Fluconazole-resistant Candida in AIDS patients. Report of two cases

Molecular Mechanism of Drug Resistance

The treatment of microbial infections has suffered greatly in this present century of pathogen dominance. Inspite of extensive research efforts and scientific advancements, the worldwide emergence of microbial tolerance continues to plague survivability. The innate property of microbe to resist any antibiotic due to evolution is the virtue of intrinsic resistance. However, the classical genetic mutations and extrachromosomal segments causing gene exchange attribute to acquired tolerance development. Rampant use of antimicrobials causes certain selection pressure which increases the resistance frequency. Genomic duplication, enzymatic site modification, target alteration, modulation in membrane permeability, and the efflux pump mechanism are the major contributors of multidrug resistance (MDR), specifically antibiotic tolerance development. MDRs will lead to clinical failures for treatment and pose health crisis. The molecular mechanisms of antimicrobial resistance are diverse as well as complex and still are exploited for new discoveries in order to prevent the surfacing of “superbugs.” Antimicrobial chemotherapy has diminished the threat of infectious diseases to some extent. To avoid the indiscriminate use of antibiotics, the new ones licensed for use have decreased with time. Additionally, in vitro assays and genomics for anti-infectives are novel approaches used in resolving the issues of microbial resistance. Proper use of drugs can keep it under check and minimize the risk of MDR spread.

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.

A study of antifungal drug sensitivity of Candida isolated from human immunodeficiency virus infected patients in Chennai, South India

Background:

The purpose of this study was to study the drug sensitivity pattern of Candida seen in HIV seropositive patients in Chennai, South India.

Materials and Methods:

36 oral rinse samples were collected from HIV seropositive individuals with (21 patients) and without (15 patients) clinical candidiasis. The type of Candidiasis, quantitative estimation, differentiation of candida species and antifungal susceptibility testing was done using different tests.

Results:

In the 21 patients with candidiasis, pseudomembranous type predominated with low CD4 counts and high colony forming units. Antifungal Drug sensitivity test revealed resistance to fluconazole which is attributed to long term exposure to the drug.

Conclusion:

The results of the study confirm the hypothesis that candidal species can be isolated in HIV positive patients with clinical candidiasis. In HIV infection there are fluconazole resistant candida species emerging mainly due to long term exposure to the drug.

Aspectos micológicos e suscetibilidade in vitro de leveduras do gênero Candida em pacientes HIV-positivos provenientes do Estado de Mato Grosso

INTRODUÇÃO: A candidíase é uma das infecções fúngicas mais frequentes entre os pacientes infectados pelo vírus da imunodeficiência humana. O presente estudo objetivou a caracterização das leveduras do gênero Candida de distintas amostras clínicas, provenientes de pacientes HIV - positivos, assim como a determinação do perfil de suscetibilidade in vitro a cinco drogas antifúngicas. MÉTODOS: A caracterização dos isolados de Candida sp foi realizada através da metodologia clássica, testes bioquímicos (zimograma e auxanograma) e morfológicos (prova do tubo germinativo e microcultivo em lâmina). Também, foram realizadas a técnica genotípica (PCR) e identificação pelo método comercial API 20C AUX (BioMeriéux). Para a determinação do perfil de suscetibilidade in vitro, foram utilizadas cinco drogas antifúngicas (cetoconazol, fluconazol, itraconazol, voriconazol e anfotericina B), através do método comercialmente disponível - Etest. RESULTADOS: Foram identificados 105 isolados de leveduras do gênero Candida provenientes de 102 pacientes infectados pelo vírus HIV. Destes, foram caracterizadas 82 (78,1%) Candida albicans, 8 (7,6%) Candida parapsilosis, 8 (7,6%) Candida tropicalis, 4 (3,8%) Candida krusei, 2 (1,9%) Candida glabrata e 1 (1%) Candida guilliermondii. CONCLUSÕES: Considerando o perfil geral de sensibilidade, 60% dos isolados foram suscetíveis a todos os antifúngicos testados, porém as espécies C. tropicalis e C. krusei demonstraram uma tendência a valores mais elevados de CIMs para os azóis do que os encontrados paraC. albicans, sugerindo resistência.

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.

Pharmacokinetics and pharmacodynamics of antifungals

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Clinical utility of antifungal pharmacokinetics and pharmacodynamics

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

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

Clinical pharmacodynamics of antifungals

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

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.

Oral candidiasis

Oral candidiasis is a common opportunistic infection of the oral cavity caused by an overgrowth of Candida species, the commonest being Candida albicans. The incidence varies depending on age and certain predisposing factors. There are three broad groupings consisting of acute candidiasis, chronic candidiasis, and angular cheilitis. Risk factors include impaired salivary gland function, drugs, dentures, high carbohydrate diet, and extremes of life, smoking, diabetes mellitus, Cushing's syndrome, malignancies, and immunosuppressive conditions. Management involves taking a history, an examination, and appropriate antifungal treatment with a few requiring samples to be taken for laboratory analysis. In certain high risk groups antifungal prophylaxis reduces the incidence and severity of infections. The prognosis is good in the great majority of cases.

Antifungal pharmacodynamics: review of the literature and clinical applications

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

Clinical correlates of antifungal macrodilution susceptibility test results for non-AIDS patients with severe Candida infections treated with fluconazole

Although the clinical correlates of the reference antifungal susceptibility test results in hematogenous and deep-seated Candida infection are still controversial, we evaluated the clinical correlates of this test in deep-seated Candida infections in non-AIDS patients. Thirty-two non-AIDS patients with hematogenous or deep-seated Candida infections were treated with intravenous fluconazole (400 mg a day), and the clinical outcomes were evaluated. Coexisting bacterial infections were treated with appropriate antibiotics, superinfection or reinfection was excluded, inadequate fluconazole therapy was avoided, and essential surgical intervention was performed. The MICs of fluconazole for these 32 Candida isolates were determined according to the M27-A procedure approved by the National Committee on Clinical Laboratory Standards. MICs were interpreted as susceptible (< or =8 microg/ml), dose-dependent susceptible (16 to 32 microg/ml), and resistant (> or =64 microg/ml) according to the criteria of the M27-A standard. The success rates were 79% (19 of 24; 95% confidence interval [CI], 59 to 93%) in the susceptible category, 66% (4 of 6; 95% CI, 19 to 95%) in the dose-dependent susceptible category, and 0% (0 of 2; 95% CI, 0 to 84%) in the resistant category. We conclude that the clinical correlation of the reference antifungal susceptibility test results is high in hematogenous and deep-seated Candida infections.

Yeasts and fluconazole susceptibility in the Philippines

Identification and fluconazole susceptibility of 579 yeasts isolated from patients in 16 medical centers throughout the Philippines in 1997-98 is reported. Speciation revealed the following distribution of yeasts (with percent occurrence): Candida albicans (49.6%); C. parapsilosis (17.2%); C. tropicalis (14.9%); C. glabrata (6.2%); C. pelliculosa (4.3%); C. krusei (2.4%); C. guilliermondii (1.9%); Trichosporon cutaneum (1.7%); Cryptococcus neoformans (0.9%); Candida famata (0.5%); C. lusitaniae (0.2%) and Saccharomyces cerevisiae (0.2%). Using an agar disk diffusion assay for fluconazole susceptibility it was determined that 94% of the isolates were susceptible, 5% dose-dependent susceptible and only 1% resistant. All isolates of C. albicans were susceptible (one being dose dependent sensitive) to fluconazole. The only yeasts resistant to fluconazole were: C. guillermondii (1 isolate), C. glabrata (3 isolates) and C. parapsilosis (1 isolate).

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

OBJECTIVE

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

DESIGN AND SETTING

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

PATIENTS AND METHODS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

Refractory mucosal candidiasis in advanced human immunodeficiency virus infection

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

Antifungal susceptibility testing of yeasts: uses and limitations

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

Treatment of fluconazole-refractory oropharyngeal candidiasis with itraconazole oral solution in HIV-positive patients

This open-label, multicenter trial evaluated the efficacy and safety of a new oral solution formulation of itraconazole in HIV+/AIDS patients with fluconazole-refractory oropharyngeal candidiasis. Seventy-four HIV+/AIDS patients with mycologically confirmed oropharyngeal candidiasis who failed fluconazole therapy (200 mg/day) were treated with 100 mg of itraconazole oral solution administered twice daily (200 mg/day) for 14 days. Patients who demonstrated an incomplete response to treatment were treated for an additional 14 days (28 days total). Clinical responders were eligible for participation in a separate 6-month maintenance protocol. If they declined further treatment, responders were monitored for 6 weeks posttreatment. The primary efficacy parameter was clinical response (i.e., no lesions or symptoms) at end of treatment. Fungal cultures were performed at baseline and at the end of treatment. Among the 74 patients who had mycologically confirmed, fluconazole-unresponsive, oropharyngeal candidiasis at baseline, 41 (55%) achieved a clinical response by day 28. The median time to response was 7 days (range, 7 to 28 days). Candida albicans was the most common pathogen isolated, either alone (62%) or in combination with another Candida species (31%). All 22 patients who entered the optional, off-therapy, 6-week follow-up phase relapsed; mean time to relapse was 13 days. Itraconazole oral solution was well-tolerated; adverse events were predominantly gastrointestinal disturbances. This trial demonstrates that itraconazole oral solution is a useful therapy in the treatment of HIV-infected patients with fluconazole-refractory oropharyngeal candidiasis.

Oropharyngeal candidiasis: a review of its clinical spectrum and current therapies

With the increased use of antibiotics and immunosuppressive agents, oropharyngeal candidiasis is becoming more common. This infection is also associated with such advances in medical management as chemotherapy and organ transplantation and with human immunodeficiency virus infection. Various topical and systemic agents are available to treat patients with candidiasis, but optimal management can be elusive. Treatment of uncomplicated oropharyngeal candidiasis in the immunocompetent patient involves selecting a particular formulation of a topical medication based on oral conditions, length of contact time, and taste, texture, and cost of the medication. Treatment of severe oropharyngeal candidiasis, particularly in patients with a compromised immune system, is often more difficult, and relapses are common. Reports of resistance to systemic agents, particularly in patients needing recurrent therapy, are increasing. Amphotericin B, long used as an intravenous agent, is now available as an oral suspension that may offer therapeutic benefits comparable to those of systemic therapy without the toxicity associated with systemic absorption.

Clinical relevance of antifungal resistance

The availability of standard guidelines (NCCLS M27 document) for antifungal susceptibility testing has facilitated the establishment of tentative interpretive breakpoints for fluconazole and itraconazole by the NCCLS. Based on correlations of MIC values with the outcomes of patients with mostly Candida infections, fluconazole MICs of > or = 64 and itraconazole MICs of > or = 1.0 microgram/mL are considered resistant. Fluconazole MICs of 16 to 32 micrograms/mL and itraconazole MICs of 0.2 to 0.5 microgram/mL were categorized as "susceptible dependent upon dose" (S-DD), that is, clinical response may be obtained with increased doses. Susceptible breakpoints for fluconazole and itraconazole correspond to < or = 8 and < or = 0.12 microgram/mL, respectively. For flucytosine, resistant and susceptible breakpoints for Candida were set at > or = 32 micrograms/mL and 4 micrograms/mL, respectively, based on historical data and the drug's pharmacokinetics for Candida. Although no breakpoints have been established for amphotericin B, clinical failure has been associated with MICs > 1.0 microgram/mL.

Treatment of murine disseminated candidiasis with L-743,872

L-743,872 (M991), which is a pneumocandin derivative, was evaluated in a mouse model of disseminated candidiasis caused by a fluconazole-resistant isolate of Candida albicans. In immunocompetent mice M991 prolonged survival at doses as low as 0.0125 mg/kg of body weight per day. In neutropenic mice 0.05 mg/kg was the lowest effective dose. M991 is a very potent drug for treatment of disseminated candidiasis.

Oral transmission of Candida albicans between partners in HIV-infected couples could contribute to dissemination of fluconazole-resistant isolates

BACKGROUND

Fluconazole resistance has emerged among Candida albicans isolates and has been associated with the prolonged or repeated use of the drug. This study was designed to discover whether transmission of oral isolates could occur between sexual partners and thereby explain fluconazole resistance in patients never treated with the drug.

MATERIALS AND METHODS

The oral flora of 10 HIV-infected couples (five heterosexual and five homosexual) were studied. In vitro susceptibility testing and genotyping (restriction fragment length polymorphism with EcoRI and HinfI) were used to delineate strain relatedness for 230 clones (five clones per sample, one to four samples per patient).

RESULTS

The genetic diversity of the clones with one DNA subtype was specific to a given patient or a given couple, except in one case in which unrelated patients shared clones of the same genotype. The persistence of clones between partners was stable over time in six out of 10 couples and only transient in one couple. Fluconazole resistance in isolates from patients who had never been treated with azoles was associated in three patients with the first episode of oropharyngeal candidiasis and treatment failure.

CONCLUSION

The observation that couples tended to share genetically indistinguishable clones was highly suggestive of transmission between partners. This phenomenon may, in part, explain the pathogenesis of oropharyngeal candidiasis and the increased frequency of fluconazole resistance both in vitro and in vivo.

Exfoliative cheilitis (EC) in AIDS: association with Candida infection

Forty-seven of 165 patients with AIDS (28.5%) showed exfoliative cheilitis (EC), predominantly of the lower lip (n = 37). Histologically, hyphae were revealed in 23 of 47 cases (49%). In 14 of 23 specimens the histological and microbiological findings were in accordance. Smears of the vermilion border revealed Candida albicans in half of the cases (51%); however, combinations with C. krusei, C. tropicalis and C. glabrata were also seen. Twenty of 35 patients given fluconazole either prophylactically or therapeutically showed clinical signs of oral candidiasis. Frequent moistening of the lips may result in infection of the vermilion border with Candida species; consequent desiccation of the lips will lead to scale formation and exfoliation. Smears of the vermilion border of the lower lip of 20 controls with AIDS were positive in four cases. Twenty HIV-negative controls without EC showed negative microbiological results for Candida species. Exfoliative cheilitis may be associated with Candida infection in some cases and may be considered another variant of candidiasis in AIDS patients.

Stable azole drug resistance associated with a substrain of Candida albicans from an HIV-infected patient

Oral candidiasis is one of the earliest and most frequent complications of a failing immune system in HIV-infected individuals. For several years, oral candidiasis has been treated effectively with azole drugs, the one most frequently used is fluconazole. Unfortunately, extensive use of the drug for treatment and prophylaxis has led to treatment failure in an increasing number of patients. In most of these cases, strains of C. albicans isolated from the infection are less susceptible to fluconazole. The development of azole resistance in strains of C. albicans has been studied biochemically and more recently with molecular techniques. One excellent example of the development of azole resistance in C. albicans has been documented in a series of 17 C. albicans isolates from a single patient over a 2-year period. During this time, the patient experienced 14 episodes of oral candidiasis and was treated with increasing doses of fluconazole. Molecular and biochemical analyses confirms that the isolates are the same strain of C. albicans and that the resistance in these isolates is stable over 600 generations, suggesting that the changes in this strain are genetic in nature. In addition, the development of resistance is correlated with the identification of a substrain or variant of the original strain, as identified by restriction fragment length polymorphism (RFLP) analysis with the moderately repetitive probe, Ca3. The analysis of this series of isolates demonstrates that azole drug resistance is associated with several small genetic changes, each of which contributes to the overall resistance of the strain. Clearly, continual use of azole drugs by a patient can select for genetic changes that render oral candidiasis refractory to treatment.

Cross-resistance phenotypes of fluconazole-resistant Candida species: results with 655 clinical isolates with different methods

Candida species test results with two broth macrodilution antifungal susceptibility methods were compared using 655 clinical isolates, and the frequency of fluconazole resistance and phenotypes of azole cross resistance are detailed. A method with an 80% inhibition endpoint (as compared to clear tube endpoint) suggested greater fluconazole susceptibility to C. albicans but had a less pronounced effect on C. glabrata, and seemed to have a negligible influence on results with C. parapsilosis and C. tropicalis. The latter were grouped as susceptible and resistant (based on achievable blood levels), respectively, by both methods. Cross resistance was method dependent and more pronounced with itraconazole than ketoconazole. In vivo correlations are needed to validate the groupings proposed by any in vitro method.

Candida albicans osteomyelitis in a liver transplant recipient: a case report and review of the literature

A 51-year-old man developed fever and back pain 2 months after orthotopic liver transplantation for end-stage liver disease secondary to chronic hepatitis C infection. CT scan demonstrated destructive lesions in T12 suggestive of osteomyelitis. Aspiration biopsy of the vertebra revealed granulomatous inflammation and yeast forms; culture yielded Candida albicans. The patient improved with intravenous amphotericin B and 5-fluorocytosine and did not require surgical intervention. Candida osteomyelitis is a rare condition and to our knowledge it has not been reported before in liver transplant recipients. Awareness of this potential complication may shorten the delay in making the definitive diagnosis, which in turn may increase the likelihood of a response without sequela.

Prophylaxis with nystatin pastilles for HIV-associated oral candidiasis

To determine whether daily use of nystatin pastilles can prevent initial outbreak or recurrence of oral candidiasis in HIV-infected patients and to identify factors associated with outbreaks during 20-week follow-up, a randomized, double-blind, placebo-controlled clinical trial was conducted. Subjects were 128 HIV-infected men (aged 27-60 years) who either had had no documented episode of oral candidiasis in the previous year or had been clinically clear of oral candidiasis for at least 72 h before randomization. Study arms were two placebo pastilles, one nystatin (200,000 U) and one placebo pastille, or two nystatin pastilles daily for 20 weeks. The main outcome measure was time to oral candidiasis, as determined by potassium hydroxide (KOH) smear and fungal culture. A multivariate proportional hazards model showed that four factors were significant (p < 0.001) in predicting time to oral candidiasis: nystatin treatment (hazard ratio 0.59), history of oral candidiasis (3.58), Candida albicans carriage (2.79), and CD4 count at randomization (0.65). In this small group of subjects, nystatin appeared to be effective in delaying onset of oral candidiasis. Patients with CD4 counts < 200 who are carriers of C. albicans and have a history of oral candidiasis may be most likely to benefit from antifungal prophylaxis.

Susceptibility testing of fungi: current status of correlation of in vitro data with clinical outcome

In summary, it is clear that in vitro susceptibility testing can predict outcome in selected clinical situations. The clearest data are from the fluconazole-treated AIDS patients with oropharyngeal candidiasis. In this setting, the homogeneity of the underlying immune defect, combined with the ease of identification and monitoring of the infection, creates a near-perfect test situation. In more complex scenarios, such as the heterogeneous population of patients enrolled in a recent study of candidemia, no such clear-cut correlation was present. The importance of host factors in the correlation of the MIC with outcome cannot be overemphasized. Examples of these parameters include patient status (underlying disease, the presence of intravascular catheters, and CD4+ T-cell number), drug pharmacokinetics (absorption and distribution), patient compliance, and drug-drug interactions. Identification of relevant factors can substantially improve the degree of the MIC-outcome correlation and thus improve the clinical utility of in vitro testing. An important feature in this entire process is the role of standardized susceptibility testing procedures. While not without flaws, the proposed NCCLS reference method has been invaluable in allowing multiple investigators to contribute data that can be used to clarify the correlation between the fluconazole MIC and outcome. While the development of simplified second-generation methods is eagerly anticipated, the role of the reference method as a common touchstone is critical. Only by use of either the reference method itself or methods with a known relationship to the reference method can this broad collaborative process really proceed. Current work is focusing on defining interpretive breakpoints for fluconazole and Candida species, refinement of the in vitro procedures used to measure susceptibility to amphotericin B, ketoconazole, and itraconazole, and the acquisition of a broad base of data on the relationship between the MIC and outcome for these three drugs. Although considerable work remains to be done, the available data suggest that solutions to each of these problems are possible and that routine susceptibility testing of fungi will become meaningful for clinical decision making in the foreseeable future.

Prophylaxis of candidiasis in patients with leukemia and bone marrow transplants

OBJECTIVES

The increased risk for systemic fungal infection and the potential fatal consequences of disseminated candidiasis in bone marrow transplant patients has prompted study of prophylaxis and early treatment of candida colonization and infection.

STUDY DESIGN

Patients with leukemia who received fluconazole prophylaxis were compared with a concurrent group of patients not given prophylaxis for fungal organisms.

RESULTS

A trend to reduction of oropharyngeal colonization by Candida albicans was seen (p = 0.07) although no significant differences in systemic candidiasis were seen. In patients with documented systemic candidiasis, oral colonization was present and systemic infection was identified after the development of ulcerative oral mucositis.

CONCLUSIONS

Our results support the potential of fluconazole to reduce oropharyngeal colonization by Candida albicans, however, we did not show prophylaxis of oral candidiasis or systemic candidiasis. These findings and reports of fluconazole-resistant candidal species and a rising number of cases of infection as a result of Candida krusei indicate the need for further studies of prophylaxis of candidal infection in patients who are anticipated to develop profound neutropenia.

Australian Dental Research Fund Trebitsch Scholarship. Efficacy of antifungal prophylaxis in bone marrow transplantation

Oral candidal infection is a common problem in bone marrow transplantation. This prospective study compared the effectiveness of antifungal prophylaxis with topical antifungals (nystatin and amphotericin B suspensions) versus oral fluconazole in 196 patients undergoing bone marrow transplantation. Oral candidosis occurred frequently in the group receiving topical antifungals (61/113, 54%), but was rare in the group receiving fluconazole (6/83, 7%). The difference in efficacy between the two groups was highly significant (p < 0.00001). There was no difference in the incidence of suspected systemic fungal infection between the two groups. While nausea was a problem with antifungal suspensions, no significant adverse reactions to fluconazole occurred. Because of greater efficacy in preventing oral candidosis and better patient tolerance, oral fluconazole is preferred to antifungal suspensions for prophylactic use in patients undergoing bone marrow transplantation.

Resistance to antifungal agents

The marked increase in the number of patients with AIDS and other forms of immunocompromise has resulted in the emergence of fungi as predominant pathogens in many institutions. Unfortunately, with the widespread use of antifungal agents to combat these infections, reports of resistance to antifungal agents have proliferated. In the present environment, the occurrence of resistance to antifungal agents is neither rare nor of negligible clinical importance. The expanding demand for antifungal agents mandates a new sense of vigilance for resistance. Although newly proposed standards for in vitro susceptibility testing should help to remove the ambiguity surrounding quantitative measurement of fungal resistance, lessons learned in the treatment of bacteria clearly now apply to fungi also: prolonged use of an antimicrobial agent will result in the selection of resistant organisms. The enlarging spectrum of resistance to antifungal agents must prompt aggressive searches for new modes of therapy. Strategies to inhibit fungal colonization, to augment host defenses, or to develop novel antifungal agents from Pseudomonas syringae or from peptide nanotubes are helping to solve this pressing clinical need.

Molecular cloning and characterization of a novel gene of Candida albicans, CDR1, conferring multiple resistance to drugs and antifungals

By functional complementation of a PDR5 null mutant of Saccharomyces cerevisiae, we have cloned and sequenced the multidrug-resistance gene CDR1 of Candida albicans. Transformation by CDR1 of a PDR5-disrupted host hypersensitive to cycloheximide and chloramphenicol resulted in resistance to cycloheximide, chloramphenicol and other drugs, such as the antifungal miconazole, with collateral hypersensitivity to oligomycin, nystatin and 2,4 dinitrophenol. Our results also demonstrate the presence of several PDR5 complementing genes in C. albicans, displaying multidrug-resistance patterns different from PDR5 and CDR1. The nucleotide sequence of CDR1 revealed that, like PDR5, it encodes a putative membrane pump belonging to the ABC (ATP-binding cassette) superfamily. CDR1 encodes a 1501-residue protein of 169.9 kDa whose predicted structural organization is characterized by two homologous halves, each comprising a hydrophobic region with a set of six transmembrane stretches, preceded by a hydrophilic nucleotide binding fold.

Fluconazole response patterns in HIV-infected patients with oropharyngeal candidiasis

A prospective study to assess the efficacy of fluconazole in oropharyngeal candidiasis in patients with HIV was conducted. A cohort of 30 HIV-positive persons with clinical and microbiologic confirmed oropharyngeal candidiasis (Candida albicans > 1000 CFU/ml) received fluconazole 100 mg daily for 7 days. In vitro antifungal susceptibility tests demonstrated a lack of fluconazole resistances. Cultures of mouth swabs were performed at the end of therapy and 2 weeks later. There was a clinical and microbiologic cure in 26 patients (87%). In 10 of these 26, cultures remained negative after 2 weeks; most of them had CD4 lymphocyte count > 400/ml. In the other 16 patients (53%), cultures showed a microbiologic relapse 2 weeks after treatment. In spite of clinical improvement, treatment failure was observed in four patients, all of them with CD4 lymphocyte count < 50 ml.

Resistant candidiasis

Mucosal (oropharyngeal, esophageal, and, in women, vaginal) candidiasis is a common infectious complication in HIV-infected patients. There is a wide range of drugs to treat or suppress Candida infections. However, with the increasingly common use of fluconazole as treatment or prophylaxis in patients with relatively advanced HIV disease, mucosal candidiasis that is clinically resistant to fluconazole is increasingly recognized. Susceptibility testing for fluconazole has not been well standardized, and laboratory and clinical correlations often have been difficult to demonstrate. However, the frequency with which Candida strains resistant to fluconazole can be isolated appears to be increasing, particularly in patients with advanced HIV disease. Anecdotal results suggest that patients who fail fluconazole therapy usually do not respond to higher doses of fluconazole, but may occasionally respond to itraconazole or ketoconazole. In vitro susceptibility to these agents does not necessarily ensure clinical efficacy. Amphotericin B is usually effective initially but requires parenteral administration. However, with any therapy, relapses tend to occur and progressively recalcitrant disease often occurs, with increasing morbidity for patients. There is a clear need for studies addressing the incidence of resistance, the risk factors for its development, and more effective therapy.

Treatment of oral candidiasis in HIV infection

Oral candidiasis is one of the most common clinical features of HIV infection. The lesion occurs in three predominant forms, and the two intraoral examples, pseudomembranous and erythematous, are equally predictive of the development of AIDS, independent of CD4 counts. The predominant species is C. albicans, although other species are occasionally found. Some studies claim correlation of salivary Candida counts with CD4 numbers or clinical stage of HIV-related disease, but this approach has not been used widely in HIV staging. Therapy with a variety of antifungal agents, including both topical and systemic drugs, is effective. New slow-release oral topical drug delivery systems may prove to be useful. Recently, examples of resistance to some drugs have been reported. Resistance may be associated with the emergence of different species.

Efficacy of oral amphotericin B in AIDS patients with thrush clinically resistant to fluconazole

Reports of thrush clinically refractory to azoles in AIDS patients are increasing with the more widespread use of these agents. We studied our own oral preparation of amphotericin B in the treatment of two AIDS patients who developed oral thrush due to Candida glabrata after prolonged fluconazole use. Improvement occurred in both in less than 1 week, with eventual clearing and absence of side effects. Oral amphotericin B may have advantages over alternatives for this increasing problem.