Evaluation of sodium polyanethanol sulfonate as a blood culture additive for recovery of Salmonella typhi and Salmonella paratyphi A
Journal of Clinical Microbiology
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 < 0.01) upon subculturing blindly at 24 h and 3 days of incubation.
... cubation. 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 > 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 l9o 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. (17) and Watson (18) observed that sodium polyanethanol sulfonate (SPS) was beneficial to the growth of Salmonella typhi in model blood culture systems. The possibility exists, however, that results of such experimental cultures may not accurately reflect those of routine clinical practice, since the models involved the use of only one or a small number of bacterial strains. Furthermore, some of the strains were laboratory adapted, and growth was assessed either in a single specimen or a largely uncharacterized pool of blood from patients (17, 19) . A search of the literature failed to reveal references clearly documenting the value of the additive for recovery of typhoid and paratyphoid (enteric fever) Salmonella spp. in a clinical setting. Von Haebler and Miles S. typhi and Salmonella paratyphi A are often isolated from blood cultures at San Lazaro Hospital (SLH), Manila, Republic of the Philippines. Prompt and efficient isolation of these agents of enteric fever is important since the disease produces protean manifestations (11, 20) . For several years, the laboratory of SLH has used tryptic soy broth (TSB) for routine hemocultures. The present study was conducted to determine whether the addition of SPS would increase the yields or expedite the recovery or both of enteric fever Salmonella from our patient population. The study was conducted in a prospective manner using duplicate, parallel cultures of blood from patients, in TSB with and without SPS. MATERIALS AND METHODS Preparation of media. TSB (Difco Laboratories, Detroit, Mich.) was prepared as recommended by the manufacturer; TSB-SPS was prepared by adding sufficient SPS (Grobax; Hoffmann-La Roche Inc., Nutley, N.J.) to yield a 0.05% concentration of the compound in TSB. The broth media were dispensed in 30-ml samples into 100-ml serum bottles, capped loosely with rubber stoppers, and autoclaved for 15 min at 121°C and 15 pounds of pressure. The broth bottles were cooled to about 60°C and capped firmly with aluminum rings and a seal crimper. When the broth had cooled to room temperature, the vacuum in the sealed bottles was removed by puncturing the rubber stoppers with a 26-gauge hypodermic needle attached to a syringe barrel (syringe minus plunger) equipped with a disposable, 0.22-p.m membrane filter (Millex; Millipore Corp., Bedford, Mass.) affixed between the needle and hub of the barrel. All broth bottles were preincubated at 37°C for 24 h and visually checked for contamination. The broth culture bottles were stored at room temperature and used within 10 days after preparation. No gaseous carbon dioxide was added to the bottles. 380 on May 7, 2020 by guest