DIAGNOSTIC REAGENTS 331 



coagulase positive staphylococci will clot Bacto-Coagulase Plasma within one 

 hour. A second reading should be made, however, after three hours incubation 

 at 37°C., before the organism can be regarded as coagulase negative. Any degree 

 of clotting, however slight, is considered positive. 



Bacto-Coagulase Plasma is satisfactory for the slide technique as reported by 

 Chapman!^ ^j^^j Moss.^^ It is also satisfactory for the slide test as described by 

 Cadness-Graves, Williams, Harper and Miles,^^ discussed by Needham, Ferris 

 and Spink, -1 This technique is particularly useful for presumptive identification 

 or screen test for coagulase positive staphylococci in large scale bacteriological 

 surveys. This test is performed by preparing a homogeneous suspension of a 

 suspected colony in a drop of water on a slide with a minimum of spreading. Mix 

 a large loop of rehydrated Bacto-Coagulase Plasma with the suspension. Coagu- 

 lase positive staphylococci will produce macroscopic clumping within 5-15 

 seconds. Delayed clumping is not indicative of a positive test. Morphological con- 

 firmation by the Gram stain is made simultaneously. 



Bacto-Coagulase Plasma is stable when stored in the refrigerator. The plasma 

 solution prepared from Bacto-Coagulase Plasma may be kept in the refrigerator 

 for several days without loss of potency. It is not satisfactory for use, however, 

 if gross contamination occurs. After being kept in the refrigerator the plasma 

 solution is cold enough to delay clotting for 10-15 minutes. This delay can be 

 prevented by warming the plasma solution to 37°C. before use. Caution: Bacto- 

 Coagulase Plasma must be kept in the refrigerator in order to preserve its sta- 

 bility. 



ij. Bact., 41:431:1941. 12 J. Bact., 47:211:1944. 



2 Science, 95:416:1942. ^ J. Bact., 50:119:1945. 



8 J, Med. Res., 10:407:1903. "J. Bact., 50:234:1945. 



*Zentr. Bakt. I Abt. Orig., 99:74:1926. is Trans. N. Y. Academy Sciences, 9:52:1946. 



6 J. Bact., 28:343:1934. i^J. Bact., 52:151:1946. 



^Proc. Sec. Exp. Biol. Med., 36:789:1937. "J. Bact., 53:367:1947. 



Path. Bact., 45:295:1937- ^^ J- Bact., 55:793:1948. 



Bact., 35:311:1938. 1^ Personal Communication. 



J. Path. Bact., 50:83:1940. 20 Lancet, 1:736:1945. 



"Am. J. Clin. Path., 11:857:1941. 21 Am. J. Clin. Path., Tech. Supp., 9:83:1945. 

 ^J. Bact., 41:431:1941. 



ij; 



BAGTO-SENSITIVITY DISKS (B403) 



Bacto-Sensitivity Disks are sterile paper disks containing known amounts of the 

 more commonly employed antibiotics and other therapeutic agents. They are 

 recommended as a rapid, practical, clinically accurate and inexpensive means of 

 determining the relative sensitivity of microorganisms to these therapeutic agents. 

 Bacto-Sensitivity Disks are especially valuable in selecting the antibiotics effec- 

 tive against chronic or persistent infections refractory to primary antibiotic 

 therapy. Three concentrations of each antibiotic are available, indicating if the 

 microorganism is very sensitive, moderately sensitive, slightly sensitive or resist- 

 ant. With proper interpretation the bacterial susceptibilities as determined with 

 these Disks give the clinician a qualitative in vitro measure of sensitivity equal to 

 that of any other procedure with less effort and often without the added time 

 necessary for pure culture isolation as in the test tube method. Bacto-Sensitivity 

 Disks are available containing three concentrations of Aureomycin, Bacitracin, 

 Chloromycetin®*, Dihydrostreptomycin, Penicillin, Polymyxin B (Aero- 

 sporin®**). Streptomycin and Terramycin. 



The use of paper disks in testing the potency of penicillin and other bacterio- 



* Chloramphenical: Parke, Davis and ** Polymyxin B: Burroughs Wellcome and 



Company. Company. 



