610 



STAPHYLOCOCCUS 



infundibuliform or saccatte, by the yellow cocci crateriform. The time of its 

 appearance is likewise subject to a considerable amount of variation ; it may be 

 noticeable after 2 days, or it may be a fortnight or even longer before it becomes 

 apparent. Speaking broadly, it may be said that the pyogenic staphylococci 

 liquefy gelatin early, the saprophytic ones late. 



On potato there is a moderate confluent growth. Loeffler's serum is a good 

 nutritive medium, on which pigment is well developed. On MacConkey's neutral 

 red lactose bile salt agar, the colonies are very small, pale pink after 24 hours, 

 and deep pink after 48 hours. 



Working with pure cultures, Chapman and Berens (1935) and Chapman (1936) find 

 that, on proteose peptone lactose agar containing a concentration of 1-300,000 crystal 

 violet, white, violet, or orange colonies with a violet fringe may be formed. As a rule, 

 the strains giving rise to either of the latter two types of colony are hsemolytic, produce 

 coagulase, and are toxic to rabbits on intravenous inoculation, while strains forming 

 white colonies are negative in all these respects. More recently. Chapman and his col- 

 eagues (1937) have described a proteose peptone lactose agar, pH 8-6, containing 0-017 per 

 cent, bromthymol blue, that is said to inhibit the growth of non-pathogenic staphylococci ; 

 and Chapman (1944) has described an alkaline bromthymol blue agar containing potassium 

 tellurite for isolation of staphylococci from the faeces. 



Variant colonial types — including rough and G forms — have been described by 

 HofFstadt and Youmans (1932), Bigger, Boland, and O'Meara (1927), and Swingle 

 (1935). 



Metabolism. — The staphylococci are facultative anaerobes, growing best in the 

 presence of oxygen. On agar plates incubated anaerobically, the growth tends to 

 spread out on the surface of the medium, so that the colonies instead of being 

 convex, are flat and effuse. Lubinski (1894) was the first 

 to point out that no pigment is produced under anaerobic 

 conditions, though, if a culture which has been incubated 

 anaerobically is exposed to the air, it soon develops its 

 characteristic colour. He found, however, that continuous 

 anaerobic cultivation generally caused a strain to lose its 

 power of producing pigment — a power which was not re- 

 gained by subsequent cultivation in the presence of 

 oxygen. 



The limits of temperature between which growth is pos- 

 sible are wide, varying from about 12° to 45° C, but as a rule 

 development is most rapid at 37° C. A slightly alkaline 

 medium of pH 7 -4-7 -6 is preferable for the initiation of 

 growth, but some growth will occur even at pH 4-0-5-0. 

 Growth is slightly increased by the addition of blood and 

 glucose to the medium ; serum has no beneficial effect. 

 According to Hucker (1924rt),the staphylococci are unable to 

 use ammonium salts as their sole source of nitrogen. Hughes 

 (1932), and later Knight (1935), both of whom have studied 

 the nutritive requirements of Staph, aureus, describe the 

 existence of an essential growth factor, which subsequent 

 Fig. V11.~ Staphy- work (Knight 1937) has shown to contain vitamin Bj and 



lococcvs aureus. nicotinic acid. The organisms can now be grown aerobically 



Agar stroke culture, . . ° , , i • i .-. i. 



24 hours 37° C on a medium contaimng only known chemical constituents, 



