Infection due to fluconazole-resistant Candida in patients with AIDS: prevalence and microbiology

Comparative Efficacy and Safety of Antifungal Agents in the Prophylaxis of Oropharyngeal Candidiasis among HIV-Infected Adults: A Systematic Review and Network Meta-Analysis

The objective of the study was to compare the efficacy and safety of antifungal agents used in the prevention of oropharyngeal candidiasis among HIV-infected adults. A systematic search was conducted in four databases (MEDLINE, Scopus, CENTRAL, and Embase) for eligible randomized control trials (RCTs). The network meta-analyses (NMA) were performed using a random-effects model. Interventions were ranked based on the efficacy and safety using the surface under the cumulative ranking curve (SUCRA). The quality of evidence was assessed using the GRADE approach. From a total of 1574 studies screened, 7 RCTs comprising 959 participants were included in NMA. The use of fluconazole as a prophylactic agent was associated with a significant reduction in incidence of OPC compared to placebo (RR, 0.45 (95% CI: 0.27–0.77)) in HIV-infected adults. The overall quality of evidence was graded as moderate. Fluconazole was ranked the best antifungal for efficacy (SUCRA—95.6%) as well as safety (SUCRA—39.3%) in HIV-infected adults. Overall, the quality of evidence was graded as moderate. Fluconazole can be considered as an effective agent with a better safety profile for the prophylaxis of OPC in HIV-infected adults. However, similar to any other antimicrobial agent, the risk of possibility of resistance must be weighed against the benefits.

Chemical Analysis and Antioxidant and Antimicrobial Activity of Essential oils from Artemisia negrei L. against Drug-Resistant Microbes

Background

Artemisia negrei L. (A. negrei) is a medicinal and aromatic plant belonging to the family Asteraceae that is more widespread in the folded Middle Atlas Mountains, Morocco.

Materials and Methods

This study was run to investigate the phytochemical composition and antioxidant, antibacterial, and antifungal activities of Artemisia negrei L. essential oil. This oil was extracted from the fresh plant material by using the Clevenger apparatus. The phytochemical composition was characterized by GC-MS. The antioxidant activity was evaluated using different methods including DPPH, β-carotene bleaching, and total antioxidant capacity. The antibacterial activity was tested vs. multidrug-resistant bacteria including both Gram-negative and Gram-positive using inhibition zones in agar media and minimum inhibitory concentration (MIC) bioassays. The antifungal activity was conducted on Candida albicans, Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum using a solid medium assay.

Results

The chromatographic characterization of essential oils of A. negrei revealed the presence of 34 compounds constituting 99.91% of the total essential oil. The latter was found to have promising antioxidant activity by all bioassays used such as DPPH, β-carotene bleaching, and total antioxidant capacity. The results obtained showed that our plant oils had potent antibacterial activity towards Gram-negative (E. coli 57, E. coli 97, K. pneumonia, and P. aeruginosa) and Gram-positive (S. aureus), so that the maximum inhibition zones and MIC values were around 18–37 mm and 3.25 to 12.5 mg/mL, respectively. The oil also showed antifungal activity towards Candida albicans, Fusarium oxysporum, and Aspergillus Niger except for flavus species.

Conclusion

The findings obtained in the work showed that A. negrei can serve as a valuable source of natural compounds that can be used as a new weapon to fight radical damage and resistant microbes.

Chemical Profiling, Antioxidant, and Antimicrobial Activity against Drug-Resistant Microbes of Essential Oil from Withania frutescens L

This work was conducted to study the chemical composition, antioxidant, antibacterial, and antifungal activities of essential oil and hydrolat from Withania frutescens. The essential oil was extracted by hydrodistillation. The chemical characterization was performed using gas chromatography-mass spectrometry (GC/MS). The antioxidant activity was studied using four different assays (DPPH, TAC, FRAP, and β-carotene bleaching). The antibacterial activity test was carried out on multidrug-resistant bacteria including Gram-negative and Gram-positive strains. Antifungal activity was tested on Candida albicans and Saccharomyces cerevisiae. The yield of essential oil (EO) obtained by hydrodistillation of W. frutescens was 0.31% majorly composed of camphor, α-thujone, carvacrol, and thymol. Regarding the antioxidant activities, the concentration of the sample required to inhibit 50% of radicals (IC50) of EO and hydrolat were 14.031 ± 0.012 and 232.081 ± 3.047 µg/mL (DPPH), 4.618 ± 0.045 and 8.997 ± 0.147 µg/mL (FRAP), 0.091 ± 0.007 and 0.131 ± 0.004 mg AAE/mg (TAC), 74.141 ± 1.040% and 40.850 ± 0.083% (β-carotene), respectively. Concerning the antibacterial activity of essential oil and hydrolat, the minimum inhibitory concentration (MIC) values found were 0.006 ± 0.001 and 6.125 ± 0.541 µg/mL (Escherichia coli 57), 0.003 ± 0.001 and 6.125 ± 0.068 µg/mL (Klebsiella pneumoniae), 0.001 ± 0.0 and 6.125 ± 0.046 µg/mL (Pseudomonas aeruginosa) and 0.012 ± 0.003 and 6.125 ± 0.571 µg/mL (Staphylococcus aureus), respectively. MIC values of essential oil and hydrolat vs. both C. albicans and S. cerevisiae were lower than 1/20,480 µg/mL. Based on the findings obtained, essential oils of Withania frutescens can be used as promising natural agents to fight free radical damage and nosocomial antibiotic-resistant microbes.

Caralluma europaea (Guss.) N.E.Br.: Anti-Inflammatory, Antifungal, and Antibacterial Activities against Nosocomial Antibiotic-Resistant Microbes of Chemically Characterized Fractions

Caralluma europaea (Guss.) N.E.Br.: (C. europaea) is a wild medicinal plant belonging to the family Apocynaceae. It is commonly used in traditional medicines for treating several diseases. The present work aims to evaluate the anti-inflammatory, antibacterial, and antifungal potentials of C. europaea fractions including hydro ethanol (ET CE), n-butanol (But CE), and polyphenol (Poly CE). The chemical composition of hydroethanol, n-butanol, and polyphenol-rich fractions from C. europaea were determined using GC-MS after silylation. The anti-inflammatory effect of hydroethanol, n-butanol, and polyphenol-rich fractions was studied by carrageenan-induced paw edema. Antibacterial and antifungal activities of hydroethanol, n-butanol, and polyphenol-rich fractions against Gram-positive bacteria, Gram-negative bacteria, and yeasts were assessed using the disc diffusion and micro-dilution assays. The findings of the chemical characterization affirmed the presence of interesting bioactive compounds in C. europaea fractions. The polyphenol-rich fraction was the best inhibitor of edema by75.68% after 6 h of treatment. The hydroethanol fraction was the most active against both bacteria and yeasts. This study contributes to society as it provides potential bioactive compounds in C. europaea extract, which may help in fighting nosocomial antibiotic-resistant microbes.

Current treatment options for vulvovaginal candidiasis caused by azole-resistant Candida species

INTRODUCTION

Clinicians are increasingly challenged by patients with refractory vulvovaginal candidiasis (VVC) caused by azole-resistant Candida species. Fluconazole resistant C.albicans is a growing and perplexing problem following years of indiscriminate drug prescription and unnecessary drug exposure and for which there are few therapeutic alternatives. Regrettably, although the azole class of drugs has expanded, new classes of antifungal drugs have not been forthcoming, limiting effective treatment options in patients with azole resistant Candida vaginitis.

AREAS COVERED

This review covers published data on epidemiology, pathophysiology and treatment options for women with azole-resistant refractory VVC.

EXPERT OPINION

Fluconazole resistant C.albicans adds to the challenge of azole resistant non-albicans Candida spp. Both issues follow years of indiscriminate drug prescription and unnecessary fluconazole exposure. Although an understanding of azole resistance in yeast has been established, this knowledge has not translated into useful therapeutic advantage. Treatment options for such women with refractory symptoms are extremely limited. New therapeutic options and strategies are urgently needed to meet this challenge of azole drug resistance.

Efflux pumps genes of clinical origin are related to those from fluconazole-resistant Candida albicans isolates from environmental water

Efflux pumps coded for by CDR1, CDR2, FLU1 and MDR1 genes could be responsible for the observed resistant phenotypes in azole-resistant Candida albicans from environmental water. This was demonstrated for clinical isolates. The aim of this study was to determine the presence and genetic similarity between efflux pump genes from clinical and environmental C. albicans isolates. Yeasts were isolated and identified using 26S rRNA gene sequencing. Disk diffusion tests were conducted. PCR was used to detect the presence of efflux genes. The fragments were sequenced and subjected to BLAST and subsequent phylogenetic analysis. Thirty seven C. albicans were identified from five selected rivers; Mooi River (19 isolates), Harts River (9 isolates), Marico River (5 isolates), Crocodile River (3 isolates) and Schoonspruit River (1 isolate). All the isolates were completely resistant to azoles. Efflux pump genes were detected in most (≥60%) of the isolates. Phylogenetic analysis showed high sequence similarity between sequences from environmental isolates and clinical isolates. Resistance to the azoles and the detection of efflux pump genes renders these antifungal agents ineffective. This is a major problem, particularly for the immune-compromised sector of the community of the North West Province and warrants further investigation.

Candida species diversity and antifungal susceptibility patterns in oral samples of HIV/AIDS patients in Baja California, Mexico

Candidiasis is the most common opportunistic fungal infection in HIV patients. The aims of this study were to identify the prevalence of carriers of Candida, Candida species diversity, and in vitro susceptibility to antifungal drugs. In 297 HIV/AIDS patients in Baja California, Mexico, Candida strains were identified by molecular methods (PCR-RFLP) from isolates of oral rinses of patients in Tijuana, Mexicali, and Ensenada. 56.3% of patients were colonized or infected with Candida. In Tijuana, there was a significantly higher percentage of carriers (75.5%). Out of the 181 strains that were isolated, 71.8% were Candida albicans and 28.2% were non-albicans species. The most common non-albicans species was Candida tropicalis (12.2%), followed by Candida glabrata (8.3%), Candida parapsilosis (2.2%), Candida krusei (1.7%), and Candida guilliermondii (1.1%). Candida dubliniensis was not isolated. Two associated species were found in 11 patients. In Mexicali and Ensenada, there was a lower proportion of Candida carriers compared to other regions in Mexico and worldwide, however, in Tijuana, a border town with many peculiarities, a higher carrier rate was found. In this population, only a high viral load was associated with oral Candida carriers. Other factors such as gender, use of antiretroviral therapy, CD4+ T-lymphocyte levels, time since diagnosis, and alcohol/ tobacco consumption, were not associated with Candida carriers.

Candida glabrata Biofilms: How Far Have We Come?

Infections caused by Candida species have been increasing in the last decades and can result in local or systemic infections, with high morbidity and mortality. After Candida albicans, Candida glabrata is one of the most prevalent pathogenic fungi in humans. In addition to the high antifungal drugs resistance and inability to form hyphae or secret hydrolases, C. glabrata retain many virulence factors that contribute to its extreme aggressiveness and result in a low therapeutic response and serious recurrent candidiasis, particularly biofilm formation ability. For their extraordinary organization, especially regarding the complex structure of the matrix, biofilms are very resistant to antifungal treatments. Thus, new approaches to the treatment of C. glabrata’s biofilms are emerging. In this article, the knowledge available on C. glabrata’s resistance will be highlighted, with a special focus on biofilms, as well as new therapeutic alternatives to control them.

Fungal Opportunistic Infections in HIV Disease

Fungal pathogens can lead to many of the complications seen in advanced HIV disease and are commonly identified in HIV-infected populations with decreased immune function. Common fungal organisms affecting individuals with AIDS include Cryptococcus neoformans, various Candida species, and Histoplasma capsulatum. While infection with these organisms can be fatal, appropriate identification and management of the condition can result in reduced mortality and the opportunity for effectivemanagement of HIV disease with highly active antiretroviral therapy. This article describes the clinical presentation and treatment of 3 fungal infections common in the immunocompromised individual with AIDS. Current antifungal therapy for themanagement of these infections is discussed. In addition, the role of newer antifungal agents in the setting of these conditions is reviewed.

Clinical pharmacology of antifungal agents to overcome drug resistance in pediatric patients

INTRODUCTION

Antifungal resistance is an emerging problem that increases morbidity and mortality in immunosuppressed pediatric patients, who suffer from invasive fungal diseases. Optimal pharmacological management is critical for the successful treatment of invasive fungal infections by resistant strains.

AREAS COVERED

This paper reviews the mechanisms of resistance of different classes of antifungal agents and the current understanding of pediatric antifungal pharmacology for overcoming antifungal resistance in children based on laboratory and clinical studies in the English literature. The therapeutic choices against fungal pathogens with intrinsic or acquired resistance are further reviewed.

EXPERT OPINION

There is a paucity of data in the pediatric population regarding the epidemiology of the resistant organisms to different antifungal agents. It is also unknown if there are more prevalent molecular mechanisms that promote antifungal resistance. Selection and dosages of the most effective antifungal agent for overcoming the antifungal resistance is crucial. However, there are limited studies guiding the optimal dosage and duration of treatment for management of emergent antifungal resistance. Further studies are warranted to elucidate the optimal pharmacology of the current antifungal agents against resistant organisms and to advance the development of new antifungal agents.

A phase 2, randomized, double-blind, multicenter trial to evaluate the safety and efficacy of three dosing regimens of isavuconazole compared with fluconazole in patients with uncomplicated esophageal candidiasis

Esophageal candidiasis is a frequent cause of morbidity in immunocompromised patients. Isavuconazole is a novel, broad-spectrum antifungal developed for the treatment of opportunistic fungal infections. This phase 2 trial compared the efficacy and safety of three oral dosing regimens of isavuconazole with an oral fluconazole regimen in the primary treatment of uncomplicated esophageal candidiasis. The isavuconazole regimens were as follows: 200 mg on day 1 and then 50 mg once daily (arm A), 400 mg on day 1 and then 400 mg once-weekly (arm B), and 400 mg on day 1 and then 100 mg once daily (arm C). Patients in arm D received fluconazole at 200 mg on day 1 and then 100 mg once daily. The minimum treatment duration was 14 days. The primary endpoint was the rate of endoscopically confirmed clinical response at end of therapy. Safety and tolerability were also assessed. Efficacy was evaluated in 153 of 160 enrolled patients. Overall, 146 (95.4%) achieved endoscopically confirmed clinical success. Each of the isavuconazole regimens was shown to be not inferior to fluconazole, i.e., arm A versus D, -0.5% (95% confidence interval [CI] -10.0 to 9.4), arm B versus D, 3.5% (95% CI, -5.6 to 12.7), and arm C versus D, -0.2% (95% CI, -9.8 to 9.4). The frequency of adverse events was similar in arm A (n = 22; 55%), arm B (n = 18; 45%), and arm D (n = 22; 58%), but higher in arm C (n = 29; 71%). In summary, efficacy and safety of once-daily and once-weekly isavuconazole were comparable with once-daily fluconazole in the primary treatment of uncomplicated esophageal candidiasis.

ESCMID* guideline for the diagnosis and management of Candida diseases 2012: patients with HIV infection or AIDS

Mucosal candidiasis is frequent in immunocompromised HIV-infected highly active antiretroviral (HAART) naive patients or those who have failed therapy. Mucosal candidiasis is a marker of progressive immune deficiency. Because of the frequently marked and prompt immune reconstitution induced by HAART, there is no recommendation for primary antifungal prophylaxis of mucosal candidiasis in the HIV setting in Europe, although it has been evidenced as effective in the pre-HAART era. Fluconazole remains the first line of therapy for both oropharyngeal candidiasis and oesophageal candidiasis and should be preferred to itraconazole oral solution (or capsules when not available) due to fewer side effects. For patients who still present with fluconazole-refractory mucosal candidiasis, oral treatment with any other azole should be preferred based on precise Candida species identification and susceptibility testing results in addition to the optimization of HAART when feasible. For vaginal candidiasis, topical therapy is preferred.

Posaconazole: when and how? The clinician's view

Posaconazole is the newest triazole antifungal agent available as an oral suspension with an extended spectrum of activity against Candida species, Aspergillus species, Cryptococcus neoformans, Zygomycetes and endemic fungi. Among posaconazole advantages are the relatively low potential of cross-resistance with other azoles, few drug interactions compared with other azoles and its activity against Zygomycetes. Randomised, double-blind trials have shown that posaconazole is effective for prophylaxis against invasive fungal infections (IFI), especially aspergillosis, in high-risk patients. Results of Phase III clinical trials and case/series reports indicate that posaconazole is effective in treating oesophageal candidiasis, including azole-refractory disease, and other IFI refractory to standard antifungal therapies. To date, posaconazole has appeared to be well tolerated even in long-term courses; it has an excellent safety profile with gastrointestinal disturbances being the most common adverse events reported. The dose of posaconazole is 200 mg three times daily for prophylaxis, 800 mg daily in two or four divided doses for the treatment of IFI and 100 mg daily (200 mg loading dose) for the treatment of oropharyngeal candidiasis. On the basis of early clinical experience, it appears that posaconazole will be a valuable aid in the management of life-threatening fungal infections.

Oral health promotion interventions on oral yeast in hospitalised and medically compromised patients: a systematic review

Yeast are major aetiological agents of localised oral mucosal lesions, and are also leading causes of nosocomial bloodstream infections. The purpose of this systematic review was to examine the effectiveness of oral health promotion interventions on the prevalence and incidence of these opportunistic oral pathogens in hospitalised and medically compromised patients. The PubMed, ISI Web of Science and Cochrane Library databases were searched for clinical trials assessing the effect of oral health promotion interventions on oral yeast. Chlorhexidine delivered in a variety of oral hygiene products appeared to have some effect on oral yeast, although some studies found equivocal effects. Although a wide array of other compounds have also been investigated, their clinical effectiveness remains to be substantiated. Likewise, the utility of mechanical oral hygiene interventions and other oral health promotion measures such as topical application of salivary substitute, remains unsettled. Although many chemical agents contained in oral hygiene products have proven in vitro activity against oral yeast, their clinical effectiveness and potential role as adjuncts or alternative therapies to conventional treatment remains to be confirmed by further high-quality randomised controlled trials. This is pertinent, given the recent emergence of yeast resistance to conventional antifungal agents.

[Onychomycosis-causing yeasts in four Mexican dermatology centers and their antifungal susceptibility to azolic compounds]

BACKGROUND

Yeasts represent the second cause of nail fungal infection in the world, and Candida albicans and Candida parapsilosis are the two most common species.

OBJECTIVES

To determine the yeast species frequency and their in vitro antifungal susceptibility, obtained from patients with clinical features suggestive of onychomycosis.

METHODS

A prospective study was carried out in four dermatological care centers in Mexico from 2004 to 2007. Clinical diagnosis was corroborated by direct examination and culture. The yeast species was determined by morphological and biochemical tests. An antifungal susceptibility test to ketoconazole, itraconazole and fluconazole by the broth microdilution method was performed on each isolate (document M27-A2).

RESULTS

One hundred sixty-six yeast isolates were obtained; the most frequently found species were C. parapsilosis (31.9%), C. albicans (22.4%) and Candida guilliermondii (12.7%). Of all isolates, 51 showed resistance to one or several of the azole compounds: 33 to itraconazole, 12 to ketoconazole and 6 to fluconazole. It was remarkable that the four Candida glabrata isolates were resistant to the three azole compounds; C. guilliermondii and Candida famata were resistant to itraconazole in 42.9% and 54.5%, respectively.

CONCLUSION

The results obtained show the importance of identifying the aetiological agent and antifungal susceptibility testing in order to avoid therapeutic failures in onychomycosis.

Oral candidiasis and angular cheilitis

Candidiasis, an often encountered oral disease, has been increasing in frequency. Most commonly caused by the overgrowth of Candida albicans, oral candidiasis can be divided into several categories including acute and chronic forms, and angular cheilitis. Risk factors for the development of oral candidiasis include immunosuppression, wearing of dentures, pharmacotherapeutics, smoking, infancy and old age, endocrine dysfunction, and decreased salivation. Oral candidiasis may be asymptomatic. More frequently, however, it is physically uncomfortable, and the patient may complain of burning mouth, dysgeusia, dysphagia, anorexia, and weight loss, leading to nutritional deficiency and impaired quality of life. A plethora of antifungal treatments are available. The overall prognosis of oral candidiasis is good, and rarely is the condition life threatening with invasive or recalcitrant disease.

Management of oropharyngeal and esophageal candidiasis in patients with HIV infection

Mucocutaneous candidiasis is frequently one of the first signs of HIV infection. Over 90% of patients with AIDS will develop oropharyngeal candidiasis at some time during their illness. Although numerous antifungal agents have been developed, azoles, both topical (clotrimazole) and systemic (fluconazole, itraconazole, voriconazole and posaconazole), have replaced older topical antifungals (gentian violet and nystatin) in the management of oropharyngeal candidiasis in these patients. The systemic azoles are generally safe and effective agents in HIV-infected patients with oropharyngeal candidiasis. A constant concern in these patients are relapses, which depend on the degree of immunosuppression and are commonly encountered after topical therapy rather than with systemic azole therapy. In patients with fluconazole-refractory mucosal candidiasis, treatment options now include itraconazole solution, voriconazole, posaconazole and the newer echinocandins (caspofungin, micafungin and anidulafungin). The objective of this article is to review the epidemiology, diagnosis and newer management modalities of oropharyngeal and esophageal candidiasis in HIV-infected individuals.

Optimal management of oropharyngeal and esophageal candidiasis in patients living with HIV infection

Mucocutaneous candidiasis is frequently one of the first signs of human immunodeficiency virus (HIV) infection. Over 90% of patients with AIDS will develop oropharyngeal candidiasis (OPC) at some time during their illness. Although numerous antifungal agents are available, azoles, both topical (clotrimazole) and systemic (fluconazole, itraconazole, voriconazole, posaconazole) have replaced older topical antifungals (gentian violet and nystatin) in the management of oropharyngeal candidiasis in these patients. The systemic azoles, are generally safe and effective agents in HIV-infected patients with oropharyngeal candidiasis. A constant concern in these patients is relapse, which is dependent on the degree of immunosuppression commonly seen after topical therapy, rather than with systemic azole therapy. Candida esophagitis (CE) is also an important concern since it occurs in more than 10% of patients with AIDS and can lead to a decrease in oral intake and associated weight loss. Fluconazole has become the most widely used antifungal in the management of mucosal candidiasis. However, itraconazole and posaconazole have similar clinical response rates as fluconazole and are also effective alternative agents. In patients with fluconazole-refractory mucosal candidiasis, treatment options now include itraconazole solution, voriconazole, posaconazole, and the newer echinocandins (caspofungin, micafungin, and anidulafungin).

Photodynamic therapy of bacterial and fungal biofilm infections

Biofilms have been found to be involved in a wide variety of microbial infections in the body, by one estimate 80% of all infections. Infectious processes in which biofilms have been implicated include common problems such as urinary tract infections, catheter infections, middle-ear infections, sinusitis, formation of dental plaque, gingivitis, coating contact lenses, endocarditis, infections in cystic fibrosis, and infections of permanent indwelling devices such as joint prostheses and heart valves. Bacteria living in a biofilm usually have significantly different properties from free-floating bacteria of the same species, as the dense and protected environment of the film allows them to cooperate and interact in various ways. One benefit of this environment is increased resistance to detergents and antibiotics, as the dense extracellular matrix and the outer layer of cells protect the interior of the community. In some cases antibiotic resistance can be increased 1000-fold. Also, the biofilm bacteria excrete toxins that reversibly block important processes such as translation and protecting the cell from bactericidal antibiotics that are ineffective against inactive targets. In the head and neck area, biofilms are a major etiologic factor in periodontitis, wound infections, oral candidiasis, and sinus and ear infections. For the past several decades, photodynamic treatment has been reported in the literature to be effective in eradicating various microorganisms using different photosensitizers, different wavelengths of light, and different light sources. PDT has been further studied to demonstrate its effectiveness for the eradication of both Gram-negative and Gram-positive antibiotic-resistant bacteria. This chapter will focus on the use of PDT in the treatment of antibiotic-resistant biofilms, antibiotic-resistant wound infections, and azole-resistant oral candidiasis using methylene blue-based photodynamic therapy.

Antifungals: need to search for a new molecular target

In the 1990s, drug resistance has become an important problem in a variety of infectious diseases including human immunodeficiency virus infection, tuberculosis, and other bacterial infections which have profound effects on human health. At the same time, there have been dramatic increase in the incidence of fungal infections, which are probably the result of alterations in immune status associated with the acquired immuno deficiency syndrome epidemic, cancer chemotherapy, and organ and bone marrow transplantation. The rise in the incidence of fungal infections has exacerbated the need for the next generation of antifungal agents, since many of the currently available drugs have undesirable side effects, are ineffective against new or reemerging fungi, or lead to the rapid development of the resistance. This review will focus on the pathogenic yeast Candida albicans, since a large body of work on the factors and mechanism associated with antifungal drug resistance in this organism is reported sufficiently. It will certainly elaborate the probable molecular targets for drug design, discovered to date.

Should resistance to azole antifungals in vitro be interpreted as predicting clinical non-response?

Published data relating clinical treatment outcomes to susceptibility of Candida species in vitro for the triazole antifungal agents fluconazole and itraconazole show a clear association between rates of treatment failure and rising minimal inhibitory concentrations for the infecting fungal isolate. However, more than 50% of patients infected with an isolate 'resistant' to a triazole by NCCLS breakpoint criteria respond successfully to treatment with the triazole. Data for antibacterial agents similarly show that the association between resistance in vitro and treatment failure in vivo is far less than perfect. Susceptibility testing therefore falls into a category similar to that of weather forecasting. Despite good test standardization and sophisticated technology, the forecasts successfully predict trends, but cannot accurately foresee temperatures or levels of precipitation at a specific time in a specific location.

Azole resistance of Candida glabrata in a case of recurrent fungemia

We describe a case of recurrent Candida glabrata fungemia that became unresponsive to fluconazole treatment. Posttreatment isolates from blood and vaginal cultures of the immunocompetent patient were azole resistant and exhibited upregulated expression of CgCDR1/CgCDR2 efflux pumps compared to the original isolates. Amphotericin B therapy eradicated the infection.

In vitro and in vivo activities of HQQ-3, a new triazole antifungal agent

The activity of HQQ-3, a new triazole antifungal agent, was evaluated and compared with those of fluconazole, ketoconazole and terbinafine in vitro and with fluconazole in vivo. HQQ-3 exhibited potent in vitro activity against clinically important fungi. The activity of HQQ-3 against Candida spp. was superior to those of fluconazole and terbinafine and comparable or superior to that of ketoconazole. HQQ-3 retained potent activity against Candida albicans strains with low levels of susceptibility to fluconazole (fluconazole MIC80s range, 4 to >64 microg/ml). Against Cryptococcus neoformans and filamentous fungi, the activity of HQQ-3 was superior to that of fluconazole. HQQ-3 also exhibited potent in vivo activity against murine systemic infections caused by C. albicns and C. krusei. The 50% effective doses against these infections were 0.12 to 1.9 mg/kg of body weight. These result suggest that HQQ-3 may be useful in the treatment of candidiasis.

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.

Typhoid fever as a cause of opportunistic infection: case report

Background

Typhoid fever is a systemic infection caused by the bacterium Salmonella enterica subspecies enterica serotype typhi, which is acquired by ingestion of contaminated food and water. Each year the disease affects at least 16 million persons world-wide, most of whom reside in the developing countries of Southeast Asia and Africa. In Italy the disease is uncommon with a greater number of cases in Southern regions than in Northern ones.

Case presentation

We report on a 57-year-old Sri-Lankan male affected by typhoid fever, the onset of which was accompanied by oropharyngeal candidiasis. This clinical sign was due to a transient cell-mediated immunity depression (CD4+ cell count was 130 cells/mm³) probably caused by Salmonella typhi infection. Human immunodeficiency virus infection was ruled out. Diagnosis of typhoid fever was made by the isolation of Salmonella typhi from two consecutive blood cultures. The patient recovered after a ten days therapy with ciprofloxacin and his CD4+ cell count improved gradually until normalization within 3 weeks.

Conclusion

Our patient is the first reported case of typhoid fever associated with oropharyngeal candidiasis. This finding suggests a close correlation between Salmonella typhi infection and transitory immunodepression.

Candida glabrata Fungemia in Transplant Patients Receiving Voriconazole after Fluconazole

The clinical impact of voriconazole resistance in Candida glabrata is not well described. Five hematopoietic stem cell transplant recipients that developed breakthrough Candida glabrata bloodstream infections while receiving voriconazole are described and the clinical management and susceptibility profiles of their isolates are reported. All patients were markedly immunosuppressed, and in all cases, voriconazole use was preceded by prolonged fluconazole exposure (median 60 days); median voriconazole exposure prior to candidemia was 48 days. Isolates from 4 patients were shown to be resistant to fluconazole and itraconazole when tested in vitro; these same isolates had MICs to voriconazole and posaconazole > or = 2 microg/ml. Clinical failure to voriconazole may result from deficits in host defense, retained infected foci, and adaptation of the organism to environmental pressures, the specific sequence and mechanisms of which warrant further study. Clinicians must maintain a high index of suspicion for these infections in highly susceptible hosts despite voriconazole therapy, particularly when voriconazole use is preceded by prolonged fluconazole exposure.

Mechanisms of azole resistance in clinical isolates of Candida glabrata collected during a hospital survey of antifungal resistance

The increasing use of azole antifungals for the treatment of mucosal and systemic Candida glabrata infections has resulted in the selection and/or emergence of resistant strains. The main mechanisms of azole resistance include alterations in the C. glabrata ERG11 gene (CgERG11), which encodes the azole target enzyme, and upregulation of the CgCDR1 and CgCDR2 genes, which encode efflux pumps. In the present study, we evaluated these molecular mechanisms in 29 unmatched clinical isolates of C. glabrata, of which 20 isolates were resistant and 9 were susceptible dose dependent (S-DD) to fluconazole. These isolates were recovered from separate patients during a 3-year hospital survey for antifungal resistance. Four of the 20 fluconazole-resistant isolates were analyzed together with matched susceptible isolates previously taken from the same patients. Twenty other azole-susceptible clinical C. glabrata isolates were included as controls. MIC data for all the fluconazole-resistant isolates revealed extensive cross-resistance to the other azoles tested, i.e., itraconazole, ketoconazole, and voriconazole. Quantitative real-time PCR analyses showed that CgCDR1 and CgCDR2, alone or in combination, were upregulated at high levels in all but two fluconazole-resistant isolates and, to a lesser extent, in the fluconazole-S-DD isolates. In addition, slight increases in the relative level of expression of CgSNQ2 (which encodes an ATP-binding cassette [ABC] transporter and which has not yet been shown to be associated with azole resistance) were seen in some of the 29 isolates studied. Interestingly, the two fluconazole-resistant isolates expressing normal levels of CgCDR1 and CgCDR2 exhibited increased levels of expression of CgSNQ2. Conversely, sequencing of CgERG11 and analysis of its expression showed no mutation or upregulation in any C. glabrata isolate, suggesting that CgERG11 is not involved in azole resistance. When the isolates were grown in the presence of fluconazole, the profiles of expression of all genes, including CgERG11, were not changed or were only minimally changed in the resistant isolates, whereas marked increases in the levels of gene expression, particularly for CgCDR1 and CgCDR2, were observed in either the fluconazole-susceptible or the fluconazole-S-DD isolates. Finally, known ABC transporter inhibitors, such as FK506, were able to reverse the azole resistance of all the isolates. Together, these results provide evidence that the upregulation of the CgCDR1-, CgCDR2-, and CgSNQ2-encoded efflux pumps might explain the azole resistance in our set of isolates.

Cloning and characterization of the lanosterol 14alpha-demethylase (ERG11) gene in Cryptococcus neoformans

The ergosterol pathway in fungal pathogens is an attractive antimicrobial target because it is unique from the major sterol (cholesterol) producing pathway in humans. Lanosterol 14alpha-demethylase is the target for a major class of antifungals, the azoles. In this study we have isolated the gene for this enzyme from Cryptococcus neoformans. The gene, ERG11, was recovered using degenerate PCR with primers designed with a novel algorithm called CODEHOP. Sequence analysis of Erg11p identified a highly conserved region typical of the cytochrome P450 class of mono-oxygenases. The gene was present in single copy in the genome and mapped to one end of the largest chromosome. Comparison of the protein sequence to a number of major human fungal pathogen Erg11p homologs revealed that the C. neoformans protein was highly conserved, and most closely related to the Erg11p homologs from other basidiomycetes. Functional studies demonstrated that the gene could complement a Saccharomyces cerevisiae erg11 mutant, which confirmed the identity of the C. neoformans gene.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Susceptibility pattern and molecular type of species-specific Candida in oropharyngeal lesions of Indian human immunodeficiency virus-positive patients

A study of oropharyngeal candidiasis (OPC) in Indian human immunodeficiency virus (HIV)/AIDS patients was conducted over a period of 15 months. This study revealed that 75% of the HIV/AIDS patients had OPC. MIC testing revealed that 5% of the Candida isolates were fluconazole resistant. A correlation between CD4(+)-T-cell counts and development of OPC in HIV/AIDS patients was also observed. Molecular typing of C. albicans isolates showed that all were genetically unrelated.

Efficacy of chlorhexidine gluconate rinse for treatment and prevention of oral candidiasis in HIV-infected children: a pilot study

PURPOSE

We evaluated the effect of chlorhexidine (CHX) 0.12% rinses on the clinical and microbiologic manifestations of oral candidiasis in HIV-infected children.

STUDY DESIGN

This was a cross-sectional, clinical intervention study of 38 HIV-positive children. Inclusion in the study was based on oral examination and positive oral culture for Candida. At baseline, subjects with no clinical lesions but who were culture-positive for Candida (N = 9) were placed on preventive therapy of CHX q.d. for 90 days. Subjects with clinical oral candidiasis (N = 9) were placed on therapeutic CHX b.i.d. All 38 subjects received oral exams at monthly intervals. At 90 days oral mucosal samples were again taken for Candida. Colony-forming units (CFU) were determined before and after CHX treatment.

RESULTS

Of 18 culture-positive subjects, 12 were included in the CFU analyses. After 3 months of CHX oral rinse therapy, Candida was undetectable in 3 children; another 8 showed an average 2-fold reduction in CFU. In 1 child the number of CFU increased modestly. Overall, the average pre- and posttreatment mean CFU was 6.18 +/- 2.19 and 2.73 +/- 3.15, respectively (P = .009). Five patients with clinical oral candidiasis at baseline, including all 3 who had pseudomembranous candidiasis, were free of signs of disease at the end of the study.

CONCLUSIONS

This study suggests that the topical disinfectant CHX may be a promising agent for treating and preventing oral candidiasis in HIV-infected children.

High prevalence of non-albicans yeasts and detection of anti-fungal resistance in the oral flora of patients with advanced cancer

Oral fungal infections frequently develop in individuals with advanced cancer. This study examined the oral mycological flora of 207 patients receiving palliative care for advanced malignant disease. Demographic details and a clinical history were documented from each participant. A tongue swab was collected and cultured on CHROMAgar Candida (CHROMAgar Paris, France). All yeasts were identified by germ tube test, API ID 32C profiles and, for Candida dubliniensis, by species-specific PCR. Susceptibility to fluconazole and itraconazole was determined by a broth microdilution assay according to the National Committee for Clinical Laboratory Standards (NCCLS). At time of sampling, 54 (26%) of the 207 subjects had clinical evidence of a fungal infection and yeasts were isolated from 139 (67%) individuals. In total, 194 yeasts were isolated, of which 95 (49%) were Candida albicans. There was a high prevalence of Candidia glabrata (47 isolates) of which 34 (72%) were resistant to both fluconazole and itraconazole. All nine isolates of C. dubliniensis recovered were susceptible to both azoles. No relationship was established between anti-fungal usage in the preceding three months and the presence of azole resistant yeasts. This study of patients with advanced cancer has demonstrated a high incidence of oral colonization with non-C. albicans yeasts, many of which had reduced susceptibility to fluconazole and itraconazole. The role of improved oral care regimes and novel anti-fungal drugs merits further attention, to reduce the occurrence of fungal infection in these patients.

Persistence of oropharyngeal Candida albicans strains with reduced susceptibilities to fluconazole among human immunodeficiency virus-seropositive children and adults in a long-term care facility

Nineteen oropharyngeal Candida albicans isolates from six children and seven adults living with AIDS at the Russia AIDS Centre, Moscow, from 1990 to 1998 were selected for molecular typing. Two fluconazole-resistant C. albicans genotypes were identified from a child who contracted human immunodeficiency virus infection during the Elista Hospital outbreak in the Kalmyk Republic in 1989. Highly related strains were observed 4 years later in the oral lesions and colonization of two patients and a health care worker. There may be a tendency for persons who are living with AIDS in a long-term care facility and who receive fluconazole therapy for oropharyngeal candidiasis to harbor and spread fluconazole-resistant C. albicans strains.

Antifungal therapy--state of the art at the beginning of the 21st century

The most relevant information on the present state of the art of antifungal chemotherapy is reviewed in this chapter. For dermatomycoses a variety of topical antifungals are available, and safe and efficacious systemic treatment, especially with the fungicidal drug terbinafine, is possible. The duration of treatment can be drastically reduced. Substantial progress in the armamentarium of drugs for invasive fungal infections has been made, and a new class of antifungals, echinocandins, is now in clinical use. The following drugs in oral and/or intravenous formulations are available: the broad spectrum polyene amphotericin B with its new "clothes"; the sterol biosynthesis inhibitors fluconazole, itraconazole, and voriconazole; the glucan synthase inhibitor caspofungin; and the combination partner flucytosine. New therapy schedules have been studied; combination therapy has found a significant place in the treatment of severely compromised patients, and the field of prevention and empiric therapy is fast moving. Guidelines exist nowadays for the treatment of various fungal diseases and maintenance therapy. New approaches interfering with host defenses or pathogenicity of fungal cells are being investigated, and molecular biologists are looking for new targets studying the genomics of pathogenic fungi.

Susceptibility testing of fungi--current status and open questions

The increase of fungal infections and the improvement of therapeutical options demand reliable antifungal susceptibility testing. In vitro susceptibility testing of fungi--in contrast to bacteria--is not yet established as a routine method. The NCCIS (National Committee for Clinical Laboratory Standards) guidelines for susceptibility testing of yeasts (and proposed for hyphomycetes) are most important for standardization. Meanwhile, essential parts of this test procedure are accepted, but it should still be improved. The concept of using only one test medium for all drugs and test organisms is not realized so far. There are also some test situations that prevent the NCCLS standard from being applied. Based on our experience, this article describes the NCCLS methods and their modifications. It places emphasis on lipophilic drugs showing controversies despite standardization. Furthermore, the prediction of MICs on the clinical outcome is discussed. Since there are some pitfalls in testing antifungals, this should be done in experienced laboratories only. The MIC has to be regarded as only one, but an important, factor in the management of fungal diseases. Host-, drug-, and pathogen-specific data should be considered simultaneously.

Antifungal drug resistance

The increasing incidence of invasive fungal infections is the result of many factors, including an increasing number of patients with severe immunosuppression. Although new drugs have been introduced to combat this problem, the development of resistance to antifungal drugs has become increasingly apparent, especially in patients who require long-term treatment or who are receiving antifungal prophylaxis, and there is growing awareness of shifts of flora to more-resistant species. The frequency, interpretation, and, in particular, mechanism of resistance to current classes of antifungal agents, particularly the azoles (where resistance has climbed most prominently) are discussed in this review.

Fluconazole susceptibility of vaginal isolates obtained from women with complicated Candida vaginitis: clinical implications

Despite considerable evidence of azole resistance in oral candidiasis due to Candida species, little is known about the azole susceptibilities of the genital tract isolates responsible for vaginitis. The fluconazole susceptibilities of vaginal isolates obtained during a multicenter study of 556 women with complicated Candida vaginitis were determined by evaluating two fluconazole treatment regimens. Of 393 baseline isolates of Candida albicans, 377 (96%) were highly susceptible to fluconazole (MICs, <8 microg/ml) and 14 (3.6%) were resistant (MICs, >or=64 microg/ml). Following fluconazole therapy, one case of in vitro resistance developed during 6 weeks of monitoring. In accordance with the NCCLS definition, in vitro fluconazole resistance correlated poorly with the clinical response, although a trend of a higher mycological failure rate was found (41 versus 19.6% on day 14). By using an alternative breakpoint of 1 micro g/ml, based upon the concentrations of fluconazole achievable in vaginal tissue, no significant differences in the clinical and mycological responses were observed when isolates (n = 250) for which MICs were <or=1 microg/ml were compared with isolates (n = 30) for which MICs were >1 microg/ml, although a trend toward an improved clinical outcome was noted on day 14 (odds ratio, >2.7; 95% confidence interval, 0.91, 8.30). Although clinical failure was uncommon, symptomatic recurrence or mycological relapse almost invariably occurred with highly sensitive strains (MICs, <1.0 microg/ml). In vitro fluconazole resistance developed in 2 of 18 initially susceptible C. glabrata isolates following fluconazole exposure. Susceptibility testing for women with complicated Candida vaginitis appears to be unjustified.