Bioingeniøren (Jun 2011)
Occurence of the alp3 gene and the R28 protein in Group A streptococci
Abstract
Background: The protein R28 of group A streptococci (GAS) is nearly identical in structure to the alpha-like protein Alp3 of group B streptococci (GBS), and the two proteins cross-react immunologically. The purpose of this study was to test the frequency of occurrence of R28 in GAS isolated from patients in Norway and to test if genes which encode some other important GBS proteins can be found in GAS. Materials and methods: 88 clinical GAS isolates were tested for possession of the genes encoding the surface-anchored and strain-variable GBS proteins Cß, Cα, Alp1, Alp2, Alp3, Alp4, and R4(Rib). In addition, 22 of the isolates were tested by Western blotting for expression of the GBS protein R3. Results and conclusions: The gene alp3 encoding the protein R28 in GAS and Alp3 in GBS was detected in 26% of the GAS isolates, significantly more often in GAS cultured from skin and soft tissue infection sites than in GAS from blood cultures or from the respiratory tract. Western blotting confirmed that alp3 PCR positive GAS strains expressed a high-molecular-mass protein, R28, but not alp3 negative isolates. None of the other GBS genes or the protein R3 were detected in the GAS isolates. The results suggest that R28 imparts advantages to GAS in the capacity to cause skin and soft tissue infection, for instance by functioning as an adhesin.
