Blood culture contamination and microbial patterns in a tertiary hospital: a six-year retrospective analysis, 2020–2025

Blood culture contamination remains an important challenge in clinical microbiology, leading to false-positive results, unnecessary antimicrobial use, increased healthcare costs, and prolonged hospitalization. Data regarding blood culture contamination in Somalia are limited. This study aimed to evaluate blood culture contamination and microbial growth patterns in a tertiary hospital in Mogadishu, Somalia, over a six-year period. A retrospective laboratory-based study included all blood culture records from Recep Tayyip Erdoğan (Ex-Digfeer) Hospital, Mogadishu, Somalia, between January 2020 and December 2025. The unit of analysis was a laboratory record; contamination classifications were taken directly from the laboratory system. Rates were summarized by year and department. Exact tests addressed sparse groups, and exploratory logistic regression adjusted for year, department, age group, and sex. A total of 8,238 blood culture records were included. Overall, 2,645 (32.11%) cultures showed microbial growth, while 5,593 (67.89%) showed no growth. Among positive cultures, 2,263 (85.56%) were classified as true positives and 382 (14.44%) as contaminated. The overall contamination rate among all blood cultures was 4.64%. The highest contamination rate among all cultures was observed in the hemodialysis department (12.89%; 95% CI: 9.13–17.90), followed by emergency, outpatient, and ancillary departments (9.11%; 95% CI: 6.90–11.94). The lowest contamination rates were observed in general intensive care (1.22%; 95% CI: 0.66–2.23), adult emergency intensive care (1.68%; 95% CI: 1.09–2.58), and neonatal intensive care units (1.83%; 95% CI: 1.28–2.61). Departmental variation remained evident with a Monte Carlo exact test ( p < 0.001) and after adjustment for year, age group, and sex (global p < 0.001). Inferential results are exploratory because repeated patient records could not be linked. Coagulase-negative staphylococci were the predominant contaminants throughout the study period. Blood culture contamination represented a substantial quality and patient safety concern in this tertiary hospital. Marked variation across hospital departments suggests the need for targeted interventions, particularly in hemodialysis, emergency, and pediatric departments. Strengthening blood culture collection practices, staff training, and quality monitoring programs may help reduce contamination and improve diagnostic accuracy.