Evaluation of factors affecting results of blood cultures

Bacteremia and sepsis are among the severe course infections that have high morbidity and mortality. Quick diagnosis and beginning treatment is important. This study was carried out to evaluate the factors affecting the results of blood culture and determination of microorganisms isolated from blood cultures received from Gaziantep University Internal Intensive Care Unit (IICU). Blood culture samples sent to our laboratory from IICU between April 1-September 31, 2013 were included in the study. Blood culture samples were taken to fully automated blood culture system BACTEC 9240 (Becton Dickinson, USA). The identification and susceptibility tests were performed by conventional methods and Phoenix 100 (Becton Dickinson, USA) panels. During the study period, 337 blood culture samples received from 180 patients were evaluated. In 155 of the samples (45.9%) reproduction was detected, in 180 of the samples (53.4%) reproduction was not detected, and in 2 of the samples (0.6%) false positivity was detected. There were no false-neativity in any of the sampless. True-positivity in 99 of the samples (53.4%) and in 56 of the samples (16.6%) contamination was found. A total of 100 bacteria were isolated from the samples where true positivity was found. In 54 of the reproducing bacteria (54%) gram-positive, in 20 of them (20%) gram-negative and 26 of them (26%) yeast were reproduced. Staphylococcus epidermidis is the most commonly isolated microorganism (14%). In 31.6% of the samples coagulase-negative staphylococci (CNS) were isolated. C.albicans (11%) and C.parapsilosis (11%) were found to be the second most commonly isolated microorganisms. The factors that may affect the results of blood cultures (how many set are taken, which region are they taken and the period after they are taken) were evaluated. Among these factors, the true reproduction is found mostly (94%) in the bottles that placed to the device in 2 hours, high contamination was observed in bottles that placed to the device in 3 hours. Although the blood culture is a valuabla diagnostic method, it is concluded that for the detection of actual results information sharing between clinic and laboratory is very important. Key words: Intensive care unit, blood culture, real positive, contamination