Increase of blood culture contamination during COVID-19 pandemic. A retrospective descriptive study

Ohki, Risa; Fukui, Yumiko; Morishita, Naomi; Iwata, Kentaro

Background: Secondary bacterial infection during the care of coronavirus disease 2019 (COVID-19) patients poses risks to the patients, but there are concerns of an increase in blood culture contamination. Methods: A retrospective comparative study was conducted from April 1 to December 31, 2020, when the patients with COVID-19 were taken care of (pandemic period, PP), and it was compared with the same period in 2019 (pre-pandemic period, pre-PP). Results: A total of 346 patients with COVID-19 were hospitalized during the study period in 2020. A total of 1,040 and 918 blood cultures were taken during PPP and PP respectively. 38 and 56 contaminations occurred during pre-PP and PP respectively (3.7% (95% CI 2.6%-5.0%), vs 6.1% (95% CI 4.6%-7.8%), P=0.015). For the ICU, 10 and 32 contaminations occurred during the same periods (5.0% (95% CI 2.4%-9.0%), vs 12.5% (95% CI 8.7%-17.1%), P=0.0097). True bacteremia in the ICU per patient-day also increased during the PP. Conclusions: We found a significant increase in blood culture contamination during the COVID-19 pandemic in the ICU setting, while true bacteremia also increased. A safe and effective way to obtain blood cultures from patients with COVID-19 should be sought.