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ABSTRACT: Using β-lactamase-negative ampicillin (ABPC)-susceptible (BLNAS) and β-lactamase-negative ABPC-resistant (BLNAR) nontypeable Haemophilus influenzae (NTHi) strains isolated from otological patients, colony biofilm was prepared on membrane filter substrates. Bactericidal activities of garenoxacin (GRNX), levofloxacin (LVFX), cefditoren (CDTR), and clavulanic acid/amoxicillin (CVA/AMPC) were examined by counting viable cells after drug exposure to biofilm cells for 6 and 24 h and by observation under a scanning electron microscope (SEM). After exposure of biofilm to the 100-fold MIC of GRNX or LVFX for 24 h, GRNX and LVFX showed potent bactericidal activity (∆log(10) CFU/ml, ≥5.1). In this case, the drug-exposure AUC, exposure concentration × 24 μg h/ml, was 64-128 % for GRNX and 121 % for LVFX of free AUC at the clinical dosage in humans, respectively. CDTR and CVA/AMPC at 100-fold MIC exhibited little bactericidal activity against biofilm cells. Under an SEM, after exposure of BLNAS and BLNAR biofilms to GRNX or LVFX, most of the biofilm matrices were transformed. Quinolones such as GRNX show potent bactericidal activity against biofilm-forming NTHi at the usual clinical dosage.
Journal of Infection and Chemotherapy 10/2012; · 1.80 Impact Factor
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ABSTRACT: The bactericidal activity and resistance selectivity of garenoxacin against Streptococcus pneumoniae with mutations in ParC (S79F) or both GyrA (S81F) and ParC (D83Y and K137N) were investigated using in vitro pharmacokinetic models simulating plasma concentrations for a standard clinical regimen [400mg once daily (q.d.)]. The efficacy of garenoxacin was compared with that of levofloxacin (500 mg q.d.) and moxifloxacin (400mg q.d.). Garenoxacin showed excellent bactericidal activity against S. pneumoniae, including quinolone-resistant S. pneumoniae (QRSP), achieving ratios of area under the plasma concentration-time curve over 24h to minimum inhibitory concentration (AUC(0-24)/MIC) ≥ 26.3, without emerging resistant subpopulations. The area above the killing curves was greater and the time to achieve 99.9% killing was shorter for garenoxacin than the corresponding values for levofloxacin and moxifloxacin. No resistant subpopulations and no additional substitution of amino acids in GyrA or ParC emerged following treatment with garenoxacin. On the other hand, in the parC mutant strain, levofloxacin and moxifloxacin treatment caused an increase in the frequency of the resistant population and an additional substitution of amino acids in GyrA (levofloxacin, S81Y/F/C; moxifloxacin, S81Y or E85K). In QRSP with mutations in GyrA and ParC, levofloxacin had no bactericidal activity, whilst the bactericidal activity of moxifloxacin was less than that of garenoxacin; moreover, an additional substitution of amino acids in ParC (S79Y) was noted. In conclusion, garenoxacin corresponding to an oral dose of 400mg showed excellent bactericidal activity against S. pneumoniae, including QRSP, without the emergence of resistant mutants.
International journal of antimicrobial agents 11/2011; 39(2):163-7. · 3.03 Impact Factor
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ABSTRACT: In this study, garenoxacin showed potent in vitro activity against clinical isolates of group G Streptococcus dysgalactiae subsp. equisimilis [minimum inhibitory concentration for 90% of the organisms (MIC(90)) = 0.125 μg/mL] and was superior to levofloxacin (MIC(90) = 1 μg/mL) and moxifloxacin (MIC(90)=0.25 μg/mL). In experimental pneumonia caused by group G S. dysgalactiae subsp. equisimilis in mice, the effective dose for 50% survival (ED(50)) of garenoxacin following single oral administration was 1.87 mg/kg, >10.7-fold and 4.6-fold less than the ED(50) values of levofloxacin (>20 mg/kg) and moxifloxacin (8.54 mg/kg), respectively. The area under the free serum concentration-time curve from 0-24 h (fAUC(0-24))/MIC ratio of garenoxacin in serum following oral administration of 20 mg/kg was 73.2, which was 8.7-11.4-fold and 1.4-fold greater than that of levofloxacin (6.44-8.46) and moxifloxacin (51.4), respectively. These results suggest that garenoxacin has potential for the treatment of infectious diseases caused by S. dysgalactiae subsp. equisimilis.
International journal of antimicrobial agents 09/2011; 38(3):226-30. · 3.03 Impact Factor
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ABSTRACT: Using an intestinal methicillin-resistant Staphylococcus aureus (MRSA)-carrying rat model, we compared the influence of piperacillin (PIPC) on the intestinal flora to those of cefazolin (CEZ), cefmetazole (CMZ), and flomoxef (FMOX). The number of MRSA did not increase after PIPC and CEZ administrations compared with the nontreated group. However, it significantly increased in the cases of FMOX and CMZ administration (P < 0.01). In the FMOX- and CMZ-treated groups, the intestinal flora was severely disrupted and the recovery of the number of Escherichia coli and Bacteroides spp. cells was delayed. On the other hand, in the PIPC- and CEZ-treated groups, the rapid recovery of bacteria that composed the intestinal flora was observed. The C(max)/MIC(50) and C(trough)/MIC(50) ratios in E. coli and Bacteroides spp. in the case of FMOX and CMZ were relatively higher than those in the case of the PIPC- and CEZ-treated groups.
Journal of Infection and Chemotherapy 01/2005; 10(6):338-42. · 1.80 Impact Factor
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ABSTRACT: The minimum inhibitory concentrations (MICs) of tosufloxacin (TFLX), levofloxacin (LVFX), ciprofloxacin (CPFX), gatifloxacin (GFLX), sparfloxacin (SPFX), azithromycin (AZM), cefteram (CFTM), cefdinir (CFDN) and cefpodoxime (CPDX) against 337 clinical isolates of Streptococcus pneumoniae isolated from Japanese hospital from 1997 to 2002 were investigated by agar plate method. The incidence of penicillin-susceptible S. pneumoniae (PSSP), penicillin-intermediate resistant S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP) in each year was studied, and the MICs of antibacterial agents against these strains were determined. As the results, the total incidence of PSSP, PISP, and PRSP was 51.0%, 40.4% and 8.6%, respectively. The incidences of PSSP from 1997 to 2002 were 46.0-55.9%, and were almost definite in each year. In quinolone antibiotics, the differences of antibacterial activity among TFLX, SPFX, and GFLX against PSSP, PISP, and PRSP, were not observed, and these 3 quinolones had potent antibacterial activity. Although CPFX and LVFX showed antibacterial activity as well as other quinolones by 2001, the CPFX-resistant or LVFX-intermediate resistant strains of PSSP were seen with 56.5% and 91.3% in 2002, respectively. Thirty percents of each PSSP, PISP, and PRSP strains were AZM-resistant strains. Such tendency of increase was recognized in PSSP. Against cephem antibiotics, the incidence of intermediate resistant and resistant strains was higher for PISP and PRSP than for PSSP. No difference in the incidence of resistant strains was noted among CFTM, CFDN, and CPDX.
The Japanese journal of antibiotics 03/2003; 56(1):27-35.
