A 5-year study of data from US hospitals provides a national picture of the prevalence and trends in Escherichia coli and Klebsiella pneumoniae isolates carrying beta-lactamase antibiotic resistance genes, researchers reported last week in Open Forum Infectious Diseases.
In the study, researchers from JMI Laboratories in Iowa conducted antibiotic susceptibility testing on 19,453 E coli and K pneumoniae isolates collected from 56 US hospitals from 2016 through 2020. Isolates that displayed reduced susceptibility to at least two of four antibiotics (ceftazidime, ceftriaxone, aztreonam, or cefepime) or resistance to carbapenems were submitted for whole-genome sequencing for identification of extended-spectrum beta-lactamase (ESBL) genes and other beta-lactamase mechanisms, which confer resistance to beta-lactam antibiotics and make E coli and K pneumoniae infections more difficult to treat.
Overall, ESBL production was noted among 14.2% of the E coli isolates and 12.5% of the K pneumoniae isolates, which corresponded to 86.8% and 91.9% of the isolates resistant to cephalosporins and/or aztreonam without carbapenem resistance, respectively. The most common ESBL gene detected was blaCTX-M-15, which accounted for 55% of ESBL producers. ESBL production was highest in Middle Atlantic states.
ESBL rates were stable over the study period, but a significant increase in ESBL-producing isolates from bloodstream infections was observed, and ESBL production significantly increased among K pneumoniae isolates as well, mainly driven by an increase in blaCTX-M.
Carbapenem resistance and carbapenemase genes were noted in 166 and 145 isolates, respectively, and rates of carabapenem-resistant Enterobacterales (CRE) declined from 44 isolates in 2016 to 28 in 2020. Carabapenems and ceftazidime-avibactam were very active against ESBL producers without carbapenem resistance, while ceftazidime-avibactam was the most active agent against CRE isolates.
"This study reliably reports the occurrence of b-lactam-resistant phenotypes and genes in U.S. hospitals, providing a national picture of the distribution of isolates with these characteristics," the study authors wrote. "The activity of new and established antimicrobial agents is also reported and provides an understanding of resistance profiles."