Identification of patients with acute AIDS-associated cryptococcal meningitis who can be effectively treated with fluconazole: the role of antifungal susceptibility testing

Antifungal Resistance in Cryptococcal Infections

Antifungal therapy, especially with the azoles, could promote the incidence of less susceptible isolates of Cryptococcus neoformans and C. gattii species complexes (SC), mostly in developing countries. Given that these species affect mostly the immunocompromised host, the infections are severe and difficult to treat. This review encompasses the following topics: 1. infecting species and their virulence, 2. treatment, 3. antifungal susceptibility methods and available categorical endpoints, 4. genetic mechanisms of resistance, 5. clinical resistance, 6. fluconazole minimal inhibitory concentrations (MICs), clinical outcome, 7. environmental influences, and 8. the relevance of host factors, including pharmacokinetic/pharmacodynamic (PK/PD) parameters, in predicting the clinical outcome to therapy. As of now, epidemiologic cutoff endpoints (ECVs/ECOFFs) are the most reliable antifungal resistance detectors for these species, as only one clinical breakpoint (amphotericin B and C. neoformans VNI) is available.

Antifungal susceptibility testing with YeastONE™ is not predictive of clinical outcomes of Cryptococcus neoformans var. grubii fungemia

Mortality rates due to Cryptococcus neoformans var. grubii fungemia remain significant despite treatment with antifungal drugs. The predictive function of antifungal susceptibility and its correlation with treatment outcome remains controversial. A retrospective study was conducted from January 1, 2009, to December 31, 2016, on 85 patients with C. neoformans var. grubii fungemia confirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. Antifungal drug susceptibility was determined using the YeastONE™ colorimetric broth microdilution method coupled with Vizion™ System following the Clinical and Laboratory Standards Institute guidelines. Six antifungal agents-amphotericin B, fluconazole, flucytosine, itraconazole, posaconazole, and voriconazole-were tested. The patients' demographic data and clinical information were abstracted for further analyses. Antifungal regimens consisting of amphotericin B with or without fluconazole or flucytosine were administered for induction treatment of these patients, followed with intravenous or oral fluconazole for maintenance therapy. Clinical outcomes were defined by 14- and 30-day mortality rates. Risk factors associated with outcomes were fitted in a logistic regression model by univariate or multivariate method. Eighty-five patients with C. neoformans var. grubii fungemia were enrolled in the study. The Sequential Organ Failure Assessment Score, Glasgow Coma Scale, Charlson comorbidity score, and adequate duration of therapy for amphotericin B were predictors for mortality in univariate analysis. Antifungal susceptibility testing with YeastONE™ does not predict clinical outcomes of C. neoformans var. grubii fungemia. Greater disease severity, high comorbidities, poor consciousness level, and inappropriate treatment were associated with increased mortality in cryptococcemia cases.

LAY ABSTRACT

Cryptococcus neoformans is an encapsulated yeast living in both plants and animals that is composed of three main serotypes: C. neoformans var. grubii, C. neoformans var. gattii, and C. neoformans var. neoformans. C. neoformans var. grubii is the most common disease-causing Cryptococcus species worldwide. C. neoformans var. gattii is more prevalent than C. neoformans var. neoformans in both tropical and subtropical regions of Asia. C. neoformans causes severe, even fatal, diseases such as pulmonary infection, bloodstream infection, skin and soft tissue infection, bone and joint infection, central nervous system infection, and disseminated infection, regardless of host immunocompetence. We conducted a retrospective study on 85 patients who contracted cryptococcemia from January 1, 2009, to December 31, 2016. This work conducted both microbiological and clinical studies involving in vitro susceptibility testing, demographic data, comorbidities, treatment modalities, and treatment outcomes. We utilized a modern medical technique-based instrument, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS; Biotyper, Bruker Daltonics, Inc.), which determines the unique proteomic fingerprint of an organism, to identify the C. neoformans serotype. We utilized Thermo Fisher Scientific™ Sensititre™ YeastONE™ colorimetric broth microdilution plates coupled with a Vizion™ Digital MIC Viewing System (a computer-assisted optical reading machine) to determine the in vitro susceptibility of amphotericin B, flucytosine, fluconazole, itraconazole, posaconazole, and voriconazole against 85 C. neoformans var. grubii blood isolates. In conclusion, the susceptibility patterns of these antifungal agents did not correlate significantly with treatment outcomes. However, a lower disease severity score, a lower Glasgow Coma Scale score, fewer comorbidities, and adequate amphotericin B treatment duration were predictors for treatment success in univariate analysis.

Nitrogen concentration affects amphotericin B and fluconazole tolerance of pathogenic cryptococci

Environmental stress often causes phenotypic changes among pathogenic cryptococci, such as altered antifungal susceptibility, changes in capsule and melanin formation, as well as altered levels of the membrane sterol and antifungal target, ergosterol. We therefore hypothesised that nitrogen limitation, a prevalent environmental stress in the natural habitat of these yeasts, might affect virulence and antifungal susceptibility. We tested the effect of different nitrogen concentrations on capsule, melanin and ergosterol biosynthesis, as well as amphotericin B (AmB) and fluconazole (FLU) susceptibility. This was achieved by culturing cryptococcal strains representing Cryptococcus neoformans and Cryptococcus gattii in media with high (0.53 g/l), control (0.42 g/l) and low (0.21 g/l) NH4Cl concentrations. India ink staining was used to determine capsule thickness microscopically, while melanin and ergosterol content were determined spectrophotometrically. We found that lower nitrogen concentrations enhanced both ergosterol and capsule biosynthesis, while a variable effect was observed on melanisation. Evaluation of drug tolerance using time-kill methodology, as well as tests for FLU heteroresistance, revealed that the low nitrogen cultures had the highest survival percentages in the presence of both AmB and FLU, and showed the highest frequency of FLU heteroresistance, suggesting that nitrogen concentration may indeed influence drug tolerance.

Co-infection by Cryptococcus neoformans fungaemia and non-tuberculous mycobacteria with Pneumocystis jiroveci pneumonia in a newly diagnosed HIV-infected patient

Opportunistic infections are common in human immunodeficiency virus (HIV)-infected patients. Co-infections with Cryptococcus neoformans and Mycobacterium species together with Pneumocystis jiroveci pneumonia (PCP) are rare and typically occur in immunocompromised individuals, particularly acquired immunodeficiency syndrome patients.

Emerging Issues in Antifungal Resistance

Invasive fungal diseases continue to cause substantial mortality in the enlarging immunocompromised population. It is fortunate that the field has moved past amphotericin B deoxycholate as the only available antifungal drug but despite new classes of antifungal agents both primary and secondary drug resistance in molds and yeasts abound. From the rise of multiple-drug-resistant Candida auris to the agrochemical selection of environmental azole-resistant Aspergillus fumigatus, it is and will be critical to understand antifungal drug resistance and both prevent and treat it with new strategies and agents.

Antifungal susceptibility does not correlate with fungal clearance or survival in AIDS-associated cryptococcal meningitis

We investigated the value of susceptibility testing in predicting response in AIDS-associated cryptococcal meningitis using clinical isolates from a randomized controlled trial of antifungal treatment (amphotericin monotherapy, amphotericin with flucytosine, or amphotericin with fluconazole). We found no correlation between antifungal susceptibility and either early or late survival, or fungal clearance.

Antifungal susceptibility testing in Candida, Aspergillus and Cryptococcus infections: are the MICs useful for clinicians?

BACKGROUND

Invasive fungal infections (IFIs) represent a global issue and affect various patient populations. In recent years, resistant fungal isolates showing increased azole or echinocandin MICs have been reported, and their potential clinical impact has been investigated.

AIMS

To provide an update on the epidemiology of resistance among fungi (e.g., Candida spp., Aspergillus spp., and Cryptococcus spp.) and to offer a critical appraisal of the relevant literature regarding the impact of MICs on clinical outcome in patients with IFI.

SOURCES

PubMed search with relevant keywords along with a personal collection of relevant publications.

CONTENT

Although antifungal resistance has been associated with a poorer response to antifungal therapy in various studies, other factors such as comorbidities, septic shock and source of infection appear to be key determinants affecting the clinical outcome of patients with IFI.

IMPLICATIONS

Future international collaborative studies are required to tease out the relative contribution of in vitro antifungal resistance on patient outcomes, thus enabling the optimization of IFI management.

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.

Minimum Inhibitory Concentration Distribution of Fluconazole against Cryptococcus Species and the Fluconazole Exposure Prediction Model

BACKGROUND

Fluconazole is lifesaving for treatment and prevention of cryptococcosis; however, optimal dosing is unknown. Initial fluconazole doses of 100mg to 2000mg/day have been used. Prevalence of fluconazole non-susceptible Cryptococcus is increasing over time, risking the efficacy of long-established standard dosing. Based on current minimum inhibitory concentration (MIC) distribution, we modeled fluconazole concentration and area under the curve (AUC) relative to MIC to propose a rational fluconazole dosing strategy.

METHODS

First, we conducted a systematic review using MEDLINE database for reports of fluconazole MIC distribution against clinical Cryptococcus isolates. Second, we utilized fluconazole concentrations from 92 Ugandans who received fluconazole 800mg/day coupled with fluconazole's known pharmacokinetics to predict plasma fluconazole concentrations for doses ranging from 100mg to 2000mg via linear regression. Third, the fluconazole AUC above MIC ratio were calculated using Monte Carlo simulation and using the MIC distribution elucidated during the systemic review.

RESULTS

We summarized 21 studies with 11,049 clinical Cryptococcus isolates. MICs were normally distributed with geometric mean of 3.4 μg/mL, median (MIC50) of 4 μg/mL, and 90th percentile (MIC90) of 16 μg/mL. The median MIC50 trended upwards from 4 μg/mL in 2000-2012 to 8 μg/mL in 2014-2018. Predicted sub-therapeutic fluconazole concentrations (below MIC) would occur in 40% with 100mg, 21% with 200mg, and 9% with 400mg. AUC/MIC ratio >100 would occur in 53% for 400mg, 74% for 800mg, 83% for 1200mg, and 88% for 1600mg.

CONCLUSIONS

Currently recommended fluconazole doses may be inadequate for cryptococcosis. Further clinical studies are needed for rational fluconazole dose selection.

Fluconazole resistance is not a predictor of poor outcome in patients with cryptococcosis

BACKGROUND

Cryptococcus isolates with high MICs to fluconazole are increasingly reported, and a potential clinical impact has been advocated. However, there are different methods to evaluate fluconazole MICs and comparative analysis among such techniques and their comprehensive correlation with clinical outcome are not available.

METHODS

Over a 13-year period (2000-2013), fluconazole MICs were determined for 62 cryptococcal isolates recovered from 22 patients with cryptococcosis using CLSI M27-A3, EUCAST, E test and Sensititre YeastOne, simultaneously. The relationship between the fluconazole MICs and the clinical outcome at week 10 was assessed in patients who received fluconazole as induction or maintenance therapy (n = 16).

RESULTS

The percentage of cryptococcal strains with MIC values ≥16 μg/mL according to different methods was CLSI 1.6%, EUCAST 16.1%, E test 31.6% and Sensititre YeastOne 53.2%. Among the 16 patients treated with fluconazole, no correlation between clinical outcome and any MIC value obtained with either method was observed. The only variable independently associated with a poor outcome was having a disseminated disease.

CONCLUSIONS

There is a weak correlation between fluconazole MICs against Cryptococcus spp. as determined by CLSI, EUCAST, E test and Sensititre YeastOne. Neither procedure could predict the clinical outcome of patients with cryptococcosis receiving fluconazole-based therapy. With present methods, fluconazole resistance in Cryptococcus may be clinically misleading.

Heteroresistance and fungi

The concept of heteroresistance refers to the heterogeneous susceptibility to an antimicrobial drug in a microorganism population, meaning that some clones may be resistant and others are susceptible. This phenomenon has been widely studied in bacteria, but little attention has been given to its expression in fungi. We review the available literature on heteroresistance in fungi and invite the reader to recognise this phenomenon as a fungal mechanism to adapt to environmental stress, which may interfere both in resistance and virulence. Finally, heteroresistance may explain the treatment failures to eradicate mycosis in some patients treated with a seemingly appropriate antifungal.

Physiological Differences in Cryptococcus neoformans Strains In Vitro versus In Vivo and Their Effects on Antifungal Susceptibility

Cryptococcus neoformans is an environmentally ubiquitous fungal pathogen that primarily causes disease in people with compromised immune systems, particularly those with advanced AIDS. There are estimated to be almost 1 million cases per year of cryptococcal meningitis in patients infected with human immunodeficiency virus, leading to over 600,000 annual deaths, with a particular burden in sub-Saharan Africa. Amphotericin B (AMB) and fluconazole (FLC) are key components of cryptococcal meningitis treatment: AMB is used for induction, and FLC is for consolidation, maintenance and, for occasional individuals, prophylaxis. However, the results of standard antifungal susceptibility testing (AFST) for AMB and FLC do not correlate well with therapeutic outcomes and, consequently, no clinical breakpoints have been established. While a number of explanations for this absence of correlation have been proffered, one potential reason that has not been adequately explored is the possibility that the physiological differences between the in vivo infection environment and the in vitro AFST environment lead to disparate drug susceptibilities. These susceptibility-influencing factors include melanization, which does not occur during AFST, the size of the polysaccharide capsule, which is larger in infecting cells than in those grown under normal laboratory conditions, and the presence of large polyploid "titan cells," which rarely occur under laboratory conditions. Understanding whether and how C. neoformans differentially expresses mechanisms of resistance to AMB and FLC in the AFST environment compared to the in vivo environment could enhance our ability to interpret AFST results and possibly lead to the development of more applicable testing methods.

Integrated therapy for HIV and cryptococcosis

Cryptococcosis has been one of the most common opportunistic infections and causes of mortality among HIV-infected patients, especially in resource-limited countries. Cryptococcal meningitis is the most common form of cryptococcosis. Laboratory diagnosis of cryptococcosis includes direct microscopic examination, isolation of Cryptococcus from a clinical specimen, and detection of cryptococcal antigen. Without appropriate treatment, cryptococcosis is fatal. Early diagnosis and treatment is the key to treatment success. Treatment of cryptococcosis consists of three main aspects: antifungal therapy, intracranial pressure management for cryptococcal meningitis, and restoration of immune function with antiretroviral therapy (ART). Optimal integration of these three aspects is crucial to achieving successful treatment and reducing the mortality. Antifungal therapy consists of three phases: induction, consolidation, and maintenance. A combination of two drugs, i.e. amphotericin B plus flucytosine or fluconazole, is preferred in the induction phase. Fluconazole monotherapy is recommended during consolidation and maintenance phases. In cryptococcal meningitis, intracranial pressure rises along with CSF fungal burden and is associated with morbidity and mortality. Aggressive control of intracranial pressure should be done. Management options include therapeutic lumbar puncture, lumbar drain insertion, ventriculostomy, or ventriculoperitoneal shunt. Medical treatment such as corticosteroids, mannitol, and acetazolamide are ineffective and should not be used. ART has proven to have a great impact on survival rates among HIV-infected patients with cryptococcosis. The time to start ART in HIV-infected patients with cryptococcosis has to be deferred until 5 weeks after the start of antifungal therapy. In general, any effective ART regimen is acceptable. Potential drug interactions between antiretroviral agents and amphotericin B, flucytosine, and fluconazole are minimal. Of most potential clinical relevance is the concomitant use of fluconazole and nevirapine. Concomitant use of these two drugs should be cautious, and patients should be monitored closely for nevirapine-associated adverse events, including hepatotoxicity. Overlapping toxicities of antifungal and antiretroviral drugs and immune reconstitution inflammatory syndrome are not uncommon. Early recognition and appropriate management of these consequences can reinforce the successful integrated therapy in HIV-infected patients with cryptococcosis.

Retrospective Study of Cryptococcal Meningitis With Elevated Minimum Inhibitory Concentration to Fluconazole in Immunocompromised Patients

This study is a retrospective chart review looking at the clinical characteristics of cryptococcal meningitis with elevated MIC to fluconazole in immunocompromised patients. These patients were more likely to have central nervous system complications without any effect on mortality.

Background. Mortality for cryptococcal meningitis remains significant, in spite of available treatment. Resistance to first-line maintenance therapy, particularly fluconazole, has been reported.

Methods. A retrospective chart review was performed on immunocompromised patients with cryptococcal meningitis, who had susceptibility testing performed between January 2001 and December 2011, at 3 hospitals in Atlanta, Georgia.

Results. A total of 35 immunocompromised patients with cryptococcal meningitis were identified, 13 (37.1%) of whom had an elevated minimum inhibitory concentration (MIC) to fluconazole (MIC ≥16 µg/mL). Eighty percent of patients were males with African American predominance, the median age was 37 years, and 80% of the patients were human immunodeficiency virus (HIV) positive. Subsequent recurrence of cryptococcal meningitis was more likely in HIV patients compared with solid organ transplant patients (P = .0366). Overall, there was a statistically significant increase in an elevated MIC to fluconazole in patients who had a history of prior azole use (odds ratio, 10.12; 95% confidence interval, 2.04–50.16). Patients with an elevated MIC to fluconazole and those with a high cerebrospinal fluid cryptococcal antigen load (≥1:512) were more likely to have central nervous system complications (P = .0358 and P = .023, respectively). Although no association was observed between an elevated MIC to fluconazole and mortality, those who received voriconazole or high-dose fluconazole (≥800 mg) for maintenance therapy were more likely to survive (P = .0288).

Conclusions. Additional studies are required to further investigate the morbidity and mortality associated with an elevated MIC to fluconazole in cryptococcal meningitis, to determine when it is appropriate to perform susceptibility testing, and to evaluate its cost effectiveness.

A retrospective research of HIV-negative cryptococcal meningoencephalitis patients with acute/subacute onset

Cryptococcal meningoencephalitis (CM) may present as an acute, subacute, or chronic infection. It manifests as a chronic process in over 75 % of cases, but, sometimes, it presents with a more acute onset, mostly in HIV-associated patients. Until now, there has been no study performed on the clinical features of HIV-negative CM patients with acute/subacute onset. We collected 106 HIV-negative patients diagnosed with CM in our hospital during a 15-year period, analyzed their epidemiological and clinical features, as well as the outcomes, and explored the independent prognosis factors and the factors related to the survival time among them. We found that impaired consciousness (23.4 % vs. 3.4 %, p = 0.017) was more common in CM patients with acute/subacute onset, while decreased cerebrospinal fluid (CSF) glucose (51.9 % vs. 75.9 %, p = 0.026) was less common. The ratio of CSF glucose/blood glucose [odds ratio (OR) 0.04, 95 % confidence interval (CI) 0.004-0.262, p = 0.02], impaired consciousness (OR 5.09, 95 % CI 1.477-17.522, p = 0.01), and hospitalization length (OR 0.98, 95 % CI 0.977-0.999, p = 0.04) were indicated to be not only independent prognosis factors in HIV-negative CM patients with acute/subacute onset, but also factors significantly related to the survival time. The results of our study demonstrated that the contact history and potential history risk factors would not affect the onset process of HIV-negative CM patients, and the mortality, hospitalization length, and survival time has not been related to the onset process. However, the ratio of CSF glucose/blood glucose, consciousness level, and hospitalization length of the HIV-negative CM patients with acute/subacute onset should be of greater focus in the clinical work.

Increased Antifungal Drug Resistance in Clinical Isolates of Cryptococcus neoformans in Uganda

Cryptococcal antigen screening is recommended among people living with AIDS when entering HIV care with a CD4 count of <100 cells/μl, and preemptive fluconazole monotherapy treatment is recommended for those with subclinical cryptococcal antigenemia. Yet, knowledge is limited of current antimicrobial resistance in Africa. We examined antifungal drug susceptibility in 198 clinical isolates collected from Kampala, Uganda, between 2010 and 2014 using the CLSI broth microdilution assay. In comparison with two previous studies from 1998 to 1999 that reported an MIC50 of 4 μg/ml and an MIC90 of 8 μg/ml prior to widespread human fluconazole and agricultural azole fungicide usage, we report an upward shift in the fluconazole MIC50 to 8 μg/ml and an MIC90 value of 32 μg/ml, with 31% of isolates with a fluconazole MIC of ≥ 16 μg/ml. We observed an amphotericin B MIC50 of 0.5 μg/ml and an MIC90 of 1 μg/ml, of which 99.5% of isolates (197 of 198 isolates) were still susceptible. No correlation between MIC and clinical outcome was observed in the context of amphotericin B and fluconazole combination induction therapy. We also analyzed Cryptococcus susceptibility to sertraline, with an MIC50 of 4 μg/ml, suggesting that sertraline is a promising oral, low-cost, available, novel medication and a possible alternative to fluconazole. Although the CLSI broth microdilution assay is ideal to standardize results, limit human bias, and increase assay capacity, such assays are often inaccessible in low-income countries. Thus, we also developed and validated an assay that could easily be implemented in a resource-limited setting, with similar susceptibility results (P = 0.52).

Comparison of Etests and Vitek 2 ® to broth microdilution for the susceptibility testing of Cryptococcus neoformans

We determined the susceptibility of 102 clinical isolates Cryptococcus neoformans from Durban, South Africa, to amphotericin B, fluconazole, flucytosine, and voriconazole using broth microdilution (BMD) according to the Clinical and Laboratory Standards Institute M27-A3 document and compared these results with Etest and Vitek 2(®). Essential agreement (EA) of Etest and Vitek 2(®) compared to BMD was determined. Low MICs that were below the epidemiological cutoff values of the 4 antifungal agents tested were demonstrated by all isolates. The EA of Etests for fluconazole, amphotericin, and voriconazole was 95.1%, 83.3%, and 91.2%, respectively, and for Vitek 2(®) EA for fluconazole, amphotericin, and flucytosine was 97.1%, 95.1%, and 97.1%, respectively. The Vitek 2(®) showed good agreement with BMD and is a suitable alternative. Etests demonstrated good EA for azoles only. Clinical cryptococcal isolates from Durban remain susceptible to current recommended antifungal therapy.

Cryptococcus neoformans meningoencephalitis in a patient with polyarteritis nodosa

Case of 59-year-old male with chronic obstructive pulmonary disease and a number of comorbidities, who has developed meningoencephalitis caused by Cryptococcus neoformans var. grubii with polyarteritis nodosa diagnosed during hospitalization, was presented. Before evidence of meningoencephalitis, the patient was being treated with ketoconazole and low doses of fluconazole (200 mg/day) for alleged candidiasis. The dosage was increased (800 mg/day) following laboratory diagnosis of C. neoformans based on positive latex agglutination test and biochemical identification of encapsulated yeast isolated from the blood and CSF. Later, the yeast identification was confirmed by sequencing analysis. Owing to inadequate clinical response, fluconazole therapy was switched to voriconazole (400 mg/day) and later to intravenous amphotericin B (1.0 mg/kg per day). Despite of a temporary stabilization and improvement, which correlated with decline of cryptococcal antigen titers (from 1:1024 to 1:8), after 6 weeks, the patient's underlying condition deteriorated due to severe pancolitis and serious nosocomial bacterial infections. The patient died of multiorgan failure several days later. Our case demonstrates a possible connection between the development of life-threatening cryptococcosis and an autoimmune vasculitis disease and emphasizes that the outcome of the management of cryptococcal meningoencephalitis is highly dependent on early diagnosis, adequate treatment, including dosage, and last but not least control of underlying disease and risk factors.

Pharmacokinetics and pharmacodynamics of fluconazole for cryptococcal meningoencephalitis: implications for antifungal therapy and in vitro susceptibility breakpoints

Fluconazole is frequently the only antifungal agent that is available for induction therapy for cryptococcal meningitis. There is relatively little understanding of the pharmacokinetics and pharmacodynamics (PK-PD) of fluconazole in this setting. PK-PD relationships were estimated with 4 clinical isolates of Cryptococcus neoformans. MICs were determined using Clinical and Laboratory Standards Institute (CLSI) methodology. A nonimmunosuppressed murine model of cryptococcal meningitis was used. Mice received two different doses of fluconazole (125 mg/kg of body weight/day and 250 mg/kg of body weight/day) orally for 9 days; a control group of mice was not given fluconazole. Fluconazole concentrations in plasma and in the cerebrum were determined using high-performance liquid chromatography (HPLC). The cryptococcal density in the brain was estimated using quantitative cultures. A mathematical model was fitted to the PK-PD data. The experimental results were extrapolated to humans (bridging study). The PK were linear. A dose-dependent decline in fungal burden was observed, with near-maximal activity evident with dosages of 250 mg/kg/day. The MIC was important for understanding the exposure-response relationships. The mean AUC/MIC ratio associated with stasis was 389. The results of the bridging study suggested that only 66.7% of patients receiving 1,200 mg/kg would achieve or exceed an AUC/MIC ratio of 389. The potential breakpoints for fluconazole against Cryptococcus neoformans follow: susceptible, ≤ 2 mg/liter; resistant, >2 mg/liter. Fluconazole may be an inferior agent for induction therapy because many patients cannot achieve the pharmacodynamic target. Clinical breakpoints are likely to be significantly lower than epidemiological cutoff values. The MIC may guide the appropriate use of fluconazole. If fluconazole is the only option for induction therapy, then the highest possible dose should be used.

Approaches to antifungal therapies and their effectiveness among patients with cryptococcosis

The goal of this study was to determine the degree to which the persistence of cryptococcosis, overall 1-year mortality, and 1-year mortality due to cryptococcosis were influenced by initial antifungal treatment regimen in a cohort of adults with cryptococcosis treated at a tertiary care medical center. Risk factors, underlying conditions, treatment, and mortality information were obtained for 204 adults with cryptococcosis from Duke University Medical Center (DUMC) from 1996 to 2009. Adjusted risk ratios (RR) for persistence and hazard ratios (HR) for mortality were estimated for each exposure. The all-cause mortality rate among patients with nonsevere disease (20%) was similar to that in the group with disease (26%). However, the rate of cryptococcosis-attributable mortality with nonsevere disease (5%) was much lower than with severe disease (20%). Flucytosine exposure was associated with a lower overall mortality rate (HR, 0.4; 95% confidence interval [CI], 0.2 to 0.9) and attributable mortality rate (HR, 0.5; 95% CI, 0.2 to 1.2). Receiving a nonrecommended antifungal regimen was associated with a higher relative risk of persistent infection at 4 weeks (RR, 1.9; 95% CI, 0.9 to 4.3), and the rate of attributable mortality among those not receiving the recommended dose of initial therapy was higher than that of those receiving recommended dosing (HR, 2.3; 95% CI, 1.0 to 5.0). Thus, the 2010 Infectious Diseases Society of America (IDSA) guidelines are supported by this retrospective review as a best-practice protocol for cryptococcal management. Future investigations should consider highlighting the distinction between all-cause mortality and attributable mortality so as not to overestimate the true effect of cryptococcosis on patient death.

Correlation of anti-fungal susceptibility with clinical outcomes in patients with cryptococcal meningitis

BACKGROUND

This study aimed to investigate the correlation of minimum inhibiting concentrations (MICs), obtained by broth micro-dilution, and clinical response in patients with cryptococcal meningitis.

METHODS

Using retrospective analyses covering the period 2001-2010, factors affecting clinical therapeutic cure in patients with cryptococcal meningitis 10 weeks after the start of anti-fungal therapy were identified. Specific emphasis was placed on the role of anti-fungal susceptibility.

RESULTS

Of 46 patients with cryptococcal meningitis identified, 21 were cured after 10 weeks of treatment. Overall, 12 strains (26.1%) were resistant to fluconazole (>8 μg/ml) and 8 (17.4%) had an MIC >1 μg/ml for amphotericin B. Twenty-three patients received combination amphotericin B and fluconazole as their initial antifungal therapy, 17 were given amphotericin B only, five received fluconazole only, and one received a combination of amphotericin B and flucytosine. After 2 weeks, all patients received fluconazole (400-600 mg daily for 8 weeks at least, then 200 mg daily thereafter). The presence of isolates resistant to fluconazole (MIC >8 μg/ml; 4.8% vs. 44%, p < 0.01) were statistically significant among patients who were cured. Anti-fungal susceptibility, reflected by fluconazole MIC >8 μg/ml, was an independent predictor of therapeutic cure at 10-week evaluation (OR = 15.7; 95% CI: 1.8-135.9; p = 0.01), but higher MIC of amphotericin B (>1 μg/ml) was not.

CONCLUSIONS

The MICs of fluconazole, determined by the CLSI method, may be a potential predictor of therapeutic cure in patients with cryptococcal meningitis.

Fluconazole resistance in cryptococcal disease: emerging or intrinsic?

With the widespread use of long-term fluconazole prophylaxis and suppressive treatment, the potential development of fluconazole resistance poses a threat to the management of cryptococcal disease. Interpretive breakpoints for the in vitro antifungal susceptibility testing of C. neoformans have not been established and it is unclear whether the fluconazole minimum inhibitory concentration (MIC) is clinically relevant. To gain insight into the management of patients with cryptococcosis who fail fluconazole therapy, we conducted a PubMed literature search for cases of fluconazole-resistant cryptococcosis reported from 1991 to 2011. A total of 20 such cases were identified in which most patients had AIDS and 30% had never had prior exposure to fluconazole. Fluconazole failure in patients with cryptococcal disease cannot be fully attributed to emerging resistance of the etiologic agent and heteroresistance is a potential alternative mechanism. There is a need to refine the definition of fluconazole-resistant cryptococcosis and additional studies of such patients will improve treatment strategies and outcomes.

Cryptococcus neoformans-Cryptococcus gattii species complex: an international study of wild-type susceptibility endpoint distributions and epidemiological cutoff values for fluconazole, itraconazole, posaconazole, and voriconazole

Epidemiological cutoff values (ECVs) for the Cryptococcus neoformans-Cryptococcus gattii species complex versus fluconazole, itraconazole, posaconazole, and voriconazole are not available. We established ECVs for these species and agents based on wild-type (WT) MIC distributions. A total of 2,985 to 5,733 CLSI MICs for C. neoformans (including isolates of molecular type VNI [MICs for 759 to 1,137 isolates] and VNII, VNIII, and VNIV [MICs for 24 to 57 isolates]) and 705 to 975 MICs for C. gattii (including 42 to 260 for VGI, VGII, VGIII, and VGIV isolates) were gathered in 15 to 24 laboratories (Europe, United States, Argentina, Australia, Brazil, Canada, Cuba, India, Mexico, and South Africa) and were aggregated for analysis. Additionally, 220 to 359 MICs measured using CLSI yeast nitrogen base (YNB) medium instead of CLSI RPMI medium for C. neoformans were evaluated. CLSI RPMI medium ECVs for distributions originating from at least three laboratories, which included ≥95% of the modeled WT population, were as follows: fluconazole, 8 μg/ml (VNI, C. gattii nontyped, VGI, VGIIa, and VGIII), 16 μg/ml (C. neoformans nontyped, VNIII, and VGIV), and 32 μg/ml (VGII); itraconazole, 0.25 μg/ml (VNI), 0.5 μg/ml (C. neoformans and C. gattii nontyped and VGI to VGIII), and 1 μg/ml (VGIV); posaconazole, 0.25 μg/ml (C. neoformans nontyped and VNI) and 0.5 μg/ml (C. gattii nontyped and VGI); and voriconazole, 0.12 μg/ml (VNIV), 0.25 μg/ml (C. neoformans and C. gattii nontyped, VNI, VNIII, VGII, and VGIIa,), and 0.5 μg/ml (VGI). The number of laboratories contributing data for other molecular types was too low to ascertain that the differences were due to factors other than assay variation. In the absence of clinical breakpoints, our ECVs may aid in the detection of isolates with acquired resistance mechanisms and should be listed in the revised CLSI M27-A3 and CLSI M27-S3 documents.

Clinical practice guidelines for the management of cryptococcal disease: 2010 update by the infectious diseases society of america

Cryptococcosis is a global invasive mycosis associated with significant morbidity and mortality. These guidelines for its management have been built on the previous Infectious Diseases Society of America guidelines from 2000 and include new sections. There is a discussion of the management of cryptococcal meningoencephalitis in 3 risk groups: (1) human immunodeficiency virus (HIV)-infected individuals, (2) organ transplant recipients, and (3) non-HIV-infected and nontransplant hosts. There are specific recommendations for other unique risk populations, such as children, pregnant women, persons in resource-limited environments, and those with Cryptococcus gattii infection. Recommendations for management also include other sites of infection, including strategies for pulmonary cryptococcosis. Emphasis has been placed on potential complications in management of cryptococcal infection, including increased intracranial pressure, immune reconstitution inflammatory syndrome (IRIS), drug resistance, and cryptococcomas. Three key management principles have been articulated: (1) induction therapy for meningoencephalitis using fungicidal regimens, such as a polyene and flucytosine, followed by suppressive regimens using fluconazole; (2) importance of early recognition and treatment of increased intracranial pressure and/or IRIS; and (3) the use of lipid formulations of amphotericin B regimens in patients with renal impairment. Cryptococcosis remains a challenging management issue, with little new drug development or recent definitive studies. However, if the diagnosis is made early, if clinicians adhere to the basic principles of these guidelines, and if the underlying disease is controlled, then cryptococcosis can be managed successfully in the vast majority of patients.

Treatment of cryptococcal meningitis in Peruvian AIDS patients using amphotericin B and fluconazole

OBJECTIVES

To describe the mycologic and clinical outcomes and factors associated with failure in Peruvian patients with AIDS-associated cryptococcal meningitis (CM) treated with amphotericin B deoxycholate (Amph B) followed by fluconazole.

METHODS

Patients were treated with intravenous Amph B 0.7 mg/kg/day for 2 or 3 weeks followed by oral fluconazole 400mg/day for 7 or 8 weeks. Clinical and laboratory evaluations including cerebrospinal fluid (CSF) studies were performed at baseline and at weeks 2 and 10.

RESULTS

The CSF cultures were negative in 25% and 68% of 47 patients at weeks 2 and 10, respectively. In the univariate analysis, baseline low body mass index (BMI), hyponatremia, low serum albumin, positive blood culture and CSF antigen titers >or=1024 were associated with a positive CSF culture at week 2. Baseline positive urine culture, positive blood culture, any positive extraneural culture and CSF opening pressure at week 2 >or=300 mm H2O were associated with a positive CSF culture at week 10. In the multivariate analysis no association was found.

CONCLUSIONS

Therapy with Amph B and fluconazole, combined with aggressive management of elevated intracranial pressure (ICP), results in low CSF sterilization rates at week 2 and acceptable CSF sterilization rates at week 10 when compared with other series.

Epidemiology and management of cryptococcal meningitis: developments and challenges

The significance of cryptococcal infection as a cause of human disease has dramatically evolved in recent years. The objective of this study was to outline the worldwide significance of cryptococcosis and review developments in the management of cryptococcal meningitis. Cryptococcus neoformans var. grubii remains an important cause of disease, particularly in hosts with acquired immunosuppression. Cryptococcus gattii, on the other hand, infects hosts with seemingly normal immune systems and a recent dramatic outbreak in a new ecologic environment highlights the emerging clinical significance of this fungal pathogen. The introduction of new antifungal agents and the adoption of strategies for controlling elevated intracranial pressure in cryptococcal meningitis have added to our therapeutic options. However, the mortality from this infection remains unacceptably high and we are faced with the specific challenges in the management of this disease.

Treatment of cryptococcosis in the setting of HIV coinfection

The HIV pandemic has been associated with a rise in the prevalence of primary and recurrent cryptococcosis. Evidence-based treatment algorithms exist for the use of antifungal drugs and maintaining normal intracranial pressure in HIV-infected hosts with cryptococcal meningitis. Further investigation is needed for the treatment of cases with refractory infections and cryptococcosis-related immune reconstitution syndrome, along with the optimal use of adjuvant therapies. Primary and secondary prevention strategies remain at the crux of global control strategies for cryptococcal disease.

Subcutaneous cryptococcosis due to Cryptococcus diffluens in a patient with sporotrichoid lesions case report, features of the case isolate and in vitro antifungal susceptibilities

Environmental fungi, in particular primary pathogens and Cryptococcus spp. can be responsible for skin lesions mimicking sporotrichosis. In this paper, we report a case of subcutaneous cryptococcosis in an apparently healthy, young male patient due to a non-C. neoformans Cryptococcus species, C. diffluens. The isolate showed in vitro phenotypic switching that may affect virulence and host inflammatory and immune responses, and in vitro resistance to amphotericin B and 5-flucytosin. This species shares several phenotypic traits with C. neoformans, and, therefore, decisive diagnosis should be based on biopsy and culturing results followed by molecular identification.

In vitro activity of the synthetic lipopeptide PAL-Lys-Lys-NH(2) alone and in combination with antifungal agents against clinical isolates of Cryptococcus neoformans

The in vitro activity of the lipopeptide PAL-Lys-Lys-NH(2) (PAL), alone or combined with either fluconazole (FLU) or amphotericin B (AMB), was investigated against 14 Cryptococcus neoformans isolates. PAL MICs ranged from 1.0 to 4.0 microg/ml. Fungicidal activity was observed. Synergy, defined as a fractional inhibitory concentration (FIC) index of < or =0.5, was observed in 21.4% of PAL/AMB interactions. Antagonism (FIC index>4) was never observed. The broad antifungal activity and the positive interactions with AMB suggest that PAL can represent a promising candidate in infections due to C. neoformans.

Symptomatic Relapse of HIV‐Associated Cryptococcal Meningitis after Initial Fluconazole Monotherapy: The Role of Fluconazole Resistance and Immune Reconstitution

BACKGROUND

Cryptococcal meningitis (CM) in South Africa is often treated with fluconazole as initial therapy. Surveillance data suggest that the prevalence of fluconazole-resistant CM is increasing, and expanding access to antiretroviral therapy is resulting in increasing recognition of immune reconstitution inflammatory syndrome. Therefore, we conducted a study to assess the contribution of these factors to CM relapse in this context.

METHODS

Patients with symptomatic relapse of CM were prospectively identified at 2 hospitals in Cape Town, South Africa, during the period of 2003-2005. Patients met the following criteria: (1) a previous laboratory-confirmed episode of CM, with resolution of symptoms after treatment; (2) reported adherence to fluconazole treatment; (3) recurrence of typical CM symptoms; (4) cerebrospinal fluid antigen test and/or culture positive for Cryptococcus neoformans; and (5) no alternative diagnosis. Data on patients' human immunodeficiency virus (HIV) and CM infections and treatment were collected and analyzed.

RESULTS

Thirty-two episodes of relapse occurred among 27 patients. Episodes were classified into 3 groups: culture-positive episodes in antiretroviral therapy-naive patients (6 episodes), culture-positive episodes in patients receiving antiretroviral therapy (15 episodes), and culture-negative episodes in patients receiving antiretroviral therapy (11 episodes). Seventy-six percent of culture-positive relapses were associated with isolates that had reduced susceptibility to fluconazole. Drug-resistant cases required prolonged intravenous therapy with amphotericin B, and despite this treatment, the mortality rate was high (54% at a median of 6 months of follow-up). Despite a long interval between initiation of antifungal therapy and initiation of antiretroviral therapy (median interval, 144 days), immune reconstitution inflammatory syndrome contributed to at least one-third of relapses.

CONCLUSIONS

After initial treatment with fluconazole, relapses of symptomatic CM are often associated with fluconazole resistance and immune reconstitution inflammatory syndrome. These data add to concern about the efficacy of fluconazole, compared with amphotericin B, for initial treatment of HIV-associated CM.

Results obtained with various antifungal susceptibility testing methods do not predict early clinical outcome in patients with cryptococcosis

The in vitro susceptibilities of Cryptococcus neoformans isolates from consecutive human immunodeficiency virus-positive and -negative patients to the antifungal agents fluconazole, amphotericin B, and flucytosine were determined by different techniques, including the CLSI method, Etest, and broth microdilution in yeast nitrogen base (YNB) medium, during a multicenter prospective study in France. The relationship between the in vitro data and the clinical outcome 2 weeks after the initiation of antifungal therapy was assessed. In addition, the correlation between the strain serotype and the in vitro activities of the antifungals was determined, and the susceptibility results obtained with the different techniques were also compared. Thirty-seven patients received a combination of amphotericin B with flucytosine as first-line therapy, 22 were treated with amphotericin B alone, and 15 received fluconazole alone. Whatever the antifungal tested, there was no trend toward higher MICs for strains isolated from patients who failed to respond to a given therapy compared to those from patients who did not with either the CLSI method, Etest, or broth microdilution in YNB medium. The MICs obtained by the CLSI or Etest method were significantly lower for serotype D strains than for serotype A strains for both fluconazole and amphotericin B, while flucytosine MICs were not different according to serotype. These findings suggest that the in vitro antifungal susceptibility of C. neoformans, as determined with the techniques used, is not able to predict the early clinical outcome in patients with cryptococcosis.

In vitro susceptibilities of Malaysian clinical isolates of Cryptococcus neoformans var. grubii and Cryptococcus gattii to five antifungal drugs

The in vitro susceptibilities of Malaysian clinical isolates of Cryptococcus neoformans var. grubii and C . gattii to five antifungal drugs (amphotericin B, flucytosine, fluconazole, itraconazole and ketoconazole) were determined using the Etest method. None of the Malaysian isolates was resistant to amphotericin B and ketoconazole. Isolates resistant to flucytosine, fluconazole and itraconazole were observed in this study. Minimum inhibition concentrations (MICs) of > or = 32 microg ml(-1) against flucytosine, > or = 64 microg ml(-1) against fluconazole and > or = 1 microg ml(-1) against itraconazole were noted in four (8.3%), two (4.2%) and one (2.1%) isolates respectively. There was no significant difference in the MICs for both Cryptococcus species (P > 0.05), indicating that C. gattii was as susceptible as var. grubii to all the antifungal drugs tested. No significant difference in the MICs for both Cryptococcus species collected from 1980 to 1990 and 2002 to 2004 were observed (P > 0.05).

In vitro susceptibility of Cryptococcus neoformans clinical isolates from Egypt to seven antifungal drugs

The in vitro susceptibility of 29 clinical isolates of Cryptococcus neoformans to fluconazole, miconazole, itraconazole, ketoconazole, flucytosine, nystatin and amphotericin B was tested by broth and colorimetric microdilution methods. Most of the isolates showed uniform patterns of susceptibility to the used antifungal agents. Only three isolates exhibited resistance [fourfold or greater rise in the minimum inhibitory concentrations (MICs)] to the tested antifungal drugs. The MIC50 and MIC90 were 0.5-8 mg l(-1) for 5-flucytosine, 0.2-8.25 mg l(-1) for nystatin, 0.5-16 mg l(-1) for fluconazole and 0.2-12.5 mg l(-1) for miconazole. However, MIC50 and MIC90 were in narrow range for the clinical yeast isolates in both methods used and showed 0.5-1 mg l(-1) for amphotericin B and 0.016-0.25 mg l(-1) for both ketoconazole and itraconazole. The combination of fluconazole plus flucytosine showed greater synergistic and fungicidal activity compared with that of fluconazole plus amphotericin B or the use of individual drugs.

Correspondence of in vitro and in vivo fluconazole dose-response curves for Cryptococcus neoformans

We conducted in vitro experiments to evaluate the susceptibility of a clinical isolate of Cryptococcus neoformans to a wide range of concentrations of fluconazole. In vitro susceptibility was tested using broth macrodilution methods modified to provide a numeric count of viable organisms. The association between the quantitative in vitro response and fluconazole drug concentrations was estimated using local nonparametric regression. Regression analysis was used to assess the correspondence between the in vitro fluconazole concentration-response curve and the murine dose-response curve observed in our previously reported murine model. The regression model was then used to predict the murine response. There was a strong correspondence between in vitro measures of response to fluconazole alone and the previously reported biologic effects seen in the mouse. In vitro antifungal drug susceptibility testing can reliably predict the murine response to fluconazole.

Evidence for human immunodeficiency virus and Cryptococcus neoformans interactions in the pro-inflammatory and anti-inflammatory responses in blood during AIDS-associated cryptococcosis

Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, -8 and-10 and soluble TNF receptor II (sTNFR II) levels were measured at baseline, and after antifungal therapy for 2 weeks and 3 months, in plasma from 75 human immunodeficiency virus (HIV)-positive and 14 HIV-negative patients with cryptococcosis, and in plasma from 14 HIV-positive controls. At baseline, TNF-alpha, IL-6 and sTNFR II levels, and cryptococcal antigen titres, were increased in patients with fungaemia compared to controls (p < 0.02). The mediator levels were not influenced by the severity of the disease or subsequent death, but sTNFR II and IL-10 levels were reduced, together with virus load, in patients receiving anti-retroviral agents (p < 0.01). During antifungal therapy, sTNFR II levels decreased (p 0.003) in parallel with the virus load and with an increase in CD4 T-cell numbers.

Capsule structure changes associated with Cryptococcus neoformans crossing of the blood-brain barrier

Cryptococcus neoformans is a yeast responsible for disseminated meningoencephalitis in patients with cellular immune defects. The major virulence factor is the polysaccharide capsule. We took advantage of a relevant murine model of disseminated meningoencephalitis to study the early events associated with blood-brain barrier (BBB) crossing. Mice were sacrificed at 1, 6, 24, and 48 hours post-intravenous inoculation, and classical histology, electron microscopy, and double immunofluorescence were used to study tissues and yeasts. Crossing of the BBB occurred early after inoculation, did not involve the choroid plexus but instead occurred at the level of the cortical capillaries, and caused early and severe damage to the structure of the microvessels. Seeding of the leptomeninges was not the primary event but occurred secondary to leakage of cortical pseudocysts. Organ invasion was associated with changes in cryptococcal capsule structure and cell size, which differed in terms of magnitude and kinetics, depending on both the organs involved, and potentially, on the bed structure of the local capillary. The rapid changes in capsule structure could contribute to inability of the host immune response to control cryptococcal infection in extrapulmonary spaces.

Evaluation of Mycograb®, amphotericin B, caspofungin, and fluconazole in combination against Cryptococcus neoformans by checkerboard and time-kill methodologies

This article reported the identification of heat shock protein 90 (hsp90) homologues by immunoblot in Cryptococcus neoformans. Mycograb, a genetically recombinant antibody against hsp90, was evaluated against 8 clinical isolates and the National External Quality Assessment Service for Microbiology strain of C. neoformans alone and in combination with amphotericin B, caspofungin, and fluconazole by checkerboard assay. At the end point of an optically clear well, the minimum inhibitory concentration (MIC) 0's ranged from 256 to 1024 microg/mL for Mycograb, from 0.5 to 1 microg/mL for amphotericin B, and from 16 to 32 microg/mL for caspofungin. The combination of Mycograb and amphotericin B produced a fractional inhibitory concentration index from 0.27 to 0.56, indicating a mainly synergistic effect, whereas for caspofungin, it varied from 0.5 to 2. At an end point of > or =50% inhibition, the MIC-2s varied from 16 to 128 microg/mL for Mycograb and from 0.125 to 16 microg/mL for fluconazole. The fractional inhibitory concentration index classified the combination as indifferent for 5 isolates, additive for 3 more isolates, and synergistic in a single isolate. Time-kill analysis on 2 isolates (F/7844 and F/10156), which had synergistic and additive results with amphotericin B, respectively, on checkerboard was performed with 4-16 microg/mL of Mycograb, 2-8 microg/mL of fluconazole, and 0.0625-2 microg/mL of amphotericin B. This demonstrated an increasingly static effect with augmenting concentrations of fluconazole and an initial static effect with amphotericin B at lower concentrations, which became fungicidal as the level of drug increased. The addition of either 4 or 8 microg/mL of Mycograb to 0.5 microg/mL of amphotericin B with C. neoformans F/7844 changed a static effect to a fungicidal effect at 8 h with an increased killing of 1.2 logs at 48 h. With C. neoformans F/10156, the addition of 16 microg/mL of Mycograb to 0.25 microg/mL of amphotericin B produced a difference in killing from 1 logarithm after 4 h to 1.5 logarithms after 48 h. These data suggest that the combination of amphotericin B and Mycograb would be worth exploring in the treatment of infection due to C. neoformans.