396 ERYSIPELOTHRIX AND LI ST E BELLA 



Morphology. — The work of Spryszak and Szymanowski (1929), Meyn (1931), 

 Redlicli (1932), and Barber (1939) has made it clear that both Erysipelothrix and 

 Listerella occur in a smooth and a rough form, each characterized by closely 

 associated morphological and colonial appearances. In the smooth form they 

 appear as small, straight or slightly curved. Gram-positive rods with rounded 

 ends, about 0-8-2-5 ^ long and 0-3-0-6 /j, broad, arranged singly, in small packets 

 or groups, or in short chains. In the rough form long filaments, up to 60 [x or 

 more, predominate, some of which are seen breaking down to form chains of bacilli. 

 Erysipelothrix is more slender than Listerella and is non-motile. The motility of 

 Listerella, however, which is said by some workers to be due to a single polar 

 flagellum and by others to peritrichate flagella, is very sluggish. According to 

 Seastone (1935) it is demonstrated best in a 4-hour glucose broth culture. Flagella 

 are said to be developed better at 25° C. than at 37° C. (see Paterson 1939, Griffin 

 and Bobbins 1944). 



Cultural Characters. — In the smooth form the colonies after 24 hours' incuba- 

 tion at 37° C. are very small, circular, convex, amorphous, and water-clear, with 

 a smooth glistening surface and entire edge. On further incubation Erysipelothrix 

 colonies show little or no increase in size ; those of Listerella become larger and 

 less transparent. In the rough form the colonies are rather larger and flatter ; 

 their matt surface, curled structure, and fimbriate edge render them not unlike 

 miniature anthrax colonies. On the whole Listerella colonies tend to be larger 

 and less transparent than those of Erysipelothrix. In gelatin stab culture the growth 

 of Erysipelothrix on first isolation is often of the lamp-brush type ; Listerella forms 

 a filiform growth with no lateral outgrowths. Erysipelothrix fails to grow on 

 MacConkey's medium ; Listerella, according to Paterson (1937) and our own 

 observations, forms small colonies on this medium, but Barber (1939) was unable 

 to confirm this. Listerella forms a soluble hsemolysin ; Erysipelothrix does not 

 (Barber 1939), though haemolysis may occur around colonies in blood agar. 



Resistance. — Most strains of Erysipelothrix are killed by exposure to moist 

 heat for 15 minutes at 55° C. ; Listerella survives this temperature for 30 minutes, 

 but is killed within 60 minutes (Barber 1939). Erysipelothrix is resistant to salting, 

 pickling and smoking, and may remain alive in putrefying carcases for months. 

 Hettche (1937) found that it survived for 4 to 5 days in drinking water, and for 

 12 to 14 days in sewage and aquarium water. Listerella is said to be fairly resistant 

 to penicillin (Foley et al. 1944). 



Growth Requirements and Metabolism. — The growth of both organisms is 

 favoured by glucose, and to a less extent by blood and serum. According to 

 Colella (1936) growth of Erysipelothrix occurs best in 0-1 per cent, glucose broth 

 and 0-5 per cent, glucose agar; larger quantities of sugar were found to be inhibitory. 

 A liver digest medium favours both organisms (Murray, Webb, and Swann 1926, 

 Vawter 1937). On first isolation, Listerella, like Erysijjelothrix, may give a band 

 growth just below the surface of a shake agar culture (Gibson 1935) ; whether 

 this is due to a preference for COg or for a lowered partial pressure of oxygen is 

 not clear. Both organisms are facultative anaerobes. Hutner (1942) found that 

 the growth requirements of Listerella were simpler than those of Erysipelothrix ; 

 Listerella could grow in peptone water without serum or thioglycollate, whereas 

 Erysipelothrix could not. Growth of Listerella is said to occur in an acid-hydrolysed 

 " vitamin-free " medium containing glucose and inorganic salts, provided riboflavin, 



