Drug Resistance and Novel Therapeutic Approaches in Invasive Candidiasis.

Candida species are the leading cause of invasive fungal infections worldwide and are associated with acute mortality rates of ~50%. Mortality rates are further augmented in the context of host immunosuppression and infection with drug-resistant Candida species. In this review, we outline antifungal drugs already in clinical use for invasive candidiasis and candidaemia, their targets and mechanisms of resistance in clinically relevant Candida species, encompassing not only classical resistance, but also heteroresistance and tolerance. We describe novel antifungal agents and targets in pre-clinical and clinical development, including their spectrum of activity, antifungal target, clinical trial data and potential in treatment of drug-resistant Candida. Lastly, we discuss the use of combination therapy between conventional and repurposed agents as a potential strategy to combat the threat of emerging resistance in Candida.

Cryptococcal meningoencephalitis: time for action.

Cryptococcal meningoencephalitis was first described over a century ago. This fungal infection is preventable and treatable yet continues to be associated with excessive morbidity and mortality. The largest burden of disease resides in people living with HIV in low-income and middle-income countries. In this group, mortality with the best antifungal induction regimen (7 days of amphotericin B deoxycholate [1·0 mg/kg per day] and flucytosine [100·0 mg/kg per day]) in a clinical trial setting was 24% at 10 weeks. The world is now at an inflection point in terms of recognition, research, and action to address the burden of morbidity and mortality from cryptococcal meningoencephalitis. However, the scope of interventional programmes needs to increase, with particular attention to implementation science that is specific to individual countries. This Review summarises causes of excessive mortality, interventions with proven survival benefit, and gaps in knowledge and practice that contribute to the ongoing high death toll from cryptococcal meningoencephalitis. TRANSLATIONS: For the Vietnamese and Chichewa translations of the abstract see Supplementary Materials section.

Fluconazole Monotherapy Is a Suboptimal Option for Initial Treatment of Cryptococcal Meningitis Because of Emergence of Resistance.

Cryptococcal meningitis is a lethal disease with few therapeutic options. Induction therapy with fluconazole has been consistently demonstrated to be associated with suboptimal microbiological and clinical outcomes. Exposure to fluconazole causes dynamic changes in antifungal susceptibility, which are associated with the development of aneuploidy. The implications of this phenomenon for pharmacodynamics of fluconazole for cryptococcal meningitis are poorly understood. The pharmacodynamics of fluconazole were studied using a hollow-fiber infection model (HFIM) and a well-characterized murine model of cryptococcal meningoencephalitis. The relationship between drug exposure and both antifungal killing and the emergence of resistance was quantified. The same relationships were further evaluated in a recently described group of patients with cryptococcal meningitis undergoing induction therapy with fluconazole at 800 to 1,200 mg/day. The pattern of emergence of fluconazole resistance followed an "inverted U." Resistance amplification was maximal and suppressed at ratios of the area under the concentration-time curve for the free, unbound fraction of the drug to the MIC (fAUC:MIC) of 34.5 to 138 and 305.6, respectively. Emergence of resistance was observed in vivo with an fAUC:MIC of 231.4. Aneuploidy with duplication of chromosome 1 was demonstrated to be the underlying mechanism in both experimental models. The pharmacokinetic (PK)-pharmacodynamic model accurately described the PK, antifungal killing, and emergence of resistance. Monte Carlo simulations from the clinical pharmacokinetic-pharmacodynamic model showed that only 12.8% of simulated patients receiving fluconazole at 1,200 mg/day achieved sterilization of the cerebrospinal fluid (CSF) after 2 weeks and that 83.4% had a persistent subpopulation that was resistant to fluconazole. Fluconazole is primarily ineffective due to the emergence of resistance. Treatment with 1,200 mg/day leads to the killing of a susceptible subpopulation but is compromised by the emergence of resistance.IMPORTANCE Cryptococcal meningitis is a lethal disease with few treatment options. The incidence remains high and intricately linked with the HIV/AIDS epidemic. In many parts of the world, fluconazole is the only agent that is available for the initial treatment of cryptococcal meningitis despite considerable evidence that it is associated with suboptimal microbiological and clinical outcomes. Fluconazole has a fungistatic mode of action: it predominantly inhibits growth rather than causing fungal killing. Our work shows that the pattern of fluconazole activity is caused by the emergence of resistance in Cryptococcus not detected by standard susceptibility tests, with chromosomal duplication/aneuploidy as the main mechanism. Resistance emergence is related to drug exposure and occurs with the use of clinically relevant regimens. Hence, fluconazole (and potentially other agents that target 14-alpha-demethylase) is compromised by an intrinsic property that limits its effectiveness. However, this resistance may be potentially overcome by dosage escalation or the use of combination therapy.

Effectiveness of an antifungal stewardship programme at a London teaching hospital 2010-16.

Background: The need for antifungal stewardship is gaining recognition with increasing incidence of invasive fungal infection (IFI) and antifungal resistance alongside the high cost of antifungal drugs. Following an audit showing suboptimal practice we initiated an antifungal stewardship programme and prospectively evaluated its impact on clinical and financial outcomes. Patients and methods: From October 2010 to September 2016, adult inpatients receiving amphotericin B, echinocandins, intravenous fluconazole, flucytosine or voriconazole were reviewed weekly by an infectious diseases consultant and antimicrobial pharmacist. Demographics, diagnosis by European Organization for Research and Treatment of Cancer (EORTC) criteria, drug, indication, advice, acceptance and in-hospital mortality were recorded. Antifungal consumption and expenditure, and candidaemia species and susceptibility data were extracted from pharmacy and microbiology databases. Results: A total of 432 patients were reviewed, most commonly receiving AmBisome® (35%) or intravenous fluconazole (29%). Empirical treatment was often unnecessary, with 82% having no evidence of IFI. Advice was given in 64% of reviews (most commonly de-escalating or stopping treatment) and was followed in 84%. Annual antifungal expenditure initially reduced by 30% (£0.98 million to £0.73 million), then increased to 20% above baseline over a 5 year period; this was a significantly lower rise compared with national figures, which showed a doubling of expenditure over the same period. Inpatient mortality, Candida species distribution and rates of resistance were not adversely affected by the intervention. Conclusions: Provision of specialist input to optimize antifungal prescribing resulted in significant cost savings without compromising on microbiological or clinical outcomes. Our model is readily implementable by hospitals with high numbers of at-risk patients and antifungal expenditure.

Toxicity of Amphotericin B Deoxycholate-Based Induction Therapy in Patients with HIV-Associated Cryptococcal Meningitis.

Amphotericin B deoxycholate (AmBd) is the recommended induction treatment for HIV-associated cryptococcal meningitis (CM). Its use is hampered by toxicities that include electrolyte abnormalities, nephrotoxicity, and anemia. Protocols to minimize toxicity are applied inconsistently. In a clinical trial cohort of AmBd-based CM induction treatment, a standardized protocol of preemptive hydration and electrolyte supplementation was applied. Changes in blood counts, electrolyte levels, and creatinine levels over 14 days were analyzed in relation to the AmBd dose, treatment duration (short course of 5 to 7 days or standard course of 14 days), addition of flucytosine (5FC), and outcome. In the 368 patients studied, the hemoglobin levels dropped by a mean of 1.5 g/dl (95% confidence interval [CI], 1.0 to 1.9 g/dl) following 7 days of AmBd and by a mean of 2.3 g/dl (95% CI, 1.1 to 3.6 g/dl) after 14 days. Serum creatinine levels increased by 37 µmol/liter (95% CI, 30 to 45 µmol/liter) by day 7 and by 49 µmol/liter (95% CI, 35 to 64µmol/liter) by day 14 of AmBd treatment. Overall, 33% of patients developed grade III/IV anemia, 5.6% developed grade III hypokalemia, 9.5% had creatinine levels that exceeded 220 µmol, and 6% discontinued AmBd prematurely. The addition of 5FC was associated with a slight increase in anemia but not neutropenia. Laboratory abnormalities stabilized or reversed during the second week in patients on short-course induction. Grade III/IV anemia (adjusted odds ratio [aOR], 2.2; 95% CI, 1.1 to 4.3; P = 0.028) and nephrotoxicity (aOR, 4.5; 95% CI, 1.8 to 11; P = 0.001) were risk factors for 10-week mortality. In summary, routine intravenous saline hydration and preemptive electrolyte replacement during AmBd-based induction regimens for HIV-associated CM minimized the incidence of hypokalemia and nephrotoxicity. Anemia remained a concerning adverse effect. The addition of flucytosine was not associated with increased neutropenia. Shorter AmBd courses were less toxic, with rapid reversibility.

Treatment principles for Candida and Cryptococcus.

The yeasts Candida and Cryptococcus spp. are important human opportunistic pathogens. Candida spp. rely on skin or mucosal breach to cause bloodstream infection, whereas Cryptococcus spp. exploit depressed cell-mediated immunity characteristic of advanced HIV infection. The treatment for both organisms relies on the administration of rapidly fungicidal agents. In candidaemia, source control is important, with removal of prosthetic material and drainage of collections, as well as hunting for and tailoring therapy to disseminated sites of infection, particularly the eyes and heart. For cryptococcal meningitis, restoration of immune function through antiretroviral therapy (ART) is key, together with careful management of the complications of raised intracranial pressure and relapsed infection, both pre- and post-ART.