THE PARATYPHOID GROUP 379 
In 1896 Achard and Bensaucle^ described paratyphoid fever and 
outlined the essential cHnical and bacteriological diagnostic differences 
between this disease and typhoi<l fever. They obtained i)aratN-phoid 
bacilli from the urine and l>lood stream of several cases, and recovered 
the organism from a secondary purulent arthritis in one of them as 
well. Schottmiiller- also obtained cultures of paratyphoid bacilli 
both from the feces and the blood stream of several cases of para- 
typhoid fever. Brion and Kayser'' separated these organisms into 
two types: B. paratyphosus alpha, which produced a slight perma- 
nent acidity in litmus milk and gave an "invisible" growth on potato 
like the typhoid bacillus; and B. paratyphosus beta, which produced 
an initial acidity in litmus milk followed by a progressively alkaline 
reaction. These observations, both clinica^ and bacteriological, have 
been confirmed by later investigations. Hadley* has found that the 
alpha type usually produces an acid reaction in milk which persists 
until the beginning of the third week. At this time the reaction has 
become practically neutral; it becomes quite alkaline by the end of 
the seventh week. The differences in reaction of the alpha and beta 
types in litmus milk are quantitative rather than qualitative. 
Morphology.— The members of the intermediate group are indis- 
tinguishable morphologically. They are rod-shaped bacilli with 
rounded ends, measuring from O.S to 1 micron in diameter, and 1.5 
to 3.5 microns n length, occurring singly or in pairs, seldom in chains. 
In actively-growing cultures the organisms may be short, almost 
ovoid. In old cuhures the organisms may be elongated; filamentous 
forms are more commonly seen in old gelatin cultures. The members 
of the group are actively motile and possess from four to twelve 
peritrichic flagella. Motility is greater in glucose broth than \n plain 
broth; this is particularly the case in young cultures. The organisms 
form no spores and appear to possess no capsules. They stain readily 
with ordinary anilin dyes; occasionally organisms from cultures several 
days old exhibit a tendency toward bipolar staining. They are 
Gram-negative. 
Isolation and Culture. —The organisms of the paratyphoid group 
grow readily upon ordinary artificial media, B. paratyphosus alpha 
somewhat less luxuriantly than the remaining members. The colonies 
produced on agar after eighteen hours' incubation at 37° C. resemble 
those of the typhoid-dysentery group— small, round and transparent — 
measuring from 1 to 3 mm. in diameter. On Endo or Andrade medium 
the colonies, like those of B. typhosus and the dysentery bacilli, 
are clear and colorless and somewhat smaller than those developing 
upon plain agar. They usually measure from 0.75 to 2 mm. in diam- 
eter. The organisms grow well in gelatin, but do not cause liquefac- 
1 Soc. med. des hop. de Paris, 1896, 3d serie, 13, 679 
2 Deutsph. med. Wchnschr., 1900, 26, 511. 
3 Munchen. med. Wchnschr., 1902, 49, 611. 
* Jour. Bacteriol., 1917, 2, 263. 
