Controlled Clinical Comparison of BacT/ALERT Standard Aerobic and Standard Anaerobic Blood Culture Bottles Inoculated Directly or after Transport in Sodium Polyanethol Sulfonate Tubes

Abstract

To assess relative performances in the BacT/ALERT blood culture system, we compared results from the direct inoculation of standard media and inoculation after the transport of blood samples in Vacutainer tubes with sodium polyanethol sulfonate. No significant differences in yields or times to detection were found for 387 clinically important isolates from 4,306 blood culture sets.Sodium polyanethol sulfonate (SPS) is a common component of blood culture media, owing to its anticoagulant, anticomplement, and antiphagocytic properties (2,3,17,18). It also inactivates lysozyme, aminoglycosides, and polymyxins (1). Although SPS has been shown to improve the recovery of commonly isolated microorganisms in older medium formulations (3,5,8,12,13,16), it inhibits the growth of Peptostreptococcus anaerobius, Neisseria gonorrhoeae, Neisseria meningitidis, Streptobacillus moniliformis, Gardnerella vaginalis, Haemophilus ducreyi, and Capnocytophaga spp. (4,7,11,14).For four decades, Vacutainer SPS tubes (BD Diagnostic Systems, Franklin Lakes, NJ) have been used at the Durham Veterans Affairs Medical Center, Durham, NC, and other institutions to transport whole blood until it can be inoculated into culture media. The historical advantages of this approach include being able to inoculate a variety of culture media and having plasma for serological testing (15). The effect that SPS transport tubes have on the yields from currently used blood culture media, however, has not been reported. Furthermore, the transfer of tube contents poses a percutaneous injury risk to laboratory staff. Consequently, we performed a controlled comparison of direct inoculation into standard BacT/ALERT (BA; bioMérieux, Inc., Durham, NC) blood culture bottles and inoculation after transport in SPS tubes. . Four-bottle kits were provided with instructions to obtain 30 ml of blood per set and to distribute 7.5 ml sequentially into a standard aerobic (SA) bottle, an SPS tube, a standard anaerobic (SN) bottle, and a second SPS tube without changing needles. Uninoculated SPS tubes contained 1.7 ml of 0.35% SPS in 0.85% sodium chloride. The SA and SN bottles each contained 40 ml of supplemented tryptic soy broth with 0.035% SPS.The filling adequacy (adequate, underfilled, or overfilled) of each bottle was measured against marked volumetric standards; 6 to 9 ml of blood was considered adequate. All bottles were processed regardless of the volume received. The contents of each SPS tube were transferred into additional SA and SN bottles in a biological safety cabinet. All four bottles were loaded onto the BA instrument and incubated for 5 days or until they were flagged as positive. The contents from flagged bottles were subcultured, and isolates were identified according to standard techniques (10).An infectious disease physician reviewed the record of each patient with a positive blood culture to determine whether an isolate represented true infection, contamination, or unknown clinical importance. These assessments were made in accordance with published cr...