Molecular Characteristics and Antimicrobial Resistance of Group B Streptococcus Strains Causing Invasive Disease in Neonates and Adults.

Lee-Chung Lin,Hsuan-Rong Huang,Shih-Ming Chu,Ming-Horng Tsai,Mei-Yin Lai,Jen-Fu Hsu,Ren-Huei Fu,Ming-Chou Chiang,Jang-Jih Lu

doi:10.3389/fmicb.2019.00264

Abstract

We aimed to analyze the molecular characteristics, clonality and antimicrobial resistance profiles of group B streptococcus (GBS) isolates collected in Taiwan from invasive diseases and carriage. Multilocus sequence typing (MLST) was used to assess the genetic diversity of 225 GBS strains from neonates and adults with invasive GBS diseases. 100 GBS strains collected from colonized pregnant women during the same period were compared, and all strains were characterized for one of nine capsule genotypes. We also determined the susceptibilities of all GBS isolates to various antimicrobial agents. The most frequently identified serotypes that caused invasive disease in neonates were III (60.6%) and Ia (17.3%), whereas type VI (32.7%), Ib (19.4%), and V (19.4%) were the most common to cause invasive disease in adults. Serotype VI was the leading type that colonized pregnant women (35.0%). Twenty-six sequence types (STs) were identified, and 90.5% of GBS strains were represented by 6 STs. ST-17 and ST-1 were more prevalent in invasive diseases in neonates and adults, respectively. The majority of serotype III and VI isolates belonged to clonal complex (CC)-17 and CC-1, respectively. ST-17 strains were more likely to cause meningitis and late-onset disease than other strains. In addition, ST-12 and ST-17 GBS strains showed the highest rate of resistance to erythromycin and clindamycin (range: 75.8–100%). In conclusion, CC-17/type III and CC-1/type VI are the most important invasive pathogens in infants and non-pregnant adults in Taiwan, respectively. GBS genotypes vary between different age groups and geographical areas and should be considered during GBS vaccine development.

Highlights

Streptococcus agalactiae is a commensal flora in human gastrointestinal and genitourinary tracts
Among the 225 invasive group B streptococcus (GBS) strains identified through the 10year period, 98 were isolated from adult patients, and 127 were isolated from neonates with either early-onset disease (n = 34) or late-onset disease (n = 93)
In all cases of GBS invasive diseases, the primary culture site was blood (n = 225), and GBS strains were isolated from the cerebrospinal fluid (CSF) in 20 neonates

Summary

Introduction

Streptococcus agalactiae (group B Streptococcus; GBS) is a commensal flora in human gastrointestinal and genitourinary tracts. One of the major contributors to virulence is the capsular polysaccharide antigen, which can be used to describe ten different GBS serotypes. Specific GBS serotypes are associated with antibiotic-resistant strains, neonatal diseases, or specific organ involvement (Ferrieri et al, 2013; Alhhazmi et al, 2016). GBS isolates can be further grouped into different sequence types (STs) using multilocus sequence typing (MLST) that identifies sequence variation among conserved housekeeping genes. Some clonal complexes (CCs), defined as genetically related STs that are grouped into clusters following phylogenetic analyses, are associated with multidrug-resistant GBS strains, hypervirulent strains, or clinically important GBS strains (Nagano et al, 2012; Campisi et al, 2016; Martins et al, 2017)

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