Streptococcus salivarius

Streptococcus salivarius is a species of spherical, gram-positive, facultative anaerobic lactic acid bacteria that is both catalase and oxidase negative. S. salivarius colonizes (usually in chains) the oral cavity and upper respiratory tract of humans just a few hours after birth, making further exposure to the bacteria harmless in most circumstances. The bacterium is considered an opportunistic pathogen, rarely finding its way into the bloodstream, where it has been implicated in cases of sepsis in people with neutropenia, (a deficiency in white blood cells).