Urine bactericidal activity against Escherichia coli isolates exhibiting different resistance phenotypes/genotypes in an in vitro pharmacodynamic model simulating urine concentrations obtained after oral administration of a 400-milligram single dose of cefditoren-pivoxil

Sitafloxacin pharmacokinetics/pharmacodynamics against multidrug-resistant bacteria in a dynamic urinary tract infection in vitro model

OBJECTIVES

Sitafloxacin is one of the newer generation fluoroquinolones with highly active against multidrug-resistant (MDR) bacteria. Our objectives were to identify the sitafloxacin pharmacokinetic/pharmacodynamic (PK/PD) index and breakpoints against MDR isolate in the urinary tract infection model.

METHODS

Forty-eight MDR isolates underwent sitafloxacin and levofloxacin microdilution susceptibility testing. A 24 h in vitro model was established that simulated the healthy subjects urodynamics of sitafloxacin fumarate injection. Ten MDR isolates (four carbapenem-resistant Escherichia coli, three carbapenem-resistant P. aeruginosa and three vancomycin-resistant E. faecium) were selected. The drug efficacy was quantified by the change in log colony counts within 24 h. A sigmoid Emax model was fitted to the killing effect data. Monte Carlo simulations were performed to assess target attainment for the sitafloxacin fumarate doses of 100 and 200 mg q24h.

RESULTS

Analysis indicated that the MICs of sitafloxacin were all significantly lower than that of levofloxacin (P < 0.01). The UAUC0-24h/MIC targets required to achieve stasis, 1-log10 killing and 2-log10 killing were 63.60, 79.49 and 99.45 (carbapenem-resistant E. coli), 60.85, 90.31 and 128.95 (carbapenem-resistant P. aeruginosa), 65.91, 77.81 and 103.11 (vancomycin-resistant E. faecium). Monte Carlo simulation showed the infusion of sitafloxacin fumarate 100 mg q24h was able to achieve 90% probability of target attainment against bacteria with MIC of 8 mg/L for the common complicated urinary tract infections.

CONCLUSIONS

Sitafloxacin fumarate injection is an alternative therapeutic agent for the treatment of UTIs caused by MDR isolates.

Cefditoren: Comparative efficacy with other antimicrobials and risk factors for resistance in clinical isolates causing UTIs in outpatients

BACKGROUND

To investigate a possible role of Cefditoren, a recently marketed in Greece third-generation oral cephalosporin in urinary infections of outpatients.

METHODS

During a multicenter survey of Enterobacteriaceae causing UTIs in outpatients during 2005-2007, Cefditoren MICs were determined by agar dilution method in a randomly selected sample of uropathogens. Susceptibility against 18 other oral/parenteral antimicrobials was determined according to Clinical and Laboratory Standards Institute methodology.

RESULTS

A total of 563 isolates (330 Escherichia coli, 142 Proteus mirabilis and 91 Klebsiella spp) was studied; MIC50/MIC90 of Cefditoren was 0.25/0.5 mg/L respectively, with 97.1% of the isolates being inhibited at 1 mg/L. All 12 strains producing ESBLs or AmpC enzymes were resistant to cefditoren. Susceptibility rates (%) for amoxicillin/clavulanic acid, cefuroxime axetil, cefotaxime, ciprofloxacin, trimethoprim/sulfamethoxazole and fosfomycin were 93.1- 94.1- 96.8-93.1-71.9 and 92.8% respectively. Cefditoren MIC was significantly higher in nalidixic/ciprofloxacin non-susceptible strains; resistance to cefditoren was not associated with resistance to mecillinam, fosfomycin nitrofurantoin and aminoglycosides. Multivariate analysis demonstrated history of urinary infection in the last two weeks or three months as risk factors for cefditoren resistance.

CONCLUSIONS

Cefditoren exhibited enhanced in vitro activity against the most common uropathogens in the outpatient setting, representing an alternative oral treatment option in patients with risk factors for resistance to first-line antibiotics.

A prospective, randomized, double dummy, placebo-controlled trial of oral cefditoren pivoxil 400mg once daily as switch therapy after intravenous ceftriaxone in the treatment of acute pyelonephritis

OBJECTIVES

To compare the clinical and bacteriological effectiveness of intravenous (IV) ceftriaxone followed by oral cefditoren pivoxil or IV ceftriaxone for acute pyelonephritis.

METHODS

A prospective randomized controlled trial of patients with a presumptive diagnosis of acute pyelonephritis was performed. Daily 2g IV ceftriaxone was initially given to all patients. After day 3, patients who satisfied the criteria for switch therapy were randomized to either group A (IV ceftriaxone) or group B (oral cefditoren pivoxil 400mg once daily).

RESULTS

Eighty-two patients were enrolled; 41 (50%) patients in group A and 41 (50%) patients in group B were evaluated. There was no statistically significant difference in baseline characteristics between the two groups. Clinical cure was observed in 39 of 41 (95.1%) patients in group A and 41 of 41 (100%) patients in group B (p=0.15, 95% confidence interval (CI) -0.12 to 0.02). Urine bacteriological eradication was found in 63.4% in group A and 60% in group B (p=0.75, 95% CI -0.18 to 0.25). There was no statistically significant difference in adverse effects between the two treatment groups.

CONCLUSION

These data suggest that IV ceftriaxone followed by oral cefditoren pivoxil is highly effective and well-tolerated for the treatment of acute pyelonephritis, even for uropathogens with a high proportion of quinolone-resistant strains.