Fluconazole-resistant Candida albicans

Design, Synthesis, and Biological Evaluation of N'-Phenylhydrazides as Potential Antifungal Agents

Fifty-two kinds of N'-phenylhydrazides were successfully designed and synthesized. Their antifungal activity in vitro against five strains of C. albicans (Candida albicans) was evaluated. All prepared compounds showed varying degrees of antifungal activity against C. albicans and their MIC80 (the concentration of tested compounds when their inhibition rate was at 80%), TAI (total activity index), and TSI (total susceptibility index) were calculated. The inhibitory activities of 27/52 compounds against fluconazole-resistant fungi C. albicans 4395 and 5272 were much better than those of fluconazole. The MIC80 values of 14/52 compounds against fluconazole-resistant fungus C. albicans 5122 were less than 4 μg/mL, so it was the most sensitive fungus (TSIB = 12.0). A11 showed the best inhibitory activity against C. albicans SC5314, 4395, and 5272 (MIC80 = 1.9, 4.0, and 3.7 μg/mL). The antifungal activities of B14 and D5 against four strains of fluconazole-resistant fungi were better than those of fluconazole. The TAI values of A11 (2.71), B14 (2.13), and D5 (2.25) are the highest. Further exploration of antifungal mechanisms revealed that the fungus treated with compound A11 produced free radicals and reactive oxygen species, and their mycelium morphology was damaged. In conclusion, the N'-phenylhydrazide scaffold showed potential in the development of antifungal lead compounds. Among them, A11, B14, and D5 demonstrated particularly promising antifungal activity and held potential as novel antifungal agents.

Antifungal activity and potential mechanism of Asiatic acid alone and in combination with fluconazole against Candida albicans

Candida albicans (C. albicans) infection remains a challenge to clinicians due to the limited available antifungals. With the widespread use of antifungals in the clinic, the drug resistance has been emerging continuously, especially fluconazole. Therefore, searching for new antifungals, active constituents of natural or traditional medicines, and approaches to overcome antifungals resistance is needed. This study investigated the activity of Asiatic acid (AA) alone and in combination with fluconazole (FLC) against C. albicans in vitro and in vivo. The in vitro studies indicated that the drug combination had a synergistic effect on FLC-resistant C. albicans, with fractional inhibitory concentration index (FICI) of 0.25. And when AA at the dose of 32 µg/mL, the drug combination group could decrease the sessile minimum inhibitory concentration (sMIC) of FLC from > 1024 µg/mL to 0.125-0.25 µg/mL within 8 h against C. albicans biofilms, even with the FICI > 0.5. In vivo, the antifungal efficacy of AA used alone and in combination with FLC was evaluated by Galleria mellonella (G. mellonella) larvae. The drug combination group prolonged the survival rate and reduced tissue invasion of larvae infected with resistant C. albicans. Furthermore, mechanism studies indicated that the antifungal effects of AA in combination with FLC might be associated with the inhibition of drug efflux pump, the accumulation of reactive oxygen species (ROS) and the inhibition of hyphal growth. These findings might provide novel insights for overcoming drug resistance of C. albicans and bring new reference data for the development and application of AA in future.

Antifungal effects and potential mechanisms of lonidamine in combination with fluconazole against Candida albicans

OBJECTIVES

The resistance of Candida albicans (C. albicans) to classical antifungals has been increasing significantly and poses great challenges to clinical treatment. The objective of this research is to evaluate whether the combination of lonidamine (LND) and fluconazole (FLC) have synergistic antifungal activity against C. albicans and to explore the underlying synergistic mechanisms against FLC-resistant C. albicans.

METHODS

The antifungal effect on resistant planktonic C. albicans and preformed biofilms were performed by broth microdilution assay and XTT reduction assay. The influence on hyphal growth, cellular ROS level, metacaspase activity and drug transporters were investigated by morphogenesis observation, DCFH-DA, FITC-VAD-FMK and rhodamine6G assay, respectively.

RESULTS

LND in combination with FLC exhibited synergistic antifungal effects against resistant planktonic C. albicans and preformed biofilms of C. albicans in the early stages (performed at 4 h and 8 h). The synergistic mechanisms associated with the inhibition of the hyphal growth and the activation of metacaspase, but were not related to mediate cellular ROS level or drug uptake and efflux in resistant C. albicans.

CONCLUSION

LND combined with FLC exhibited synergistic antifungal activity against resistant C. albicans, and the synergistic mechanisms were related to anti-biofilms and reduce virulence factors.

EXPERT OPINION

The emergence of fluconazole-resistant Candida albicans strains poses great challenges to clinical treatment. Drug combination of non-antifungals and fluconazole has attracted a lot of attention to overcome Candida albicans drug resistance.

Dispiropyrrolidine tethered piperidone heterocyclic hybrids with broad-spectrum antifungal activity against Candida albicans and Cryptococcus neoformans

Invasive fungal infections along with rising incidence of resistance to antifungal drugs pose increasing threat to immunocompromised individuals, including cancer patients. In this study, we examined the antifungal activity of dispiropyrrolidine tethered piperidone heterocyclic hybrids. Results indicate that compounds 5a and 6i have demonstrated a potent antifungal effect on multiple fungal strains, including Candida albicans, without exhibiting cytotoxicity to mammalian cells. Furthermore, these two compounds exhibited significant inhibition on Candida albicans hyphae and biofilm development that surpasses the FDA-approved antifungal drug currently used for treatment. Taken together, our results suggest that 5a and 6i are promising candidates for development into new antifungal drugs.

Broad-spectrum antifungal activity of spirooxindolo-pyrrolidine tethered indole/imidazole hybrid heterocycles against fungal pathogens

Invasive fungal infections are one of the leading causes of nosocomial bloodstream infections with a limited treatment option. A series of derivatized spirooxindolo-pyrrolidine tethered indole and imidazole heterocyclic hybrids have been synthesized, and their antifungal activity against fungal strains were determined. Here we characterize the antifungal activity of a specific spirooxindolo-pyrrolidine hybrid, dubbed compound 9c, a spirooxindolo-pyrrolidine tethered imidazole synthesized with a 2-chloro and trifluoromethoxy substituent. The compound 9c exhibited no cytotoxicity against mammalian cell line at concentrations that inhibited fungal strains. Compound 9c also significantly inhibited the fungal hyphae and biofilm formation. Our results indicate that spirooxindolo-pyrrolidine heterocyclic hybrids potentially represent a broad class of chemical agents with promising antifungal potential.

Secondary bile acids inhibit Candida albicans growth and morphogenesis

Candida albicans is one of the most common causes of fungal infections in humans with a significant mortality rate. However, the factors involved in C. albicans gastrointestinal (GI) colonization remain unclear. We hypothesize that secondary bile acids have direct antifungal activity against C. albicans and may play a critical role in maintaining GI colonization resistance against C. albicans. In this study, we investigated the effect of secondary bile acids including lithocholic acid (LCA) and deoxycholic acid (DCA) on C. albicans growth and morphogenesis. Results indicate that LCA and DCA at in vivo cecal micelle concentrations inhibit C. albicans growth in vitro. Interestingly, LCA and DCA also significantly inhibited the germ tube, hyphae and biofilm formation in C. albicans. In addition, pre-treatment of C. albicans with LCA and DCA significantly reduced the percentage of C. albicans cells attached to a colon cancer cell line. Collectively, our results demonstrate that secondary bile acids play an important role in controlling the growth and morphological switching of C. albicans. Results from this study demonstrate that secondary bile acid possess direct antifungal activity against C. albicans, explaining a potential mechanism for gastrointestinal colonization resistance against C. albicans.

nBioChip, a Lab-on-a-Chip Platform of Mono- and Polymicrobial Biofilms for High-Throughput Downstream Applications

With an estimated 80% of infections being associated with a biofilm mode of growth and the ensuing recalcitrance of these biofilms with respect to conventional antibiotic treatment leading to high mortality rates, there is a dire and unmet need for the development of novel approaches to prevent, treat, and control these infections. Both bacteria and fungi are capable of forming biofilms that are inherently fragile and often polymicrobial in nature, which further complicates treatment. In this work, we showcase a nanobiofilm chip as a convenient platform for culturing several hundreds of mono- or polymicrobial biofilms and for susceptibility testing. This platform enables true ultra-high-throughput screening for antimicrobial drug discovery or diagnostics or for addressing fundamental issues in microbiology.

Current in vitro techniques for the culture of microorganisms, and particularly of delicate microbial biofilms, are still mostly limited to low-density plates and manual labor and are not amenable to automation and true high-throughput (HT) applications. We have developed a novel fully automated platform for the formation of mono- and polymicrobial biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans at the nanoscale level. The nBioChip is robotically printed, robustly handled, and scanned using a standard microarray reader. Using this technique, hundreds to thousands of identical nanobiofilms encapsulated in hydrogel spots were cultured on microscope slides. The spots can withstand the washing steps involved in screening assays. The miniaturized biofilms demonstrated characteristics similar to those displayed by conventionally formed macroscopic biofilms, including (i) three-dimensional architectural features, (ii) synthesis of exopolymeric matrix material, and (iii) elevated resistance to antibiotic treatment. On the basis of our results, the nBioChip can generate reliable high-throughput antimicrobial susceptibility testing (HT-AST) in 12 to 18 h. The chip serves as a proof-of-concept universal platform for high-throughput drug screening and other downstream applications and furthers understanding of microbial interactions in mixed-species communities at the nanoscale level.

IMPORTANCE With an estimated 80% of infections being associated with a biofilm mode of growth and the ensuing recalcitrance of these biofilms with respect to conventional antibiotic treatment leading to high mortality rates, there is a dire and unmet need for the development of novel approaches to prevent, treat, and control these infections. Both bacteria and fungi are capable of forming biofilms that are inherently fragile and often polymicrobial in nature, which further complicates treatment. In this work, we showcase a nanobiofilm chip as a convenient platform for culturing several hundreds of mono- or polymicrobial biofilms and for susceptibility testing. This platform enables true ultra-high-throughput screening for antimicrobial drug discovery or diagnostics or for addressing fundamental issues in microbiology.

Antifungal activity of Rubus chingii extract combined with fluconazole against fluconazole-resistant Candida albicans

This study aimed to investigate the antifungal activity of Rubus chingii extract in combination with fluconazole (FLC) against FLC-resistant Candida albicans 100 in vitro. A R. chingii extract and FLC-resistant C. albicans fungus suspension were prepared. The minimum inhibitory concentration and fractional inhibitory concentration index of R. chingii extract combined with FLC against C. albicans were determined, after which growth curves for C. albicans treated with R. chingii extract, FLC alone and a combination of these preparations were constructed. Additionally, the mechanisms of drug combination against C. albicans were explored by flow cytometry, gas chromatographic mass spectrometry and drug efflux pump function detection. R. chingii extract combined with FLC showed significant synergy. Flow cytometry suggested that C. albicans cells mainly arrest in G1 and S phases when they have been treated with the drug combination. The drug combination resulted in a marked decrease in the ergosterol content of the cell membrane. Additionally, efflux of Rhodamine 6G decreased with increasing concentrations of R. chingii extract. R. chingii extract combined with FLC has antifungal activity against FLC-resistant C. albicans.

Nosocomial Infection Caused by Antibiotic-Resistant Organisms in the Intensive-Care Unit

Resistance to antimicrobial agents is an evolving process, driven by the selective pressure of heavy antibiotic use in individuals living in close proximity to others. The intensive care unit (ICU), crowded with debilitated patients who are receiving broad-spectrum antibiotics and being cared for by busy physicians, nurses, and technicians, serves as an ideal environment for the emergence of antibiotic resistance. Problem pathogens presently include multiply resistant gram-negative bacilli, methicillin-resistantStaphylococcus aureus, and the recently emerged vancomycin-resistant enterococci. The prevention of antimicrobial resistance in ICUs should focus on recognition via routine unit-based sur veillance, improved compliance with handwashing and barrier precautions, and antibiotic-use policies tailored to individual units within hospitals.

Epidemiology of infections in cancer patients

Although major advances in the care of cancer patients over the past several decades have resulted in improved survival, infectious complications remain a significant cause of morbidity and mortality. To successfully identify, treat, and prevent infections, a comprehensive understanding of risk factors that predispose to infection and of commonly encountered pathogens is necessary. In addition, clinicians must keep abreast of the changing epidemiology of infections in this population. As therapeutic modalities continue to evolve, as established pathogens become increasingly drug resistant, and as new pathogens are discovered, successful management of infections will continue to present challenges in the years to come.

A novel polyamide SL-A92 as a potential fungal resistance blocker: synthesis and bioactivities in Candida albicans

AIM

To synthesize a novel polyamide SL-A92 and evaluate its bioactivity against drug resistance in Candida albicans.

METHODS

SL-A92 was synthesized using N-hydroxybenzotriazole (HOBT)/N,N'-dicyclohexylcarbodiimide (DCC) in solution phase. Its antifungal activities and effects on strain growth were tested using the micro-broth dilution method and growth curves, respectively. Induced drug resistance in the C. albicans collection strain SC5314 was obtained by incubation with fluconazole (12 microg/mL) for 21 passages. Meanwhile, incubations with SL-A92 plus fluconazole were also carried out in SC5314 strains, and the MIC(80)s were used to evaluate the inhibitory effects of SL-A92 on drug resistance during the induction process. Real time RT-PCR was performed to investigate the CDR1 and CDR2 mRNA levels in induced SC5314 strains.

RESULTS

SC5314 strain induced by the combination of fluconazole and SL-A92 (200 microg/mL) did not develop drug resistance. On day 24, the CDR1 and CDR2 mRNA levels in SC5314 strain co-treated with fluconazole and SL-A92 relative to fluconazole alone were 26% and 24%, respectively, and on day 30 the CDR1 and CDR2 mRNA levels were 43% and 31%, respectively.

CONCLUSION

SL-A92 can block the development of drug resistance during the fluconazole induction process, which partially results from the down-regulation of CDR1 and CDR2.

Proteomic analysis reveals a synergistic mechanism of fluconazole and berberine against fluconazole-resistant Candida albicans: endogenous ROS augmentation

Our previous study showed that concomitant use of berberine (BBR) and fluconazole (FLC) provided a synergistic action against FLC-resistant Candida albicans (C. albicans) clinical strains in vitro. To clarify the mechanism underlying this action, we performed a comparative proteomic study in untreated control cells and cells treated with FLC and/or BBR in 2 clinical strains of C. albicans resistant to FLC. Our analyses identified 16 differentially expressed proteins, most of which were related to energy metabolisms (e.g., Gap1, Adh1, and Aco1). Functional analyses revealed that FLC + BBR treatment increased mitochondrial membrane potential, decreased intracellular ATP level, inhibited ATP-synthase activity, and increased generation of endogenous reactive oxygen species (ROS) in FLC-resistant strains. In addition, checkerboard microdilution assay showed that addition of antioxidant ascorbic acid or reduced glutathione reduced the synergistic antifungal activity of FLC + BBR significantly. These results suggest that mitochondrial aerobic respiration shift and endogenous ROS augmentation contribute to the synergistic action of FLC + BBR against FLC-resistant C. albicans.

Antifungal activity of the plant Dodonaea viscosa var. angustifolia on Candida albicans from HIV-infected patients

was to determine the minimum inhibitory concentration (MIC) and the time taken by Dodonaea viscosa var. angustifolia (PLE) a South African medicinal plant, chlorhexidine gluconate (CHX) and triclosan (TRN) to kill Candida albicans. 41 strains of Candida albicans were investigated, 20 from HIV-positive patients, 20 from HIV-negative subjects and Candida albicans ATCC 90028. The MICs of an acetone extract of PLE, CHX and TRN were measured using a microtitre double dilution technique, and the time taken to kill 99.5% of the strains was determined. The MICs of PLE, CHX and TRN were 6.25-25, 0.008-0.16 and 0.0022-0.009 mg/ml, respectively. PLE killed all the test strains within 30s and CHX 40% of the isolates from HIV-positive patients and 20% of strains from HIV-negative subjects in 1 min. During the same time TRN killed 55% and 35% of isolates from HIV-positive and HIV-negative patients. Dodonaea viscosa var. angustifolia has antifungal properties and is more effective than commercially available mouthrinses.

Membrane fluidity and lipid composition of fluconazole resistant and susceptible strains of Candida albicans isolated from diabetic patients

Ten clinical isolates of Candida albicans, five strains belonging to each of fluconazole resistant and susceptible groups isolated from diabetic patients, were studied for the membrane fluidity and lipid composition. Compared to fluconazole susceptible strains, fluconazole resistant ones exhibited enhanced membrane fluidity as measured by fluorescence polarization technique. The increased membrane fluidity was reflected in the decreased p-values exhibited by the resistant strains. On the other hand, susceptible isolates contained higher amount of ergosterol, almost twice as compared to resistant isolates which might have contributed to their lower membrane fluidity. However, no significant alteration was observed in the phospholipid and fatty acid composition of these isolates. Labeling experiments with fluorescamine dye revealed that the percentage of the exposed aminophospholipid, phosphatidylethanolamine was highest in the resistant strains as compared to the susceptible strains, indicating a possible overexpression of CDR1 and CDR2 genes in resistant strains. The results presented here suggest that the changes in the ergosterol content and overexpression of ABC transporter genes CDR1 and CDR2 could contribute to fluconazole resistance in C. albicans isolated from diabetic patients.

Safety and efficacy of posaconazole in the long-term treatment of azole-refractory oropharyngeal and esophageal candidiasis in patients with HIV infection

PURPOSE

To evaluate safety and efficacy of long-term posaconazole in HIV-infected patients with azole-refractory oropharyngeal candidiasis and/or esophageal candidiasis.

METHOD

In this noncomparative, open-label study, participants received oral posaconazole 400 mg twice daily (bid) for 3 months. Enrolled patients (N = 100) included 60 from a previous 1-month acute study of posaconazole and 40 posaconazole-naïve participants. Participants with a clinical response could be followed untreated for up to 1 month afterwards. Participants who relapsed during follow-up, showed improvement at the end of 3 months of treatment (EOT), or were cured but likely to benefit from further therapy could continue on posaconazole 400 mg bid for up to 12 months.

RESULTS

In the modified intent-to-treat population, clinical response (cure or improvement) occurred in 85.6% (77/90) at EOT. The results were similar in the previously treated participants and the posaconazole-naïve participants, 88.1% (52/59) and 80.6% (25/31), respectively. Posaconazole was well-tolerated, showing a similar safety profile during the 3-month study period and during suppressive therapy. The most frequently reported treatment-related adverse event was vomiting (4/100, 4%) during the early follow-up period (on or before day 105) and elevated hepatic enzymes (3/51, 6%) during the long-term follow-up (after day 105).

CONCLUSION

Oral posaconazole 400 mg bid demonstrated long-term safety, tolerability, and efficacy, offering a long-term, suppressive treatment option for HIV-infected participants with azole-refractory mucosal candidiasis.

Fcr1p inhibits development of fluconazole resistance in Candida albicans by abolishing CDR1 induction

Overexpression of Candida drug resistance 1 (CDR1) gene in Candida albicans (C. albicans), an efflux pump, is one of the major mechanisms contributing to drug resistance. C. albicans for fluconazole resistance 1 protein (Fcr1p) is a member of the family of zinc cluster proteins homologous to Pdr1p and Pdr3p (pleiotropic drug resistance protein) mediating azole resistance in Saccharomyces cerevisiae (S. cerevisiae) by regulating the expression of pleiotropic drug resistance 5 (PDR5) homologous to C. albicans CDR1. A previous study has showed that for fluconazole resistance 1 (FCR1) could also confer azole resistance in S. cerevisiae pdr1 pdr3 mutant by regulating PDR5. Therefore, we investigated the role of FCR1 in the development of C. albicans azole resistance in vitro and in vivo. Our results showed that Fcr1p inhibited fluconazole (FLC) resistance development in C. albicans through abolishing the induction of CDR1 expression by FLC, and in contrast FLC resistance development was accelerated resulting from the deletion of FCR1.

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.

Potent in vitro synergism of fluconazole and berberine chloride against clinical isolates of Candida albicans resistant to fluconazole

In vitro interaction of fluconazole and berberine chloride was investigated against 40 fluconazole-resistant clinical isolates of Candida albicans. Synergism in fungistatic activity was found with the checkerboard microdilution assay. The findings of agar diffusion tests and time-kill curves confirmed the synergistic interaction, but no antagonistic action was observed.

A Multicenter Randomized Trial Evaluating Posaconazole versus Fluconazole for the Treatment of Oropharyngeal Candidiasis in Subjects with HIV/AIDS

BACKGROUND

Oropharyngeal candidiasis is the most common opportunistic infection among persons infected with human immunodeficiency virus (HIV). Use of some agents is hampered by lack of efficacy, emergence of resistance, adverse events, and need for intravenous administration. Posaconazole is an extended-spectrum triazole with potent in vitro activity against Candida species, including Candida albicans, Candida glabrata, and Candida krusei (including fluconazole-resistant strains).

METHODS

This multicenter, randomized, evaluator-blinded study of subjects with HIV infection and oropharyngeal candidiasis compared efficacy of posaconazole with that of fluconazole. Subjects received either 200 mg of posaconazole or fluconazole oral suspension on day 1, followed by 100 mg/day for 13 days. The primary study end point--clinical success (cure or improvement) on day 14--was evaluated for 329 subjects. Durability of clinical success was evaluated on day 42.

RESULTS

Three hundred fifty subjects received posaconazole (n = 178) or fluconazole (n = 172). Clinical success occurred in 155 (91.7%) of 169 posaconazole recipients and in 148 (92.5%) of 160 fluconazole recipients (95% confidence interval, -6.61% to 5.04%), indicating that posaconazole was not inferior to fluconazole. On day 14, mycological success was 68% in both arms, but by day 42, significantly more posaconazole recipients than fluconazole recipients continued to have mycological success (40.6% vs. 26.4%; P=.038). Fewer posaconazole recipients than fluconazole recipients experienced clinical relapse (31.5% vs. 38.2%). Adverse events were similar between treatment arms.

CONCLUSIONS

Results demonstrate that posaconazole was as effective as fluconazole in producing a successful clinical outcome. However, posaconazole was more effective in sustaining clinical success after treatment was stopped.

A randomized study of the use of fluconazole in continuous versus episodic therapy in patients with advanced HIV infection and a history of oropharyngeal candidiasis: AIDS Clinical Trials Group Study 323/Mycoses Study Group Study 40

BACKGROUND

In human immunodeficiency virus (HIV)-infected patients, fluconazole prophylaxis is associated with reductions in the rate of fungal infection. However, concerns exist with regard to the use of fluconazole prophylaxis and the risk of development of fluconazole treatment-refractory infections.

METHODS

We performed a randomized, open-label trial that compared oral fluconazole given continuously (200 mg 3 times weekly; the "continuous fluconazole arm") with fluconazole that was provided only for episodes of orophayngeal candidiasis (OPC) or esophageal candidiasis (EC) (the "episodic fluconazole arm") in HIV-infected persons with CD4+ T cell counts of <150 cells/mm3 and a history of OPC. The primary study end point was the time to development of fluconazole-refractory OPC or EC, which was defined as lack of response to 200 mg fluconazole given daily for 14 or 21 days, respectively.

RESULTS

A total of 413 subjects were randomized to receive continuous fluconazole, and 416 were randomized to receive episodic fluconazole. After 42 months, 17 subjects (4.1%) in the continuous fluconazole arm developed fluconazole-refractory OPC or EC infections, compared with 18 subjects (4.3%) in the episodic fluconazole arm, with no difference between treatment arms with regard to the time to development of a fluconazole-refractory infection within 24 months (P=.88, by log-rank test) or before the end of the study (P=.97, by the log-rank test). Continuous fluconazole therapy was associated with fewer cases of OPC or EC (0.29 vs. 1.08 episodes per patient-year; P<.0001) and fewer invasive fungal infections (15 vs. 28 episodes; P=.04, by chi2 test), but not with improved survival, compared with episodic fluconazole therapy.

CONCLUSION

Continuous fluconazole therapy is not associated with significant risk of fluconazole-refractory OPC or EC, compared with episodic fluconazole therapy, in HIV-infected patients with access to active antiretroviral therapy.

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.

New agents for the treatment of systemic fungal infections – current status

Systemic antifungal chemotherapy is enjoying its most dynamic era. More antifungal agents are under development than ever before, including agents in entirely new classes. Major goals of current investigations are to identify compounds with a wide spectrum of activity, minimal toxicity and a high degree of target specificity. The antifungal drugs in development include new azoles {voriconazole, posaconazole (formerly SCH-56592), ravuconazole (formerly BMS-207147)}, lipid formulations of amphotericin B, a lipid formulation of nystatin, echinocandins {anidulafungin (formerly, LY-303366, VER-002), caspofungin (formerly MK-991), micafungin (formerly FK-463)}, antifungal peptides other than echinocandins, and sordarin derivatives. This discussion reviews the currently available antifungal agents and summarises the developmental issues that surround these new systemic antifungal drugs.

Importance of antifungal drug-resistance: clinical significance and need for novel therapy

The incidence of fungal infections has increased dramatically over the past few decades due to the increase in the members of the population susceptible to such infections. This population includes individuals undergoing chemotherapy for cancer, those enduring long-term treatment with antibacterial agents, those receiving immunosuppressive drugs following transplantations, or those immunosuppressed due to diseases, such as AIDS, or malignancies. Newer antifungal agents, namely the triazoles, have aided in both the treatment of fungal infections and in the prevention of disease in susceptible individuals. However, resistance to the azoles, as well as to the polyenes, has resulted in clinical failures. Only a few potential antifungal targets have been exploited to date and there is a critical need for the discovery and development of novel antifungal agents that will result in improved therapy in this ever-expanding patient population. An increased intensity in the study of fungal pathogens at the molecular level holds the key to such advances.

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.

Azole susceptibility patterns and genetic relationship among oral Candida strains isolated in the era of highly active antiretroviral therapy

We performed a cross-sectional study to analyze patterns of azole susceptibility of oral isolates in the highly active antiretroviral therapy (HAART) era and compared current data with those obtained for isolates from 1994. We further identified patients with relapsing oral pharyngeal candidiasis (OPC) who had been included in a similar study in 1994. For these subjects, we compared the susceptibility pattern for the OPC isolates, and if a modification of azole resistance was observed, we analyzed the genotypic pattern for the 1994 and 2000 isolates to determine whether the dominant strain was closely related. We included 69 consecutive HIV-infected subjects with 137 episodes of OPC who were admitted to our ward from January to June 2000. Ninety-two strains (67%) and 21 non- strains (15%) were isolated. We identified 24 episodes of OPC caused by two different species. Compared with the pre-HAART era, the fluconazole resistance of isolates significantly decreased from 45% to 10% (p <.001). Itraconazole resistance decreased from 37% to 7% (p <.001). Ketoconazole resistance (3% in 1994) was not detected more. Nine patients whose isolate was susceptible to all azole drugs had a previous isolate resistant to all azole drugs. We observed that these isolates exhibited different fingerprint profiles. Our findings demonstrate that most cases of HIV-associated OPC observed in the HAART era are caused by azole-susceptible strains. The reversion of an isolate from azole resistant to azole susceptible is related to strain replacement.

Pharmacokinetics and tissue distribution of a new partricin A derivative (N-dimethylaminoacetyl-partricin A 2-dimethylaminoethylamide diaspartate) in mice

A single-dose trial in mice (1.25 mg/kg SPA-S-753 or 1 mg/kg amphotericin B [AmB] by intravenous route) was performed to study the pharmacokinetics, tissue distribution, and urinary excretion of a new polyene, SPA-S-753 (N-dimethylaminoacetyl-partricin A 2-dimethylaminoethylamide diaspartate), in comparison with AmB. Antibiotic concentrations were determined by microbiological assay (agar diffusion method). The elimination half-lives in serum were 15.1 and 19.8 h, respectively, for SPA-S-753 and AmB; the area under the curve from 0 to infinity values were 49.3 for SPA-S-753 and 23.6 microg. h/mL for AmB, because of the higher serum levels of SPA-S-753 found just after administration. The tissue concentrations of SPA-S-753 were lower than those of AmB in liver and lungs but higher in the kidneys. The urine concentrations of SPA-S-753 and the percent of the administered dose recovered from the urine were quite low in mice, whereas those of AmB were higher.

Esterase activity in various Candida species

The aim of the present study is to ascertain esterase activities of various species of Candida. A total of 125 strains isolated and identified by conventional methods were tested for esterase activity using the Tween 80 opacity test. Our results showed that 58 of 59 strains of Candida albicans, all of the Candida tropicalis strains (n = 38) and all of the Candida guilliermondii strains (n = 3) produced positive results, whereas the remaining Candida species did not. The Tween 80 opacity test is a useful method because it is simple, economical and easy to prepare and interpret.

Prevalence of fluconazole-resistant strains of Candida albicans in otherwise healthy outpatients

BACKGROUND

In contrast to the immunosuppressed patient population, the prevalence of fluconazole-resistant strains of Candida albicans among healthy individuals has not been extensively studied.

METHODS

Candida species were cultured form 50 healthy outpatients with clinical signs of oral candidiasis. Following one week of the recommended fluconazole regimen, post-treatment cultures were obtained. Both pre- and post-treatment yeasts were identified and in vitro susceptibility testing was performed using the NCCLS M-27A method. Strains were further differentiated using established cDNA probes.

RESULTS

Forty-four patients (88%) had positive C.albicans cultures prior to treatment. Antifungal susceptibility testing of these strains demonstrated no in vitro resistance to fluconazole. At post-treatment evaluation, eight patients (18%) had persistent signs of infection and 10 patients (23%) had positive Candida sp. cultures despite no clinical signs of infection. DNA analysis confirmed that the same C. albicans strain was present both in the pre-treatment and the post-treatment cultures.

CONCLUSIONS

Our results showed that the presence of fluconazole-resistant strains of C.albicans does not appear to be prevalent among healthy outpatients furthermore, in vitro antifungal susceptibility testing does not always predict successful therapy in these patients.

Evolution of antifungal susceptibility among Candida species isolates recovered from human immunodeficiency virus-infected women receiving fluconazole prophylaxis

The effect of fluconazole on the susceptibility of Candida isolates recovered from women infected with human immunodeficiency virus (HIV) was evaluated in a randomized, double-blind, placebo-controlled trial. Women with CD4(+) cell counts of < or =300 cells/mm(3) received either fluconazole (200 mg/week) or placebo as prophylaxis. The antifungal susceptibility of specimens was evaluated. One patient who received fluconazole and 2 patients assigned to placebo had Candida albicans isolates recovered that were resistant to fluconazole (MIC, > or =64 microg/mL). Eleven patients assigned fluconazole and 4 patients assigned placebo had non-albicans Candida strains (all Candida glabrata) recovered that were resistant to fluconazole. There was significant azole cross-resistance among the non-albicans Candida species isolates. Although the rate of azole resistance did not significantly increase after fluconazole prophylaxis, there was a trend toward more in vitro azole resistance in C. glabrata isolates from patients assigned fluconazole. Moreover, the majority of resistant vaginal isolates of Candida species were recovered after initiation of open-label fluconazole use.

Two-year surveillance on fluconazole susceptibility of Candida spp isolates in a general and university hospital in Rome

Fluconazole susceptibility was tested in 385 clinical yeast isolates (285 Candida albicans, 38 C. glabrata, 31 C. tropicalis, 31 other Candida subsp.) using the agar disk diffusion test. Yeasts were collected from specimens obtained from outpatients (69) and inpatients (intensive care unit: 79 isolates, major burn unit: 31 isolates, hematology ward: 45 isolates, gynecology ward: 67 isolates, other wards: 94 isolates). Three hundred and fifty-six (92%) yeast isolates showed to be susceptible, 18 (5%) were susceptible dose-dependent, and 10 (3%) were resistant to fluconazole. Of the resistant group, 3 isolates were C.albicans, while seven were Candida non-albicans (2 C. rugosa, 2 C. humicola, 1 C. tropicalis, 1 C. ciferrii, 1 C. glabrata). The disk-diffusion method was easy to perform and there were no difficulties in the interpretation of inhibition zone diameters. Fluconazole maintained a good activity against Candida spp despite its extensive use for the prophylaxis and treatment of fungal infections.

A systematic review of the effectiveness of antifungal drugs for the prevention and treatment of oropharyngeal candidiasis in HIV-positive patients

OBJECTIVE

A systematic review of randomized clinical trials published between 1966 and April 2000 was undertaken to determine the strength of evidence for the effectiveness of antifungal drugs (nystatin, clotrimazole, amphotericin B, fluconazole, ketoconazole, and itraconazole) to prevent and treat oral candidiasis in human immunodeficiency virus-positive patients.

STUDY DESIGN

An automated database search identified 366 articles. Six met inclusion and exclusion criteria with respect to prophylaxis; 12 met criteria for treatment of oral candidiasis.

RESULTS

The evidence for the prophylactic efficacy of fluconazole is good, although insufficient to draw conclusions about the other antifungals. Evidence for treatment effectiveness is insufficient for amphotericin B but good for nystatin, clotrimazole, fluconazole, ketoconazole, and itraconazole.

CONCLUSION

Suggestions for strengthening the evidence base include the following: use of larger, more well-defined groups; control for immunologic status, viral load, history of oral candidiasis, past exposure to antifungals, baseline oral Candida carriage, drug interactions, and antiretroviral therapy; and consistent use of compliance monitors, fungal speciation, and susceptibility testing.

Oropharyngeal candidiasis in patients with human immunodeficiency virus: correlation of clinical outcome with in vitro resistance, serum azole levels, and immunosuppression

Azole-resistant thrush has emerged as a problem in people who are infected with human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS), especially those who have low CD4 cell counts who have had a previous relapse of oral candidiasis, and in those who require long-term suppressive antifungal therapy. Because of the development of a standardized methodology for antifungal susceptibility testing and interpretive criteria for resistance testing, studies of the clinical predictive value of in vitro results are possible. In this study, 61% of organisms isolated from patients who were receiving azole therapy and who had clinically resistant thrush had minimal inhibitory concentration values that would classify the isolate as "resistant" or "susceptible dose dependent." In contrast, 86% of isolates from patients with thrush that was clinically responsive to an azole were classified in vitro as "susceptible" or "susceptible dose dependent." No resistant isolates were detected in samples obtained from asymptomatic control patients who were not exposed to azole drugs. Serum levels of azole and CD4 cell counts were also important parameters with regard to prediction of response. We conclude that in vivo and in vitro correlations compare favorably to studies of susceptibility testing in bacteria.

A two year global evaluation of the susceptibility of Candida species to fluconazole by disk diffusion

The in-vitro activity of fluconazole against 46,831 yeast isolates collected over a two-year period from 57 laboratories in 33 countries worldwide was assessed using a disc diffusion method. Candida albicans was the organism isolated most frequently, accounting for 68.6% of the total number of isolates. C. glabrata, C. tropicalis, C parapsilosis and C. krusei and Cryptococcus neoformans represented 9.9, 4.7, 4.3, 1.9, and 1.4% of isolates respectively during the 2 year period and rates varied markedly between countries. In 1999 data blood isolates represented 4.9% of all isolates and intensive care unit isolates represented 9.9%. In both the 1998 and 1999 data, 99% of C. albicans were fully susceptible (S) to fluconazole, and 95.6% of all species of yeasts tested were S or susceptible-dose dependent (S-DD) to fluconazole. No emerging trends of resistance were noted with any of the Candida spp. tested as 96% of all isolates retained susceptibility (S or S-DD) to this agent.

The ALS gene family of Candida albicans

The ALS gene family of Candida albicans encodes large cell-surface glycoproteins that are implicated in the process of adhesion to host surfaces. ALS genes are also found in other Candida species that are isolated from cases of clinical disease. Genes in the ALS family are differentially regulated by physiologically relevant mechanisms. ALS genes exhibit several levels of variability including strain- and allele-specific size differences for the same gene, strain-specific differences in gene regulation, the absence of particular ALS genes in certain isolates, and additional ALS coding regions in others. The differential regulation and genetic variability of the ALS genes results in a diverse cell-surface Als protein profile that is also affected by growth conditions. The ALS genes are one example of a gene family associated with pathogenicity mechanisms in C. albicans and other Candida species.

Divergent solid-phase synthesis and candidacidal activity of MUC7 D1, a 51-residue histidine-rich N-terminal domain of human salivary mucin MUC7

Domain 1 of the low-molecular-weight human salivary mucin, designated MUC7 D1, spans the 51 N-terminal amino acid residues. This domain contains a 15-residue basic histidine-rich subdomain (R3-Q17) which has 53% sequence similarity to histatin 5 (Hsn-5), a salivary molecule known to exert potent in vitro cidal activity against Candida albicans and many other medically important fungi. The MUC7 D1-15mer and its derivatives have previously been synthesized in our laboratory and their candidacidal activities have been found to be inferior to that of Hsn-5. We were therefore intrigued to explore the candidacidal potency of the full-length MUC7 D1 (51-mer). Linear solid-phase synthesis of this domain has been accomplished following standard Fmoc chemistry. The problems of partial coupling, owing to the peptide chain length, at several stages of the solid-phase step-by-step synthesis were circumvented either by double-coupling techniques or efficient coupling procedures. The MUC7 D1 peptide was purified to homogeneity by conventional reverse-phase HPLC using two columns connected in series. Secondary structure of the purified peptide was assessed by circular dichroism (CD) spectroscopy in phosphate buffer and trifluoroethanol and compared to that of MUC7 D1-15mer and Hsn-5. The MUC7 D1 candidacidal activity was assessed against azole-sensitive and azole-resistant C. albicans strains and was found, unlike that of the MUC7 D1-15mer, to be comparable with that of Hsn-5, indicating that in addition to Hsn-5, MUC7 D1 could provide an attractive alternative to the classical antifungal agents. The candidacidal potency of MUC7 D1, like that of MUC7 D1-15mer, and of Hsn-5, appears to be largely dependent on peptide charge, irrespective of alpha-helical structure.

Antifungal pharmacodynamics: review of the literature and clinical applications

Invasive fungal infections are seen with growing frequency, likely due to increases in numbers of patients at risk of infection. Optimal selection and dosing of antifungal agents are important, as these infections are often refractory to available therapy. In contrast to antibacterials, studies examining the pharmacodynamic properties of antifungals and their application in treating invasive disease often are lacking. Agents administered for invasive infections are amphotericin B, flucytosine, and azole antifungals. Several drugs are under investigation, such as posiconazole, voriconazole, and the echinocandins, and preliminary pharmacodynamic data likely will help shape dosing regimens. Clinical trials that investigated dosage and administration, as well as the potential benefits of combination and sequential therapy, are addressed. In addition, antifungal susceptibility and animal models of infection are discussed.

In-vitro synergistic effect of fluconazole with nonsteroidal anti-inflammatory agents against Candida albicans strains

The in-vitro interaction and synergistic activity of the combination of fluconazole with some nonsteroidal anti-inflammatory drugs (sodium salicylate, piroxicam, tenoxicam and diclofenac sodium) were investigated in Candida albicans strains (n=7) by the microdilution checkerboard assay. The results were evaluated visually and by a spectrophotometric microplate reader at 492 nm wavelength. Fractional inhibitory index was calculated for every strain and combination according to the minimal inhibitory concentration (MICs). The combination of fluconazole with sodium salicylate, tenoxicam and diclofenac sodium showed synergy against 5, 5 and 3 of the C. albicans strains, respectively. The effect of fluconazole with piroxicam was synergistic against one strain but indifferent/additive against the others. These data suggest that combinations of sodium salicylate, tenoxicam and diclofenac sodium with fluconazole may prove to be useful as chemotherapeutic agents for the treatment of C. albicans infections caused by especially fluconazole-resistant strains. However, additional preclinical work and in vivo studies are necessary to determine their definite clinical use.

Susceptibility testing of voriconazole, fluconazole, itraconazole and amphotericin B against yeast isolates in a Turkish University Hospital and effect of time of reading

Voriconazole is a promising azole effective against a variety of fungi, including yeasts. In this study, we tested in vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against some ATCC and reference strains and 250 clinical yeast isolates. We also evaluated the effect of time of reading on MIC results. Voriconazole was the most active agent against Candida and Trichosporon isolates, including the putatively fluconazole-resistant C. krusei (MIC(90) 0.25 microg/ml) and C. glabrata (MIC(90) 0.5 microg/ml). Amphotericin B MICs were scattered in a considerably narrow range in both RPMI 1640 and Antibiotic Medium 3. MICs at 24 hours and 48 hours were similar in general for all antifungals tested. The highest percentage of strains that showed 24-hour and 48-hour MICs within +/-1-log(2) dilution was observed for amphotericin B tested in RPMI (99%), and the lowest for amphotericin B tested in Antibiotic Medium 3 (80%). In conclusion, voriconazole is very effective against a wide spectrum of Candida species and 24-hour readings could substitute 48-hour MIC evaluation.

Amphotericin B oral suspension for fluconazole-refractory oral candidiasis in persons with HIV infection. Adult AIDS Clinical Trials Group Study Team 295

OBJECTIVE

To determine the efficacy and safety of amphotericin B oral suspension (ABOS) for the treatment of fluconazole refractory oral candidiasis in persons with HIV infection.

DESIGN AND SETTING

A prospective, multicenter, open label trial at 25 study centers within the AIDS Clinical Trials Group.

PATIENTS AND METHODS

Individuals with diffuse oral candidiasis after 14 days of treatment with 200 mg of fluconazole daily (more than five plaques or a single plaque > 3 cm largest length) were treated with ABOS, 100 mg/ml, 5 ml swish and swallow, four times daily for 14 days. Thereafter incomplete or non-responders received an additional 14 days of therapy and responders received maintenance ABOS twice daily for up to 6 months. Relapses during maintenance ABOS were treated by increasing the dose to four times daily.

MAIN OUTCOME MEASURES

To demonstrate an ABOS clinical response rate > 33% and a treatment-limiting toxicity rate < 50%. Clinical response was defined as the absence of mouth pain and the presence of less than five oral plaques, the largest being < 3 cm largest dimension.

RESULTS

Fifty-eight subjects with a median age of 39 years and a median CD4 count of 10 x 10(6) cells/l were enrolled. Four subjects were excluded from the analysis because of inadequate follow-up after randomization (n = 3) or the presence of active esophageal disease (n = 1). Of the remaining 54 subjects, 23 (42.6%; 95% lower confidence interval, 31.1%) were classified as responders after 28 days. Five subjects (9%) stopped treatment due to toxicity. Relapse occurred in 16 responders (70%).

CONCLUSIONS

Amphotericin B oral suspension is well tolerated but has limited efficacy for the treatment of fluconazole refractory oral candidiasis.

Refractory mucosal candidiasis in advanced human immunodeficiency virus infection

We conducted a multicenter, prospective study of the risk factors, natural history, and outcome of fluconazole-refractory mucosal candidiasis (FRMC) in 832 persons with advanced human immunodeficiency virus (HIV) infection (median CD4 cell count, 14/mm3) during 1994-1996. FRMC was defined as mucosal candidiasis that failed to resolve despite 14 days of therapy with daily doses (> or =200 mg) of fluconazole. Thirty-six persons (4.3%) had FRMC (35, oral; 1, esophageal), for an incidence of 4.2 per 100 person-years (859.7 total years of follow-up). In a multivariate model, the use of trimethoprim-sulfamethoxazole within 6 months of enrollment (relative risk [RR], 2.39; P=.04) and the use of fluconazole daily or every other day (RR, 5.64; P=.004) were significantly associated with the development of FRMC. The median survival after the development of FRMC was 32.6 weeks. In conclusion, the annual incidence of FRMC was <5%. Refractory candidiasis was a poor prognostic indicator. Daily or every-other-day use of fluconazole was associated with the development of refractory infection.

Antifungal susceptibility testing of yeasts: uses and limitations

With recent developments in the field of mycology, such as increased incidence of fungal infections, the introduction of newer, safer antifungals, and the emergence of resistance, the need for clinically relevant antifungal susceptibility testing methods is obvious. Studies performed over the past decade have allowed the National Committee for Clinical Laboratory Standards Subcommittee on Antifungal Testing to achieve consensus on a new standardized broth dilution method for in vitro susceptibility testing of yeasts (NCCLS M27-A). Once the reproducibility of the M27-A document was established, tentative breakpoints for fluconazole and itraconazole were derived. The availability of a standardized procedure for determining the minimum inhibitory concentrations (MICs) of antifungal agents is an important tool in drug discovery and development. In addition, it provides means for detection of resistant strains and, in the case of oropharyngeal candidiasis, means for patient management. Copyright 2000 Harcourt Publishers Ltd.

Epidemiology of oropharyngeal Candida colonization and infection in patients receiving radiation for head and neck cancer

Oral mucosal colonization and infection with Candida are common in patients receiving radiation therapy for head and neck cancer. Infection is marked by oral pain and/or burning and can lead to significant patient morbidity. The purpose of this study was to identify Candida strain diversity in this population by using a chromogenic medium, subculturing, molecular typing, and antifungal susceptibility testing of clinical isolates. These results were then correlated with clinical outcome in patients treated with fluconazole for infection. Specimens from 30 patients receiving radiation therapy for head and neck cancer were cultured weekly for Candida. Patients exhibiting clinical infection were treated with oral fluconazole. All isolates were plated on CHROMagar Candida and RPMI medium, subcultured, and submitted for antifungal susceptibility testing and molecular typing. Infections occurred in 27% of the patients and were predominantly due to Candida albicans (78%). Candida carriage occurred in 73% of patients and at 51% of patient visits. Yeasts other than C. albicans predominated in carriage, as they were isolated from 59% of patients and at 52% of patient visits. All infections responded clinically, and all isolates were susceptible to fluconazole. Molecular typing showed that most patients had similar strains throughout their radiation treatment. One patient, however, did show the acquisition of a new strain. With this high rate of infection (27%), prophylaxis to prevent infection should be evaluated for these patients.

Antifungal activity of local anesthetics against Candida species

OBJECTIVE

To evaluate the activity of benzydamine, lidocaine, and bupivacaine, three drugs with local anesthetic activity, against Candida albicans and non-albicans strains and to clarify their mechanism of activity.

METHODS

The minimal inhibitory concentration (MIC) was determined for 20 Candida strains (18 clinical isolates and two American Type Culture Collection strains). The fungistatic activity was studied with the fluorescent probe FUN-1 and observation under epifluorescence microscopy and flow cytometry. The fungicidal activity of the three drugs was assayed by viability counts. Membrane alterations induced in the yeast cells were evaluated by staining with propidium iodide, by quantitation of intracellular K+ leakage and by transmission electron microscopy of intact yeast cells and prepared spheroplasts.

RESULTS

The MIC ranged from 12.5-50.0 microg/mL, 5.0-40.0 mg/mL, and 2.5-10.0 mg/mL for benzydamine, lidocaine, and bupivacaine, respectively. The inhibitory activity of these concentrations could be detected with the fluorescent probe FUN-1 after incubation for 60 minutes. A very fast fungicidal activity was shown by 0.2, 50, and 30 mg/mL of benzydamine, lidocaine, and bupivacaine, respectively.

CONCLUSIONS

At lower concentrations, the tested drugs have a fungistatic activity, due to yeast metabolic impairment, while at higher concentrations they are fungicidal, due to direct damage to the cytoplasmic membrane.