EVALUATION OF TIME TO POSITIVITY IN DETECTION OF MICROORGANISM USING BACTECTM 9050 IN A TERTIARY CARE HOSPITAL OVER A PERIOD OF ONE YEAR

Blood stream infections are being reported as one of the most important cause of morbidity and mortality, more commonly in the developing than in the developed countries of the world. Early and accurate identification of the microorganism responsible for the infection permits early initiation of targeted broad spectrum empirical therapy. 1 The automated blood culture systems which have been introduced, have improved in their capacity to detect and isolate the microorganisms much earlier than the conventional culture techniques which were used earlier. The use of culture bottles with specific resins which help in nullifying the antimicrobial effect and improve the growth of the microorganisms are recommended. 1The following study was done using the BACTEC (TM) 9050 system to estimate and compare the time to positivity of various microorganisms. 800 samples comprising of blood and body fluids were tested using BACTEC (TM) 9050 and the time to positivity indicated from the time of processing, to the time of beep were calculated & analyzed. Of 800 samples, 146 (17.9%) were positive for growth by BACTECTM 9050 culture system. 15 (1.8%) were false positive (no growth on further processing by aerobic culture techniques from a positive beep in BACTEC (TM) 9050). The microorganisms isolated from the positive cultures included both pathogenic, non-pathogenic bacteria and fungi. The mean detection time, for the isolated microorganisms was around 24 hours. The pathogenic microorganisms isolated had a shorter time to positivity than the nonpathogenic organisms. Since all the cultures were positive by 72 hours, our data supports a four day incubation period for isolating microorganisms using automated blood culture systems. Hence, automated BACTECTM 9050 is reliable, fast, accurate and cost effective, with high sensitivity, specificity for isolating microorganisms from samples.