;^80 THE ALCALIGENES- DYSENTERY— TYPHOID GROUP 
tion. They produce acid and gas in glucose and mannitol; lactose and 
saccharose are not fermented. The alpha type seems to be a fairly 
homogeneous one, but the beta types, rather widely distril^uted 
throughout the mammalia, are subject to considerable variation in 
their secondary cultural and biochemical characteristics.^ 
il/?7/,-.— Plain milk is not coagulated. All the members of the group 
except B. paratyphosus alpha cause a slow change in this medium, 
which becomes thin, brownish and almost opalescent after two or 
more weeks' incubation. In litmus milk the cream ring is colored a 
deep blue-green, which is so constant as to be suggestive diagnos- 
tically. B. paratyphosus alpha produces a slight acidity which is 
permanent; the milk assumes a lilac color. B. paratyphosus beta 
and other members of the group produce a transient acidity- which 
is followed by a progressive alkalinity, associated with the liberation 
of small amounts of ammonia.^ 
All members of the intermediate group produce considerable tur- 
bidity in plain and sugar broths. A pellicle may develop in plain 
broth after several days' incubation. Potato: B. paratyphosus 
alpha grows much like the typhoid bacillus on potato; the growth is 
nearly invisible on acid potato, but comparatively luxuriant. On 
alkaline potato the growth is brownish. B. paratyphosus beta pro- 
duces a brownish growth even on slightly acid potato, which resembles 
that characteristic of B. coli. 
The members of the intermediate group are all aerobic, facultatively 
anaerobic. The minimum temperature of growth is about 6° to 8° C, 
the optimum 37° C, and growth ceases at approximately 44° C. The 
resistance of the members of the intermediate group to environmental 
conditions, drying and to chemicals is similar to that of the typhoid 
bacillus. They are, however, somewhat more resistant to heat; an 
exposure of fifteen minutes at 70° C. or of five minutes at 75° C, 
kills the bacilli. This is a point of importance in meats infected 
with the organisms; temperatures lower than 75° C. in the center of 
the meat cannot be relied upon to remove danger of infection. Higher 
temperatures, 100° C, are preferable to remove all danger from the 
poisonous substances of the bacilli, which are not destroyed by gastro- 
intestinal digestion. 
Products of Growth. — (a) ChemicaJ. — Furatypho'id bacilli are rather 
more active proteolytical'y than typhoid and dysentery bacilli, but 
they produce neither phenols nor, as a rule, indol.^ Glucose and 
mannitol are fermented with the formation of carbon dioxide and 
hydrogen, lactic acid and smaller amounts of acetic and formic acids. 
Paratyphosus alpha, unlike the beta types, does not ferment xylose. 
1 See Jordan: Jour. Infer. Dis., 1917, 20, 457, 571; 1918, 22, 252, 511; 23, 537; 1919, 
25, 135; 1926, 26, 427. 
'■^ For an explanation of the phenomenon, see page 254. 
^ Kendall and Haner: Jour. Infec. Dis., 1922, 30, 232. 
■< Kendall, Day and Walker: Jour. Am. Chem. Soc, 1913, 35, 1221 
