Comparison of blood culture contamination and true positivity between Emergency treatment unit, Intensive care units and General wards in a Tertiary care centre in Southern Sri Lanka: A cross-sectional study

Isolation of the bacterial pathogens in blood is a gold standard test to diagnose bloodstream infections. The contamination of the sample during collection is the main drawback leading to the mismanagement of patients. This study aimed to compare blood culture contamination (BCC) and true positivity (TP) between Emergency Treatment Unit (ETU), Intensive Care Units (ICUs) and general wards (GWs) and to assess contaminants and true pathogens. A cross-sectional study was performed from January 2022 to April 2022 in Teaching Hospital Karapitiya (THK). All consecutive peripheral blood culture reports from patients admitted to the ETU, ICUs and GWs wards in THK were included. We analyzed proportions of contaminant and true positive blood cultures, and variables associated with BCC. Of all 1859 blood cultures, the total positives were 396 (21.3%). The overall BCC rate was 8.5% and the BCC rate in ETU (12.5%) is significantly higher than GWs (7.8%) and ICUs (6.5%)(OR 2.3; 95% CI 1.2-4.3). The overall TP was 12.8%. The time-to-positivity of the true pathogen was significantly less compared to the contaminant (16.3 vs 24.6 hours). The predominant contaminant and true pathogen were coagulase-negative Staphylococcus spp. (83.6%) and E.coli (25.2%) respectively. The BCC was significantly higher in patients above 65 years (p<0.001). The blood culture contamination was significantly higher in ETUs compared to ICUs and GWs. Gram-positive bacteria were the predominant contaminant, and the majority of true pathogens were Gram-negative. Adherence to protocols and education and training of staff are mandatory to reduce contamination.