Biochemical and Antigenic Relationships of the Paracolon Bacteria

Abstract

The biochemical and antigenic relationships of paracolon bacteria among themselves and to normal coliform bacteria and to Salmonella were studied. Of 456 paracolon cultures isolated from feces. urine or blood a wide variety of biochem. types were encountered and on the basis of their IMVic reactions they were divided into paracolon Aerobacter, paracolon intermediates, and paracolon Escherichia. Paracolon cultures producing acid only in carbohydrates were considered anaerogenic paracolon. Several biochemical types wen1 established under each section. The majority of cultures produced acid and gas in lactose from 3-40 days, some produced acid and a few were lactose-negative. With the exception of certain paracolon Aerobacter the colonies of paracolon bacteria could not be distinguished from the colonies of Salmonella on E. M. B. and SS. agar. A marked continuity of antigens was obtained with the paracolon bacteria as compared to normal coliforms which were investigated in a previous study. 47.8% of 140 paracolon Aerobacter, 52.5% of 40 paracolon intermediates, and 58.2% of 223 paracolon Escherichia cultures were found to be sorologically identical or closely related. Two of the 4 anaerogenic biochemical types exhibited serological homogeneity. Antigens common to paracolon and normal coliforms were found; also antigens of certain paracolon and normal coliforms were identified with several of the known somatic antigens of Salmonella. However, reactions were obtained with paracolon organisms in Salmonella anti-serums which could not be attributed to any of the known Salmonella components. No common H antigens were demonstrated between Salmonella and paracolon bacteria. An antigen of the same thermolability as the Vi antigen was found common to normal coliform, paracolon bacteria, and Eberthella typhosa. The pathogenicity of paracolon bacteria is discussed and some evidence . was found indicating an etiological role for certain paracolon types in mild or acute gastroenteritis of short duration. The problems of taxonomy in the family Enterobacteriaceae are considered and it is recommended that 3 spp., aerogenes, freundii, and coli, be included in one genus and that cloacae be dropped and also that Eberthella typhosa and E. sendai be classified as Salmonella and that the remaining spp. of the genus be considered collectively anaerogenic coliforms or paracolon bacteria.