A new analysis of US antimicrobial resistance (AMR) data from 2012 through 2022 shows that the burden of drug-resistant infection in hospitals fell but remains substantial.
The study, conducted by researchers with the Centers for Disease Control and Prevention (CDC), found that six bacterial pathogens associated with healthcare accounted for nearly 570,000 drug-resistant infections in US hospital patients in 2022. That figure reflects a decline from the 600,000 resistant infections estimated by the CDC in 2017.
But while rates of several drug-resistant community- and hospital-onset infections declined during the first part of the study period, the COVID-19 pandemic ushered in a significant increase in resistant infections in hospitalized patients.
The authors of the [study](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2831512), published late last week in _JAMA Network Open_, say the findings suggest that new strategies for reducing resistant pathogens are needed.
"Our findings underscore the need for innovative prevention strategies to reduce the burden of antimicrobial resistance, as current interventions may be insufficient," they wrote.
### Overall decline masks sharp uptick during COVID
To provide updated estimates for rates for community- and hospital-onset AMR infections, the researchers analyzed US inpatient hospitalization data from two databases that include select patient, microbiology, and facility-level data.
Using those data, the researchers identified patients who had a clinical culture yielding an organism of interest with an accompanying antimicrobial susceptibility test. Community-onset cases were defined as incident cultures collected before day 4 of hospitalization, and hospital-onset cases as those with cultures obtained on day 4 or later.
The six pathogens of interest were methicillin-resistant _Staphylococcus aureus_ (MRSA), vancomycin-resistant _Enterococcus_ (VRE), extended-spectrum cephalosporin-resistant _Escherichia coli_ and _Klebsiella pneumoniae_ (ESCR-EK), carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant _Acinetobacter_ spp (CRAsp), and multidrug-resistant (MDR) _Pseudomonas aeruginosa._ Both the CDC and the World Health Organization have labeled these pathogens high priority because of their limited treatment options and ability to cause severe infections.
The study cohort included 332 to 606 hospitals per year from 2012 through 2022 and more than 7 million clinical cultures. The six pathogens accounted for 569,749 cases and 179.6 cases per 10,000 hospitalizations in 2022. Of these infections, 437,657 (77%) were community-onset and 132,092 (23%) were hospital-onset. The biggest contributors to infections were MRSA (251,854; 44%) and ESCR-EK (200,884; 35%).
> Our findings underscore the need for innovative prevention strategies to reduce the burden of antimicrobial resistance, as current interventions may be insufficient.
Overall, the rate of resistant infections declined from 209.6 to 179.6 per 10,000 hospitalizations from 2012 through 2022. But the decrease was uneven; within the study period there was a decline in the rate of resistant infections from 2012 to 2016, a plateau from 2016 through 2018, an increase that began in 2019 and peaked in 2020 at 197 cases per 10,000 hospitalizations, and then another decline.
While rates of hospital-onset MRSA, VRE, CRE, CRAsp, and MDR _P aeruginosa_ saw periods of decline from 2012 to 2019, all six pathogens experienced a significant increase in hospital-onset rates in 2020 to 2021. This increase, which has been [well-documented](https://www.cidrap.umn.edu/healthcare-associated-infections-rose-2020-cdc-says) by the CDC and others, was driven by COVID-19–related hospital surges.
"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," the authors wrote. They add that reduced use of infection control practices in hospitals during the pandemic—because staff were busy treating COVID patients—may have also increased AMR.
"Our findings suggest a need for prevention interventions that can maintain effectiveness despite strain on health care systems and workers," they wrote.
### Steadier decline in community-onset infections
Community-onset infections fell from 2012 through 2022, driven by reductions in community-onset MRSA, VRE, and MDR _P aeruginosa_ infections. In particular, there were dramatic declines in community-onset MRSA infection in children.
But the one pathogen that saw a steady increase in community-onset infections over the period was ESCR-EK. The authors say the increase can be attributed to _E coli_ sequence type (ST)131, which has emerged in recent years as a frequent source of severe, MDR infections—primarily urinary tract infections—worldwide.
"The success of this strain may be due to antibiotic use or strain virulence characteristics," they explained. "Additionally, community transmission may be increasing due to increasing ESCR _E coli_ intestinal carriage among healthy individuals."
The authors note that because their study captures only 11% to 18% of US hospitalizations over the period, more comprehensive AMR data are needed to provide a more complete picture of the burden of AMR in US hospitals. But they hope that their analysis can at least give healthcare professional a sense of where to start in their efforts to address the problem.
"These analyses can inform health care partners of the pathogens and populations that can be prioritized for intervention to achieve the biggest impact in reducing antimicrobial resistance," they concluded.