RESUMEN
BACKGROUND: The minimum inhibitory concentration (MIC) is a measure of antimicrobial susceptibility testing (AST) of a given antibiotic but provides insufficient information when bacterial killing is crucial, e.g., when treating immunocompromised patients. In these cases, the minimum bactericidal concentration (MBC) is a more reliable measure of antibiotic activity. Here, we aim to demonstrate and recommend combinations of methods for MIC and MBC measurements. We also aim to emphasize the importance of uniform protocols for these procedures including the time point for reading MIC results, which the authors suggest to be 20h. METHODS: To address the challenges with obtaining fast and reliable readouts on MIC as well as the kinetic and end-point effects of antibiotics, the broth micro dilution method, a calorimetric method and a microscopy-based screening system (MBSS) were evaluated in this study. For MBC determination, fluorophore staining with SYTO9 and propidium iodide was compared to the broth regrowth method. RESULTS: Three scenarios for combining the MIC and MBC methods depending on the investigators' primary concern (time, cost or sensitivity) are presented. Further, as the MBSS and the isothermal microcalorimetry method detected delayed bacterial growth up to 18h after initiation of experiments, the importance of reading MIC testing after a full 20h is emphasized. A one-fold change in MIC values can be observed when comparing data obtained at 16h and 20h of incubation. CONCLUSION: The authors suggest that combining MIC and MBC determinations will provide more detailed understanding of the bacteria susceptibility to antibiotic drugs and result in more clinically relevant data and optimized therapies. Furthermore, establishing 20h as a time point for reading MIC results will provide more uniform data across laboratories.
Asunto(s)
Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Pruebas de Sensibilidad Microbiana/métodos , Bacterias/crecimiento & desarrollo , Técnicas Bacteriológicas/métodos , Costos y Análisis de Costo , Humanos , Sensibilidad y Especificidad , Factores de TiempoRESUMEN
Bacterial biofilm-associated chronic sinusitis in cystic fibrosis (CF) patients caused by Pseudomonas aeruginosa infections and the lack of available treatments for such infections constitute a critical aspect of CF disease management. Currently, inhalation therapies to combat P. aeruginosa infections in CF patients are focused mainly on the delivery of antimicrobials to the lower respiratory tract, disregarding the sinuses. However, the sinuses constitute a reservoir for P. aeruginosa growth, leading to re-infection of the lungs, even after clearing an initial lung infection. Eradication of P. aeruginosa from the respiratory tract after a first infection has been shown to delay chronic pulmonary infection with the bacteria for up to two years. The challenges with providing a suitable treatment for bacterial sinusitis include: (i) identifying a suitable antimicrobial compound; (ii) selecting a suitable device to deliver the drug to the sinuses and nasal cavities; and (iii) applying a formulation design, which will mediate delivery of a high dose of the antimicrobial directly to the site of infection. This review highlights currently available inhalable antimicrobial formulations for treatment and management of biofilm infections caused by P. aeruginosa and discusses critical issues related to novel antimicrobial drug formulation design approaches.