Trimethoprim-sulfamethoxazole activity and pharmacodynamics against glycopeptide-intermediate Staphylococcus aureus.

STUDY OBJECTIVE: To determine the activity of trimethoprim-sulfamethoxazole (TMP-SMX) against glycopeptide-intermediate Staphylococcus aureus (GISA). DESIGN: In vitro study. SETTING: University laboratory. MEASUREMENTS AND MAIN RESULTS: Minimum inhibitory concentrations (MICs) of TMP-SMX were determined for three GISA strains. Time-kill assays were conducted at 1 x MIC and at simulated peak serum concentrations (Cmax). Two dosing regimens of TMP-SMX were investigated: TMP-SMX 8 mg (TMP)/kg/day and TMP-SMX 15 mg/kg/day, each divided into two doses/day Both dosages were studied against each strain in a two-compartment in vitro model to determine concentration-related activity. All isolates were susceptible to TMP-SMX. In time-kill studies at 1 x MIC, TMP-SMX was bacteriostatic against all isolates and bactericidal against two of three strains at simulated Cmax. The 15 mg/kg/day (divided-dose) regimen provided the best overall reduction in colony-forming units/ml. CONCLUSION: All GISA strains were susceptible to TMP-SMX. In addition, it appears that TMP-SMX may have concentration-dependent antibacterial activity against these organisms. As an option in the management of GISA infection, TMP-SMX merits further study.

Evaluation and cost assessment of fluoroquinolones in community-acquired respiratory infections.

Several new fluoroquinolones have been marketed since the late 1990s. Fluoroquinolones are an effective treatment for most community-acquired respiratory tract infections, including acute sinusitis, acute exacerbations of chronic bronchitis and community-acquired pneumonia. However, other antibiotics, including beta-lactams, macrolides, tetracyclines and trimethoprim-sulfamethoxazole, are also effective against these respiratory infections. From a managed care perspective, it is the subtle differences between the drugs in the eradication of bacterial pathogens, adverse effects, dose regimens, compliance issues, bacterial resistance and cost that determine the best choice for the management of pneumonia, sinusitis or exacerbations of chronic bronchitis. The potential for bacterial resistance is perhaps the only significant barrier to extensive fluoroquinolone use in community-acquired respiratory tract infections. Cost-effectiveness must be balanced with quality care, both from an individual perspective and that of the greater society.