Demonstration of synergy with fluconazole and either ibuprofen, sodium salicylate, or propylparaben against Candida albicans in vitro

Pitavastatin Calcium Confers Fungicidal Properties to Fluconazole by Inhibiting Ubiquinone Biosynthesis and Generating Reactive Oxygen Species

Fluconazole (FLC) is extensively employed for the prophylaxis and treatment of invasive fungal infections (IFIs). However, the fungistatic nature of FLC renders pathogenic fungi capable of developing tolerance towards it. Consequently, converting FLC into a fungicidal agent using adjuvants assumes significance to circumvent FLC resistance and the perpetuation of fungal infections. This drug repurposing study has successfully identified pitavastatin calcium (PIT) as a promising adjuvant for enhancing the fungicidal activity of FLC from a comprehensive library of 2372 FDA-approved drugs. PIT could render FLC fungicidal even at concentrations as low as 1 μM. The median lethal dose (LD50) of PIT was determined to be 103.6 mg/kg. We have discovered that PIT achieves its synergistic effect by inhibiting the activity of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, thereby impeding ubiquinone biosynthesis, inducing reactive oxygen species (ROS) generation, triggering apoptosis, and disrupting Golgi function. We employed a Candida albicans strain that demonstrated a notable tolerance to FLC to infect mice and found that PIT effectively augmented the antifungal efficacy of FLC against IFIs. This study is an illustrative example of how FDA-approved drugs can effectively eliminate fungal tolerance to FLC.

Drug repurposing for fungal infections

The rise of multidrug-resistant bacteria is a well-recognized threat to world health, necessitating the implementation of effective treatments. This issue has been identified as a top priority on the global agenda by the World Health Organization. Certain strains, such as Candida glabrata, Candida krusei, Candida lusitaniae, Candida auris, select cryptococcal species, and opportunistic Aspergillus or Fusarium species, have significant intrinsic resistance to numerous antifungal medicines. This inherent resistance and subsequent suboptimal clinical outcomes underscore the critical imperative for enhanced therapeutic alternatives and management protocols. The challenge of effectively treating fungal infections, compounded by the protracted timelines involved in developing novel drugs, underscores the pressing need to explore alternative therapeutic avenues. Among these, drug repurposing emerges as a particularly promising and expeditious solution, providing cost-effective solutions and safety benefits. In the fight against life-threatening resistant fungal infections, the idea of repurposing existing medications has encouraged research into both established and new compounds as a last-resort therapy. This chapter seeks to provide a comprehensive overview of contemporary antifungal drugs, as well as their key resistance mechanisms. Additionally, it seeks to provide insight into the antimicrobial properties of non-traditional drugs, thereby offering a holistic perspective on the evolving landscape of antifungal therapeutics.

Fluconazole-Loaded Ibuprofen In Situ Gel-Based Oral Spray for Oropharyngeal Candidiasis Treatment

Oral candidiasis is a fungal infection affecting the oral mucous membrane, and this research specifically addresses on a localized treatment through fluconazole-loaded ibuprofen in situ gel-based oral spray. The low solubility of ibuprofen is advantageous for forming a gel when exposed to an aqueous phase. The 1% w/w fluconazole-loaded in situ gel oral sprays were developed utilizing various concentrations of ibuprofen in N-methyl pyrrolidone. The prepared solutions underwent evaluation for viscosity, surface tension, contact angle, water tolerance, gel formation, interface interaction, drug permeation, and antimicrobial studies. The higher amount of ibuprofen reduced the surface tension and retarded solvent exchange. The use of 50% ibuprofen as a gelling agent demonstrated prolonged drug permeation for up to 24 h. The incorporation of Cremophor EL in the formulations resulted in increased drug permeation and exhibited effective inhibition against Candida albicans, Candida krusei, Candida lusitaniae, and Candida tropicalis. While the Cremophor EL-loaded formulation did not exhibit enhanced antifungal effects on agar media, its ability to facilitate the permeation of fluconazole and ibuprofen suggested potential efficacy in countering Candida invasion in the oral mucosa. Moreover, these formulations demonstrated significant thermal inhibition of protein denaturation in egg albumin, indicating anti-inflammatory properties. Consequently, the fluconazole-loaded ibuprofen in situ gel-based oral spray presents itself as a promising dosage form for oropharyngeal candidiasis treatment.

Can nonsteroidal anti-inflammatory drugs (NSAIDs) be repurposed for fungal infection?

Nonsteroidal anti-inflammatory drugs (NSAIDs) are an important class of anti-inflammatory drugs widely used for the treatment of musculoskeletal disorders, mild-to-moderate pain, and fever. This review aimed to explain the functional role and possible mechanisms of the antifungal effects of NSAIDs alone or in combination with antifungal drugs in vitro and in vivo. Several studies reported that NSAIDs such as aspirin, ibuprofen, diclofenac, indomethacin, ketorolac, celecoxib, flurbiprofen, and nimesulide had antifungal activities in vitro, either fungistatic or fungicidal, against different strains of Candida, Aspergillus, Cryptococcus, Microsporum, and Trichophyton species. These drugs inhibited biofilm adhesion and development, and yeast-to-hypha conversion which may be related to a prostaglandin E2 (PGE2)/PGEx-dependent mechanism. Modulating PGE2 levels by NSAIDs during fungal infection can be introduced as a possible mechanism to overcome. In addition, some important mechanisms of the antifungal activities of NSAIDs and their new derivatives on fungi and host immune responses are summarized. Overall, we believe that using NSAIDs along with classical antifungal drugs has the potential to be investigated as a novel therapeutic strategy in clinical studies. Furthermore, combination therapy can help manage resistant strains, increase the efficacy of antifungal drugs, and reduce toxicity.

Strategies of targeting CYP51 for IFIs therapy: Emerging prospects, opportunities and challenges

CYP51, a monooxygenase associated with the sterol synthesis pathway, is responsible for the catalysis of the 14-methyl hydroxylation reaction of lanosterol precursors. This enzyme is widely present in microorganisms, plants, and mammals. In mammals, CYP51 plays a role in cholesterol production, oligodendrocyte formation, oocyte maturation, and spermatogenesis. In fungal cells, CYP51 is an enzyme that synthesizes membrane sterols. By inhibiting fungal CYP51, ergosterol synthesis can be inhibited and ergosterol membrane fluidity is altered, resulting in fungal cell apoptosis. Thus, targeting CYP51 is a reliable antifungal strategy with important implications for the treatment of invasive fungal infections (IFIs). Many CYP51 inhibitors have been approved by the FDA for clinical treatment. However, several limitations of CYP51 inhibitors remain to be resolved, including fungal resistance, hepatotoxicity, and drug-drug interactions. New broad-spectrum, anti-resistant, highly selective CYP51 inhibitors are expected to be developed to enhance clinical efficacy and minimize adverse effects. Herein, we summarize the structural features and biological functions of CYP51 and emphatically analyze the structure-activity relationship (SAR) and therapeutic potential of different chemical types of small-molecule CYP51 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CYP51 for clinical practice.

Synergistic Antifungal Interaction between Pseudomonas aeruginosa LV Strain Metabolites and Biogenic Silver Nanoparticles against Candida auris

Candida auris has been found to be a persistent colonizer of human skin and a successful pathogen capable of causing potentially fatal infection, especially in immunocompromised individuals. This fungal species is usually resistant to most antifungal agents and has the ability to form biofilms on different surfaces, representing a significant therapeutic challenge. Herein, the effect of metabolites of Pseudomonas aeruginosa LV strain, alone and combined with biologically synthesized silver nanoparticles (bioAgNP), was evaluated in planktonic and sessile (biofilm) cells of C. auris. First, the minimal inhibitory and fungicidal concentration values of 3.12 and 6.25 μg/mL, respectively, were determined for F4a, a semi-purified bacterial fraction. Fluopsin C and indolin-3-one seem to be the active components of F4a. Like the semi-purified fraction, they showed a time- and dose-dependent fungicidal activity. F4a and bioAgNP caused severe changes in the morphology and ultrastructure of fungal cells. F4a and indolin-3-one combined with bioAgNP exhibited synergistic fungicidal activity against planktonic cells. F4a, alone or combined with bioAgNP, also caused a significant decrease in the number of viable cells within the biofilms. No cytotoxicity to mammalian cells was detected for bacterial metabolites combined with bioAgNP at synergistic concentrations that presented antifungal activity. These results indicate the potential of F4a combined with bioAgNP as a new strategy for controlling C. auris infections.

Synergistic antifungal interaction of N-(butylcarbamothioyl) benzamide and amphotericin B against Cryptococcus neoformans

Introduction

Cryptococcus neoformans is one of the leading causes of invasive fungal infections worldwide. Cryptococcal meningoencephalitis is the main challenge of antifungal therapy due to high morbidity and mortality rates, especially in low- and middle-income countries. This can be partly attributed to the lack of specific diagnosis difficulty accessing treatment, antifungal resistance and antifungal toxicity.

Methods

In the present study, the effect of the synthetic thiourea derivative N-(butylcarbamothioyl) benzamide (BTU-01), alone and combined with amphotericin B (AmB), was evaluated in planktonic and sessile (biofilm) cells of C. neoformans.

Results

BTU-01 alone exhibited a fungistatic activity with minimal inhibitory concentrations (MICs) ranging from 31.25 to 62.5 μg/mL for planktonic cells; and sessile MICs ranging from 125.0 to 1000.0 μg/mL. BTU-01 caused a concentration-dependent inhibitory activity on cryptococcal urease and did not interfere with plasma membrane fluidity. Molecular docking was performed on Canavalia ensiformis urease, and BTU-01 showed relevant interactions with the enzyme. The combination of BTU-01 and AmB exhibited synergistic fungicidal activity against planktonic and sessile cells of C. neoformans. Microscopic analysis of C. neoformans treated with BTU-01, alone or combined with AmB, revealed a reduction in cell and capsule sizes, changes in the morphology of planktonic cells; a significant decrease in the number of cells within the biofilm; and absence of exopolymeric matrix surrounding the sessile cells. Neither hemolytic activity nor cytotoxicity to mammalian cells was detected for BTU-01, alone or combined with AmB, at concentrations that exhibited antifungal activity. BTU-01 also displayed drug-likeness properties.

Conclusion

These results indicate the potential of BTU-01, for the development of new strategies for controlling C. neoformans infections.

Design, Synthesis, and Biological Evaluation of Dual-Target COX-2/CYP51 Inhibitors for the Treatment of Fungal Infectious Diseases

The design of novel dual-target (COX-2/CYP51) inhibitors was proposed in the study, and three series of compounds were constructed though the pathway of skeleton screening and combination; their molecular structures were synthesized and evaluated. Most of the compounds exhibited significant antifungal ability. Among them, potential compounds (10a-2, 16b-3) with excellent antifungal and anti-drug-resistant fungal ability (MIC₅₀, 0.125-2.0 μg/mL) were selected for the subsequent mechanistic study. On the one hand, these compounds could block the ergosterol biosynthesis pathway by inhibiting CYP51 and influence the internal physiological function of fungal cells, which included the increase of the ROS level, the anomaly of ΔΨ_m, and the emergence of an apoptotic state. On the other hand, these compounds also effectively showed COX-2 inhibition ability, eliminated the inflammatory reaction of the infected region, and activated the body's immune function. In summary, this study not only provided a novel antifungal drug design pathway but also discovered excellent target compounds.

Immunomodulatory responses of differentially polarized macrophages to fungal infections

Macrophages, the first line of defense against invasive fungi in the innate immune system, are widely distributed in the blood and tissues of the body. In response to various internal and external stimulators, macrophages can polarize into classically activated macrophages (M1) and alternatively activated macrophages (M2). These two types of polarized macrophages play different roles in antifungal activity and in maintaining the steady-state balance between inflammation and tissue repair. However, the antifungal mechanisms of M1- and M2-type macrophages have not been fully described. In this review, the immune regulatory mechanisms against pathogenic fungi of these two classical types of macrophages in various tissues are summarized. The effects of antifungal factors on macrophage differentiation are also highlighted. The description of these data, on the one hand provides valuable insight for future investigations and also highlights new strategies for the treatment of pathogenic fungal infections.

Drug repurposing against Candida auris: A systematic review

Candida auris is a drug-resistant pathogen with several reported outbreaks. The treatment of C. auris infections is difficult due to a limited number of available antifungal drugs. Thus, finding alternative drugs through repurposing approaches would be clinically beneficial. A systematic search in PubMed, Scopus and Web of Science databases, as well as Google Scholar up to 1 November 2021, was conducted to find all articles with data regarding the antifungal activity of non-antifungal drugs against the planktonic and biofilm forms of C. auris. During database and hand searching, 290 articles were found, of which 13 were eligible for inclusion in the present study. Planktonic and biofilm forms have been studied in 11 and 8 articles (with both forms examined in 6 articles), respectively. In total, 22 and 12 drugs/compounds have been reported as repositionable against planktonic and biofilm forms of C. auris, respectively. Antiparasitic drugs, with the dominance of miltefosine, were the most common repurposed drugs against both forms of C. auris, followed by anticancer drugs (e.g. alexidine dihydrochloride) against the planktonic form and anti-inflammatory drugs (e.g. ebselen) against the biofilm form of the fungus. A collection of other drugs from various classes have also shown promising activity against C. auris. Following drug repurposing approaches, a number of drugs/compounds from various classes have been found to inhibit the planktonic and biofilm forms of C. auris. Accordingly, drug repurposing is an encouraging approach for discovering potential alternatives to conventional antifungal agents to combat drug resistance in fungi, especially C. auris.

Fluconazole-COX Inhibitor Hybrids: A Dual-Acting Class of Antifungal Azoles

When used in combination with azole antifungal drugs, cyclooxygenase (COX) inhibitors such as ibuprofen improve antifungal efficacy. We report the conjugation of a chiral antifungal azole pharmacophore to COX inhibitors and the evaluation of activity of 24 hybrids. Hybrids derived from ibuprofen and flurbiprofen were considerably more potent than fluconazole and comparable to voriconazole against a panel of Candida species. The potencies of hybrids composed of an S-configured azole pharmacophore were higher than those with an R-configured pharmacophore. Tolerance, defined as the ability of a subpopulation of cells to grow in the presence of the drug, to the hybrids was lower than to fluconazole and voriconazole. The hybrids were active against a mutant lacking CYP51, the target of azole drugs, indicating that these agents act via a dual mode of action. This study established that azole-COX inhibitor hybrids are a novel class of potent antifungals with clinical potential.

Antifungal Combination of Ethyl Acetate Extract of Poincianella pluviosa (DC.) L. P. Queiros Stem Bark With Amphotericin B in Cryptococcus neoformans

Cryptococcus neoformans is the leading cause of cryptococcosis, an invasive and potentially fatal infectious disease. Therapeutic failures are due to the increase in antifungal resistance, the adverse effects of drugs, and the unavailability of therapeutic regimens in low-income countries, which limit the treatment of cryptococcosis, increasing the morbidity and mortality associated with these infections. Thus, new antifungal drugs and innovative strategies for the cryptococcosis treatment are urgently needed. The aim of the present study was to evaluate the effect of ethyl acetate fraction (EAF) of Poincianella pluviosa stem bark on planktonic and biofilm mode of growth of C. neoformans. Furthermore, the interaction between the EAF and amphotericin B (AmB) was evaluated in vitro and in Galleria mellonella infection model. Minimal inhibitory concentrations (MICs) of EAF ranged from 125.0 to >1,000.0 μg/ml and >1,000.0 μg/ml for planktonic and sessile cells, respectively. The combination between EAF and AmB exhibited a synergistic fungicidal activity toward C. neoformans, with a fractional inhibitory concentration index (FICI) ranging from 0.03 to 0.06 and 0.08 to 0.28 for planktonic and sessile cells, respectively. Microscopy analyses of planktonic C. neoformans cells treated with EAF, alone or combined with AmB, revealed morphological and ultrastructural alterations, including loss of integrity of the cell wall and cell membrane detachment, suggesting leakage of intracellular content, reduction of capsule size, and presence of vacuoles. Moreover, EAF alone or combined with AmB prolonged the survival rate of C. neoformans-infected G. mellonella larvae. These findings indicate that P. pluviosa may be an important source of new compounds that can be used as a fungus-specific adjuvant for the treatment of cryptococcosis.

Cotreatment with Aspirin and Azole Drugs Increases Sensitivity of Candida albicans in vitro

Purpose

This study aimed to investigate the effects of aspirin (acetyl salicylic acid [ASA]) combined with fluconazole (FCA), itraconazole (ITR), or voriconazole (VRC) on Candida albicans under planktonic and biofilm conditions.

Methods

A total of 39 clinical C. albicans strains were used to perform the in vitro drug sensitivity assay under different conditions using the M27-A4 broth microdilution method. The minimal inhibitory concentrations (MICs) and fractional inhibitory concentration index (FICI) values were calculated. C. albicans ZY23 was chosen for the further analyses.

Results

Under planktonic conditions, the half maximal MIC (MIC₅₀) values of FCA, ITR, and VRC were 64-0.5 μg/mL, 32-0.0625 μg/mL, and 16-0.125 μg/mL, respectively, when applied, whereas in combination with ASA, the values decreased to 32-0.25 μg/mL, 8-0.0313 μg/mL, and 8-0.0313 μg/mL, respectively. Under biofilm conditions, FCA, ITR, or VRC alone showed MIC₅₀ values of 128-8 μg/mL, 32-4 μg/mL, and 32-0.5 μg/mL, whereas in combination with ASA the values were decreased to 32-0.5 μg/mL, 16-0.5 μg/mL, and 8-0.0625 μg/mL, respectively. Analysis of the FICI showed that the sensitization rate of ASA to FCA, ITR, and FCA under planktonic conditions was 43.59%, whereas the sensitization rates of ASP to FCA, ITR, and FCA under biofilm conditions were 46.15%, 46.15%, and 48.72%, respectively. Additionally, the time-growth and time-kill curves of C. albicans ZY23 further verified the synergistic effects of ASA on azole drugs.

Conclusion

ASA may act as an enhancer of the inhibitory effects of azole drugs on the growth of clinical C. albicans under planktonic and biofilm conditions.

Drug Repurposing in Medical Mycology: Identification of Compounds as Potential Antifungals to Overcome the Emergence of Multidrug-Resistant Fungi

Immunodepression, whether due to HIV infection or organ transplantation, has increased human vulnerability to fungal infections. These conditions have created an optimal environment for the emergence of opportunistic infections, which is concomitant to the increase in antifungal resistance. The use of conventional antifungal drugs as azoles and polyenes can lead to clinical failure, particularly in immunocompromised individuals. Difficulties related to treating fungal infections combined with the time required to develop new drugs, require urgent consideration of other therapeutic alternatives. Drug repurposing is one of the most promising and rapid solutions that the scientific and medical community can turn to, with low costs and safety advantages. To treat life-threatening resistant fungal infections, drug repurposing has led to the consideration of well-known and potential molecules as a last-line therapy. The aim of this review is to provide a summary of current antifungal compounds and their main resistance mechanisms, following by an overview of the antifungal activity of non-traditional antimicrobial drugs. We provide their eventual mechanisms of action and the synergistic combinations that improve the activity of current antifungal treatments. Finally, we discuss drug repurposing for the main emerging multidrug resistant (MDR) fungus, including the Candida auris, Aspergillus or Cryptococcus species.

Alternative treatment of fungal infections: Synergy with non-antifungal agents

Fungal infections are responsible for high mortality rates in immunocompromised and high-risk surgical patients. Therapy failures during the last decades due to increasing multidrug resistance demand innovative strategies for novel and effective antifungal drugs. Synergistic combinations of antifungals with non-antifungal agents highlight a pragmatic strategy to reduce the development of drug resistance and potentially repurpose known compounds with other functions to bypass costly and time-consuming novel drug development.

Indifferent effect of nonsteroidal anti-inflammatory drugs (NSAIDs) combined with fluconazole against multidrug-resistant Candida auris

Background and Purpose:

Emergence and development of antifungal drug resistance in Candida species constitute a serious concern. Candida auris as an emerging multidrug-resistant fungus is the most important public health threat with high levels of mortality and morbidity. Almost all C. auris isolates are resistant to fluconazole, and there have been reports of elevated minimum inhibitory concentrations (MICs) to amphotericin B and echinocandins. To overcome the growing challenge of antifungal resistance, a valuable alternative option would be the use of drug combination.

Materials and Methods:

The present study evaluated the in vitro combination of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, diclofenac and aspirin with fluconazole against fluconazole-resistant C. auris in comparison to other fluconazole-resistant Candida species, including C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, and C. krusei originating from patients with candidiasis.

Results:

The MIC ranges of fluconazole-ibuprofen and fluconazole-diclofenac decreased from 32-256 to 32-128 and 16-256 µg/ml, respectively and remained the same for fluconazole-aspirin against C. auris. However, the combination of fluconazole with ibuprofen resulted in a synergistic effect for 5 strains, including C. albicans (n=2), C. tropicalis (n=1), C. glabrata (n=1), and C. krusei (n=1), by decreasing the MIC of fluconazole by 2-3 log₂ dilutions.

Conclusion:

Although the interaction of NSAIDs with fluconazole was not synergistic against fluconazole-resistant C. auris isolates, no antagonism was observed for any combinations. Therefore, combination with newer azole agents needs to be conducted.

Reversal of Azole Resistance in Candida albicans by Sulfa Antibacterial Drugs

Invasive candidiasis presents an emerging global public health challenge due to the emergence of resistance to the frontline treatment options, such as fluconazole. Hence, the identification of other compounds capable of pairing with fluconazole and averting azole resistance would potentially prolong the clinical utility of this important group. In an effort to repurpose drugs in the field of antifungal drug discovery, we explored sulfa antibacterial drugs for the purpose of reversing azole resistance in Candida In this study, we assembled and investigated a library of 21 sulfa antibacterial drugs for their ability to restore fluconazole sensitivity in Candida albicans Surprisingly, the majority of assayed sulfa drugs (15 of 21) were found to exhibit synergistic relationships with fluconazole by checkerboard assay with fractional inhibitory concentration index (ΣFIC) values ranging from <0.0312 to 0.25. Remarkably, five sulfa drugs were able to reverse azole resistance in a clinically achievable range. The structure-activity relationships (SARs) of the amino benzene sulfonamide scaffold as antifungal agents were studied. We also identified the possible mechanism of the synergistic interaction of sulfa antibacterial drugs with azole antifungal drugs. Furthermore, the ability of sulfa antibacterial drugs to inhibit Candida biofilm by 40% in vitro was confirmed. In addition, the effects of sulfa-fluconazole combinations on Candida growth kinetics and efflux machinery were explored. Finally, using a Caenorhabditis elegans infection model, we demonstrated that the sulfa-fluconazole combination does possess potent antifungal activity in vivo, reducing Candida in infected worms by ∼50% compared to the control.

Antimicrobial Activity of Ibuprofen against Cystic Fibrosis-Associated Gram-Negative Pathogens

Clinical trials have demonstrated the benefits of ibuprofen therapy in cystic fibrosis (CF) patients, an effect that is currently attributed to ibuprofen's anti-inflammatory properties. Yet, a few previous reports demonstrated an antimicrobial activity of ibuprofen as well, although none investigated its direct effects on the pathogens found in the CF lung, which is the focus of this work. Determination of ibuprofen's in vitro antimicrobial activity against Pseudomonas aeruginosa and Burkholderia species strains through measurements of the endpoint number of CFU and growth kinetics showed that ibuprofen reduced the growth rate and bacterial burden of the tested strains in a dose-dependent fashion. In an in vitroPseudomonas biofilm model, a reduction in the rate of biomass accumulation over 8 h of growth with ibuprofen treatment was observed. Next, an acute Pseudomonas pneumonia model was used to test this antimicrobial activity after the oral delivery of ibuprofen. Following intranasal inoculation, ibuprofen-treated mice exhibited lower CFU counts and improved survival compared with the control animals. Preliminary biodistribution studies performed after the delivery of ibuprofen to mice by aerosol demonstrated a rapid accumulation of ibuprofen in serum and minimum retention in lung tissue and bronchoalveolar lavage fluid. Therefore, ibuprofen-encapsulated polymeric nanoparticles (Ibu-NPs) were formulated to improve the pharmacokinetic profile. Ibu-NPs formulated for aerosol delivery inhibited the growth of P. aeruginosa in vitro and may provide a convenient dosing method. These results provide an additional explanation for the previously observed therapeutic effects of ibuprofen in CF patients and further strengthen the argument for its use by these patients.

Identification of small molecules that disrupt vacuolar function in the pathogen Candida albicans

The fungal vacuole is a large acidified organelle that performs a variety of cellular functions. At least a sub-set of these functions are crucial for pathogenic species of fungi, such as Candida albicans, to survive within and invade mammalian tissue as mutants with severe defects in vacuolar biogenesis are avirulent. We therefore sought to identify chemical probes that disrupt the normal function and/or integrity of the fungal vacuole to provide tools for the functional analysis of this organelle as well as potential experimental therapeutics. A convenient indicator of vacuolar integrity based upon the intracellular accumulation of an endogenously produced pigment was adapted to identify Vacuole Disrupting chemical Agents (VDAs). Several chemical libraries were screened and a set of 29 compounds demonstrated to reproducibly cause loss of pigmentation, including 9 azole antifungals, a statin and 3 NSAIDs. Quantitative analysis of vacuolar morphology revealed that (excluding the azoles) a sub-set of 14 VDAs significantly alter vacuolar number, size and/or shape. Many C. albicans mutants with impaired vacuolar function are deficient in the formation of hyphal elements, a process essential for its pathogenicity. Accordingly, all 14 VDAs negatively impact C. albicans hyphal morphogenesis. Fungal selectivity was observed for approximately half of the VDA compounds identified, since they did not alter the morphology of the equivalent mammalian organelle, the lysosome. Collectively, these compounds comprise of a new collection of chemical probes that directly or indirectly perturb normal vacuolar function in C. albicans.

Potential Antifungal Targets against a Candida Biofilm Based on an Enzyme in the Arachidonic Acid Cascade-A Review

Candida is an important opportunistic fungal pathogen, especially in biofilm associated infections. The formation of a Candida biofilm can decrease Candida sensitivity to antifungal drugs and cause drug resistance. Although many effective antifungal drugs are available, their applications are limited due to their high toxicity and cost. Seeking new antifungal agents that are effective against biofilm-associated infection is an urgent need. Many research efforts are underway, and some progress has been made in this field. It has been shown that the arachidonic acid cascade plays an important role in fungal morphogenesis and pathogenicity. Notably, prostaglandin E2 (PGE₂) can promote the formation of a Candida biofilm. Recently, the inhibition of PGE₂ has received much attention. Studies have shown that cyclooxygenase (COX) inhibitors, such as aspirin, ibuprofen, and indomethacin, combined with fluconazole can significantly reduce Candida adhesion and biofilm development and increase fluconazole susceptibility; the MIC of fluconazole can be decrease from 64 to 2 μg/ml when used in combination with ibuprofen. In addition, in vivo studies have also confirmed the antifungal activities of these inhibitors. In this article, we mainly review the relationship between PGE₂ and Candida biofilm, summarize the antifungal activities of COX inhibitors and analyze the possible antifungal activity of microsomal prostaglandin E synthase-1 (MPGES-1) inhibitors; additionally, other factors that influence PGE₂ production are also discussed. Hopefully this review can disclose potential antifungal targets based on the arachidonic acid cascade and provide a prevailing strategy to alleviate Candida albicans biofilm formation.

Antifungal adjuvants: Preserving and extending the antifungal arsenal

As the rates of systemic fungal infections continue to rise and antifungal drug resistance becomes more prevalent, there is an urgent need for new therapeutic options. This issue is exacerbated by the limited number of systemic antifungal drug classes. However, the discovery, development, and approval of novel antifungals is an extensive process that often takes decades. For this reason, there is growing interest and research into the possibility of combining existing therapies with various adjuvants that either enhance activity or overcome existing mechanisms of resistance. Reports of antifungal adjuvants range from plant extracts to repurposed compounds, to synthetic peptides. This approach would potentially prolong the utility of currently approved antifungals and mitigate the ongoing development of resistance.

In Vitro Interactions between Non-Steroidal Anti-Inflammatory Drugs and Antifungal Agents against Planktonic and Biofilm Forms of Trichosporon asahii

Increasing drug resistance has brought enormous challenges to the management of Trichosporon spp. infections. The in vitro antifungal activities of non-steroidal anti-inflammatory drugs (NSAIDs) against Candida spp. and Cryptococcus spp. were recently discovered. In the present study, the in vitro interactions between three NSAIDs (aspirin, ibuprofen and diclofenac sodium) and commonly used antifungal agents (fluconazole, itraconazole, voriconazole, caspofungin and amphotericin B) against planktonic and biofilm cells of T. asahii were evaluated using the checkerboard microdilution method. The spectrophotometric method and the XTT reduction assay were used to generate data on biofilm cells. The fractional inhibitory concentration index (FICI) and the ΔE model were compared to interpret drug interactions. Using the FICI, the highest percentages of synergistic effects against planktonic cells (86.67%) and biofilm cells (73.33%) were found for amphotericin B/ibuprofen, and caspofungin/ibuprofen showed appreciable percentages (73.33% for planktonic form and 60.00% for biofilm) as well. We did not observe antagonism. The ΔE model gave consistent results with FICI (86.67%). Our findings suggest that amphotericin B/ibuprofen and caspofungin/ibuprofen combinations have potential effects against T. asahii. Further in vivo and animal studies to investigate associated mechanisms need to be conducted.

Combination of fluconazole with silver nanoparticles produced by Fusarium oxysporum improves antifungal effect against planktonic cells and biofilm of drug-resistant Candida albicans

Silver nanoparticles (AgNPs) have been extensively studied because of their anti-microbial potential. Here, we evaluated the effect of biologically synthesized silver nanoparticles (AgNPbio) alone and in combination with fluconazole (FLC) against planktonic cells and biofilms of FLC-resistant Candida albicans AgNPbio exhibited a fungicidal effect, with a minimal inhibitory concentration (MIC) and fungicidal concentration ranging from 2.17 to 4.35 μg/ml. The combination of AgNPbio and FLC reduced the MIC of FLC around 16 to 64 times against planktonic cells of allC. albicans There was no significant inhibitory effect of AgNPbio on biofilm cells. However, FLC combined with AgNPbio caused a significant dose-dependent decrease in the viability of both initial and mature biofilm. All concentrations of AgNPbio, alone or in combination with FLC, were not cytotoxic to mammalian cells.The results highlight the effectiveness of the combination of AgNPbio with FLC against FLC-resistant C. albicans.

Potent drugs that attenuate anti-Candida albicans activity of fluconazole and their possible mechanisms of action

Fluconazole (FLCZ) is a first-line drug for treating Candida albicans infections, but clinical failure due to reduced sensitivity is a growing concern. Our previous study suggested that certain drug combinations pose a particular challenge in potently reducing FLCZ's anti-C. albicans activity, and cyclooxygenase inhibitors formed the major group of these attenuating drugs in combination with FLCZ. In this study, we examined the effects of diclofenac sodium (DFNa) and related compounds in combination with FLCZ against C. albicans, and investigated their possible mechanisms of interaction. DFNa, ibuprofen, and omeprazole elevated the minimum inhibitory concentration (MIC) of FLCZ by 8-, 4-, and 4-fold, respectively; however, loxoprofen sodium and celecoxib did not. An analogue of DFNa, 2,6-dichlorodiphenylamine, also elevated the MIC by 4-fold. Gene expression analysis revealed that diclofenac sodium induced CDR1 efflux pump activity, but not CDR2 activity. In addition, an efflux pump CDR1 mutant, which was manipulated to not be induced by DFNa, showed less elevation of MIC compared to that shown by the wild type. Therefore, DFNa and related compounds are potent factors for reducing the sensitivity of C. albicans to FLCZ partly via induction of an efflux pump. Although it is not known whether such antagonism is relevant to the clinical treatment failure observed, further investigation of the molecular mechanisms underlying the reduction of FLCZ's anti-C. albicans activity is expected to promote safer and more effective use of the drug.

Antifungal and antihepatotoxic effects of sepia ink extract against oxidative stress as a risk factor of invasive pulmonary aspergillosis in neutropenic mice

BACKGROUND

There is a great need for novel strategies to overcome the high mortality associated with invasive pulmonary aspergillosis (IPA) in immunocompromised patients. To evaluate the antifungal and antihepatotoxic potentials of Sepia ink extract, its effect on liver oxidative stress levels was analyzed against IPA in neutropenic mice using amphotercin B as a reference drug.

MATERIALS AND METHODS

Eighty neutropenic infected mice were randomly assigned into four main groups. The 1(st) group was treated with saline, neutropenic infected (NI), the 2(nd) group was treated with ink extract (200 mg/kg) (IE) and the 3(rd) group was treated with amphotericin B (150 mg/kg) (AMB) and 4(th) group was treated with IE plus AMB. Treatment was started at 24 h after fungal inoculation (1×10(9) conidia/ml).

RESULTS

The present study revealed good in vitro and in vivo antifungal activity of IE against A. fumigatus. IE significantly reduced hepatic fungal burden and returns liver function and histology to normal levels. Compared with the untreated infected group, mice in the IE, AMB, and IE+ AMB groups had increased glutathione reduced (GSH) and superoxide dismutase (SOD) and significantly reduced malondialdehyde (MDA) levels at 24 and 72 h after inoculation with A. fumigatus conidia.

CONCLUSION

It is then concluded that in combination with antifungal therapy (AMB), IE treatment can reduce hepatic fungal burden, alleviate hepatic granulomatous lesions and oxidative stress associated with IPA in neutropenic mice.

Synergy of the antibiotic colistin with echinocandin antifungals in Candida species

OBJECTIVES

Candida albicans is the most prevalent fungal pathogen of humans, causing a wide range of infections from harmless superficial to severe systemic infections. Improvement of the antifungal arsenal is needed since existing antifungals can be associated with limited efficacy, toxicity and antifungal resistance. Here we aimed to identify compounds that act synergistically with echinocandin antifungals and that could contribute to a faster reduction of the fungal burden.

METHODS

A total of 38 758 compounds were tested for their ability to act synergistically with aminocandin, a β-1,3-glucan synthase inhibitor of the echinocandin family of antifungals. The synergy between echinocandins and an identified hit was studied with chemogenomic screens and testing of individual Saccharomyces cerevisiae and C. albicans mutant strains.

RESULTS

We found that colistin, an antibiotic that targets membranes in Gram-negative bacteria, is synergistic with drugs of the echinocandin family against all Candida species tested. The combination of colistin and aminocandin led to faster and increased permeabilization of C. albicans cells than either colistin or aminocandin alone. Echinocandin susceptibility was a prerequisite to be able to observe the synergy. A large-scale screen for genes involved in natural resistance of yeast cells to low doses of the drugs, alone or in combination, identified efficient sphingolipid and chitin biosynthesis as necessary to protect S. cerevisiae and C. albicans cells against the antifungal combination.

CONCLUSIONS

These results suggest that echinocandin-mediated weakening of the cell wall facilitates colistin targeting of fungal membranes, which in turn reinforces the antifungal activity of echinocandins.

In vitro interactions between aspirin and amphotericin B against planktonic cells and biofilm cells of Candida albicans and C. parapsilosis

The increase in drug resistance and invasion caused by biofilm formation brings enormous challenges to the management of Candida infection. Aspirin's antibiofilm activity in vitro was discovered recently. The spectrophotometric method and the XTT {2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide} reduction assay used for data generation make it possible to evaluate fungal biofilm growth accurately. The combined use of the most commonly used methods, the fractional inhibitory concentration index (FICI) and a newly developed method, the ΔE model, which uses the concentration-effect relationship over the whole concentration range instead of using the MIC index alone, makes the interpretation of results more reliable. As an attractive tool for studying the pharmacodynamics of antimicrobial agents, time-kill curves can provide detailed information about antimicrobial efficacy as a function of both time and concentration. In the present study, in vitro interactions between aspirin (acetylsalicylic acid [ASA]) and amphotericin B (AMB) against planktonic cells and biofilm cells of Candida albicans and C. parapsilosis were evaluated by the checkerboard microdilution method and the time-kill test. Synergistic and indifferent effects were found for the combination of ASA and AMB against planktonic cells, while strong synergy was found against biofilm cells analyzed by FICI. The ΔE model gave more consistent results with FICI. The positive interactions in concentration were also confirmed by the time-kill test. Moreover, this approach also revealed the pharmacodynamics changes of ASA and synergistic action on time. Our findings suggest a potential clinical use for combination therapy with ASA and AMB to augment activity against biofilm-associated infections.

Antimicrobial activity of Piper gaudichaudianum Kuntze and its synergism with different antibiotics

One of the oldest forms of medical practice is the use of plants for the treatment and prevention of diseases that affect humans. We have studied the antimicrobial activity and synergism of Piper gaudichaudianum Kuntze with different antibiotics. The crude extract from the leaves of P. gaudichaudianum was submitted to chromatographic separation, resulting in five fractions. Fraction F3 contained a chromone (2,2-dimethyl-6-carboxycroman-4-one), and fraction F2 contained isomers that are prenylated derivatives of benzoic acid [4-hydroxy-(3',7'-dimethyl-1'-oxo-octa-E-2'-6'-dienyl)benzoic acid and 4-hydroxy-(3',7'-dimethyl-1'-oxo-octa-2'-Z-6'-dienyl) benzoic acid]. The chemical structures of both compounds were determined by analysis of ¹H-NMR, ¹³C-NMR, COZY, DEPT, HMQC, and HMBC spectral data, and by comparison with data in the literature. The crude extract, fraction F2, and fraction F3 showed good activity against Staphylococcus aureus, Bacillus subtilis, and Candida tropicalis. The two benzoic acid derivatives only showed activity against S. aureus and B. subtilis. The bioauthographic analysis showed an inhibition zone only in fraction F2. Fractions F2 and F3 showed synergism in combination with ceftriaxone, tetracycline, and vancomycin. Morphological changes in form and structure were found by scanning electron microscopy in S. aureus treated with the combination of fraction F2 with vancomycin.

In vitro analyses of the effects of heparin and parabens on Candida albicans biofilms and planktonic cells

Infections and thromboses are the most common complications associated with central venous catheters. Suggested strategies for prevention and management of these complications include the use of heparin-coated catheters, heparin locks, and antimicrobial lock therapy. However, the effects of heparin on Candida albicans biofilms and planktonic cells have not been previously studied. Therefore, we sought to determine the in vitro effect of a heparin sodium preparation (HP) on biofilms and planktonic cells of C. albicans. Because HP contains two preservatives, methyl paraben (MP) and propyl paraben (PP), these compounds and heparin sodium without preservatives (Pure-H) were also tested individually. The metabolic activity of the mature biofilm after treatment was assessed using XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction and microscopy. Pure-H, MP, and PP caused up to 75, 85, and 60% reductions of metabolic activity of the mature preformed C. albicans biofilms, respectively. Maximal efficacy against the mature biofilm was observed with HP (up to 90%) compared to the individual compounds (P < 0.0001). Pure-H, MP, and PP each inhibited C. albicans biofilm formation up to 90%. A complete inhibition of biofilm formation was observed with HP at 5,000 U/ml and higher. When tested against planktonic cells, each compound inhibited growth in a dose-dependent manner. These data indicated that HP, MP, PP, and Pure-H have in vitro antifungal activity against C. albicans mature biofilms, formation of biofilms, and planktonic cells. Investigation of high-dose heparin-based strategies (e.g., heparin locks) in combination with traditional antifungal agents for the treatment and/or prevention of C. albicans biofilms is warranted.

Potent synergic effect between ibuprofen and azoles on Candida resulting from blockade of efflux pumps as determined by FUN-1 staining and flow cytometry

OBJECTIVES

Resistance to antifungals often relates to efflux pumps exporting drugs; several modulators may block them, reverting resistance. Verapamil, beta-oestradiol and progesterone, known efflux pump inhibitors of human neoplastic cells, and ibuprofen were tested as potential modulators of resistance of Candida spp.

METHODS

Forty-two clinical isolates of Candida (38 fluconazole-resistant), two ATCC type strains and two C. albicans strains with known mechanisms of fluconazole resistance were incubated with subinhibitory concentrations of the modulators. After exposure, MICs of fluconazole, itraconazole and voriconazole were re-determined. Simultaneously, yeasts exposed to modulators were stained with FUN-1 and analysed by flow cytometry. 3H-labelled itraconazole was also used to study efflux in the presence and absence of modulators.

RESULTS

Fluconazole MICs decreased in most strains after exposure to modulators, including control strains with documented efflux overexpression. No significant MIC variation was noticed for: all C. krusei strains tested, for the resistant strain by target change, for susceptible strains, and for a very few other clinical isolates. Reverted resistant phenotypes showed cross-resistance to itraconazole and to voriconazole, which was also reverted by the modulators. For these strains, an increase in FUN-1 staining and increased accumulation of 3H-labelled itraconazole were noticed after incubation with modulators.

CONCLUSIONS

Resistance related to overexpression of efflux pumps was common among clinical isolates and could be reverted by the assayed modulators, particularly ibuprofen. The mechanism of resistance in all tested C. krusei and in a few other strains seems, however, to be of a different nature. Ibuprofen is a promising compound in association with azoles, deserving future clinical trials. FUN-1 proved to be a good marker of efflux in Candida.

Reassessment of the in vitro synergistic effect of fluconazole with the non-steroidal anti-inflammatory agent ibuprofen against Candida albicans

We reassessed the in vitro synergistic effect of fluconazole with the non-steroidal anti-inflammatory agent ibuprofen against the pathogenic yeast Candida albicans. No synergistic effect of fluconazole combined with ibuprofen was seen against fluconazole-susceptible strains, but a remarkable effect was seen against fluconazole-resistant strains (FIX index: 0.02-0.03). Furthermore, vigorous growth of the microorganism, the so-called 'Eagle effect', was observed at concentrations higher than the minimal inhibitory concentrations of ibuprofen and fluconazole. Our results suggest that the combination of ibuprofen and fluconazole should prove useful for treating infection caused by fluconazole-resistant C. albicans.

Influence of acetylsalicylic acid (aspirin) on biofilm production by Candida species

Candida spp. are important causative agents of infections associated with biofilm formation. Management of biofilm-related infections is extremely difficult and therefore new therapeutic solutions are needed. This study for the first time explored the possible effect of aspirin on Candida spp. Biofilm-producing capacity. Two strains of C. guilliermondii, and one strain per species of C. kefyr, C. glabrata, C. albicans, and C. parapsilosis were included in the study. The antifungal property of aspirin was tested by the broth microdilution method, while effect of aspirin on biofilm formation was determined by the microtiter-plate test. The minimal inhibitory concentrations of aspirin obtained ranged from 2.17 to 8.67 mM and minimal fungicidal concentrations were from 4.33 to 8.67 mM. The concentrations of aspirin which induced statistically significant decrease in biofilm formation ranged from 0.43 mM to 1.73 mM of aspirin, depending on the tested yeast strain. Therefore, the significant effects of aspirin on growth and biofilm formation of Candida spp. were achieved only with suprapharmacological concentrations of the drug. The influence of the inoculum size on the effect of aspirin on biofilm formation was determined for C. albicans only and a significant decrease was observed also at suprapharmacological concentrations of aspirin, irrespective of the inoculum size. The results obtained in the present study show aspirin to be a drug with the potential to affect and suppress biofilm formation by Candida spp., and provide support for further investigation.

Effects of aspirin and other nonsteroidal anti-inflammatory drugs on biofilms and planktonic cells of Candida albicans

Prostaglandins are now known to be produced by Candida albicans and may play an important role in fungal colonization. Their synthesis in mammalian cells is decreased by inhibitors of the cyclooxygenase isoenzymes required for prostaglandin formation. In the present study, a catheter disk model system was used to investigate the effects of nonsteroidal anti-inflammatory drugs (all cyclooxygenase inhibitors) on biofilm formation by three strains of C. albicans. Seven of nine drugs tested at a concentration of 1 mM inhibited biofilm formation. Aspirin, etodolac, and diclofenac produced the greatest effects, with aspirin causing up to 95% inhibition. Celecoxib, nimesulide, ibuprofen, and meloxicam also inhibited biofilm formation, but to a lesser extent. Aspirin was active against growing and fully mature (48-h) biofilms; its effect was dose related, and it produced significant inhibition (20 to 80%) at pharmacological concentrations. Simultaneous addition of prostaglandin E(2) abolished the inhibitory effect of 25 or 50 micro M aspirin. At 1 mM, aspirin reduced the viability of biofilm organisms to 1.9% of that of controls. Surviving cells had a wrinkled appearance, as judged by scanning electron microscopy, and consisted of both yeasts and hyphae. Treatment with other cyclooxygenase inhibitors, such as etodolac, resulted in biofilms that consisted almost entirely of yeast cells. In conventional assays for germ tube formation, these drugs produced significant inhibition, whereas aspirin had little effect. Our findings suggest that cyclooxygenase-dependent synthesis of fungal prostaglandin(s) is important for both biofilm development and morphogenesis in C. albicans and may act as a regulator in these physiological processes. Our results also demonstrate that aspirin possesses potent antibiofilm activity in vitro and could be useful in combined therapy with conventional antifungal agents in the management of some biofilm-associated Candida infections.

Antifungal activity of Thymus oils and their major compounds

The increasing recognition and importance of fungal infections, the difficulties encountered in their treatment and the increase in resistance to antifungals have stimulated the search for therapeutic alternatives. Essential oils have been used empirically. The essential oils of Thymus (Thymus vulgaris, T. zygis subspecies zygis and T. mastichina subspecies mastichina) have often been used in folk medicine. The aim of the present study was to evaluate objectively the antifungal activity of Thymus oils according to classical bacteriological methodologies - determination of the minimal inhibitory concentration (MIC) and the minimal lethal concentration (MLC) - as well as flow cytometric evaluation. The effect of essential oils upon germ tube formation, an important virulence factor, was also studied. The mechanism of action was studied by flow cytometry, after staining with propidium iodide. The chemical composition of the essential oils was investigated by gas chromatography (GC) and gas chromatography/mass spectroscopy (GC/MS). The antifungal activity of the major components (carvacrol, thymol, p-cymene and 1,8-cineole) and also possible interactions between them were also investigated. The essential oils of T. vulgaris and T. zygis showed similar antifungal activity, which was greater than T. mastichina. MIC and MLC values were similar for all the compounds tested. At MIC values of the essential oils, propidium iodide rapidly penetrated the majority of the yeast cells, indicating that the fungicidal effect resulted primarily from an extensive lesion of the cell membrane. Concentrations below the MIC values significantly inhibited germ tube formation. This study describes the potent antifungal activity of the essential oils of Thymus on Candida spp., warranting future therapeutical trials on mucocutaneous candidosis.

Antifungal activity of nonantifungal drugs

The antifungal activity of synthetic, nonchemotherapeutic compounds, antineoplastic agents and antibacterial drugs, such as sulphonamides, has been known since the early 20th century (1932). In this context, the term "nonantifungal" is taken to include a variety of compounds that are employed in the management of pathological conditions of nonfungal infectious etiology but have been shown to exhibit broad-spectrum antifungal activity. In this review, the antifungal properties of compounds such as chlorpromazine, proton pump inhibitors, antiarrhythmic agents, cholesterol-lowering agents, antineoplastic and immunosuppressive agents, antiparasitic drugs and antibiotics are described. Since fungi are eukaryotic cells, they share many pathways with human cells, thus increasing the probability of antifungal activity of "nonfungal drugs". The potential of these drugs for treatment of fungal infections has been investigated sporadically using the drugs alone or in combination with "classic" antifungal agents. A review of the literature, supplemented with a number of more recent investigations, suggests that some of these compounds enhance the activity of conventional antifungal agents, eliminate natural resistance to specific antifungal drugs (reversal of resistance) or exhibit strong activity against certain fungal strains in vitro and in animal models. The role of these agents in the epidemiology and in the clinical manifestations of fungal infections and the potential of certain drugs for treatment of invasive fungal infections require further investigation.

Preclinical assessment of the efficacy of mycograb, a human recombinant antibody against fungal HSP90

Mycograb (NeuTec Pharma plc) is a human genetically recombinant antibody against fungal heat shock protein 90 (HSP90). Antibody to HSP90 is closely associated with recovery in patients with invasive candidiasis who are receiving amphotericin B (AMB). Using in vitro assays developed for efficacy assessment of chemotherapeutic antifungal drugs, Mycograb showed activity against a wide range of yeast species (MICs against Candida albicans [fluconazole [FLC]-sensitive and FLC-resistant strains], Candida krusei, Candida tropicalis, Candida glabrata, and Candida parapsilosis, 128 to 256 microg/ml). Mycograb (4 or 8 microg/ml) showed synergy with AMB, the fractional inhibitory index being 0.09 to 0.31. Synergy was not evident with FLC, except for FLC-sensitive C. albicans. Murine kinetics showed that Mycograb at 2 mg/kg produced a maximum concentration of drug in serum of 4.7 microg/ml, a half-life at alpha phase of 3.75 min, a half-life at beta phase of 2.34 h, and an area under the concentration-time curve from 0 to t h of 155 microg. min/ml. Mycograb (2 mg/kg) alone produced significant improvement in murine candidiasis caused by each species: (i). a reduction (Scheffe's test, P < 0.05) in the mean organ colony count for the FLC-resistant strain of C. albicans (kidney, liver, and spleen), C. krusei (liver and spleen), C. glabrata (liver and spleen), C. tropicalis (kidney), and C. parapsilosis (kidney, liver, and spleen) and (ii). a statistically significant increase in the number of negative biopsy specimens (Fisher's exact test, P < 0.05) for C. glabrata (kidney), C. tropicalis (liver and spleen), and C. parapsilosis (liver). AMB (0.6 mg/kg) alone cleared the C. tropicalis infection but failed to clear infections caused by C. albicans, C. krusei, C. glabrata, or C. parapsilosis. Synergy with AMB, defined as an increase (Fisher's exact test, P < 0.05) in the number of negative biopsy specimens compared with those obtained using AMB alone, occurred with the FLC-resistant strain of C. albicans (kidney), C. krusei (spleen), C. glabrata (spleen), and C. parapsilosis (liver and spleen). Only by combining Mycograb with AMB was complete resolution of infection achieved for C. albicans, C. krusei, and C. glabrata.

In vitro activity of propyl gallate-azole drug combination against fluconazole- and itraconazole-resistant Candida albicans strains

AIMS

The influence of an antioxidant, propyl gallate (PG), on the in vitro antifungal activity of itraconazole and fluconazole, was investigated to determine whether PG could increase the antifungal activity and reduce strain resistance.

METHODS AND RESULTS

Susceptibility tests were performed against azole-resistant isolates of Candida albicans by the microbroth dilution method in the presence of PG at 400 microg ml-1. PG-triazole combination brought about a marked reduction of inhibitory azole concentration. In particular, the MIC90 for itraconazole and fluconazole dropped from 1 microg ml-1 to 0.125 microg ml-1 and from > 64 microg ml-1-8 microg ml-1, respectively.

CONCLUSION

It is likely that more than one mechanism is involved in the above synergistic interaction, including effects of PG on ATP synthesis, thus reducing the ABC transporters activity, or an effect on the target of azole, i.e. the P-450 cytochrome.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PG-triazole combination may have a role in future topical antifungal strategies but other studies are warranted.

Antimycotic activity and phagocytosis effects of econazole in combination with ibuprofen isobuthanolammonium against vaginal strains

Vaginal infections caused by Candida spp., other yeasts and Trichomonas vaginalis are problematic mainly due to the various factors involved in development of infection and to the failure of common treatments. In this study we investigated the presence of synergistic activity of econazole and ibuprofen isobuthanolammonium against 310 different vaginal isolates, by using the microdilution broth assay to test in vitro antimicrobial activity and the effect of the two drugs on phagocytosis and intramacrophagic cellular killing of mouse peritoneal macrophages. The effect of sub-inhibitory concentrations of econazole / ibuprofen isobuthanolammonium combination on Candida albicans germ tube formation was also evaluated. The in vitro antifungal activity of econazole was notably improved by addition of ibuprofen isobuthanolammonium. Macrophage killing of C. albicans was significantly increased by the two drugs and also germ-tube formation was significantly affected. We conclude that the addition of ibuprofen isobuthanolammonium to econazole provides better in vitro antifungal activity. However, further studies are needed to elucidate the in vivo action of this formulation.

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.

The effects of salicylate on bacteria

Salicylate and related compounds, such as aspirin, have a variety of effects in eucaryotic systems and are well known for their medicinal properties. Salicylate also has numerous effects on bacteria, yet only a handful of individuals within the scientific community appreciate these findings. From a bacterial viewpoint, growth in the presence of salicylate can be both beneficial and detrimental. On one hand, growth of certain bacteria in the presence of salicylate can induce an intrinsic multiple antibiotic resistance phenotype. On the other hand, growth in the presence of salicylate can reduce the resistance to some antibiotics and affect virulence factor production in some bacteria. This review provides an overview of the effects salicylate has on various bacterial species.

Synergistic fungistatic effects of lactoferrin in combination with antifungal drugs against clinical Candida isolates

Because of the rising incidence of failures in the treatment of oropharyngeal candidosis in the case of severely immunosuppressed patients (mostly human immunodeficiency virus [HIV]-infected patients), there is need for the development of new, more effective agents and/or compounds that support the activity of the common antifungal agents. Since lactoferrin is one of the nonspecific host defense factors present in saliva that exhibit antifungal activity, we studied the antifungal effects of human, bovine, and iron-depleted lactoferrin in combination with fluconazole, amphotericin B, and 5-fluorocytosine in vitro against clinical isolates of Candida species. Distinct antifungal activities of lactoferrin were observed against clinical isolates of Candida. The MICs generally were determined to be in the range of 0.5 to 100 mg. ml(-1). Interestingly, in the combination experiments we observed pronounced cooperative activity against the growth of Candida by using lactoferrin and the three antifungals tested. Only in a limited concentration range was minor antagonism detected. The use of lactoferrin and fluconazole appeared to be the most successful combination. Significant reductions in the minimal effective concentrations of fluconazole were found when it was combined with a relatively low lactoferrin concentration (1 mg/ml). Such combinations still resulted in complete growth inhibition, while synergy of up to 50% against several Candida species was observed. It is concluded that the combined use of lactoferrin and antifungals against severe infections with Candida is an attractive therapeutic option. Since fluconazole-resistant Candida species have frequently been reported, especially in HIV-infected patients, the addition of lactoferrin to the existing fluconazole therapy could postpone the occurrence of species resistance against fluconazole. Clinical studies to further elucidate the potential utility of this combination therapy have been initiated.