In a new 10-year analysis, the CDC found antimicrobial resistance in hospitals declined from 2012 to 2019, but rose again during the acute COVID-19 pandemic years (2020-2021). In addition, 1 specific set of pathogens saw increases over this time period, but the others remained stable or saw decreases.
The study looked at 6 pathogens including, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus spp (VRE), extended-spectrum cephalosporin-resistant Escherichia coli and Klebsiella spp (excluding Klebsiella aerogenes) (ESCR-EK) suggestive of extended-spectrum β-lactamase production, carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant Acinetobacter spp (CRAsp), and multidrug-resistant (MDR) Pseudomonas aeruginosa. CDC and the World Health Organization have identified these pathogens as high priority to be aware of and address. The results were published in JAMA Network Open.
“The percentage resistant for MRSA, VRE, CRE, CRAsp, and MDR P aeruginosa was stable or decreased from 2012 to 2022,” The investigators wrote. “Among hospital-onset E coli and Klebsiella spp, the percentage of ESCR-EK cases in nonsterile body sites increased from 12.2% (95% CI, 10.7%-13.6%) in 2012 to 19.7% (95% CI, 17.7%-21.7%) in 2022; and increased from 17.5% (95% CI, 14.4%-20.7%) to 24.5% (95% CI, 21.5%-27.4%) among normally sterile body sites.”
The investigators pointed out that there were differences by region and species. “Among hospital-onset CRE, hospital-onset CR K pneumoniae rates decreased from 2012 to 2022 while hospital-onset CR E cloacae complex and E coli rates did not decrease. Hospital-onset CRE rates decreased in the Northeast US census region with stable or increased rates in other regions,” the investigators wrote.
They also noted resistant infections differences amongst the sexes and age groups. “Rates of hospital-onset MRSA, CRE, CRAsp, and MDR P aeruginosa were higher among males and all hospital-onset resistant case rates were higher in the subpopulations aged 55 to 64 years and 65 to 74 years compared with younger patients.”
Study Parameters
This was a cohort study examining data from 2012 to 2022 that included inpatient hospitalizations, clinical cultures, and facility-level characteristics. The investigators included hospital-months when in the dynamic cohort the institution reported at least 1 culture with microbial growth accompanied by antimicrobial susceptibility testing (AST) results in the month.
Cases were defined as incident nonsurveillance cultures yielding an organism of interest with sufficient AST results for a phenotype of interest. The PINC-AI and Becton Dickinson Insights databases were utilized for the study.
What You Need to Know
Resistance rates for MRSA, VRE, CRE, CRAsp, and MDR P aeruginosa were mostly stable or decreased over the 10-year period. However, ESCR-EK infections (E coli and Klebsiella spp.) increased significantly, particularly in nonsterile and sterile body sites. Regional, species, sex, and age-related differences were also observed, with older adults (55-74) and males having higher rates of hospital-onset resistant infections.
The pandemic caused a reversal in resistance declines, with increased hospital-onset resistant cases in 2020-2021 for all 6 pathogens studied.
The study emphasizes the need for sustained and adaptable infection prevention efforts—especially during healthcare system strain like the pandemic.
The Pandemic’s Effect on Resistance
This study confirms previous reports around the acute phase of the pandemic and its effects on HAI. The investigators pointed out that the pandemic, especially in 2020, saw an increase in hospital-onset resistant case rates, which they noted has been reported in other studies. There were a number of factors that happened during the acute phase of the pandemic that could have resulted in these changes in resistance patterns.
“Changes to health care use during the COVID-19 pandemic, such as decreases in overall admissions, surges in high-risk patients with COVID-19, and higher proportions of patients who were sicker and did not have COVID-19 contributed to increased hospital-onset resistant case rates,” they wrote.
Additionally, the investigators saw an increase in the average patient stays per hospitalization from 2020 to 2022, which of course can lead to further hospital-associated infections.
“This suggests an increase in patients with severity of illness that continued when COVID-19 hospitalizations declined and may reflect larger trends in an aging US population with increased chronic illness or a move to manage less acute patients in outpatient care,” they reported. “Additionally, infection control practices like contact precautions for patients with some resistant pathogens and monitoring excess antimicrobial use decreased during the pandemic, which may have led to increased antimicrobial resistance.”
Further strategies are needed to combat resistance, according to CDC. One of the biggest takeaways from the study is the need for consistent infection prevention within hospitals especially during a time of significant healthcare burden such as the pandemic.
“Increases in hospital-onset rates for all 6 pathogens in 2020 emphasized that prevention efforts may not be sufficient in times of additional health care strain…Our findings suggest a need for prevention interventions that can maintain effectiveness despite strain on health care systems and workers,” the investigators wrote.
Reference
1. Wolford H, McCarthy NL, Baggs J, et al. Antimicrobial-Resistant Infections in Hospitalized Patients. JAMA Netw Open. 2025;8(3):e2462059. doi:10.1001/jamanetworkopen.2024.62059
