A Pooled Paracolobactrum Intermedium Antiserum for Screening in Enteric Bacteriology.

Recent investigations of the antigenic relationships of all Paracolobactrum cultures isolated in the Florida State Board of Health, Jacksonville, laboratory during 1946 and 1947 (Stuart, Galton, and McGann: J. Bact., 46, 411, 1948) revealed that 40 per cent of these cultures were Paracolobactrum intermedium. It was also found that many of the P. intermedium cultures belonged to the Bethesda group described by Edwards, West, and Bruner (J. Bact., 55, 711, 1948). Because of the biochemical similarity of these organisms to Salmonella, a great deal of time and many media and frequently Salmonella antiserums are necessary for differentiation. In an effort to obtain a rapid method of screening these cultures in a diagnostic laboratory handling large volumes of routine enteric cultures, a pooled P. intermedium antiserum was prepared. This antiserum consisted of a pool of 6 of the 9 basic antiserums used in the original study of the 765 P. internedium cultures (Stuart, Galton, and McGann, 1948). Those selected for the pool were 5883, 7328, 14011, 20157, 20158, and 20565. They were pooled in amounts of 2.5 ml each. All cultures giving a suspicious Salmonella reaction on Kligler's iron agar slants (KIA, 1 per cent sucrose added) were subsequently tested for urea breakdown and indole production. If both tests were negative the cultures were slide-tested in a 1:5 dilution of the pooled Paracolobactrum antiserum. After approximately 500 KIA slants that showed a suspicious Salmonella reaction with this pooled P. intermedium antiserum were checked, no positive reactions were obtained with the cultures that failed to produce H2S. This was not surprising as, with the exception of an occasional variant, all of the P. intermedium cultures that have been studied by various investigators have produced H2S. It was also noted that the suspicious KIA slants that produced H25 were rarely ureaor indole-positive. Therefore, the procedure shown in diagram 1 wasused routinely. Thismethod hasreducedby more than 50 per cent the number of rapid urea and indole tests performed on suspicious KIA slants forming H2S. During the past four months the pooled P. intermedium antiserum has been in use routinely in the examination of 3,718 fecal cultures in the Jacksonville laboratory. From 263 specimens, cultures that showed acid and gas in KIA and