Antimicrobial resistance to cefotaxime and ertapenem in Enterobacteriaceae: the effects of altering clinical breakpoints

Abstract

Introduction: The Clinical and Laboratory Standards Institute (CLSI) updated its antimicrobial susceptibility testing interpretation criteria for Enterobacteriaceae. This study assessed the effects of clinical breakpoint changes in the CLSI 2009 to 2012 guidelines on antibiotic susceptibility testing reports. Methodology: In total, 2,076 non-duplicate clinical isolates of Enterobacteriaceae were analyzed. The disk diffusion method was used for susceptibility testing. The CLSI 2009-12 clinical breakpoints were applied to determine susceptibility of cefotaxime and ertapenem. Combined-disk testing was used for phenotypic confirmation of extended-spectrum beta-lactamase (ESBL) production. Results: In total, Enterobacteriaceae resistance rates to cefotaxime increased from 13.1% using the CLSI 2009 guidelines to 23.6% with the CLSI 2010-12 guidelines, and the resistance rates to ertapenem were 0.4%, 1.0% and 0.8% with CLSI 2009, 2011 and 2012, respectively. Based on the 2010-12 CLSI criteria, all ESBL-producing Escherichia coli and Klebsiella pneumoniae were resistant to cefotaxime. Marked differences in susceptibility to ertapenem between the 2009 CLSI criteria and 2012-12 CLSI criteria were noted in ESBL-producing K. pneumoniae. Conclusions: Breakpoints changes in the updated CLSI guidelines resulted in higher resistance rates to cefotaxime and ertapenem. In addition, the effects were different in individual Enterobacteriaceae species. As a result, clinicians may opt to use alternative antimicrobial agents. Upon implementation of the newer CLSI guidelines, laboratories should be aware of the possible consequences and closely monitor the effects.

Antimicrobial resistance of selected invasive bacteria in a tertiary care center: results of a prospective surveillance study

“…This was mainly attributed to increased CBPs for cephalosporins and fluoroquinolones. Liu et al observed a 10.5% increase in Enterobacteriaceae resistance rates to cefotaxime due to the CLSI CBP change from 2009 to 2010 guidelines, as well as 6.6% and 13.2% increase in resistance rates of K. pneumoniae, respectively [19]. However, the most likely causes of high MDR Gram-negative rates in this study are the overconsumption of antibiotics and the lack of both general and bacteria-specific healthcare strategies for prevention and control of hospitalacquired infections.…”

Secular trends in Klebsiella pneumoniae isolated in a tertiary-care hospital: increasing prevalence and accelerated decline in antimicrobial susceptibility

“…The change made by CLSI in the carbapenem breakpoints for Enterobacteriaceae (7) may have additionally reduced the rate of isolate susceptibility to these drugs, particularly for ertapenem (19) (20) . However, the major reason for the increase in K. pneumoniae resistance to carbapenems is probably the international dissemination of bacterial clones, such as the CC11 clonal complex, which express genes that regulate the carbapenemases, including Klebsiella pneumoniae carbapenemase (KPC), oxacillinase 48 (OXA-48), and New Delhi metallo-β-lactamase (NDM) (21) (22) .…”

Commentary: Impact of CLSI Breakpoint Changes on Microbiology Laboratories and Antimicrobial Stewardship Programs

“…With the implementation of the new breakpoints, it is anticipated that microbiology laboratories will be reporting more isolates as either intermediate or resistant to the tested antibiotics, potentially leading to increased prescribing of broad-spectrum antibiotics. An assessment of 2,076 nonduplicate clinical Enterobacteriaceae isolates using disk diffusion to compare the 2009 breakpoint to the 2010 breakpoint saw resistance to the thirdgeneration cephalosporin cefotaxime jump from 13.1% to 23.6% (16). Another assessment of 3,713 nonduplicate Gram-negative bacillus isolates with susceptibility determinations performed by disk diffusion using the CLSI 2009, CLSI 2010, CLSI 2011, and EUCAST 2011 guidelines found that, in aggregate, rates of resistance to cefepime, ceftriaxone, and ertapenem increased from (17).…”