620 LABORATORY HINTS 



The Staphylococcus pyogenes aureus. 



Occurs as a diplococcus in grape-like masses, non-motile, no 

 spores. Gram-posilive. General turbidity in broth, liquefies gelatin 

 with an orange-yellow sediment, on agar and blood serum a pale, then 

 later a golden streak is formed. Staphylococcus pyogenes albus pro- 

 duces a white and Staphylococcus pyogenes citreus a lemon-yellow 

 growth on agar and blood serum. 



The Bacillus pyocyaneus. 



A small bacillus found in blue-green pus, very motile. Non- 

 sporing. Creamy growth on agar with greenish fluorescence, liquefies 

 gelatin rapidly. Gram-negative. The pigments, pyocyanin and pyo- 

 xanthin, can be extracted with chloroform. 



The Streptococcus pyogenes. 



In chains, ten to fifteen bacteria in pus, thirty to forty bacteria in 

 broth cultures. Gram-positive. Grows well with or without oxvgen. 

 Produces turbidity in broth, but growth ceases after four days owing 

 to the production of an inhibitory metabolic substance. Slow growth 

 on gelatin without liquefaction. Coley's fluid is from Streptococcus 

 pyogenes and Bacillus prodigiosus, grown together for two weeks and 

 sterilized by heat 65° C. 



The Gonococcus. 



Small coffee-bean in shape, usually in pairs, a strict parasite. 



Does not grow on ordinary media, but can be cultivated on blood 

 or blood serum agar. A pure culture has a raised greyish-white 

 mulberry appearance. 



The Meningococcus. 



The Diplococcus intracellularis meningitidis is Gram-positive. 



Grows on blood agar at blood heat, occurs within the pus cells as 

 a diplococcus, produces epidemic cerebrospinal meningitis (or spotted 

 fever). 



The Diplococcus pneumoniae. 



Usually seen as a diplococcus, but sometimes in chains of pus. 



The cocci are oval or lance-shaped in a gelatinous capsule. 



Gram-positive. Grows well on blood serum, but not readily seen. 



Does not grow well on gelatin. In cultivation the capsule is lost. 



No growth on potato. Produces curdling and acid with milk. 



The Micrococcus melitensis. 



Small, in pairs or singly or short chains with active Brownian 

 movement. Slow growth, in three to four days small semi-transparent 

 droplets on agar, which later become yellowish-orange. On gelatin 

 a dirty white streak without liquefaction. Gram-negative. It occurs 

 in the blood and milk of goats. 



