THE PARACOLON GROUP 677 



the coliform bacilli — M.R., V.P., indole, citrate, and ceUobiose — find that they can be 

 divided roughly into three main groups according to whether they resemble the coli, 

 intermediate, or aerogenes types. Within the separate sub-divisions many of the strains 

 were found to be antigenicaUy similar, but a number remained that could not be classified 

 by serological means. For the sake of example the fermentation reactions of a few of 

 the paracolon bacilli that have received names are set out in Table 44. For a fuller 

 description of their characters the reader is referred to papers by Castellani (1902-14, 

 1907, 1912, 1938), Castellani and Chalmers (1920), Archibald (1911), Chalmers and Mac- 

 donald (1916) ; but it must be understood that the nomenclature of all these organisms 

 may have to be revised when a satisfactory basis of classification is eventually laid down. 

 More recently Sevitt (1945), who studied 108 strains of paracolon bacilli, mostly isolated 

 from cases of infantile diarrhoea, found that they could be classified into four groups on 

 their reactions in sucrose and dulcitol. Serologically five main antigens could be defined, 

 though many strains were heterogeneous. Some strains, besides containing one or more 

 of the A-E series of antigens, were characterized by the additional inclusion of a Shigella 

 alkalescens antigen, or of antigens found in the Flexner or Newcastle groups. 



It is of interest to note that Dudgeon has recorded a considerable series of 

 cases of acute vu-inary infectioij, associated with a pyrexial reaction simulating enteric 

 fever, and caused by a late-lactose-fermenting coliform bacillus. Lactose is fermented 

 slowly, saccharose is unchanged, mannitol and dulcitol are fermented with the production 

 of acid and gas, and Utmus milk is rendered acid and usually clotted (Dudgeon 1924, 

 Dudgeon and Pulvertaft 1927). It may be noted that this organism is hsemolytic for 

 human red cells, and that Dudgeon and his colleagues (Dudgeon et al. 1921, 1922) have 

 shown that strains of Bad. coli from the faeces, or from the urine in cases of cystitis, 

 may be divided into hsemolytic and non-hsemolytic types. The hsemolytic strains are 

 particularly frequent in certain types of acute urinary infection. It may clearly be neces- 

 sary to elaborate our classification, when these, or other tests, have been applied to the 

 group as a whole. Paracolon baciUi have Ukewise been isolated by Webb (1937) in 

 Mauritius from the urinary tract of patients suffering from enteric-Like fevers, pyehtis, 

 or cystitis, but they differed in some respects from the organism described by Dudgeon. 

 Agglutinins were usually demonstrable in the serum of the patients in titres varying 

 from 1/25 to 1/250. 



The strains that have from time to time been described as Bad. coli anaerogenes, on 

 account of their failure to produce gas from certain carbohydrates, are probably related 

 either to some members of this group, or to the late-lactose-fermenting types of the 

 Shigella group. 



The curious organism described by Massini (1907) as Bad. coli mutahile is itself a non- 

 lactose-fermenting strain, but is characterized by the property of giving rise to lactose 

 fermenting mutants, which show no tendency to revert to the parent form. This species 

 has been discussed in some detail in Chapter 9. It may be noted that Dulaney and 

 Michelson (1935) have recently described a severe epidemic of diarrhoea in infants, appar- 

 ently caused by this organism. It is clearly alUed to the paracolon group of Bacteria ; 

 though the exact relationship remains obscure. 



It will be convenient to describe at this point an organism originally isolated by Castel- 

 lani (1912), and studied in more detail by Khaled (1923). This species. Bad. asiaticum, 

 is a non-lactose-fermenter, and on this criterion would be excluded from the coUform 

 group. In saccharose, however, it forms both acid and gas ; and in its ability to attack 

 this sugar it differs sharply from the gas-forming, non-lactose-fermenting bacilli of the 

 paratyphoid group that will be considered in Chapter 30. It differs from them also 

 in its abiUty to form indole. Bad. asiaticum is a motile bacillus having the usual 

 characters of the genus. It ferments dextrose, mannitol and saccharose with the 

 formation of acid and gas, but produces no change in lactose or dulcitol. It acidifies, 

 but does not clot milk. It usually forms indole. It does not liquefy gelatin. It appears 

 to be a cause of enteric-Uke infections in man, particularly in the tropics. 



