Effect of Sodium Citrate on Growth of Bacteria in Blood Culture

Abstract

Background: This study compared the growth of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Haemo-philus influenzae in blood culture bottles containing anticoagulants, sodium polyanethol sulfonate (SPS) and sodium citrate. Methods: One hundred and fifty colony forming units of five different bacterial species were inoculated into standard aerobic (SA) and standard anaerobic (SN) bottles and were combined with 5 mL of human blood in solution with SPS or sodium citrate. Time to detection (TTD) was then monitored using the BacT/ Alert 3D system (bioMerieux Inc.). Results: Compared to the bacteria-only controls, cultures containing S. aureus, E. coli, P. aeruginosa, and S. pneumoniae plus SPS blood or citrated blood trended toward reduced TTD in both SA and SN bottles ; however, there was no significant difference in TTD between SPS and sodium citrate anticoagulant. Although H. influenzae showed a remarkable difference in TTD between SPS (SA 14.8 h, SN 15.0 h) and sodium citrate (SA 23.5 h, SN 18.3 h), this difference was not statistically significant (P=0.10). Conclusion: Addition of blood enhanced growth of bacteria. All experimental bacteria except H. influen-zae showed similar TTD in SPS blood and citrated blood. These results support the usefulness of sodium citrate anticoagulant for artificial inoculation in blood culture bottles.