524 VIBRIO 



Morphology. — -Slightly curved bacillus, often resembling a comma. Varies considerably 

 in size, l'5-4 /j. X 0-2-0-4 /j.. One end often blunter than the other ; ends 

 rounded ; axis generally curved ; sides converging or parallel. Arranged singly, 

 or in s-shaped pairs ; sometimes short chains are found, and sometimes spirals. 

 In the intestinal contents, arranged like fish in a stream. In old cultures the 

 bacilli are very small, resembling granules, and stain poorly. Involution forms 

 numerous. Actively motile by a single polar flagellum. Gram-negative. Non- 

 sporing. Non-acid-fast. 



Agar Plate. — 24 hours at 37' C. Round, 1-2 mm. in diameter, low convex, translucent, 

 greyish-yellow colonies with smooth, or finely granular, glistening surface and 

 entire edge, and of amorphous or finely granular structure ; consistency butyrous ; 

 easily emulsifiable. 7 days ; slightly larger ; edge entire or undulate ; surface some- 

 times studded with small, knob-like secondary colonies ; colony is sometimes 

 surrounded by a narrow, effuse, transparent peripheral extension. Crystals often 

 formed in the medium. 



Agar Stroke. — 24 hours at 37° C. Good, raised, translucent, greyish-yellow layer of growth, 

 with smooth, glistening surface, and edge formed of single colonies. 7 days ; 

 surface sometimes studded with small, knob-like secondary colonies. Crystals 

 often formed in the medium. 



Gelatin Plate. — -2 days at 23° C. Round, 0-5 mm. in diameter, amorphous, raised or 

 low convex, greyish-white, opaque colonies, with smooth or slightly granular 

 surface and entire or crenated edge. Zone of liquefaction around colony ; small 

 flocculi of growth in liquefied gelatin. 



Gelatin Stab. — 3 days at 22° C. Good filiform growth, confluent at top, discrete below, 

 extending to bottom of tube. Infundibuliform or napiform liquefaction; thick, 

 yellowish- brown pellicle on surface of liquid gelatin, and coarsely granular 

 turbidity. 



Broth.— 24: hours at 37° C. Abundant growth with moderate turbidity, a slight powdery 

 deposit, and a thick surface pellicle, breaking up on shaking into coarse membranous 

 and granular pieces. 



Loeffler's Serum. — 10 days at 37° C Good growth with partial liquefaction. 



Horse Blood Agar Plates. — 24 hours at 37° C. Abundant growth ; colonies are surrounded 

 for 2 mm. by a zone of a- or /S-haamolysis. 



Potato. — 7 days at 37° C. Good, confluent, cafe-au-lait growth with smooth glistening 

 surface. 



MacConkey Plate. — 24 hours at 37° C. Good growth of clear, colourless colonies smaller 

 than those on agar. After 7 to 9 days the colonies take on a reddish colour. 



Resistance.^Not specially resistant. Easily killed by drying. Destroyed by heat at 

 55° C. in 15 minutes. Dried on linen or threads they survive 1 to 3 days. Killed 

 by 0-5 per cent, phenol in a few minutes. Survive in clean tap water up to 30 

 days, but perish in 24 hours in cesspool water. 



Metabolism. — Strongly aerobic ; very slight growth noticeable on agar and in broth after 

 a week under strictly anaerobic conditions. Optimum temperature 37° C. ; limits 

 16^2° C. Optimum pH 7-0-8-0. Limits for growth pH 6-4-9-6. Growth favoured 

 slightly by blood. Grows well and rapidly in peptone water. No soluble hsemolysin 

 formed for sheep or goat cells. Proteolytic and diastatic ferments secreted. 



Biochemical.— Acid, no gas, in glucose, maltose, mannitol, and sucrose in 1 to 3 days ; 

 after 14 days there may be slight acid in lactose. L.M. acid, or acid and clot in 

 14 days. Indole +. Cholera-red reaction -[-. M.R.— . V.P. — . Nitrates re- 

 duced. NH3-I-. HjS -f in 14 days. Catalase-[-. M.B. reduction -f. 



Antigenic Structure. — All strains have a common O antigen, but 3 sub-types are distinguish- 

 able. Immune sera prepared by injection of rabbits, goats, or horses with living 

 vibrios contain specific bacteriolysins, demonstrable by Pfeiffer's test. 



Pathogenicity. — Causes Asiatic cholera in human beings. A similar disease may be repro- 



