Bacterial genetics and human immunity to group B streptococci.
Serotype III group B Streptococcus agalactiae (GBS) are the most common cause of neonatal sepsis and meningitis. We have classified type III GBS by restriction digest patterns of chromosomal DNA and demonstrated that a subgroup of genetically related strains (RDP type III-3) causes the majority of type III GBS neonatal infection. Genetic differences between type III GBS strains contribute significantly to differences in virulence and host immune responses. While 100% of less virulent RDP type III-1 and III-2 organisms express C5a-ase, an inhibitor of neutrophil chemotaxis, only 63% of virulent RDP type III-3 isolates have functional C5a-ase. Functional differences in type III GBS C5a-ase are attributable to a shared genetic polymorphism, supporting our genetic classification. The mean capsular sialic acid content of virulent RDP type III-3 strains is significantly higher than that of less virulent strains, suggesting that capsular sialylation is also genetically regulated. C5a-ase is not critical for all RDP type III-3 strains to be invasive because the higher capsular sialic acid content of III-3 strains limits complement activation. The identification of these and additional genetic differences between GBS strains has important implications for our understanding of the pathogenesis of these important human infections.
Adderson
E E
EE
Department of Infectious Diseases, St. Jude Children's Research Hospital, 332 N. Lauderdale Street, Memphis, Tennessee 38105, USA.
Takahashi
S
S
Bohnsack
J F
JF
D018829:Adhesins, Bacterial; D010450:Endopeptidases / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D007231:Infant, Newborn; D013045:Species Specificity; D013290:Streptococcal Infections / Q000209:etiology / Q000276:immunology*; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
D018829:Adhesins, Bacterial; D010450:Endopeptidases; C053088:C5a peptidase