 2012): emergence of a new epidemic type IV/clonal complex 17 clone

“…The same scenario was observed among neonatal (2/64 cases; 3%) for the years 2000 to 2004 [12] and non-pregnant adult infections (2/225 cases; 1%) from 2001 to 2008 [14]. After 2010, reports from Brazil Ireland and the US [15][16][17][18] revealed an increased prevalence of serotype IV in colonisation and infection, suggesting the possibility that this serotype could be emerging as an important pathogen, as happened with serotype V during the 1990s [19].…”

“…This situation has changed in the last decade, when some countries, including the US, saw the emergence of serotype IV among colonising and invasive GBS isolates [15,16]. This scenario may become risky if the emergence of serotype IV combines with antibiotic resistance, which was the case in our study where co-resistance to second-line macrolide antibiotics was observed in recent years (2010-2012).…”

“…The sudden increase of GBS serotype IV detection in different countries does not rely on the emergence of type IV/CC17 only, as other genetic lineages (such as CC1 and CC23) or different types of pulsed-field gel electrophoresis have been identified, constituting the majority of the serotype IV isolates [15][16][17][18]20]. A careful surveillance of GBS type IV/ST291 emergence is recommended, in order to define its host specificity, tropism, virulence potential and antibiotic resistance phenotype.…”

Emergence of Serotype IV Group B Streptococcus Adult Invasive Disease in Manitoba and Saskatchewan, Canada, Is Driven by Clonal Sequence Type 459 Strains

“…To our knowledge, this proportion is the highest ever reported for serotype IV GBS adult invasive disease. While we did not characterize the GBS serotype distribution among colonized pregnant women (these studies are under way in our laboratories), others have observed increasing numbers of serotype IV strains among colonizing isolates (17,18,(38)(39)(40). Studies aimed at developing a capsular polysaccharide antigen-based GBS vaccine are ongoing worldwide, with several formulations that do not include serotype IV already under clinical trials (41).…”

“…In the United States, longitudinal surveillance suggests that the proportion of serotype IV GBS isolates from nonpregnant adults increased from 0.2% in 1998 to 1999 to 5.7% in 2005 to 2006 (2). In 2010, serotype IV strains were shown to be responsible for 16% of early onset neonatal infections in the state of Minnesota (17,18). Consistent with this emergence, when we characterized a collection of 600 invasive strains from the province of Ontario, Canada, we found that serotype IV isolates were responsible for 6.2% of cases of GBS invasive disease (19).…”