Blood culture contamination in Babcock University Teaching Hospital, Nigeria: A five-year retrospective study Contamination des hémocultures au Hôpital Universitaire de Babcock, Nigeria: une étude rétrospective sur cinq ans

Abstract

Background: Bloodstream infections are a leading cause of morbidity and mortality among in-patients globally. Blood culture is the ‘gold standard’ test for the diagnosis of bloodstream infections. The value of this valuable investigation in the diagnosis of infections however may be affected when an organism of questionable evidence is isolated, which occurs mainly due to contamination during the pre-analytical phase. Blood culture contamination can lead to the administration of unnecessary antibiotics, wastage of hospital resources, and risks to patient life. Hence, this study aimed to analyse the blood culture contamination rate in a private tertiary hospital in southwest Nigeria.
Methodology: This was a retrospective observational study of patients with clinical features of bloodstream infections at Babcock University Teaching Hospital, Ilishan-Remo, Ogun State, Nigeria between January 2018 and December 2022. Blood culture results of patients in the wards or units of the hospital were reviewed, and contamination rates and organisms isolated from positive blood cultures were documented. Data were analysed using SPSS version 22.0
Results: A total of 1,612 non-repetitive blood cultures were obtained from 1,612 patients (910 males and 702 females) during the study period, out of which 397 (24.6%) were positive, 1215 (75.4%) were negative, and 124 (7.7%) were deemed as contaminants. The contamination rate was higher in females (8.7%) than in males (6.9%), although the difference was not statistically significant (x²=1.501, OR=0.7816, 95% CI=0.5416-1.128, p=0.2204). The contamination rate was higher in adults (8.1%) than children (7.3%) with the highest contamination occurring in the age group 35-39 years (9.0%), although the difference was not statistically significant (x²=0.3227, OR=0.8835, 95% CI=0.6120-1.276, p=0.5700). The female surgical ward (11.9%) had the highest contamination rate while the accident and emergency had the lowest contamination rate (1.3%) but the difference was not statistically significant (x²=11.825, p=0.2970). Coagulase-negative staphylococci were the predominant blood culture contaminants. The contamination rate increased during the 5 years from 4.8% in 2018 to 9.4% in 2022
Conclusion: The rate of blood culture contamination in our study is higher than the acceptable international rate, and mainly due to normal skin microbiota, suggesting challenges during sample collection. There is a need for a multidimensional approach to minimize blood culture contamination and hence avoid unnecessary antibiotic use.