Streptococcus salivarius is a species of spherical

Sphere

A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

, Gram-positive

Gram-positive

Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 bacteria which colonize the mouth and upper respiratory tract

Upper respiratory tract

The upper respiratory tract or upper airway primarily refers to the parts of the respiratory system lying outside of the thorax or above the sternal angle. Another definition commomly used in medicine is the airway above the glottis or vocal cords...

 of humans a few hours after birth, making further exposure to the bacteria harmless. The bacteria is considered an opportunistic pathogen

Opportunistic infection

An opportunistic infection is an infection caused by pathogens, particularly opportunistic pathogens—those that take advantage of certain situations—such as bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, one with a healthy immune system...

, rarely finding its way into the bloodstream, where it has been implicated in septicemia cases in people with neutropenia

Neutropenia

Neutropenia, from Latin prefix neutro- and Greek suffix -πενία , is a granulocyte disorder characterized by an abnormally low number of neutrophils, the most important type of white blood cell...

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S. salivarius has distinct characteristics when exposed to different environmental nutrients. For example, in the laboratory, if a SYTA plate is used, then S. salivarius is able to use the sucrose in the SYTA plate to produce a capsule around itself. However, if grown on GYC plate, with no sucrose, instead only glucose, then S. salivarius is not able to make a capsule from glucose.

More importantly, in the laboratory, S. salivarius can show a distinct clearing on GYC plates. This is because S. salivarius can ferment the glucose yielding lactic acid. Next, the lactic acid actually reacts with the calcium carbonate in the GYC plate, resulting in zones of clearings on the plate.http://www.phac-aspc.gc.ca/msds-ftss/msds149e.html

Agglutination

Agglutination (biology)

Agglutination is the clumping of particles. The word agglutination comes from the Latin agglutinare, meaning "to glue."This occurs in biology in three main examples:...

 of Streptococcus salivarius is often used in the diagnosis of atypical pneumonia

Atypical pneumonia

Atypical pneumonia aka "walking pneumonia" is a pneumonia not caused by one of the more traditional pathogens, and with a clinical presentation inconsistent with typical pneumonia. It can be caused by a variety of microorganisms...

 caused by Haemophilus influenzae

Haemophilus influenzae

Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...

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