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Wednesday, February 25, 2015

Streptococcus equi zooepidemicus


Keywords: Streptococcus equi var. zooepidemicus, infertility, equine

This image shows a culture of Streptococcus equi var. zooepidemicus on blood agar. The author's record is devoid of details for this image but it was probably isolated from a mare with endometritis because it is a common genital pathogen in mares.

Streptococcus equi var. zooepidemicus is also a common commensal bacterium, easily isolated from normal horses. This is important to bear in mind when cultures are positive for Streptococcus zooepidemicus because contamination from the perineal area will often produce false positive cultures.


Image size: 1664 x 1440px

The image shows beta hemolysis (complete hemolysis) around the colonies of bacteria. This is due to an exotoxin produced by many Streptococcal species. Some of those species cause partial hemolysis (alpha hemolysis) as well, but not Streptococcus equi var. zooepidemicus

Note: It is common for clinicians to refer Streptococcus equi var. zooepidemicus by its short form, Streptococcus zooepidemicus or even more colloquially,  "Strep zoo", forgetting perhaps that this bacterium is one of two subspecies of Streptococcus equi . The other is Streptococcus equi  var. equi , the well known cause of Strangles in horses. Streptococcus equi var. zooepidemicus is a gram-positive coccoid bacterium occurring in pairs or long chains on stained preparations. It is usually sensitive to penicillin and its derivatives.