Staining of coagulase-positive staphylococci with fluorescent antisera.

The fluorescent antibody staining technique was adapted by i\Ioody, Goldman, and Thomason (J. Bacteriol., 72, 357, 1956) for the identification of Mllalleomyces pseudomallei and has been used to identify additional microorganisms. This note reports the application of the direct fluorescent staining technique to the detection and identification of coagulase-positive staphylococci. Cowan (J. Pathol. Bacteriol., 48, 169, 1939) using the slide agglutination test, classified Staphylococcus aureus into three serological types which he designated as 1, II, and III. Christie and Keogh (J. Pathol. Bacteriol., 51, 189, 1940) tested a number of staphylococci and found that unadsorbed types I and II antisera agglutinated all coagulase-positive and none of the coagulasenegative staphylococci. Antisera were prepared against two strains of S. aureus, types I and II (ATCC no. 12598 Cowan type I; no. 12599 Cowan type II), according to the method described by Christie and Keogh. Both antisera reacted with the homologous and heterologous antigen to a titer of 1:1280. The antisera were conjugated with fluorescein isothiocyanate according to the method described by Riggs (Master's Thesis, University of Kansas, 1957). All smears were prepared by the direct staining technique and observed with a Leitz Ortholux microscope equipped with a 150 w ultraviolet light. Two hundred and eighteen coagulase-positive cultures isolated from human and animal sources were received and their coagulase activity retested with dehydrated plasma. The cultures were grown on nutrient agar slants at 37 C for 24 hr and smears were stained with unadsorbed fluorescent S. aureus types I and II antisera. Of the 218 cultures, 201 stained with type I antiserum and all 218 stained with type II antiserum. The two fluorescent antisera were then used to test 253 cultures of gram-positive cocci isolated from various food products. Of these, 44 were coagulase-positive. Forty-three stained with fluorescent type I antiserum and 44 stained with type II antiserum. All of the coagulase-negative cultures tested failed to stain with either of the fluorescent antisera. The growth from 10 Loeffler blood serum slants, inoculated from nose and throat swabs, 670 [VOL. 77 NOTES