A Serological Study of Proteus Rettgeri and Similar Organisms.

In 1942 a report was made on the studies of a group of citrate-positive organisms, isolated from fecal specimens in the course of examinations for enteric pathogens, that could not be classified biochemically or serologically in any of the established groups (Cope and Kilander, 1942). They were gram-negative anaerogenic bacilli, resembling shigellae in most of their biochemical reactions. Lactose was not fermented and gas was not produced from glucose during a 30-day period of incubation at 37 C. Although motility was not usually observed at the time of isolation, most of the transplants showed growth of organisms that were motile. Serologically there was no relationship to the Salmonella, Shigella, or EbertheUa groups. One of the strains, designated as 1544, was selected as the type str and was used in the preparation of antiserum. This serum agglutinated many of the strains that were biochemically similar, but no attempt was made at that time to place these strains in any of the recognized tribes. Since the publication of that report, other observers have encountered and reported on similar strains. In Bergey's Manual (Breed et al., 1948) the strains that decompose urea are classified as Proteus rettgeri and those not decomposing urea as Paracolobactrum. It is not the purpose of the present study to prove or to disprove such classification. Organisms of this type are frequently isolated from specimens received from cases of acute dysentery, and because we have in several instances been able to demonstrate homologous agglutinins in the blood of patients harboring such organisms, we feel that they may have a place in the list of incitants of enteric disorders. It was our purpose in undertaking this study to determine: (1) whether these organisms constitute one or more distinct serological groups possesing specific L, H, and 0 antigens, (2) whether this group could be classified by serological methods in the same manner as the Salmonella and the Shigella paradysenteriae groups, and (3) whether it is possible to demonstrate agglutinins in the sera of patients harboring these organisms. Five strains were selected as type strains for this study and were designated by the letters A (strain 1544), B, C, D, and E. The essential biochemical reactions of each of these type strains are outlined in table 1. Strains not decomposing urea when cultured on the medium of Rustigian and Stuart (1941) were transferred to Christensen's medium (1946). There was no evidence of urea decomposition in either of these media by the two type strains D and E. Agglutination tests revealed no Shigela antigens to be present in any of the type strains. A Proteus morganii antiserum, likewise, did not agglutinate any of the five strains. Tests were also made for Salmonella antigens by Dr. P. R.