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I P Balcabao

Publications and source records attributed to I P Balcabao.

10 recordsLinked to original sources
PubMed2001

Influence of the decrease in ciprofloxacin susceptibility and the presence of human serum on the in vitro susceptibility of Streptococcus pneumoniae to five new quinolones.

Sixty recent Streptococcus pneumoniae isolates with different susceptibilities to ciprofloxacin (14 with MIC 0.5 mg/L, 10 with MIC 1 mg/L, eight with MIC 2 mg/L, 11 with MIC 4 mg/L and 17 with MIC > or =8 mg/L) were tested against five new quinolones using Todd-Hewitt broth with and without 80% serum. The final inoculum was 5 x 10(5) cfu/mL. Gemifloxacin and clinafloxacin exhibited the lowest MIC90 values and resistance rates (percentage above and defined breakpoint) with and without serum for strains with a ciprofloxacin MIC of > or =4 mg/L. Other quinolones tested were less active against strains with reduced ciprofloxacin susceptibility. The presence of serum did not affect susceptibility to moxifloxacin, but increased the resistance rates to other new quinolones for strains with high ciprofloxacin MICs.

Anti-Infective Agents↗
PubMed2000

In vitro activity of clarithromycin against penicillin-susceptible and penicillin-resistant strains of Streptococcus pneumoniae in a pharmacodynamic simulation model.

Clarithromycin has shown enhanced activity against Streptococcus pneumoniae, but increased resistance to macrolides has been observed in recent years. Our aim was to investigate its activity against strains of S. pneumoniae with variable susceptibility to this antibiotic and to penicillin. We determined killing curves using the Centriprep-10 pharmacodynamic simulation model, which permits using varying antibiotic concentrations to mimic a pharmacokinetic human profile in serum (corresponding to an oral dose of 500 mg). Four strains of S. pneumoniae were tested. In susceptible strains, clarithromycin showed bactericidal activity (reductions of up to 2.97 log10 cfu/ml of the initial inoculum). In resistant strains, clarithromycin showed a bacteriostatic effect (<1 log10 cfu/ml reduction). Penicillin-susceptible strains showed higher reductions than penicillin-resistant strains. This effect is important owing to the high minimum inhibitory concentration (MIC) of one of the resistant strains (32 microg/ml). More studies are needed to explain this bacteriostatic activity.

Anti-Bacterial Agents↗
PubMed1999

Efficacy of trovafloxacin in an in vitro pharmacodynamic simulation of an intraabdominal infection.

An in vitro model simulating trovafloxacin concentrations in human serum after standard doses was used to investigate the activity of this drug with time against Bacteroides fragilis, Escherichia coli, Enterococcus faecalis and Staphylococcus aureus. Antibiotic concentrations used for each incubation period were: 4.24 mg/l (0-1 h), 3.69 mg/l (1-3 h), 3.25 mg/l (3-6 h), 2.38 mg/l (6-8 h), 1.35 mg/l (8-24 h). A 99.9% initial inoculum reduction (> 3 log10 cfu/ml) was defined as bactericidal activity. Bactericidal activity against these organisms was obtained with trovafloxacin after the first hour of incubation, and similar activity was obtained against B. fragilis, E. faecalis and S. aureus after 3 h, when they were tested individually. When the strains were tested as mixed culture, there was bactericidal activity against E. coli after 1 h incubation and after 3 h for S. aureus. This activity was observed against B. fragilis and E. faecalis after 6 h incubation in the mixed culture assays and after 3 h when organisms were tested individually. Regrowth was not observed over a 24 h period. These data show that trovafloxacin might be effective in intraabdominal infections caused by mixed aerobic and anaerobic microorganisms.

Abdominal Abscess↗
PubMed1999

Does the degree of penicillin susceptibility of Streptococcus pneumoniae affect the bactericidal activity of co-amoxiclav versus oral cephalosporins at physiological concentrations? An in vitro pharmacodynamic simulation.

An in vitro model simulating amoxicillin-clavulanic acid (co-amoxiclav) versus oral cephalosporin serum concentrations was used to explore activity over time against penicillin-susceptible and non-susceptible Streptococcus pneumoniae. Initial inoculum reduction > 4 log cfu/ml (>99.9%) was obtained with co-amoxiclav against both strains. Cefuroxime, cefpodoxime and cefaclor achieved a similar reduction against the susceptible strain, but no reduction against the non-susceptible strain.

Amoxicillin-Potassium Clavulanate Combination↗
PubMed1998

In vitro activities of co-amoxiclav at concentrations achieved in human serum against the resistant subpopulation of heteroresistant Staphylococcus aureus: a controlled study with vancomycin.

The effects of concentrations that simulated those in human serum after a single intravenous dose of amoxicillin (2 g), amoxicillin-clavulanic acid (2,000 and 200 mg, respectively), or vancomycin (500 mg), on the viability and beta-lactamase activity of two isogenic (beta-lactamase and non-beta-lactamase producer) heteroresistant Staphylococcus aureus strains were studied in an in vitro pharmacodynamic model. A reduction of > or = 97% of the initial inoculum was obtained with vancomycin and amoxicillin-clavulanic acid against both strains, with respect to the total bacterial population and the oxacillin-resistant subpopulation. The same pattern was observed with amoxicillin and the beta-lactamase-negative strain. beta-Lactamase activity in the beta-lactamase-positive strain changed over time parallel to viability, decreasing with amoxicillin-clavulanic acid or vancomycin and increasing in the amoxicillin and control groups. Clavulanic acid concentrations achievable in serum that changed over time allowed amoxicillin to act against the beta-lactamase-producing methicillin-resistant S. aureus to a similar extent as vancomycin.

Amoxicillin↗
PubMed1997

Pharmacodynamic effects of amoxicillin versus cefotaxime against penicillin-susceptible and penicillin-resistant pneumococcal strains: a phase I study.

Serum bactericidal activity against a penicillin-susceptible strain and a penicillin-resistant strain of Streptococcus pneumoniae (amoxicillin and cefotaxime MICs, 0.001 and 1 microg/ml, respectively, and MBCs, 0.01 and 2 microg/ml, respectively) was measured in 12 healthy volunteers who each received an oral 875-mg dose of amoxicillin and an intramuscular 1-g dose of cefotaxime in a crossover fashion. The areas under the bactericidal activity-time curves for the two strains were found to be similar for both antibiotics despite the significantly higher (P < 0.002) AUC/MIC and peak level/MIC values for cefotaxime.

Adult↗
PubMed1997

In vitro assessment of the effect of clavulanic acid at concentrations achieved in human serum on the bactericidal activity of amoxicillin at physiological concentrations against Staphylococcus aureus: implications for dosage regimens.

The effects on Staphylococcus aureus viability and beta-lactamase activity of concentrations that simulated those in human serum after a combined dose of 875 mg of amoxicillin and 125 mg of clavulanic acid were studied in an in vitro pharmacodynamic model. Six hours of preexposure to concentrations of the amoxicillin-clavulanic acid combination that were higher than the amoxicillin-clavulanic acid MIC led to a reduction of the initial inoculum of >90% and to a significant decrease of beta-lactamase activity versus those of the control even from 6 h, when concentrations were subinhibitory. The postantibiotic effect and post-beta-lactamase inhibitor effect contributed to these results.

Amoxicillin↗
PubMed1996

Ex vivo antibacterial properties of rufloxacin compared with those of norfloxacin in a study with healthy volunteers.

Twelve adult males participated in a randomized crossover phase I clinical trial comparing serum bactericidal titers (SBTs), urine bactericidal titers (UBTs), and urine killing rates (UKRs) against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, after the administration of single 400-mg doses of rufloxacin and norfloxacin at different times up to 72 h postdose. SBTs were significantly higher (P < 0.05) against E. coli from 8 to 48 h and against S. aureus from 4 to 24 h with rufloxacin. UBTs for E. coli were higher (P < 0.05) for norfloxacin at early sample times (0 to 8 h) but higher for rufloxacin (P < 0.05) at sample times from 16 h on for both E. coli and S. aureus. Similar UKRs were obtained for both quinolones for 0 to 2 h and 8 to 12 h, but the UKR was maintained for 72 h with rufloxacin. The high and sustained mean levels of rufloxacin in urine (> 35 micrograms/ml), median UBTs (> 32 for E. coli and 16 for S. aureus) and UKRs for E. coli suggest prolonged urine antibacterial activity (for at least 72 h) and its use as a single 400-mg dose in the treatment of uncomplicated cystitis.

Adult↗
PubMed1996

Activities against Streptococcus pneumoniae of amoxicillin and cefotaxime at physiological concentrations: in vitro pharmacodynamic simulation.

An in vitro model simulating amoxicillin and cefotaxime concentrations in human serum (after standard doses) was used to explore the activities of these drugs over time against penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae strains. An initial inoculum reduction percentage of > or = 90% was obtained with amoxicillin and maintained for 2 to 8 h, regardless of the strain tested. In contrast, experiments showed that cefotaxime had significantly (P < 0.001) less capability to reduce initial inocula of the penicillin-resistant pneumococci from 0.5 h on than amoxicillin, despite the same in vitro susceptibility to amoxicillin and cefotaxime in both strains.

Amoxicillin↗