Application of Fluorescent Antibody for Detecting Capsular Substances in Staphylococcus aureus

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.

Induction of Resistance with Heat‐Killed Unencapsulated Strains of Staphylococcus epidermidis against Challenge with Encapsulated Strains of Staphylococcus epidermidis

“…Absorption of protective antibodies in rabbit hyperimmune sera prepared with unencapsulated strains of Staphylococcus epidermidis with cell surface polysaccharide of strain SE-360 those rabbit hyperimmune sera prepared with the encapsulated strains. This situation is similar to that described concerning the production of capsular-type antigens in unencapsulated strains of S. aureus (17,18,23), although the amounts produced were small for these strains in comparison to those for the encapsulated strains in both instances. Therefore, association with the production of capsular antigen is a regular phenomenon among ordinary strains of S. epidermidis (6).…”

The Expression of Capsule in Serum-Soft Agar by Staphylococcus Aureus Isolated From Human Clinical Sources

“…After laboratory subculture, 35% of 77 isolates showed evidence of encapsulation when assessed by the SSA technique, a prevalence which is significantly higher than that reported previously from human clinical cases (Yoshida, 1971;Yoshida et al, 1979). Nonetheless, this was still considerably less than was reported for isolates from bovine mastitis of which > 90% were encapsulated when examined by a similar technique .…”

“…Examination of large numbers of hospital isolates by the latter method in two studies yielded 4.2% and 3.8% encapsulated organisms respectively (Yoshida et al, 1970;Yoshida et al, 1979). Similar levels were reported for S. aureus strains isolated from bovine mastitis (Yokomizo et al, 1977).…”

“…The capsule on the Smith strain is large and easily observed while on other strains that produce diffuse colonies in SSA it is not, yet such strains show evidence of additional surface components by fluorescence microscopy (Yoshida et al, 1979) and by electronmicroscopy . Electronmicroscopy and biochemical analysis of the surface components of microbes has created confusion in terminology (Bowles and Marsh, 1982), and controversy over the definition of encapsulation of S. aureus is long standing (Mudd, 1965).…”

“…Recently, when milk from cows with mastitis was inoculated directly into serum-soft agar (SSA) 90% of the S. aureus isolates showed evidence of capsules but the majority lost their capsule on subculture Opdebeeck and Norcross, 1983). Furthermore, capsular antigen has been identified by fluorescence microscopy on strains considered to be negative when assessed in SSA (Yoshida et al, 1979). However, by appropriate manipulation of the growth environment, expression of the capsule in SSA has been induced in strains not previously exhibiting this characteristic (Yoshida et al, 1974;Opdebeeck et al, unpublished observation).…”