Blood culture contamination (BCC) is mainly caused by commensal bacteria, during sample collection. It results in unnecessary antibiotic exposure, prolonged hospitalisation, additional microbiology workup and significant adverse health-economic burden. We… Click to show full abstract
Blood culture contamination (BCC) is mainly caused by commensal bacteria, during sample collection. It results in unnecessary antibiotic exposure, prolonged hospitalisation, additional microbiology workup and significant adverse health-economic burden. We aimed to investigate the short- and long-term impact of the COVID-19 pandemic on the incidence of BCC. We conducted a retrospective, observational cohort study at Geneva University Hospitals (HUG). We included all BCCs from January 2018 to December 2023, collected as part of a prospective hospital-wide surveillance by the infection control team. Data were analyzed using segmented Poisson regression models to evaluate BCC incidence rate ratios (IRRs) across three periods: pre-COVID-19 (2018–2019), during COVID-19 (2020–2021), and post-COVID-19 peak (2022–2023). Out of 456,873 collected blood cultures, 1,247 BCCs were identified (0.27%). The contamination rate per 1000 samples increased from 1.53 pre-COVID-19 to 2.94 during COVID-19 and 3.52 post-COVID-19. Compared to the pre-COVID-period, incidence rate ratios (IRRs) for BCC increased during COVID-19 (IRR 1.84, 95% CI 1.58–2.15) and post-COVID-19 peak (IRR 2.29, 95% CI 1.97–2.66). During COVID-19, proportions of BCC were increased in intensive care units (27.4%, n = 127) and returned to baseline level post-COVID-19 (17.3%, n = 93, p < 0.001); whereas, in other wards, BCC remained elevated (42.2%, n = 227) in the post-COVID-19 period. We observed a significant rise in BCC incidence during and after the COVID-19 peak. The persistently elevated post-peak rates highlight ongoing challenges in regaining optimal aseptic blood culture collection practices and the need for further exploration of persisting factors increasing BCC rates.