The surveys concerning the microflora of external ocular infections in the United States generally indicate that staphylococci are the commonest bacteria encountered.* Therefore, the need commonly arises (for obvious epidemiologic, bacteriologic, and clinical reasons) to differentiate the pathogenic from the nonpathogenic strains. In the past such criteria as hemolysis on blood plates, fermentation of mannitol, pigmentation, and liquefaction of gelatin have been employed. However, it is generally agreed that these characteristics can only serve as presumptive evidence of pathogenicity, since the nonpathogenic strains may also exhibit similar reactions, usually to a slighter degree. Furthermore, the pathogenic strains may vary considerably in their biochemical reactions as well as in the production of pigment.
The ability of certain staphylococci to coagulate citrated or oxalated plasma was first described in 1903 by Loeb.4 Cruickshank5 and Thygeson, as well as others, maintain that the coagulase test is the most reliable and convenient
SUIE T, TAYLOR FW. Incidence of Coagulase-Positive Staphylococci in external Ocular Infections. AMA Arch Ophthalmol. 1955;53(5):706-707. doi:10.1001/archopht.1955.00930010714015