The Occurrence of R‐protein Among Isolates of Group B Streptococci From Human Sources

Abstract

A total of 241 clinical isolates of group B streptococci were tested for presence of R‐protein by applying the double diffusion‐in‐gel technique on streptococcal extracts against monospecific anti‐R protein serum, radio‐labelled protein A and anti‐R protein serum or S. aureus, Cowan I coated with antibodies against group A streptococci, T‐type 28. The first two methods proved more sensitive than the latter. R‐protein was detected in 51% of 43 type II strains and in 87% of 102 type III strains, whereas none of 79 type Ia and none of 17 type Ib strains contained R‐protein. Among 30 isolates from blood and cerebrospinal fluid of infants with neonatal infections, R‐protein was detected in 43%, one of two type II strains and 12/14 type III strains. Tests of 37 paired strains from infant/mother pairs showed concordant results with respect to presence or absence of R‐protein in the isolates.