Abstract
Neonatal invasive disease caused by group B Streptococcus (GBS) represents a significant public health care concern globally. However, data related to disease burden, serotype distribution, and molecular epidemiology in China and other Asian countries are very few and specifically relative to confined regions. The aim of this study was to investigate the genetic characteristics of GBS isolates recovered from neonates with invasive disease during 2013–2014 at Guangzhou and Changsha hospitals in southern mainland China. We assessed the capsular polysaccharide type, pilus islands (PIs) distribution and hvgA gene presence in a panel of 26 neonatal clinical isolates, of which 8 were recovered from Early Onset Disease and 18 from Late Onset Disease (LOD). Among 26 isolates examined, five serotypes were identified. Type III was the most represented (15 cases), particularly among LOD strains (n = 11), followed by types Ib (n = 5), V (n = 3), Ia (n = 2) and II (n = 1). We performed whole-genome sequencing analysis and antimicrobial susceptibility testing on the 14 serotype III isolates belonging to the hypervirulent Clonal Complex 17 (serotype III-CC17). The presence of PI-2b alone was associated with 13 out of 14 serotype III-CC17 strains. Genome analysis led us to identify two multi-drug resistance gene clusters harbored in two new versions of integrative and conjugative elements (ICEs), carrying five or eight antibiotic resistance genes, respectively. These ICEs replaced the 16 kb-locus that normally contains the PI-1 operon. All isolates harboring the identified ICEs showed multiple resistances to aminoglycoside, macrolide, and tetracycline antibiotic classes. In conclusion, we report the first whole-genome sequence analysis of 14 GBS serotype III-CC17 strains isolated in China, representing the most prevalent lineage causing neonatal invasive disease. The acquisition of newly identified ICEs conferring multiple antibiotic resistance could in part explain the spread of this specific clone among Chinese neonatal isolates and underlines the need for a constant epidemiological surveillance.
Highlights
In the 1970s Streptococcus agalactiae emerged as predominant pathogen causing sepsis and meningitis in neonates and infants younger than 3 months in the United States and other Western countries (Baker, 2013)
This study reports the first whole-genome sequencing analysis of group B Streptococcus (GBS) clinical isolates collected in China from neonates with invasive disease
Among the 26 neonatal isolates analyzed in this study, we found that most were serotype III, and all type III except one belonged to the well-known hypervirulent CC17 lineage (Musser et al, 1989)
Summary
In the 1970s Streptococcus agalactiae (group B Streptococcus, GBS) emerged as predominant pathogen causing sepsis and meningitis in neonates and infants younger than 3 months in the United States and other Western countries (Baker, 2013). The introduction of national guidelines recommending universal screening of pregnant women for GBS carriage and use of intrapartum antibiotic prophylaxis during delivery has significantly reduced the incidence of EOD (Puopolo et al, 2005; Melin, 2011). These guidelines have no effect on LOD incidence and their implementation is not feasible in most low and middle-income countries (Dagnew et al, 2012; Johri et al, 2013). Alternative strategies, such as maternal immunization are under evaluation (Melin and Efstratiou, 2013; Nuccitelli et al, 2015; Donders et al, 2016)
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