666 



BACTERIUM 



TABLE 41 

 Fermentative Types of Bad. coli (Winslow et al). 



Serological Differentiation. — Several attempts have been made to study the 

 antigenic structure of various strains of Bact. coli by the method of agglutination. 

 The results display an extreme heterogeneity of antigenic factors (Mackie 1913, 

 Mirra 1936, Bredenbroker 1938, Stuart et al. 1940). In some instances, as in the 

 haemolytic strains of Bact. coli isolated by Dudgeon from cases of acute urinary 

 infection, there is evidence that antigenically homogeneous groups may be related 

 to particular infective conditions (Dudgeon et al. 1921, 1922). The same suggestion 

 is apparent in the work of Lovell (1937) on Bact. coli strains isolated from calves 

 that had died from white scours. Using the precipitin test, he obtained evidence 

 of the existence of two antigens : one, a soluble specific carbohydrate substance, 

 associated with the capsule and probably similar to or identical with that pre- 

 viously described by D. E. Smith (1927) ; the other, of undetermined nature, 

 contained in the body of the bacillus. Of 110 strains from 45 calves, he was able 

 to place 79 in one of eight different types. It is interesting to note that some 

 coliform strains contain or H antigens found in members of the Salmonella 

 group (see Chapter 30). The detailed antigenic analysis of the coliform bacilli 

 remains for future study. 



Stamp and Stone (1944) have described the presence of a common antigen- 

 referred to as the a-antigen — in many members of the coliform and paracolon 

 group. It is more heat-stable than the H-antigen, withstanding a temperature 

 of 75° C. for 1 hour, but less so than the 0-antigen, being inactivated at 100° C. 

 in 15 minutes. It is destroyed by exposure for 1 hour to alcohol at 65° C. It is 

 commonest in recently isolated strains, and tends to be lost on subculture. Agglu- 

 tinins to the a-antigen are not uncommon in rabbit sera, and may lead to confusion 

 in the identification of suspected pathogenic organisms. 



Pathogenicity. — The majority of the lactose-fermenting coliform bacilli appear 

 to be non-pathogenic under ordinary conditions. The M.R. — , V.P. -|- group 

 have their normal habitat on plants; the M.R. +, V.P.—, citrate + group 

 appear to live in the soil ; while the M.R. -f, V.P. — , citrate — forms are normal 

 intestinal parasites. Under abnormal conditions these bacilli may cause acute 

 or chronic infective lesions in the urinary tract, or elsewhere (see Chapter 67). 

 It seems probable also that they may sometimes play a part in the causation of 

 enteritis, in man or in animals, though their role appears generally to be a secondary 

 one. There is, however, some evidence that, in newly born animals, the advent 

 to the intestine of Bact. coli, or of particular races of this organism, may result 

 in a local enteritis or even general septicaemia. Smith and Little (1922) and Smith 

 and Orcutt (1925), for example, attributed the disease in newly born calves known 



