Evaluation of Ciprofloxacin and Levofloxacin Disk Diffusion and Etest Using the 2019 Enterobacteriaceae CLSI Breakpoints

Abstract

In 2019, the Clinical and Laboratory Standards Institute (CLSI) published revisions to the Enterobacteriaceae ciprofloxacin and levofloxacin breakpoints. We evaluated the performance of disk diffusion and Etest compared to that of reference broth microdilution by use of the revised breakpoints. Fifty-eight Enterobacteriaceae isolates with ciprofloxacin MICs of 0.5 g/ml or 1.0 g/ml on initial testing were specifically selected for evaluation. These MICs are susceptible by the 2018 breakpoints and not susceptible by the 2019 breakpoints. For ciprofloxacin disk diffusion, the categorical agreement (CA) was 46.6%, with 0 very major errors (VME), 4 major errors (ME) (21.1%), and 27 minor errors (mE) (46.6%) using the 2019 CLSI disk breakpoints. For levofloxacin, the CA was 72.4%, with 0 VME, 0 ME, and 16 mE (27.6%) using the 2019 CLSI disk breakpoints. Using an error rate-bound evaluation method, levofloxacin but not ciprofloxacin disk diffusion yielded an acceptable minor error rate of Ͻ40% for isolates with an MIC plus or minus 1 doubling dilution of the intermediate breakpoint. For Etest compared to the reference broth microdilution, the essential agreement was 100% for both ciprofloxacin and levofloxacin and the CA was 81.0% and 65.5%, respectively. No VME or ME were observed by Etest, and 11 minor errors for ciprofloxacin (19.0%) and 20 (34.5%) for levofloxacin were observed. By the error rate-bound method, the minor error rate for ciprofloxacin was acceptable, but minor error rates for levofloxacin remained outside the acceptance range (i.e., 42.6% for isolates with an MIC within 1 dilution of the breakpoint). In general, the disk diffusion and Etest methods performed well with this challenging collection of isolates, although laboratories must be aware of minor errors, particularly for isolates with results near the breakpoint.

Antimicrobial Susceptibility Pattern of Porcine Respiratory Bacteria in Spain

“…The measurement of antimicrobial susceptibility is carried out by MIC determination that is more reproducible and comparable between laboratories [11] than disk diffusion techniques due to concerns about disk quality, performance issues [18,19] and variability intrinsically associated to some antimicrobials for the disk diffusion technique [20]. The MIC is the lowest antimicrobial concentration that inhibits in vitro the growth of the target bacteria in specific conditions of in vitro incubation.…”

Bee venom-derived antimicrobial peptide melectin has broad-spectrum potency, cell selectivity, and salt-resistant properties

“…Antimicrobial Activity. Antimicrobial activity assay to determine the minimum inhibitory concentration (MIC) of melectin as described by the National Committee of Clinical and Laboratory Standard methods 36 . Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium KCTC 1926, Klebsiella pneumoniae KCTC 2208, and antibiotic-resistant strains were incubated in culture medium at 37 °C.…”

Levofloxacin Versus Ciprofloxacin in the Treatment of Urinary Tract Infections: Evidence-Based Analysis

“…Levofloxacin shows advantage over ciprofloxacin in terms of efficacy, disease reoccurrence and adverse event (Zhang et al, 2012). On the contrary, microbiology evidence shows that the uropathogen is more sensitive to ciprofloxacin (Afriyie et al, 2018;Humphries et al, 2019). Currently, no evidence-based medical research has been published worldwide on this topic, which makes our study the first systematic review and metaanalysis in the world.…”