When the COVID-19 pandemic reached France early in 2020, the enforced nationwide lockdown deeply altered lifestyle as well as hospital processes and modalities of care. The aim of the study was to evaluate the impact during the lockdown of the first epidemic wave on the epidemiology of bacteremia in one French University Hospital.

Retrospective cohort study including adult patients with positive blood culture between 23^rd March to 24^th May 2020. The clinical-microbiological characteristics were compared with those of the period from 25^th March to 26^th May 2019. The data were adjusted to the number of hospitalizations (h).

In 2020, 189 bacteremia were diagnosed from 1939 vials (9658 hospitalizations, 10911 emergency room consultations) compared to 143 from 1976 vials (14797 hospitalizations, 16493 emergency room consultations) recorded in 2019. The incidence of bacteremia increased up to 19.7 per 1000h in 2020 vs 9.7 in 2019 (p < 0.001). The main differences (2020 vs 2019) were: Staphylococcus aureus bacteremia (2.4 vs 1.0/1000h, p = 0.012), polymicrobial bacteremia (2.2 vs 0.9/1000h p = 0.013) and Gram-negative bacteremia (8.9 vs 4.3/1000h, p < 0.01). Conversely, Streptococcus pneumoniae incidence decreased (0 vs 0.47/1000h, p = 0.047). The standardized incidence ratio calculation confirmed these results.

The lockdown and the impact of the first wave of the Covid-19 pandemic on the health system resulted in increased hospital-diagnosed bacteremia and decreased pneumococcal bacteremia. Disruption and overload of ICUs, lockdown with preventive control measures, and decrease in human-to-human interaction may have been the main reasons.