PFEIFFERELLA MALLEI 491 



cultures there may be great variation in length and to a less extent in thickness ; 

 long filaments showing true or false branching, club, pear, flask, and other irregular 

 forms have been described. Staining is usually uneven, deeply stained alternating 

 with poorly stained or unstained areas ; bipolar staining is common. Non-motile ; 

 non-capsulated ; non-sporing ; Gram-negative ; non-acid-fast. 



Agar Plate. — 2 days at 37° C Round, convex, amorjihous, translucent, greyish-yellow 

 colonies, 0-5-1 -0 mm. in diameter, with smooth glistening surface and entire edge ; 

 butyrous in consistency and easily emulsifiable. 9 days, colonies are 1-2 mm. in 

 diameter, more opaque, and may have a very finely granular surface ; sometimes 

 the centre is coloured shghtly brown. 



Agar Slope. — 2 days at 37° C. Moderate, confluent, raised, greyish-yellow, translucent 

 growth with beaten-copper surface and edge undulate or formed of single colonies. 

 Medium unchanged. Not so profuse as growth of Bad. colt. 



Gelatin Stab. — 7 days at 20° C. Poor to moderate, fihform growth, extending nearly to 

 the bottom of the tube, and consisting of small discrete colonies ; raised surface 

 growi,h about 3 mm. in diameter. No liquefaction. After 6 weeks the growth 

 is often brownish in colour. If incubated at 37° C, gelatin is said to be perman- 

 ently liquefied in 4 to 6 weeks. 



Broth. — 2 days at 37° C. Moderate growth with moderate uniform turbidity and a shght 

 powdery sediment disintegrating completely. No surface growth. 14 days, ring 

 growth is present, and there is a moderate, viscous deposit, very difficult to dis- 

 integrate. 



Horse Blood Agar Plate. — 3 days at 37° C. Good growth of round, low convex, greyish- 

 green, opaque colonies, 1 mm. in diameter. No haemolysis, but plate is browned. 



Loefflers Serum. — 3 days at 37° C. Scanty growth, barely visible, of flat, discrete colonies, 

 0-3 mm. in diameter. No liquefaction. 



Potato. — 2 days at 37° C. Moderate, raised, greyish-yellow growth. After 4 days the 

 colour deepens to cafe-au-lait, and in 10 days to chocolate. 



MacConkeys Agar. — 9 days at 37° C. No growth. 



Resistance. — Killed by moist heat in 10 minutes at 55° C. Cultures dried on threads may 

 live for 3 or 4 weeks ; but infected pus or discharge, when dried, usually becomes 

 sterile in a few days. Killed by 2 per cent, phenol in 1 hour, by 1/1000 HgClj 

 in 15 minutes, and by calcium hypochlorite with 2 parts of free chlorine per million 

 in 30 minutes. In culture the organism rarely survives longer than a month or 

 6 weeks. 



Metabolism. — Aerobe ; either no growth at all, or only very shght growth after 14 days, 

 under strict anaerobic conditions. Optimum temperature 37° ; little or no growth 

 below 20° C. On culture media it grows slowly ; growth is often not apparent 

 for 2 days. Tendency to formation of brownish pigment in cultures, especially 

 on potato. No haemolysin is produced. 



Biochemical. — Acid, no gas in glucose, and sometimes very slight acid in salicin ; no other 

 sugars fermented. L.M. sUght acid ; after 2 to 3 weeks a clot forms, and the 

 litmus is partly decolorized at the bottom. Indole—; M.R. — ; V.P. — ; nitrates 

 reduced ; HjS slight -\- ; NH3 -j- ; M.B. reduction — ; catalase shght -j-. 



Antigenic Structure. — By agglutination, absorption, and complement fixation there appear 

 to be at least two types of Pf. mallei, of which one is related to Pf. whitmori. Saka- 

 moto (1930) has isolated from culture filtrates of Pf. mallei a relatively non-specific 

 nucleo-protein substance, and a soluble specific polysaccharide which gives a pre- 

 cipitation reaction with immune sera. 



Pathogenicity. — Causes glanders or farcy in horses, mules, asses, and man. Experi- 

 mentally the disease can be reproduced in equines, goats, cats, and guinea-pigs ; 

 sheep, rabbits, dogs, rats and mice are less susceptible ; pigs and cattle are resistant. 

 Intraperitoneal injection of the male guinea-pig is followed in 2 days by sweUing 

 of the testicles ; after 3 or 4 days the two layers of the tunica vaginahs are gummed 



