By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center
SOURCE: Zhu N, Rawson TM, Mookerjee S, et al. Changing patterns of bloodstream infections in the community and acute care across two COVID-19 epidemic waves: A retrospective analysis using data linkage. Clin Infect Dis 2021;Oct 1:ciab869. doi: 10.1093/cid/ciab869. [Online ahead of print].
Researchers at the Imperial College Hospital and School of Public Health in London examined patterns of bloodstream infection (BSI), hospital stay, and mortality before and during two waves of COVID-19 between January 2020 and February 2021. The first major wave peaked in April 2020 and the next major wave, which was more serious and deadlier, began in the fall of 2020, peaking in January 2021. During both major pandemic waves in London, hospital personnel and supplies were stretched thin, despite suspension of elective admissions during peak COVID-19 activity and the truncation of laboratory support services.
For the purposes of this analysis, a positive bloodstream infection was defined as two positive cultures with the same species within a 24-hour period; single cultures and those with skin commensals were regarded as contaminates. Positive cultures taken within 48 hours of admission were regarded as community-acquired BSI, and those obtained more than 48 hours after admission were considered hospital-onset BSI.
In total, 34,044 blood cultures were obtained in 19.9% of admissions; blood cultures were obtained in 59.9% of those admitted to the ICU. Despite a decrease in the number of total hospital admissions by 65% during the surges, mostly because of the suspension of elective activities, blood cultures were obtained at a rate nearly double that of pre-COVID, up from 86.8/1,000 patient days pre-COVID to 150.7/1,000 patient days during both COVID surges. Of these, 6.8% of blood cultures contained bacterial and/or fungal growth, one-third of which were from ICU patients.
Increases in both contaminated and non-contaminated blood cultures were observed during both COVID surges. Coagulase-negative Staphylococcus were isolated in 47.8% of cultures during both surges, up from 24.8% pre-COVID. Overall, 41.3% of cultures were considered contaminated during both surges, up from 31.5% pre-COVID. A total of 1,250 true-positive blood cultures occurred in 1,047 BSI, including 653 community acquired and 394 hospital acquired. Despite the decrease in hospital admissions, hospital-onset BSI increased from 97.3/100,000 patient days pre-COVID to 132.8/100,000 and 190.9/100,000 during the first and second surge, respectively. For those patients in the ICU, the rate of hospital-onset BSI increased from 101.3/100,000 patient days pre-COVID to 421/100,000 patient days during the second wave, a 400% increase.
The rate of hospital-onset BSI was 170.2/100,000 and 90.1/100,000 in those with and without COVID infection, respectively (P < 0.05). The largest observed increase in hospital-acquired bloodstream pathogens was caused by methicillin-resistant Staphylococcus aureus (MRSA), up from 0.8 pre-COVID to 4.9 during the first wave and 6.0 during the second wave (per 100,000 patient days).
During both surges, patients with hospital-acquired BSI recorded an all-cause hospital mortality rate of 32.1%, up 24% from pre-COVID. Length of stay was on average 20.2 days longer in patients with hospital-acquired BSI.
The authors believe both the higher rate of contaminated cultures and the increase in hospital-acquired BSI can be directly traced to the effect of both COVID surges on the hospital system, with disruptions in care and breakdown of usual infection prevention practices. The severity of illness, prolonged hospital stays, use of mechanical ventilation, and use of immune-modulating agents in people with COVID also may have contributed to the observed increases in hospital-acquired BSI and attendant mortality.
Severity of illness, prolonged hospital stays, use of mechanical ventilation, and use of immune-modulating agents in patients with COVID-19 may have contributed to observed increases in hospital-acquired blood stream infections and attendant mortality.
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