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Background Combination therapy can increase efficacy of antibiotics and prevent emergence of resistance. Ceftazidime/avibactam and fosfomycin may be empirically combined for this purpose, but a systematic and quantitative evaluation of this combination is needed. Objectives In this study, a systematic analysis of the pharmacodynamic interactions of ceftazidime/avibactam and fosfomycin in clinical and isogenic Escherichia coli strains carrying genes coding for several carbapenemases or ESBLs was performed and pharmacodynamic interactions were quantified by modelling and simulations. Methods Pharmacodynamic interactions were evaluated in 'dynamic' chequerboard experiments with quantification of viable bacteria in eight isogenic and six clinical E. coli strains. Additionally, supplemental time–kill experiments were performed and genomic analyses were conducted on representative fosfomycin-resistant subpopulations. Models were fitted to all data using R and NONMEM®. Results Synergistic drug interactions were identified for 67% of the clinical and 75% of the isogenic isolates with a mean EC50 reduction of >50%. Time–kill experiments confirmed the interactions and modelling quantified EC50 reductions up to 97% in combination and synergy prevented regrowth of bacteria by enhanced killing effects. In 9 out of 12 fosfomycin-resistant mutants, genomic analyses identified previously reported mutations. Conclusions The broad synergistic in vitro activity of ceftazidime/avibactam and fosfomycin confirms the potential of the application of this drug combination in clinics. The substantial reduction of the EC50 in combination may allow use of lower doses or treatment of organisms with higher MIC values and encourage further research translating these findings into the clinical setting. [ABSTRACT FROM AUTHOR]

Objectives: Cefoxitin is frequently used for surgical antibiotic prophylaxis (SAP). Using microdialysis, we evaluated whether the currently recommended dosing regimen is appropriate to maintain cefoxitin subcutaneous tissue concentrations above the MIC for pathogens involved in abdominal surgical site infection.Methods: Data from eight patients undergoing major abdominal surgery were analysed using population pharmacokinetic modelling, and Monte Carlo simulations were conducted to determine the PTA for aerobic and anaerobic pathogens. ClinicalTrials.gov: NCT02703857.Results: Only 2.3% and 47.4% of the simulated patients maintained cefoxitin subcutaneous concentrations above the MIC breakpoint for anaerobic (MIC = 16 mg/L) and aerobic (MIC = 8 mg/L) pathogens, respectively. New simulations with administration of a loading dose followed by a constant infusion of cefoxitin were conducted and demonstrate that, notwithstanding using the same total dose per unit of time, continuous infusion of cefoxitin can cover aerobes in 96.6% of the simulated patients, but remains insufficient for anaerobic bacteria.Conclusions: The recommended dosing regimen of cefoxitin is insufficient for covering the usual bacteria during abdominal surgery. Administration of a loading dose followed by a constant infusion should be considered for aerobic bacteria and cefoxitin should be avoided as SAP for anaerobic bacteria. [ABSTRACT FROM AUTHOR]

Objectives: The objective of this study was to characterize the pharmacokinetics of unbound and total concentrations of daptomycin in infected ICU patients with various degrees of renal impairment. From these results, the probability of attaining antimicrobial efficacy and the risks of toxicity were assessed.Methods: Twenty-four ICU patients with various renal functions and requiring treatment of complicated skin and soft-tissue infections, bacteraemia, or endocarditis with daptomycin were recruited. Daptomycin (Cubicin®) at 10 mg/kg was administered every 24 h for patients with creatinine clearance (CLCR) ≥30 mL/min and every 48 h for patients with CLCR <30 mL/min. Total and unbound plasma concentrations and urine concentrations of daptomycin were analysed simultaneously following a population pharmacokinetic approach. Simulations were conducted to estimate the probability of attaining efficacy (unbound AUCu/MIC >40 or >80) or toxicity (Cmin >24.3 mg/L) targets.Results: Exposure to unbound daptomycin increased when the renal function decreased, thus increasing the probability of reaching the efficacy targets, but also the risk of toxicity. Modifications of the unbound fraction (fu) of daptomycin did not affect the pharmacokinetics of unbound daptomycin, but did affect the pharmacokinetics of total daptomycin.Conclusions: Daptomycin at 10 mg/kg q24h allowed efficacy pharmacokinetic/pharmacodynamic targets for ICU patients with CLCR ≥30 mL/min to be reached. For patients with CLCR <30 mL/min, halving the rate of drug administration, i.e. 10 mg/kg q48h, was sufficient to reach these targets. No adverse events were observed, but the toxicity of the 10 mg/kg q24h dosing regimen should be further assessed, particularly for patients with altered renal function. [ABSTRACT FROM AUTHOR]

Objectives: Optimal dosing for nebulized gentamicin is unknown. We compared the pulmonary and systemic pharmacokinetics (PK) of gentamicin following intravenous and nebulized administration in mechanically ventilated patients.Methods: Twelve critically ill male patients with ventilator-associated pneumonia received a 30 min intravenous infusion of 8 mg/kg gentamicin , followed 48 h afterwards by the same dose nebulized. Blood samples were collected immediately before and until 24 h after intravenous and nebulized administration; mini-bronchoalveolar lavages (mini-BALs) were performed at 3 and 7 h or 5 and 10 h (six patients each) after each intravenous and nebulized administration. The PK analysis was conducted using a population approach.Results: After intravenous administration, concentrations of gentamicin measured in epithelial lining fluid (ELF) were very variable, and overall in the same range of magnitude (from 0.3 to 28 mg/L) as in plasma. After nebulization, gentamicin concentrations were much higher (∼3800-fold) in ELF than in plasma. The average systemic bioavailability of nebulized gentamicin was estimated to be 5%, with considerable inter-individual variability. Compared with intravenous administration, after nebulization the exposure (expressed as AUC) to gentamicin was 276-fold greater in ELF and 18-fold lower in plasma.Conclusions: Compared with intravenous administration, nebulization of gentamicin in patients with ventilator-associated pneumonia provides higher pulmonary concentrations and lower systemic concentrations but the inter-individual variability is large. [ABSTRACT FROM AUTHOR]

Objectives: Optimal dosing for nebulized colistin methanesulfonate (CMS), the prodrug of colistin, is unknown. We describe the pulmonary and systemic pharmacokinetics of CMS and colistin following nebulization of 0.5 million IU (MIU) of CMS in ventilated patients. Methods: Twelve critically ill patients received 0.5 MIU of CMS administered every 8 h as 30 min nebulizations. Blood samples were collected immediately before and until 8 h after first nebulization; mini-bronchoalveolar lavage (mini-BAL) was performed at 1 and 5 h or 3 and 8 h (six patients each) post-dose. Pharmacokinetic analysis was performed for CMS and colistin plasma concentrations using a non-compartmental method. ClinicalTrials.gov: NCT01060891. Results: After nebulization, CMS concentrations in epithelial lining fluid (ELF) were much higher (100- to 1000-fold) than those in plasma. Concentrations of colistin in ELF should be consideredwith caution because when <6mg/L in BAL, colistin bound to mini-BAL devices. Nevertheless, CMS and colistin concentrations in ELF were much lower than expected from previous results with a 2MIU dose. From CMS plasma pharmacokinetics it was shown that CMS systemic bioavailability was only slightly decreased for the 0.5MIU dose compared with 2MIU. Conclusions: This study shows that CMS concentrations were much higher (100- to 1000-fold) in ELF than in plasma after a 0.5 MIU aerosol of CMS, but much lower (10-fold) than expected from previous results with a 2 MIU dose. Therefore, until new pharmacokinetic and pharmacodynamic assessments of the treatment of ventilator-associated pneumonia with nebulized CMS are performed, the 2 MIU dose should be preferred to the 0.5 MIU dose. [ABSTRACT FROM AUTHOR]

The article discusses the case of a young adult patient who was diagnosed with acute respiratory failure due to intra-alveolar haemorrhage. The patient's treatment regimen include intravenous vancomycin and veno-venous extracorporeal membrane oxygenation (ECMO). A persistent Staphylococcus epidermidis pulmonary infection was seen in the patient. It notes the continued deterioration of the patient's condition and subsequently died in spite of therapy and complete bacteria eradication.