Between 2016 and 2019, the incidence for all key Gram-positive and Gram-negative bloodstream infections (BSI) increased. However, in 2020, the incidence of the majority of key Gram-negative BSI (GNBSI) decreased. Escherichia coli was the most common cause of GNBSI during 2016 to 2020, and despite a 13.8% decrease in its incidence between 2019 and 2020, it remained a significant concern; particularly as the observed reduction was predominantly due to community-onset cases.

The incidence of all key GNBSI, except for E. coli, increased between 2020 and 2021, equal or greater to the incidence observed in 2019.

The GNBSI antimicrobial resistance (AMR) burden increased year-on-year between 2016 and 2019, with an overall increase of 25.7%. After which there was a 15.7% reduction from 15,960 to 13,450 estimated resistant BSI, between 2019 and 2020. While there has been an increase in many of the key GNBSI incidence between 2020 and 2021, the AMR burden has continued to decrease – by a further 11.0% - in 2021, with an estimate of 11,970 key AMR BSI lower than the 2016 burden estimate  of 12,700. This is predominantly because of the continued reduction in E. coli BSI. However, it is of note that the estimated number of resistant Klebsiella pneumoniae increased 9.7% between 2020 and 2021 (from 1,751 in 2020 to 1,921 in 2021).

In 2021, the thirty-day all-cause case fatality rate in patients with key resistant GNBSI was 17.1% and 15.6% amongst patients with sensitive GNBSI infections.

The underlying causes of reductions in both BSI and AMR BSI incidence in 2020 were likely to be multifactorial; with significant changes in population-level behaviour and healthcare provision (reduced social mixing, reduced healthcare seeking, reduction in secondary care referrals and GP testing) resulting from the COVID-19 pandemic response. The GNBSI AMR burden has continued to decrease in 2021; however, there were continued lockdowns in early 2021 and substantially less completed elective care pathways between January 2020 and July 2021 than pre-pandemic numbers. As such, it is not yet known if the reductions in AMR GNBSI burden will be sustained, or, as social mixing and healthcare provision continue to return to pre-pandemic levels, whether the AMR burden will start to increase again.