Evaluation of the E test for fluconazole susceptibility testing of Candida albicans isolates from oropharyngeal candidiasis

Catheter-associated urinary tract infections in intensive care units at a university hospital in Turkey

In this study, urinary catheter utilization rates, the causative agents for catheter-associated urinary tract infection (CAUTI) and their antimicrobial susceptibilities in intensive care units (ICUs) in 2009 were investigated at Gazi university hospital. We aimed to determine the causative agents and risk factors for CAUTIs, and antimicrobial susceptibilities of the pathogens; and also sensitivities of Candida spp. to antifungal agents with Microdilution and E-test. The most common etiological agents of CAUTIs were Candida spp. (34.7%). The most frequently isolated Candida spp. was C.albicans (52.4%). All C. albicans spp. were sensitive to fluconazole. Microdilution, used as a reference method to determine the sensitivity to antifungal agents, was compared with E test. E test was found to be sufficient to analyze sensitivity to amphotericin B, caspofungin, fluconazole and voriconazole, but inappropriate for itraconazole. E.coli and Klebsiella spp. were found to be causative agents for CAUTI in 20.6% and 9.9% of cases respectively. Pseudomonas spp. and Acinetobacter spp. were isolated in 14% and 8.2% of the cases, respectively. All E.coli and Klebsiella strains were found sensitive to carbapenems. Carbapenem sensitivity was found in 47.1% and 30% of the cases infected with Pseudomonas and Acinetobacter strains, respectively. According to our results, fluconazole therapy seems to be an appropriate choice for the treatment of CAUTIs caused by C.albicans. Third and fourth generation cephalosporins should not be used for empirical treatment because of the high prevalence of extended spectrum beta-lactamase production among E.coli and Klebsiella isolates.

Pharmacokinetics and pharmacodynamics of antifungals

Application of pharmacodynamic principles to antifungal drug therapy of Candida and Aspergillus infections has provided and understanding of the relationship between drug dosing and treatment efficacy. Observations of the pharmacodynamics of triazoles and AmB have correlated with the results of clinical trials and have proven useful for validation of in vitro susceptibility breakpoints. Although there remain many unanswered questions regarding antifungal pharmacodynamics, available data suggest usefulness in the application of pharmacodynamics to antifungal clinical development. Future application of these principles should aid in the design of optimal combination antifungal therapies.

Fluconazole MIC and the fluconazole dose/MIC ratio correlate with therapeutic response among patients with candidemia

We tested 32 Candida isolates recovered in the early 1990s from the bloodstreams of patients with candidemia for in vitro susceptibility to fluconazole and determined if MIC and/or the daily dose of fluconazole/MIC ratio correlated with the response to therapy. This is a unique data set since 87.5% (28/32) of patients were treated with fluconazole doses now considered to be inadequate (/= 64 mug/ml) isolates were 67% (14/21), 20% (1/5), and 0% (0/6), respectively. A dose/MIC ratio >50 was associated with a success rate of 74% (14/19), compared to 8% (1/13) for a dose/MIC ratio Collapse

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MESH Headings

• Adolescent
• Adult
• Aged
• Antifungal Agents/administration & dosage
• Antifungal Agents/pharmacology
• Antifungal Agents/therapeutic use
• Candida/classification
• Candida/drug effects
• Candidiasis/drug therapy
• Candidiasis/microbiology
• Child, Preschool
• Dose-Response Relationship, Drug
• Fluconazole/administration & dosage
• Fluconazole/pharmacology
• Fluconazole/therapeutic use
• Fungemia/drug therapy
• Fungemia/microbiology
• Humans
• Microbial Sensitivity Tests/standards
• Middle Aged
• Prospective Studies
• Treatment Failure
• Treatment Outcome

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Affiliation(s)

Cornelius J Clancy University of Florida College of Medicine, P.O. Box 100277, JHMHC, Gainesville, FL 32610, USA.
Victor L Yu
Arthur J Morris
David R Snydman
M Hong Nguyen

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Clinical utility of antifungal pharmacokinetics and pharmacodynamics

PURPOSE OF REVIEW

Historically the anti-infective dose and dosing interval chosen in clinical trials have been based on an arbitrary goal of maintaining drug levels in serum above the minimum inhibitory concentration of infecting pathogens for most if not all of the dosing interval. Subsequent United States Food and Drug Administration approval of a dosing regimen is then based on clinical success in treatment trials. Over the past decade, the emergence of drug resistance has limited the clinical utility of an increasing number of antimicrobial agents. However, early in drug development clinical trials do not often define the impact of infection with these less susceptible pathogens. The field of pharmacodynamics provides analysis tools that can help predict the likelihood of treatment success with various antimicrobial treatment regimens against susceptible and resistant pathogens.

RECENT FINDINGS

In-vitro and animal model studies have begun to define the pharmacodynamic characteristics of a variety of antifungal compounds. In-vivo studies have demonstrated that the pharmacodynamic target associated with efficacy is similar among antifungal drugs within the same class and have shown the importance of considering protein. Analysis of clinical trial data suggests that the pharmacodynamic target identified in animal model studies is predictive of outcomes in humans.

SUMMARY

Antifungal pharmacodynamics can be used to understand the relationship between drug dosing, in-vitro susceptibility and treatment efficacy. Consideration of these relationships can be used to optimize dosing regimens with current antifungal agents, to develop susceptibility breakpoint guidelines, and in the design of dosing regimens for drugs in early development.

Antifungal pharmacokinetics and pharmacodynamics: understanding the implications for antifungal drug resistance

Pharmacodynamics (PDs) describe the relationship between drug exposure and outcome. The drug exposures in these analyses are most commonly expressed in a variety of pharmacokinetic terms. The outcome of interest with anti-infective therapy is either microbiologic resolution or a clinical surrogate of treatment efficacy. An in vitro measure of drug potency, such as the minimum inhibitory concentration (MIC) is also frequently considered in this relationship. Examination of the relationships among drug pharmacokinetics, MIC, and efficacy has provided a framework for choice of antifungal drug and dose. These analyses provide a PD target for drug class/organism combinations. The PD target can be useful for defining the upper MIC limit for a drug-dosing regimen that would be expected to result in treatment efficacy. The PD target can be used to optimize dosing regimens and to aid in defining susceptibility breakpoints.

Clinical pharmacodynamics of antifungals

Application of pharmacodynamic principles to antifungal drugs has provided an understanding of the relationship between drug dosing and treatment outcomes similar to that observed in antibacterial pharmacodynamics. Initial observations with triazole pharmacodynamics have correlated with clinical trial results and proved useful for validation of in vitro susceptibility breakpoints. Pharmacodynamic studies have been invaluable for clinical trial dosing design for numerous antibacterial drugs in the development stage. More recently, pharmacodynamics has been used for the development of treatment guidelines. Although there remain many unanswered questions regarding antifungal pharmacodynamics, available data suggest usefulness in the application of pharmacodynamics to antifungal clinical development.

Recomendaciones para el diagnóstico micológico y estudios de sensibilidad a los antifúngicos

The guidelines presented herein, which are based on the indications established by various studies and expert opinions, analyze several issues related to laboratory diagnosis of invasive fungal infections in immunosuppressed patients.

Susceptibility testing of yeasts to fluconazole by Etest and agar-diffusion disk test using the synthetic agar medium Mycoplate

A total of 50 clinical Candida isolates was tested against fluconazole using both the Etest and the agar-diffusion disk test on the synthetic agar medium Mycoplate. Inhibition zones were readable, although a residual yeast growth occurred within the inhibition zones. The diameter of the inhibition zones in the disk test correlated very well with the logarithmically transformed minimal inhibitory concentrations measured with the Etest. For an inhibition zone diameter equal to or greater than 22 mm, using a 25 microg disk, the isolates were considered as fluconazole-susceptible, and for zone diameters less than 22 mm, dose-dependent susceptibility (S-DD) or resistance to fluconazole was assumed. These results are in agreement with those of other authors. The Mycoplate medium appeared to be suitable for testing yeasts for their susceptibility to fluconazole.

Oral candidal infections and antimycotics

The advent of the human immunodeficiency virus infection and the increasing prevalence of compromised individuals in the community due to modern therapeutic advances have resulted in a resurgence of opportunistic infections, including oral candidoses. One form of the latter presents classically as a white lesion of "thrush" and is usually easily diagnosed and cured. Nonetheless, a minority of these lesions appears in new guises such as erythematous candidosis, thereby confounding the unwary clinician and complicating its management. Despite the availability of several effective antimycotics for the treatment of oral candidoses, failure of therapy is not uncommon due to the unique environment of the oral cavity, where the flushing effect of saliva and the cleansing action of the oral musculature tend to reduce the drug concentration to sub-therapeutic levels. This problem has been partly circumvented by the introduction of the triazole agents, which initially appeared to be highly effective. However, an alarming increase of organisms resistant to the triazoles has been reported recently. In this review, an overview of clinical manifestations of oral candidoses and recent advances in antimycotic therapy is given, together with newer concepts, such as the post-antifungal effect (PAFE) and its possible therapeutic implications.

Antifungal susceptibility testing: practical aspects and current challenges

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

Determination of minumum inhibitory concentrations of Candida species isolated from vaginal swab specimens by using broth macrodilution and E-test

The purpose of the present study was to evaluate the utility of the E-test in determining the antifungal susceptibility of Candida species. A total of 50 Candida strains, including 34 Candida albicans and 16 non-albicans were isolated from vaginal swab specimens from women suffering from vaginitis. The minimum inhibitory concentrations (MICs) of amphotericin B, fluconazole and ketoconazole were detected by using broth macrodilution and the E-test. When the results of the two tests were compared, the MIC values were considered acceptable if the difference between the two assays was no more than two-fold (+/-1dilution). The acceptable rates were: 84% for amphotericin B, 97% for fluconazole and 78% for ketoconazole. Finally, MICs of C. albicans against the tested antifungal agents were generally lower than for non-albicans strains. These results suggest that the E-test can be used for the determination of MIC values for Candida species isolates.

Commercial systems for fluconazole susceptibility testing of yeasts: comparison with the broth microdilution method

Fluconazole susceptibility was tested in 100 clinical yeast isolates (65 Candida albicans, 13 C. glabrata, 8 C. tropicalis, 7 C. parapsilosis, 3 Saccharomyces cerevisiae, 1 each of C. krusei, C. lusitaniae, Cryptococcus neoformans, Rhodotorula glutinis) and two control strains (Candida krusei ATCC 6258, C. parapsilosis ATCC 22019) using broth microdilution (reference method), disk diffusion, Etest strips, Sensititre YeastOne, Candifast, Integral System Yeasts. Using M27-A breakpoints, isolates were classified as susceptible (81%), susceptible-dose dependent or Resistant with broth dilution. Rates of concordance with the reference method were good for Sensititre YeastOne, Etest and disc-diffusion (81.2%-94.7%) but very low for the Candifast (3.1%) and Integral System (16.6%), which classified most susceptible isolates as resistant. Lack of standardisation (inoculum, medium composition) and non-objective interpretation schemes may be the cause of their poor performance. Sensititre YeastOne, Etest and disc-diffusion are potentially useful for fluconazole antifungal susceptibility testing of yeasts in clinical laboratories.

A comparative evaluation of Etest and broth microdilution methods for fluconazole and itraconazole susceptibility testing of Candida spp

The Etest strip is a promising tool of broad application in clinical microbiology. The method provides MIC readings and is easier to perform than broth microdilution. We carried out a study to compare the MICs of fluconazole and itraconazole obtained by the Etest with those obtained by broth microdilution, performed according to the guidelines of the NCCLS document M27-A, with 402 clinical isolates (360 Candida albicans, 17 Candida tropicalis, nine Candida krusei, nine Candida glabrata and seven Candida parapsilosis) and seven control isolates. The agreement between MICs by the two methods (at +/- 2 dilutions) was 74.5% for fluconazole and 61.4% for itraconazole. These results suggest that further development is necessary to standardize the medium and incubation conditions before introduction of the Etest as a routine method in the clinical microbiology laboratory for fluconazole and itraconazole susceptibility testing.

Fluconazole sensitivities of Candida species isolated from the mouths of terminally ill cancer patients

Oral candidosis is common in advanced cancer and is often treated with the systemic triazole antifungal drug fluconazole. This study examined the species of yeast present in the mouths of 30 patients with advanced cancer and determined their sensitivity to fluconazole. Thirty-five yeast isolates were collected from a total of 25 (83 percent) of the patients sampled. The two most common species were Candida albicans (15 isolates) and C. glabrata (11 isolates)--with smaller numbers of C. tropicalis, C. parapsilosis, C. guilliermondii, C. inconspicua, and Saccharomyces cerevisiae. The minimal inhibitory concentrations (MIC) of fluconazole for the strains of C. albicans were generally low (median 0.19 microgram/ml) but were considerably higher for C. glabrata (median 2 micrograms/ml). The remaining species demonstrated MICs similar to those for C. albicans, with the exceptions of C. inconspicua and Saccharomyces cerevisiae, which were relatively insensitive. In conclusion, non-albicans yeasts are common in the mouths of patients with advanced cancer and these may have reduced sensitivity to fluconazole. Mycological diagnosis is a valuable aid to management.