Evaluation of Blood Culture Contamination Rates and Their Clinical Impact in a Teaching Hospital in Benin City, Edo State

Blood culture contamination is a persistent quality challenge in clinical microbiology laboratories that leads to unnecessary antibiotic use, prolonged hospital stays, and additional diagnostic costs. This prospective audit study evaluated blood culture contamination rates and their clinical consequences at the University of Benin Teaching Hospital, Benin City, Edo State, in the South South geopolitical zone of Nigeria. All blood culture sets submitted to the clinical microbiology laboratory over a six-month period in 2024 were reviewed. Contamination was defined as growth of skin commensals such as coagulase-negative Staphylococcus, Corynebacterium species, or Bacillus species not Bacillus anthracis in a single culture bottle without clinical correlation. A total of 1,200 blood culture sets were reviewed. The overall contamination rate was 9.4 percent, exceeding the recommended acceptable threshold of 3 percent. Phlebotomy team training level was identified as the most significant predictor of contamination events. Clinical audit revealed that 68 percent of contaminated culture results triggered additional diagnostic workup and 41 percent prompted unnecessary antibiotic prescription changes. Each contaminated set incurred an average additional cost of approximately 45,000 naira. The study recommends implementation of dedicated phlebotomy teams, standardized skin antisepsis protocols, and quarterly contamination rate reporting as a laboratory quality indicator at UBTH Benin City. Keywords: blood culture contamination, clinical microbiology, Benin City, laboratory quality, antibiotic stewardship.