Comparison of the postantibiotic and postantibiotic sub-MIC effects of levofloxacin and ciprofloxacin on Staphylococcus aureus and Streptococcus pneumoniae

Abstract

The postantibiotic subminimum inhibitory concentration effect (PA SME) may simulate in vivo drug exposure more accurately than the postantibiotic effect (PAE) since subinhibitory concentrations of drug persist between antibiotic dosings. In this study, we compared the PAEs and PA SMEs of levofloxacin and ciprofloxacin for clinical isolates of fluoroquinolone-susceptible Staphylococcus aureus and Streptococcus pneumoniae. At two times the MIC, PAEs of levofloxacin were an average of 0.6 h longer than the PAEs obtained for ciprofloxacin for methicillin-susceptible and methicillin-resistant S. aureus strains. The PAEs of levofloxacin and ciprofloxacin ranged from 1.8 to 3.1 and 1.1 to 2.4 h, respectively. Continued exposure of the methicillin-resistant strain to 1/16, 1/8, and 1/4 the MIC resulted in PA SMEs of 6.5, 15.3, and >22.3 h, respectively, for levofloxacin and 3.8, 8.0, and 12.3 h, respectively, for ciprofloxacin. For isolates of S. pneumoniae, at two times the MIC of both fluoroquinolones, the average PAEs of levofloxacin and ciprofloxacin were equivalent: 1.3 h for the penicillin-susceptible isolate and 0.6 h for the penicillin-resistant isolate. Continued exposure of the penicillin-susceptible S. pneumoniae strain to 1/16, 1/8, and 1/4 the MIC resulted in average PA SMEs of 1.0, 1.4, and 2.8 h, respectively, for levofloxacin and 1.8, 2.0, and 2.5 h, respectively, for ciprofloxacin. Continued exposure of penicillin-resistant S. pneumoniae to 1/16, 1/8, and 1/4 the MIC of the same fluoroquinolones resulted in average PA SMEs of 0.6, 1.1, and 2.9 h, respectively, for levofloxacin and 0.6, 1.1, and 1.5 h, respectively, for ciprofloxacin. The PA SMEs observed demonstrate the superior activity of levofloxacin against methicillin-susceptible or methicillin-resistant S. aureus. Although PAEs were similar for the penicillin-susceptible and penicillin-resistant S. pneumoniae strains, the PA SME of levofloxacin at one-fourth the MIC was longer for penicillin-resistant S. pneumoniae.

Postantibiotic effect and postantibiotic sub-minimum inhibitory concentration effect of valnemulin against Staphylococcus aureus isolates from swine and chickens

“…The results obtained from this study were consistent with the conclusions of a previous report by Licata et al . (). BC‐3205, a novel semi‐synthetic pleuromutilin derivative, was studied in neutropenic murine infection model.…”

Post-antibiotic effect of orbifloxacin against Escherichia coli and Pseudomonas aeruginosa isolates from dogs

“…The PAE and PA-SME of orbifloxacin were examined in comparison with enrofloxacin, and were performed in accordance with procedures described previously [7]. Each strain was grown in the logarithmic growth phase to a concentration of approximately 5 × 10 6 colony-forming units (CFU)/mL and was prepared for use in PAE experiments.…”

“…These results suggest that MICs can affect the periods of PAE and PA-SME in bacteria. However, Licata et al [7] reported that the two strains of Staphylococcus aureus , with the same MICs, showed different PAEs and PA-SMEs. Therefore, the effect of MICs on PAEs and PA-SMEs in bacteria requires further investigation.…”

Effects of Intracanal Irrigant MTAD Combined with Nisin at Sub-Minimum Inhibitory Concentration Levels on Enterococcus faecalis Growth and the Expression of Pathogenic Genes

“…study, strains with higher MICs of orbifloxacin and enrofloxacin consistently showed shorter PAE and PASME when compared to those with lower MICs [17]. In another study, two strains of Staphylococcus aureus with the same MICs showed different PAE and PASME [20]. Thus, the MIC of antibiotics was not a unique dependent factor for PASME, and the relationship of the MICs of antibiotics with PASME requires further investigation.…”