402 ERYSIPELOTHRIX AND LI ST E BELLA 



Morphology. — Stuooth form. Small, straight or slightly curved rods, 0-8-2-5 // long and 

 0-5-0-6 n broad. Arranged singly, in pairs side liy side or in V-form, in small 

 packets, or in short chains. Rough form. Long interlacing filaments, some of 

 A^hich show segmentation into rods. Filaments are particularly alnnidant in cultures 

 at room temperature. Sluggishly motile by polar, or according to some workers 

 peritrichate, flagella. Stains fairly uniformly, but sometimes shows beading. 

 Non-sporing. Gram-positive. 



Agar Plate. — 24 hours, 37° C. Poor to moderate growth, having shghtly acid smell 

 reminiscent of the acne baciUus. Smooth form. Circular, low convex or convex, 

 amorphous colonies, 0-2-0-8 mm. in diameter, with smooth mirror-Uke surface 

 and entire edge ; almost transparent by transmitted, greyish-yellow by reflected 

 light ; butyrous in consistency and easily emulsifiable. 48 hours. Shghtly larger, 

 0-8-1 -0 mm. in diameter, with tendency to crinkling of edge. Older colonies are 

 up to 1-5 mm. in diameter, and have a brownish shghtly granular centre and a 

 translucent effuse periphery with a finely crenated margin ; when magnified, the 

 colony has a poached-egg appearance. Rough form. 48 hours. Rather larger 

 than the smooth form, 1-5-20 mm. in diameter, flatter, with a matt surface, 

 umbonate centre, and a finely fimbriate edge. After 5 days colony may reach 

 5 mm. in diameter, and show a small, smooth, darker centre with a wide, more 

 effuse, translucent, finely gi-anular peripheral extension having a fimbriate edge. 



Agar Slope. — 24 hours, 37° C. Thin, raised, confluent, translucent growth with beaten- 

 copper surface and finely crenated edge. Growth becomes niore abundant on 

 further incubation. Rough form is similar, but shows a shghtly spreading edge. 



Gelatin Stab. — Slow, filiform growth, not Uquefying the gelatin ; narrow surface growth. 



Broth. — 24 hours, 37° C. Smooth form. Slight to moderate turbidity, with slight powdery 

 deposit disintegrating on shaking ; no surface growth. Rough form. Little or 

 no turbidity, with thread-like masses of deposit that are diflicult to disintegrate. 



Horse Blood Agar Plate. — 24 hours, 37° C. Circular, low convex colonies, 0-7-1-2 mm. 

 in diameter, with smooth mirror-hke surface and entire or very finely crinkled 

 edge ; milky white by reflected Ught. Colonies are surrounded by a narrow zone of 

 more or less complete /S-hsemolysis. 



Loeffler's Serum. — 2 days, 37° C. Thin, raised growth, like that on agar, with shghtly 

 beaten-copper surface and very finely crenated edge ; no liquefaction, even after 

 3 weeks. 



MacConkey's Agar. — 24 hours, 37° C. Circular, convex, colourless colonies, 0- 1-0-4 mm. 

 in diameter, with smooth surface and entire edge. 5 days. No increase in size 

 or change in colour, but surface tends to be shghtly granular and edge shghtly 

 irregular. 



Potato.— 2 days, 37° C. Shghtly raised, greyish-white growth, with finely granular surface 

 and very finely crenated edge. 



Glucose Agar Shake. — 2 days, 37° C. Tiny colonies throughout medium. May be a band 

 growth, on first isolation, just below surface. 



Resistarice. — Survives moist heat for 30 minutes at 55° C, but is killed within 60 minutes. 

 Cultures remain viable for several months. 



Metabolism,. — Aerobic and facultatively anaerobic. Optimum temperature for growth 

 30°-37° C. ; growth occurs between 20° and 44° C. Growth favom-ed by glucose 

 and hver extract, and to a less extent by blood and serum. )S-haemolysis occurs 

 around colonies on horse blood agar ; weak soluble hsemolysin formed in broth 

 cultiu-es. 



Biochemical. — Sugar reactions are variable. Usually produces acid in glucose, maltose, 

 saUcin, mannose, rhamnose, and dextrin, and slowly or in only small amount 

 in lactose, sucrose, and glycerol. L.M. shght acid. Indole negative. M.R. +. 

 V.P. ±. Nitrate reduction negative. M.B. reduction weakly positive. HjS nega- 

 tive. NH3 in serum peptone water weakly positive. Catalase +. 



