Serotype IIIStreptococcus agalactiaefrom Bovine Milk and Human Neonatal Infections1

John F Bohnsack,April A Whiting,Anne J Blaschke-Bonkowsky,Gabriela Martinez,Nicola Jones,Naiel Bisharat,Elisabeth E Adderson,Shauna Detrick,Marcelo Gottschalk

doi:10.3201/eid1008.030917

Abstract

Streptococcus agalactiae (group B streptococcus [GBS]) causes invasive human infections and bovine mastitis. This study examined the genetic relationship between bovine and human serotype III GBS by using molecular techniques that classify human serotype III GBS into four distinct phylogenetic lineages. Bovine serotype III GBS were largely contained in two lineages, which are distinct from the two major lineages (restriction digest types III-2 and III-3) that infect human neonates. One of the bovine lineages closely resembles the human III-1 lineage, whose members occasionally cause human neonatal infections. The bovine strains in the other lineage characteristically have an initiation factor IF2 gene (infB) H allele and multilocus sequence types that are not found in human GBS strains. Evidence suggests that this "H allele" lineage is related to the human III-3 lineage. These results support the assertion that human and bovine GBS are largely unrelated and provide further insight into the genetic relation between human and bovine GBS.

Highlights

IntroductionStreptococcus agalactiae (group B streptococcus [GBS]) causes invasive human infections and bovine mastitis
Streptococcus agalactiae causes invasive human infections and bovine mastitis
Serotype III GBS that bear the D allele are unlikely to be isolated from humans because all human GBS strains bearing the D allele have far been serotype Ia

Summary

Introduction

Streptococcus agalactiae (group B streptococcus [GBS]) causes invasive human infections and bovine mastitis. Bovine serotype III GBS were largely contained in two lineages, which are distinct from the two major lineages (restriction digest types III-2 and III-3) that infect human neonates. The bovine strains in the other lineage characteristically have an initiation factor IF2 gene (infB) H allele and multilocus sequence types that are not found in human GBS strains. Evidence suggests that this “H allele” lineage is related to the human III-3 lineage. Serotype III Streptococcus agalactiae be assigned to each restriction digest pattern type by a distinct set of molecular markers, which include analysis of nucleotide substitutions in the centrally conserved region of the translation infB, the presence or absence of the inserted sequences GBSi1 and IS1548 in three chromosomal loci, and MLST [9,11]

Methods

Results

Conclusion