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Keel R.A.,Center for Anti Infective Research and Development | Sutherland C.A.,Center for Anti Infective Research and Development | Aslanzadeh J.,Hartford Hospital | Nicolau D.P.,Center for Anti Infective Research and Development | And 2 more authors.
Diagnostic Microbiology and Infectious Disease | Year: 2010

We examined the potential correlation between vancomycin and daptomycin MIC for 298 Staphylococcus aureus by broth microdilution (BMD), Etest, and MicroScan ®. Etest and BMD identified a significant, albeit poor, correlation between MICs (ρ = 0.29, P < .01, and ρ = 0.15, P = .01, respectively), but no correlation (ρ = 0.08, P = .18) was observed with MicroScan. © 2010 Elsevier Inc.


MacVane S.H.,Center for Anti Infective Research and Development | Housman S.T.,Center for Anti Infective Research and Development | Nicolau D.P.,Center for Anti Infective Research and Development | Nicolau D.P.,Hartford Hospital
Clinical Pharmacology: Advances and Applications | Year: 2014

Purpose: Microdialysis is a valuable technique for studying the distribution of drugs into interstitial fluid, the target site for a pharmacologic effect. Due to incomplete equilibrium, retrodialysis is a method used to correct for relative recovery. The impact of two-drug combinations on probe recovery, however, remains unknown. Methods: In vitro microdialysis was conducted for five antibiotics (avibactam, cefepime, ceftaroline, piperacillin-tazobactam, and vancomycin), representing three empiric antimicrobial regimens, to assess the impact of two-drug combinations on probe recovery. Recoveries were compared between single and two-drug treatments. Results: Recoveries by gain and loss were linear with their molecular weight. During all gain experiments, recoveries were similar when tested alone or in combination with another antibiotic. Unacceptable differences in recovery by loss were observed for cefepime in the presence of vancomycin (-21%) and vancomycin in the presence of piperacillin-tazobactam (-22%). Conclusion: Differences among in vitro recovery by loss suggest two-drug combinations may impact dialysate recovery during in vivo retrodialysis procedures, particularly when larger molecular weight drugs (ie, vancomycin) are involved. Importantly, there were no differences during gain experiments. In vitro studies, as performed here, should be conducted for each potential two-drug combination, prior to their combined use for in vivo retrodialysis. © 2014 MacVane et al.


PubMed | Center for Anti Infective Research and Development
Type: Journal Article | Journal: Diagnostic microbiology and infectious disease | Year: 2010

We examined the potential correlation between vancomycin and daptomycin MIC for 298 Staphylococcus aureus by broth microdilution (BMD), Etest, and MicroScan(). Etest and BMD identified a significant, albeit poor, correlation between MICs ( = 0.29, P < .01, and = 0.15, P = .01, respectively), but no correlation ( = 0.08, P = .18) was observed with MicroScan.


PubMed | Center for Anti Infective Research and Development
Type: Journal Article | Journal: Antimicrobial agents and chemotherapy | Year: 2010

We evaluated cefepime exposures in patients infected with Pseudomonas aeruginosa to identify the pharmacodynamic relationship predictive of microbiological response. Patients with non-urinary tract P. aeruginosa infections and treated with cefepime were included. Free cefepime exposures were estimated by using a validated population pharmacokinetic model. P. aeruginosa MICs were determined by Etest and pharmacodynamic indices (the percentage of the dosing interval that the free drug concentration remains above the MIC of the infecting organism [fT > MIC], the ratio of the minimum concentration of free drug to the MIC [fC(min)/MIC], and the ratio of the area under the concentration-time curve for free drug to the MIC [fAUC/MIC]) were calculated for each patient. Classification and regression tree analysis was used to partition the pharmacodynamic parameters for prediction of the microbiological response. Monte Carlo simulation was utilized to determine the optimal dosing regimens needed to achieve the pharmacodynamic target. Fifty-six patients with pneumonia (66.1%), skin and skin structure infections (SSSIs) (25%), and bacteremia (8.9%) were included. Twenty-four (42.9%) patients failed cefepime therapy. The MICs ranged from 0.75 to 96 microg/ml, resulting in median fT > MIC, fC(m)(in)/MIC, and fAUC/MIC exposures of 100% (range, 0.8 to 100%), 4.3 (range, 0.1 to 27.3), and 206.2 (range, 4.2 to 1,028.7), respectively. Microbiological failure was associated with an fT > MIC of < or =60% (77.8% failed cefepime therapy when fT > MIC was < or =60%, whereas 36.2% failed cefepime therapy when fT > MIC was >60%; P = 0.013). A similar fT > MIC target of < or =63.9% (P = 0.009) was identified when skin and skin structure infections were excluded. While controlling for the SSSI source (odds ratio [OR], 0.18 [95% confidence interval, 0.03 to 1.19]; P = 0.07) and combination therapy (OR, 2.15 [95% confidence interval, 0.59 to 7.88]; P = 0.25), patients with fT > MIC values of < or =60% were 8.1 times (95% confidence interval, 1.2 to 55.6 times) more likely to experience a poor microbiological response. Cefepime doses of at least 2 g every 8 h are required to achieve this target against CLSI-defined susceptible P. aeruginosa organisms in patients with normal renal function. In patients with non-urinary tract infections caused by P. aeruginosa, achievement of cefepime exposures of >60% fT > MIC will minimize the possibility of a poor microbiological response.


PubMed | Center for Anti Infective Research and Development and Hartford Hospital
Type: Journal Article | Journal: Clinical therapeutics | Year: 2015

Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are frequently isolated pathogens in the hospital setting, and antimicrobial resistance among these organisms is on the rise. In an attempt to meet the challenge of gram-negative resistance, new therapies, including ceftolozane/tazobactam (C/T), were recently approved by the Food and Drug Administration, and others are in late-stage development. The purpose of this study is to describe the in vitro potency of C/T and other parenteral antimicrobials against a geographically diverse population of E coli, K pneumoniae, and P aeruginosa collected in US hospitals.In 2013 to 2014, 44 hospitals provided nonduplicate, nonurine isolates of E coli (n = 1306), K pneumoniae (n = 1205), and P aeruginosa (n = 1257) from adult inpatients. MICs for C/T and 11 other antimicrobials were determined with broth microdilution methods.The carbapenems, C/T, and colistin displayed the highest percentage of susceptibility and lowest MIC90 against the Enterobacteriaceae, followed by piperacillin/tazobactam (TZP), cefepime, tobramycin, aztreonam, ceftriaxone, and ciprofloxacin. C/T displayed the greatest potency (MIC90 = 2 mg/L) and 97% susceptibility of all compounds against P aeruginosa. In addition, C/T was highly active against P aeruginosa that were nonsusceptible to the carbapenems or TZP or were multidrug resistant and extended-spectrum -lactamase-producing Enterobacteriaceae.This national survey reported high levels of nonsusceptibility to antimicrobials among both Enterobacteriaceae and P aeruginosa. In contrast, many of these resistant pathogens were susceptible to C/T. These data highlight the enhanced potency of C/T and its potential utility for commonly encountered gram-negative nosocomial pathogens.


PubMed | Center for Anti Infective Research and Development and Hartford Hospital
Type: | Journal: Clinical pharmacology : advances and applications | Year: 2014

Microdialysis is a valuable technique for studying the distribution of drugs into interstitial fluid, the target site for a pharmacologic effect. Due to incomplete equilibrium, retrodialysis is a method used to correct for relative recovery. The impact of two-drug combinations on probe recovery, however, remains unknown.In vitro microdialysis was conducted for five antibiotics (avibactam, cefepime, ceftaroline, piperacillin-tazobactam, and vancomycin), representing three empiric antimicrobial regimens, to assess the impact of two-drug combinations on probe recovery. Recoveries were compared between single and two-drug treatments.Recoveries by gain and loss were linear with their molecular weight. During all gain experiments, recoveries were similar when tested alone or in combination with another antibiotic. Unacceptable differences in recovery by loss were observed for cefepime in the presence of vancomycin (-21%) and vancomycin in the presence of piperacillin-tazobactam (-22%).Differences among in vitro recovery by loss suggest two-drug combinations may impact dialysate recovery during in vivo retrodialysis procedures, particularly when larger molecular weight drugs (ie, vancomycin) are involved. Importantly, there were no differences during gain experiments. In vitro studies, as performed here, should be conducted for each potential two-drug combination, prior to their combined use for in vivo retrodialysis.

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