Assessing the effect of delay in transit and processing on pathogen recovery from blood cultures in the bd bactectm fx system at Clinical Microbiology Laboratory, College of Health Sciences, Makerere University, Kampala

Abstract

Blood culturing is still considered as the gold standard done by microbiology laboratories with aim of detecting microbial pathogens related to blood stream infections, in turn guide antibiotic therapy. The Clinical and Laboratory Standards Institute (CLSI) recommends processing of blood cultures within 2 hours of sample collection. This study aimed at investigating how delay in transit and delayed incubation would affect microbial recovery from blood cultures. Blood culture samples from different off-site facilities with a transit time greater 12 hours were followed, blood culture bottles (adult and pediatric) were spiked with sterile blood containing selected commonly isolated bacterial strains of Escherichia coli, Staphylococcus aureus and Streptococcus pneumoniae and stored at different time periods. 91 blood culture samples were followed, 5 samples turned positive and 86 samples turned negative, indicating reduced chances of obtaining a positive result with an extended transit time beyond the recommended time. it was found that mean time to detection for the three isolates increased gradually from 2 hours (8.087h vs13.56h, ped vs adult) ,4hours (9.66h vs 15.99h, ped vs adult), 6hours (14.37h vs 24.3h, ped vs adult), 12hours (16.74h vs 27.6h, ped vs adult), 24hours (19.5h vs 30.8h, ped vs adult) and finally to 48hours (25.73h vs 33.87h, ped vs adult). These results suggest that time lags encountered during transit and before incubation have a negative impact on microbial yields from blood cultures and an increase on time to detection of the pathogens.