A Study of the B. coll Group. 
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spoiid to types isolated and classified by MacConkey, the commonest is the 
No. 71 type (34 strains) (Table VI). Of the series isolated from urine this 
type was also the most prevalent, though among the faecal strains the B. coli 
communis was the commonest. Collectively, however, the most prevalent 
types in my series were B. MacConkey No. 71 and B. coli communis. 
With comparatively few exceptions, the G-ram-negative bacilli found in 
urinary sepsis, as shown, are normal inhabitants of the intestine, and this 
parallelism between the faecal and urinary types is a further confirmation of 
the generally accepted view that these infections are auto-infections from the 
bowel. 
As indicated above, the A sub-group comprises the most frequently 
occurring types of coliform bacilli, the so-called typical varieties. This 
group also appears to embrace the largest number of different varieties or 
types (36). While organisms of the sub-groups B and C are less frequently 
met with in excremental material, they nevertheless represent characteristic 
faecal organisms. Organisms of the anaerogenes type are of comparatively 
rare occurrence, but, as shown, this type may be associated with certain 
cases of urinary sepsis. 
The Serological Investigation of the B. coli Group. 
The following serological studies were originally carried out with a view 
to throwing further light on the biological relationships of the various types 
of B. coli and its congeners. The agglutination and complement-deviation 
reactions of immune sera to certain of the commoner varieties were studied, 
and the results, apart from their bearing on this particular question, 
represent observations of considerable interest from the purely immunological 
standpoint. 
Agglutination Eeactions. 
While in the case of B. typhosus, precise species specificity is characteristic 
of an agglutinating antiserum, among the coliform bacilli a much more 
restricted degree of specificity was observed — specificity for the individual 
strain. 
An immune serum to a particular strain of B. typhosus will agglutinate 
most B. typhosus strains with little variation in degree; immune sera to 
certain B. coli types, on the other hand, have been found to exert little or no 
action on other strains identical as regards cultural reactions to that used 
for immunisation. 
Several authors have drawn attention to the high degree of specificity of 
B. coli agglutinins (Van Everen, Pfaundler, Cany, Wolf, Amiradzibi), but 
the agglutination reactions of these organisms have not been accurately studied 
in correlation with their classification into different types qua cultural 
reactions ; thus Amiradzibi immunised guinea-pigs against five strains which 
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