What are group B streptococci and how are they classified?
Lancefield group B streptococci (GBS), also called Streptococcus agalactiae, form part of the normal bacterial flora of the female genital tract and can be part of normal skin and gut bacteria of men or women. Under certain conditions, GBS can act as an opportunistic pathogen, causing serious disease. The term group B refers to the presence of a particular antigen on the surface of the bacterium, which is used for laboratory identification. Streptococci are grouped according to these surface antigens, each type of antigen being allocated a letter of the alphabet; hence we have Lancefield groups A to W (excluding I and J), named after Dr Rebecca Lancefield who first devised this classification scheme. Streptococci are also classified into pyogenic (‘pus-forming’) streptococci, which include groups A, B, C, and G, and non-pyogenic (non “pus-forming’) streptococci which encompasses the mitis, anginosus, bovis, salivarius and mutans sub-groups. Streptococcus pneumoniae, otherwise known as
