Comparison between the time to detection of pathogenic and nonpathogenic microorganisms from blood culture specimens using the BACTECTM FX machine to determine the optimal incubation time

Introduction: Bloodstream infections can lead to a high rate of life-threatening sepsis, morbidity and mortality, requiring early and accurate detection. The gold standard for diagnosing bacteremia is blood culture. The recommended incubation time of blood cultures is five days minimum, but studies have shown that five-day incubation is unnecessary. This study aims to determine the optimal blood incubation time on the BACTEC™ FX machine. Methods: This is an analytic observational study with a cross-sectional retrospective approach. The samples resulted from tests in the Clinical Microbiology Laboratory and medical record data of patients at Dr. Soetomo Regional Public Hospital, Surabaya, with suspected bacteremia and fungemia-positive blood cultures based on tests with the BACTEC™ FX machine who met the inclusion criteria. Samples were analyzed for Time to Detection (TTD) and identification results. TTD of 96–120 hours was analyzed to assess the occurrence of Laboratory-Confirmed Bloodstream Infection (LCBI). Results: From a total of 2,221 samples, 875 (39.4%) pathogenic microorganisms and 1,346 (60.6%) nonpathogenic microorganisms were identified. At TTD < 24 hours, the number of pathogenic microorganisms was higher, reaching 86.6%, than that of nonpathogenic microorganisms, reaching 68.8%. Whereas at TTD of 24–< 48 hours, nonpathogenic microorganisms had a higher count, reaching 23.1%, than pathogenic microorganisms, reaching 10.1%. A total of 2,203 (99.2%) microorganisms were identified at TTD < 96 hours, and as many as 18 (0.8%) microorganisms with TTD > 96 hours. Conclusion: There is no difference in the distribution of pathogenic and nonpathogenic microorganisms at TTD < 96 hours and TTD 96–120 hours. Based on tests using the BACTEC™ FX machine, five LCBI-group microorganisms based on NHSN criteria were found with TTD of 96–120 hours, namely Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Trichosporon asahi, and coagulase-negative Staphylococcus, and thirteen non-LCBI-group microorganisms were identified.