598 



ORDER IV. EUBACTERIALES 



1. Listeria monocytogenes (Murray et 

 al., 1926) Pirie, 1940. {Bacterium monocyto- 

 genes Murray, Webb and Swann, Jour. Path, 

 and Bact., 29, 1926, 407; Pirie, Science, 91, 

 1940, 383.) 



mo.no.cy.to'ge.nes. Gr. adj. menus 

 alone, single; Gr. noun cytus a hollow, a 

 vessel; M.L. noun cytus a cell; M.L. noun 

 monocytum a blood cell, monocyte; Gr. v. 

 gennaio to produce; M.L. adj. monocytogenes 

 monocyte-producing. 



Small rods, 0.4 to 0.5 by 0.5 to 2.0 microns, 

 with rounded ends, slightly curved in some 

 culture media, occurring singly and in 

 V-shaped or parallel pairs. Motile by means 

 of peritrichous flagella (Paterson, Jour. 

 Path, and Bact., 48, 1939, 25) at 2.5° C. to 

 room temperatures with a tendency to re- 

 duced motility in time at 37° C. (Griffin, 

 Jour. Bact., 48, 1944, 114). Not acid-fast. 

 Gram-positive. 



Gelatin: Growth is confined to the needle 

 track. No liquefaction. 



In 0.25 per cent agar, 8.0 per cent gelatin, 

 1.0 per cent glucose semisolid medium, 

 growth along the stab in 24 hours at 37° C. 

 followed by irregular, cloudy e.xtensions 

 into the medium; growth spreads slowly 

 through the entire medium. This is charac- 

 teristic (Seastone, Jour. Exp. Med., 62, 

 1935,203). 



Sheep liver extract agar colonies: Circu- 

 lar, smooth, butyrous, slightly flattened, 

 transparent by transmitted and milky by 

 reflected light. 



Sheep liver extract agar slant: Confluent, 

 flat, transparent, butyrous growth. 



Peptone agar: Growth is thinner than on 

 liver extract agar. 



Blood agar: Improved growth with zone 

 of hemolysis around colonies varjang with 

 the species of blood. 



Peptone broth: Turbid; flocculent sedi- 

 ment. 



Litmus milk: Slightly acid, decolorized. 

 No coagulation. 



Glycerol-potato: No apparent growth. 



Inspissated ox serum: Grows as a very 

 thin, transparent film. 



Dorsett's egg medium: Very thin film. 



Indole not produced. 



Hydrogen sulfide not produced. 



Acid but no gas from glucose, salicin and 



trehalose promptly, more slowly or variable 

 from maltose, lactose, dextrin, sucrose, 

 rhamnose, melezitose, soluble starch and 

 glycerol. Tends to be negative on arabinose 

 and galactose. No action on xylose, manni- 

 tol, dulcitol, inulin or inositol. 



Esculin hydrolyzed in 24 hours (Sohier, 

 Ann. Inst. Past., 74, 1948, 57). 



All cultures give off a penetrating, rather 

 acid smell. 



Nitrites not produced from nitrates. 



Catalase-positive. 



Aerobic, facultatively anaerobic. 



Optimum temperature, 37° C; grows at 

 all temperatures down to 2.5° C. Thermal 

 death point, 58° to 59° C. in 10 minutes. 

 Survives eight weeks in 20 per cent NaCl at 

 4° C. (Wramby, Skandinavisk Vetinartid- 

 skriften, 34, 1944, 279). 



Animal inoculations: Intravenous or 

 intraperitoneal injection of rabbits with 

 cultures results in a very marked increase 

 in monocytes circulating in the blood. This 

 is the most striking character of the organ- 

 ism, and it is exhibited by strains derived 

 from all sources. Monocytosis is induced 

 by extracted chloroform-soluble lipid (Stan- 

 ley, Australian Jour. Exp. Biol, and Med., 

 27, 1949, 123). Infection is characterized by 

 necrotic or granulomatous foci in various 

 organs. Causes conjunctivo-keratitis when 

 instilled into the conjunctiva of rabbits and 

 guinea pigs (Anton, Zent. f. Bakt., I Abt., 

 Orig., 131, 1934, 89; also see Julianelle, Proc. 

 Exp. Biol, and Med., 40, 1939, 362); also 

 produces this effect in the horse and ham- 

 ster. 



Serological characters: Paterson (Jour. 

 Path, and Bact., 51, 1940, 427) and Seeliger 

 and Linzenmeier (Ztschr. f. Hyg., 136, 1953, 

 335) conclude from studies of the flagellar 

 and somatic antigens that four types may 

 be recognized in this species; these do not 

 bear any relation to the host species or to 

 the geographical area from which they were 

 isolated. 



Relationships to other species: Possibly 

 identical with Bacterium hepatis Hiilphers 

 (Sven. Vet. Tidskrift,^, 1911,271) according 

 to Nyfeldt (Sven. Vet. Tidskrift, 30, 1940, 

 280). Further comparative studies are 

 needed, however, before this can be deter- 



