726 SALMONELLA 



Agar Plate. — 24 hours at 37° G. Commonest type of colony is circular, low convex, 

 greyish-yellow, faintly translucent, 1-3 mm. in diameter, with smooth surface and 

 entire edge ; butyrous in consistency and emulsifies easily. Surface may be 

 irregular though smooth, and edge may be coarsely undulate or finely but irregularly 

 indented. Colonies that are left at room temperature, after preliminary incubation 

 at 37° C, may develop a so-called mucoid wall. 



Agar Slope. — 24 hours at 37° C. Abundant, raised, faintly translucent, greyish -yellow 

 growth with glistening, smooth or beaten-copper surface and entire or undulate 

 edge. 



Gelatin Stab. — 7 days at 20° C. Good fihform growth, with moderate growth on the 

 surface. No liquefaction. 



Broth. — 24 hours at 37° G. Abundant growth with uniform turbidity, which continues 

 to increase sUghtly for 2-3 days. SUght to moderate powdery deposit, disintegratmg 

 readily on shaking. No surface growth. 



MacGonkey's Agar. — 24 hours at 37° G. Yellow colonies, 1-3 mm. in diameter, often 

 of vine-leaf type. 



Desoxycholate Gitrate Agar. — 24 hours at 37° G. Colourless colonies, 1-2 mm. in diameter, 

 sometimes with a black centre. 



Wilson and Blair's Agar. — 48 hours at 37° C If closely packed, colonies are about 1 mm. 

 in diameter, and appear faintly greenish ; if discrete with room to spread, they 

 are larger, flatter, and darkish in colour with a metaUic she«n. 



Resistance. — Killed by moist heat at 55° C. in half an hour. Cultures at room temperature, 

 or preferably on egg medium in the ice-chest, hve for months. 



Metabolism. — Aerobe and facultative anaerobe. Grows between about 15° and 42° C, 

 best at 37° C. May form a mucoid, capsular material at room temperature. Grows 

 well in Bitter's medium containing ammonium salts as the main source of nitrogen. 

 No hsemolysin formed. 



Biochemical. — Acid and gas in glucose, maltose, mannitol, sorbitol, dulcitol, arabinose, 

 trehalose and xylose, but not in lactose, sucrose, salicin or adonitol. Reactions 

 variable in rhamnose and inositol, in d-, I- and i- tartrates, and in citrate ; mucate 

 generally fermented in one day. Variable reaction in Stern's medium. Occasional 

 variants fail to form gas. Fermentative sub-division based mainly on failure to 

 ferment (^-tartrate or rhamnose. H2S +. Indole negative. M.R. +. V.P. — . 

 Nitrates reduced. NH3 +• M.B. reduced. Catalase+ + . Koser's citrate—. 

 Gas formation in MacConkey broth at 44° C. negative. 



Antigenic Structure. — Diphasic flagellated bacillus. Antigenic formula [I], IV, [V], 

 XII . . . b < — > 1, 2 . . . Strains lacking the V somatic antigen — the odense 

 variety — are said to be commoner in carriers than in acute cases. 



Pathogenicity. — Gives rise as a rule to paratyphoid fever in human beings ; but may be 

 responsible for acute gastro-enteritis, followed or not after some days by the usual 

 febrile disease. Strains from cases of gastro-enteritis often ferment rf-tartrate, 

 which strains from cases of paratyphoid fever seldom do. Has occasionally 

 been isolated from domestic animals, but is not known to cause disease in 

 them under natural conditions. Inoculated intraperitoneaUy into mice in a dose 

 of about 500 million bacilli, it produces death in 1 to 3 days. Post mortem there 

 is some peritonitis and enlargement of the spleen. The bacUh can be recovered 

 in culture from the spleen and heart blood. 



GROUP A. 



Salm. paratyphi A A.F. [1], II, XII . . . a — . 



Isolated from enteric fever in man (Gwyn 1898, Schottmiiller 1900, 1901, Brion and 

 Kayser 1902). Causes enteric fever, but not acute gastro-enteritis, in man. Has once 

 been isolated from a pig (Broudin 1927), but is not a natural pathogen of animals. Growth 

 is poorer than that of most other salmonellse. DifFei'ent strains vary in their HjS pro- 



