Application of Fluorescent Antibody for Detecting Capsular Substances in Staphylococcus aureus

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Abstract
A fluorescent antibody technique was developed for the determination of the capsular‐type of strains of Staphylococcus aureus. It compared favourably with the method using serum‐soft agar (Yoshida 1972). With the new technique, many populations of encapsulated and unencapsulated strains were investigated. Of 1421 fresh isolates of Staph. aureus, 54 were encapsulated and among these 54·8% and 48·1% were mono‐ and polyvalent, respectively. Capsular‐type antigens A and B were found in 92·5% and 44·4% of strains respectively; capsular‐types C and D were found relatively infrequently. In the other group, of unencapsulated strains, capsular‐type antigen production was demonstrated in 125 out of 163 strains examined. Mono‐ and polyvalent capsular‐types (A and B antigen producing strains) comprised 77·6% and 22·4%. respectively. In these capsular‐types A and B were found in 54·4% and 62·4%, respectively: capsular‐type antigen C and D producing strains were again infrequent. These results indicate that a majority of ordinary Staph. aureus strains produce capsular‐type antigens although isolation of the encapsulated strains is infrequent.