Evaluation of sodium polyanethanol sulfonate as a blood culture additive for recovery of Salmonella typhi and Salmonella paratyphi A.

A total of 640 blood specimens from patients in an area endemic for enteric fever were cultured in parallel in tryptic soy broth with and without sodium polyanethanol sulfonate (SPS). A total of 95 specimens were positive for Salmonella spp., 54 for Salmonella typhi, and 41 for Salmonella paratyphi A in one or both bottles of a set. Significantly higher rates of recovery were obtained from the SPS-containing medium (P less than 0.01) upon subculturing blindly at 24 h and 3 days of incubation. Subcultures performed at 7, 14, and 21 days also yielded a greater number of positive cultures with SPS than without it, although the differences between the two media were not significant (P greater than 0.05). Neither of the media yielded 100% of the positive cultures. Moreover, even if the results of the two media were combined, 34 and 19% of the isolates would have been missed if the specimens had not been incubated to 14 and 21 days, respectively. The data indicate that SPS aids in early recovery of S. typhi and S. paratyphi A from blood cultures, and additionally, that under the conditions used in the study, incubation beyond a 1-week period is required for efficient isolation of these organisms from blood.