Assessment of blood culture contamination rate in a tertiary care hospital: A single centre study of south India

Background : Blood culture is the gold standard for the diagnosis of bacteremia. Contaminated blood cultures have been recognized as a troublesome issue. Emergency departments and intensive care units (ICU) are particularly susceptible to contaminated blood cultures. Methods : It was a retrospective study carried out on blood cultures submitted to department of microbiology from in patients in intensive care units (ICU’s) at SVIMS, tirupathi during three year period from January 2017 to December 2019. Results : A total number of blood cultures during this period were 46325, in which conventional were 27211, and automated bactalert were 19114. Among these, 4298 and 5456 were positive blood culture samples in conventional and automated blood cultures respectively. Contaminated blood cultures were 598 by conventional and 728 by automated bacTAlert 3D system methods. The mean blood contamination rate was 2.8, 3.2, 2.4 for 2017,2018,2019 respectively. Coagulase negative staphylococcus was the most predominant isolate, followed by Aerobic spore bearers (ASB) and diptheroids. Staphylococcus hominis was the most common isolated species of CONS. The greater number of samples were from Emergency medicine department followed by Nephrology department. Conclusion: Strict implementation of disinfectants, educational interventions, sampling from separate venipuncture sites under aseptic precautions, hand hygiene , proper infection control practices before and after collecting the sample are important in decreasing blood culture contamination rate