In vitro susceptibilities of clinical and environmental isolates of Cryptococcus neoformans to five antifungal drugs

Advanced approach for antifungal susceptibility and characterization of resistance properties in clinical and environmental isolates of Cryptococcus species complex

BACKGROUND

Meningitis due to Cryptococcus neoformans/gattii is a fatal infection affecting immunocompromised population worldwide. Amphotericin B (AmB), fluconazole (FLC) and 5-flucytosine are the drugs of choice to treat the infection. We studied antifungal susceptibility pattern of clinical and environmental cryptococcal species using newer approach and analyze their resistant characteristics.

METHODS

Eighty clinical (54 C. neoformans and 26 C. gattii) and 18 environmental (14 C. neoformans and 4 C. gattii) isolates were subjected to antifungal susceptibility testing by automated (VITEK2C) method. Minimum inhibitory concentrations (MIC) were analyzed statistically. Genomic DNA of FLC resistant isolates was extracted and amplified to detect presence of CnAFR1 gene.

RESULTS

C. neoformans showed 1.85% and 21.4% AmB resistance, and 1.85% and 28.5% FLC- resistance, whereas C. gattii showed 25% and 50% FLC-resistance among clinical and environmental isolates respectively. MIC values were significantly (p < 0.05) different for the isolates from 2 sources. CnAFR1 gene sequence analysis revealed phylogenetic relationship among the resistant isolates.

CONCLUSIONS

This pioneering study provides an insight into the sensitivity patterns of clinical and environmental cryptococcal isolates from south India. The recent emergence of AmB-resistance may transpire as a challenge for the clinicians. As the clinical and environmental isolates are phylogenetically evolved from CnAFR1 gene of Filobasidiella neoformans, the resistance is most probably an inherent attribute. This study emphasizes the need for speciation and antifungal susceptibility testing of cryptococcal isolates from clinical sources to institute appropriate antifungal therapy and to reduce the mortality and morbidity.

Cryptococcus neoformans/gattii Species Complexes from Pre-HIV Pandemic Era Contain Unusually High Rate of Non-Wild-Type Isolates for Amphotericin B

Introduction

The Cryptococcus neoformans/gattii species complexes are a leading cause of fatality among HIV-infected patients. Despite the unavailability of clinical breakpoints (CBPs) for antifungal agents, epidemiological cutoff values (ECVs) were recently proposed, and non-wild-type isolates for polyenes and azoles are being increasingly reported. However, the distributions of the susceptibility patterns for pre-HIV-era isolates have not been studied.

Methods

We determined the in vitro antifungal susceptibility patterns of 233 Cryptococcus isolates, collected at the National Institutes of Health, USA, in pre-HIV pandemic era, to study minimum inhibitory concentrations (MICs) to the important drugs for cryptococcosis and to compare the results with strain genotypes. Amphotericin B susceptibility was compared to published ECV of C. neoformans.

Results

The 233 Cryptococcus strains consisted of 89.7% C. neoformans species complex and 10.3% C. gattii species complex. Most were from clinical sources (189, 81.1%), and the major molecular type was VNI (146, 62.7%). The highest geometric mean (GM) was observed for fluconazole (GM = 0.96 µg/mL) while the lowest was for itraconazole (GM = 0.10 µg/mL). MICs to fluconazole in C. gattii species complex were significantly higher than C. neoformans species complex (p < 0.001). Moreover, C. neoformans/VNI strains showed significantly higher MICs than others such as C. neoformans/VNII to fluconazole (p < 0.0001) and C. deneoformans/VNIV to amphotericin B (p = 0.022) and fluconazole (p = 0.008). In our collection of 167 clinical C. neoformans species complex strains, 85 (50.9%), 24 (14.4%), and 3 (1.8%) strains had an amphotericin B (AMB)-MIC of 1, 2, and 4 µg/mL, respectively. The high percentage (66.9%, 79/118 strains) of non-wild-type clinical C. neoformans VNI strains, using an AMB-ECV of 0.5 µg/mL, was found. Moreover, 25 of 28 (89.3%) C. neoformans VNI strains from environmental and veterinary sources also had AMB-MICs above 0.5 µg/mL. In general, there was no significant difference in GM AMB-MIC of the clinical strains isolated from patients with (35 patients) and without (78 patients) prior AMB treatment (0.85 vs 0.76; p = 0.624). GM MIC of the environmental strains was not significantly different from that of the prior AMB-treatment strains (0.98 vs 0.76, p = 0.159) and the post-AMB-treatment strains (0.98 vs 0.85, p = 0.488).

Conclusion

The high rate of non-wild-type among these otherwise naive isolates to amphotericin B is unexpected. Confirmation with more strains from a later era is needed.

Amphotericin B-loaded solid lipid nanoparticles (SLNs) and nanostructured lipid carrier (NLCs): effect of drug loading and biopharmaceutical characterizations

The aim of this study was to further investigate the effect of drug loading, drug entrapment efficiency, the drug release profiles and biopharmaceutical point of views of amphotericin B (AmB) lipid formulations, that is, degree of aggregation by UV-spectroscopy, in vitro hemolytic and antifungal activities. The optimum drug loading was 2.5% by weight corresponded to lipid fraction in formulation. Increasing of the drug entrapment was achieved by blending small amount of phospholipid in solid lipid nanoparticle (SLN) dispersions. All AmB lipid dispersions were less aggregated species and hemolytic response than Fungizone^® indicating that lipid nanoparticles could reduce its toxicity. The sustained release profiles of AmB formulations depended on its aggregated form and entrapment efficiency. Too high AmB loaded (5% w/w) showed a biphasic drug release profile probably due to some amounts of drug deposited on the nanosphere surface including in continuous phase which promptly released. For in vitro antifungal testing, all AmB lipid formulations were equal and more effective than both AmB itself and Fungizone^®. These observations suggested that AmB loaded SLNs, nanostructured lipid carriers and modified SLNs by blending lecithin could enhance AmB solubility, prolong release characteristics, reduce toxicity and improve antifungal activity.

Antifungal susceptibility of clinical and environmental Cryptococcus neoformans and Cryptococcus gattii isolates in Jabalpur, a city of Madhya Pradesh in Central India

In this study, we present antifungal susceptibility data of clinical and environmental isolates of Central Indian Cryptococcus neoformans (Serotype A, n = 8 and n = 50 respectively) and Cryptococcus gattii (Serotype B, n = 01 and n = 04 respectively). Susceptibilities to fluconazole, itraconazole and ketoconazole were determined by using NCCLS broth micro-dilution methodology. The total number of resistant strains for fluconazole in case of C. neoformans and C. gattii showed a significant difference by using chi-square test (p < 0.05*), while considering fisher's exact p value was nonsignificant (p > 0.05). However, the total number of resistant strains for itraconazole and ketoconazole was not found statistically significant. A comparison of geometric means of clinical and environmental strains of C. gattii and C. neoformans was not found statistically significant using student ‘t’ test (p value > 0.05 NS). Though less, the antifungal data obtained in this study suggests that primary resistance among environmental and clinical isolates of C. neoformans and C. gattii against tested antifungal was present and C. gattii comparatively was less susceptible than C. neoformans var. grubii isolates to fluconazole than to itraconazole and ketoconazole. A continuous surveillance of antifungal susceptibility of clinical and environmental isolates of C. neoformans and C. gattii is desirable to monitor the emergence of any resistant strains for better management of cryptococcosis patients.

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.

Comparative analysis of the Vitek 2 antifungal susceptibility system and E-test with the CLSI M27-A3 broth microdilution method for susceptibility testing of Indian clinical isolates of Cryptococcus neoformans

The emergence of antifungal resistance among Cryptococcus neoformans isolates is a matter of great concern. The Clinical and Laboratory Standards Institute (CLSI) broth microdilution reference method (BMD) for antifungal susceptibility testing of C. neoformans is tedious and time-consuming. Consequently, there is a greater need for a reproducible in vitro susceptibility testing method for use in clinical microbiology laboratories. By random amplified polymorphic DNA analysis, the 62 Indian clinical isolates were characterized as Cryptococcus neoformans var. grubii. We evaluated the susceptibilities of these isolates for amphotericin B (AMB) and fluconazole (FLC) by two commercial techniques, i.e., Vitek 2 and E-test against the CLSI M27-A3 BMD. The essential agreement (EA) between the Vitek 2 and E-test with the reference procedure for FLC was similar (82.2%). For AMB, EA of 92 and 76% was obtained with E-test and Vitek 2. Excellent categorical agreement (CA) (98.3% and 100% by Vitek 2 and E-test, respectively) was obtained for AMB. The CA for FLC was 81 and 77.4% by Vitek 2 and E-test. We conclude that both E-test and Vitek 2 system have acceptable levels of accuracy for susceptibility testing of both the drugs. Both of them could identify fluconazole-resistant strains. Vitek 2 could be used for testing susceptibility of voriconazole and 5-flucytosine also at the same time.

Correlation of the in vitro antifungal drug susceptibility with the in vivo activity of fluconazole in a murine model of cerebral infection caused by Cryptococcus gattii

Forty Cryptococcus gattii strains were submitted to antifungal susceptibility testing with fluconazole, itraconazole, amphotericin B and terbinafine. The minimum inhibitory concentration (MIC) ranges were 0.5-64.0 for fluconazole, <0.015-0.25 for itraconazole, 0.015-0.5 for amphotericin B and 0.062-2.0 for terbinafine. A bioassay for the quantitation of fluconazole in murine brain tissue was developed. Swiss mice received daily injections of the antifungal, and their brains were withdrawn at different times over the 14-day study period. The drug concentrations varied from 12.98 to 44.60 μg/mL. This assay was used to evaluate the therapy with fluconazole in a model of infection caused by C. gattii. Swiss mice were infected intracranially and treated with fluconazole for 7, 10 or 14 days. The treatment reduced the fungal burden, but an increase in fungal growth was observed on day 14. The MIC for fluconazole against sequential isolates was 16 μg/mL, except for the isolates obtained from animals treated for 14 days (MIC = 64 μg/mL). The quantitation of cytokines revealed a predominance of IFN-γ and IL-12 in the non-treated group and elevation of IL-4 and IL-10 in the treated group. Our data revealed the possibility of acquired resistance during the antifungal drug therapy.

Genotyping of Mexican Cryptococcus neoformans and C. gattii isolates by PCR-fingerprinting

Cryptococcosis in México is caused by both species of the Cryptococcus species complex i.e., Cryptococcus neoformans and C. gattii. The current study was aimed to determine genetic variability of 72 Mexican clinical isolates using PCR-fingerprinting with the primer M13. PCR fingerprinting revealed 55 VNI, five VNII, three VNIII, one VNIV, two VGI, two VGII, two VGIII and two VGIV isolates among those studied. The results show that most cryptococcosis cases in México are AIDS related and are caused by C. neoformans var. grubii, genotypes VNI and VNII. In addition this study revealed for the first time the presence of genotypes VNIV and VGII among Mexican clinical isolates. The present data show that all genotypes that have been described for the Cryptococcus species complex are found in México, indicating a much wider geographic distribution of genotypes than previously reported. The molecular analysis of Mexican cryptococcal isolates generated PCR-fingerprinting patterns which will provide references for future typing studies to allow the integration of Mexican cryptococcal genotypes into the ongoing global genotyping study of the Cryptococcus species complex.

Cryptococcus neoformans serotype A and Cryptococcus gattii serotype B isolates differ in their susceptibilities to fluconazole and voriconazole

This study presents antifungal susceptibility data for environmental isolates of Cryptococcus neoformans serotype A (n=32) and Cryptococcus gattii serotype B (n=18) to fluconazole and voriconazole employing disc diffusion and Etest methods. The disc diffusion test was performed on Mueller-Hinton agar as recommended by the Clinical and Laboratory Standards Institute (CLSI). For comparison, the disc diffusion test and Etest were also performed on RPMI-1640 agar supplemented with 2% glucose. The plates were incubated at 35 degrees C and read after 48h. Comparison of geometric mean inhibition zone diameters revealed that C. gattii isolates were significantly less susceptible than C. neoformans isolates to fluconazole (P=0.001) and voriconazole (P<0.0001). Similar results were obtained on RPMI agar by disc diffusion test and Etest, showing significantly reduced susceptibility for C. gattii isolates. Notwithstanding differences in the susceptibilities of the two species to fluconazole and voriconazole, they appeared susceptible according to the CLSI breakpoints recommended for some Candida spp. To what extent these differences in the susceptibilities of C. neoformans and C. gattii impact on the therapeutic management of cryptococcosis is unclear, although some studies have reported less favourable response in cases caused by the latter species.

Pharmacotherapy of yeast infections

The rise of immunocompromised individuals in our society has provoked a significant emergence in the number of patients affected by opportunistic pathogenic yeast. The microorganisms with a major clinical incidence are species from the genera Candida (especially Candida albicans) and Cryptococcus (particularly Cryptococcus neoformans), although there has been a significant increase in other pathogenic yeasts, such as Trichosporon spp. and Rhodotorula spp. In addition, there are an increasing number of patients infected by yeasts that were not previously considered as pathogenic, such as Saccharomyces cerevisiae. The management of these infections is complicated and is highly dependent on the susceptibility profile not only of the species but also of the strain. The available antifungal compounds belong mainly to the polyene, azole and candin families, which show a distinct spectrum of activity. This review summarizes the current knowledge about the use of the main antifungals for treating infections caused by the yeast species with the most significant clinical relevance, including the susceptibility profiles exhibited by these species in vitro.

[Behaviour azole fungicide and fluconazole in Cryptococcus neoformans clinical and environmental isolates]

The activity of azole fungicides for agronomical use (epoxiconazole, difenoconazole and cyproconazole) was evaluated in comparison with the therapeutic antifungal agent fluconazole, on 23 environmental samples of Cryptococcus neoformans var neoformans isolated from pigeon feces that were collected from farms with agricultural practices using azole compounds, and on 11 clinical samples isolated from patients with cryptococcosis. Sensitivity tests were performed using the agar dilution technique. The minimum inhibitory concentration capable of inhibiting 50% of the environmental isolates (MIC 50) was 6.00 microg/ml to epoxiconazole, 1.00 microg/ml for difenoconazole, 2.00 microg/ml for cyproconazole and 64.00 microg/ml for fluconazole. Among the clinical isolates the MIC 50 values were 2.00 microg/ml, 0.38 microg/ml, 1.00 microg/ml and 16.00 microg/ml for epoxiconazole, difenoconazole, cyproconazole and fluconazole, respectively. The MIC 50 values for environmental isolates were greater than the MIC 50 values for clinical isolates. In our study, in relation to the same antifungal agent, the environmental samples presented significantly different behaviour in relation to the clinical samples (p<0.05). Differences in the MIC values (p<0.05) presented by fluconazole and the other antifungal agents for agronomical use, both in the environmental isolates and in the clinical isolates, were also observed.

Antifungal susceptibility of Cryptococcus neoformans and Cryptococcus gattii isolates from decayed wood of trunk hollows of Ficus religiosa and Syzygium cumini trees in north-western India

BACKGROUND

We present antifungal susceptibility data on environmental isolates of Cryptococcus neoformans (serotype A, n=117) and Cryptococcus gattii (serotype B, n=65) cultured from decayed wood of trunk hollows of Ficus religiosa and Syzygium cumini trees.

METHODS

Susceptibilities to amphotericin B, fluconazole, ketoconazole, itraconazole and voriconazole were determined by using Etest. The MICs were read after 48 h as per the guidelines provided by the manufacturer.

RESULTS

The MIC90s and susceptibility ranges for C. neoformans isolates were as follows: 0.094 (0.004-0.25) mg/L for amphotericin B, 4 (0.032-12) mg/L for fluconazole, 0.094 (0.004-0.75) mg/L for itraconazole, 0.064 (0.002-0.19) mg/L for ketoconazole, and 0.047 (0.006-0.125) mg/L for voriconazole, whereas for C. gattii isolates these were 0.125 (0.023-0.5) mg/L for amphotericin B, 8 (0.032-16) mg/L for fluconazole, 0.75 (0.006-2) mg/L for itraconazole, 0.125 (0.003-0.19) mg/L for ketoconazole, and 0.094 (0.004-0.125) mg/L for voriconazole. A comparison of the geometric means of MICs (mg/L) revealed that C. gattii was less susceptible than C. neoformans to amphotericin B (0.075 versus 0.051, P=0.0003), fluconazole (2.912 versus 2.316, P=0.003), itraconazole (0.198 versus 0.0344, P<0.0001), ketoconazole (0.072 versus 0.037, P<0.0001), and voriconazole (0.045 versus 0.023, P<0.0001).

CONCLUSIONS

The antifungal susceptibility data obtained in this study indicate that the occurrence of primary resistance among environmental isolates of C. neoformans serotype A and C. gattii serotype B is rare, and serotype B isolates are less susceptible than serotype A isolates.

Molecular typing and antifungal susceptibility of clinical sequential isolates of Cryptococcus neoformans from Sao Paulo State, Brazil

The antifungal susceptibility profiles and the genetic variability of 83 sequential clinical isolates of Cryptococcus neoformans, including four Cryptococcus gattii isolates, obtained from 38 Sao Paulo AIDS patients with cryptococcal meningitis were assessed by electrophoretic karyotyping and random amplified polymorphic DNA (RAPD) analysis. The majority of the Cryptococcus neoformans isolates were highly susceptible to amphotericin B and fluconazole. Twenty percent of the minimum inhibitory concentration values for amphotericin B varied from 0.5 to 1 micro g mL(-1). For fluconazole, 22% occurred in the range 8-16 mug mL(-1). Sequential isolates from nine patients showed a trend towards lower susceptibility to fluconazole, flucytosine, itraconazole and amphotericin B. The results of molecular typing by electrophoretic karyotyping and RAPD analysis showed the presence of 22 electrophoretic karyotypes (EK) and 15 RAPD profiles that were highly correlated. Our results provided evidence for the occurrence of genetic changes in some strains associated with microevolution during the course of infection. We also observed both microevolution and simultaneous coinfection with two distinct Cryptococcus neoformans strains in one patient. In some patients, we found changed EK- and RAPD patterns in association with increased MIC values.

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 to antifungal agents of environmental Cryptococcus spp. isolated in the city of Ribeirão Preto, São Paulo, Brazil

Infections by Cryptococcus strains other than C. neoformans have been detected in immunocompromised patients. Of these strains, three are considered human pathogens: C. albidus, C. laurenttii, and C. uniguttulatus. This study deals with the in vitro susceptibility of Cryptococcus to drugs such as amphotericin B, itraconazole, fluconazole, and 5-fluorocytosine. Environmental Cryptococcus isolates (50) distributed as follows: C. neoformans var. neoformans (16), C. albidus (17), C. laurentii (14), and C. uniguttulatus (3) were evaluated by the micro and macrodilution techniques, according to EUCAST and NCCLS recommendations, respectively. Considering both methodologies the respective minimal inhibitory concentrations (MIC) were 0.125 and 2 microg/ml for amphotericin B, 0.06 and 8 microg/ml for itraconazole, and 0.5 and more than 64 microg/ml for fluconazole and 5-fluorocytosine. Agreement percentages for the two methodologies were 100% for amphotericin B and fluconazole for all the strains tested. For itraconazole, the agreement percentage was 81.3% in the C. neoformans strain and 100% for all the others. All species had a agreement percentage of 94.1 to 100% when susceptibility to 5-fluorocytosine was tested. It is concluded that environmental isolates of C. neoformans var. neoformans, C. albidus, C. laurentii, and C. uniguttulatus may show high MICs against certain drugs, suggesting in vitro primary resistance to the antifungals tested.

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.

Antifungal susceptibilities of clinical and environmental isolates of Cryptococcus neoformans in goiânia city, Goiás, Brasil

We evaluated the antifungal activities of amphotericin B, fluconazole, itraconazole and voriconazole in 70 Cryptococcus neoformans strains obtained from cerebrospinal fluid from AIDS patients and 40 C. neoformans strains isolated from the environment. Four clinical isolates were identified as C. neoformans var. gattii. The susceptibility test was done using a broth microdilution method according to NCCLS M27-A2. Range minimal inhibitory concentrations (MICs) for C. neoformans clinical isolates were 0.06-1.0 µg/mL for amphotericin B, 0.125-8 µg/mL for fluconazole, 0.03-0.5 µg/mL for itraconazole and 0.03-0.25 µg/mL for voriconazole. C. neoformans environmental isolates showed range MICs 0.015-0.125 µg/mL, 0.25-2.0 µg/mL, 0.007-0.125 µg/mL and 0.03-0.25 µg/mL for amphotericin B, fluconazole, itraconazole and voriconazole respectively. The MICs results obtained from clinical and environmental isolates showed similar pattern of susceptibility and no resistance has been found in our isolates.

DNA fingerprinting pattern and susceptibility to antifungal drugs in Cryptococcus neoformans variety grubii isolates from Barcelona city and rural environmental samples

Cryptococcus neoformans var. grubii (serotype A) was isolated from 12 soil samples mixed with pigeon droppings (16.9%) from 71 soil samples in Barcelona and rural areas of Catalonia. C. neoformans was not isolated from indoor dust and Eucalyptus debris. PCR fingerprinting was performed in 22 representative isolates and all of them corresponded to the VNI pattern. Susceptibility testing for the 22 isolates of C. neoformans var. grubii showed that all of them were susceptible to amphotericin B. Three isolates presented MICs (Minimal Inhibitory Concentrations) > or = 1 microg/ml to Itraconazole, five MICs > or = 1 microg/ml to ketoconazole and four were fluconazole resistant, (MICs > or = 64 microg/ml), while three of them were shown to have MICs > or = 1 microg/ml to voriconazole. In spite that all isolates presented the same DNA fingerprinting pattern, the susceptibility to antifungals is very variable. The possibility of acquiring cryptococcosis infection with primarily resistant environment strains is feasible.

The isolation, characterization and antifungal susceptibilities of Cryptococcus neoformans from bird excreta in Klang Valley, Malaysia

The occurrence of Cryptococcus neoformans in bird excreta in Klang valley, Malaysia was determined in this study. Of 544 samples of bird excreta collected from a local zoo, pet shops and public areas, 20 strains of C. neoformans were isolated. All C. neoformans strains were serotype A and thus identified as C. neoformans variety grubii. All did not produce color changes on canavanine-glycine-bromothymol blue agar. All were of alpha-mating types, as determined by a pheromone-specific PCR assay. The antifungal susceptibility testing using agar diffusion method Neo-sensitabs showed that all were susceptible to amphotericin B, fluconazole and itraconazole.

Human cryptococcosis: relationship of environmental and clinical strains of Cryptococcus neoformans var. neoformans from urban and rural areas

Forty-five clinical and 55 environmental strains of Cryptococcus neoformans var. neoformans from São Paulo, Brazil, were tested for their susceptibilities to amphotericin B, fluconazole, itraconazole, and flucytosine by the broth microdilution method according to the National Committee of Clinical Laboratory Standards guidelines. Electrophoretic karyotypes analysis by counter-clamped homogeneous electrophoresis was used to compare their genetic relatedness. Molecular typing revealed three clinical profiles very similar to two environmental profiles and an identical environmental and clinical profile. The results showed that human cryptococcosis can be acquired from environmental strains, which had similar minimum inhibitory concentration values to clinical strains, for antifungal agents.

In vitro antifungal susceptibility of Cryptococcus gattii

We have determined the in vitro susceptibilities of 57 strains of Cryptococcus gattii to nine antifungal agents and have compared the MICs for these strains with those for C. neoformans. MICs were determined by a microdilution reference method. Albaconazole and ravuconazole (MICs of 0.04 and 0.05 microg/ml, respectively) showed the best activities. Micafungin showed no activity (MIC of >128 microg/ml). In general, C. gattii was less susceptible than C. neoformans to all drugs tested, with the exception of amphotericin B and flucytosine.

Antifungal susceptibilities of Cryptococcus neoformans

Susceptibility profiles of medically important fungi in less-developed countries remain uncharacterized. We measured the MICs of amphotericin B, 5-flucytosine, fluconazole, itraconazole, and ketoconazole for Cryptococcus neoformans clinical isolates from Thailand, Malawi, and the United States and found no evidence of resistance or MIC profile differences among the countries.

The lipid formulations of amphotericin B

Amphotericin B spectrum covers most of the fungal pathogens involved in human diseases. Its use is limited by infusion-related effects and nephrotoxicity. As a result of strong lipophilic properties, encapsulation in liposomes or binding to lipid complexes led to the development of lipid formulations in an attempt to increase both efficacy and safety. Three lipid formulations of amphotericin B are commercially available: a liposomal preparation, a lipid complex and a colloidal dispersion. They differ in their lipid composition, shape, pharmacokinetic behaviour and clinical effects. The nephrotoxicity of these formulations is significantly decreased compared to their parent compound. Infusion-related events are lowest with liposomal amphotericin B. Increased efficacy of the lipid formulations over conventional amphotericin B, however, still has to be demonstrated. These formulations are mainly indicated for the treatment of documented fungal infections in patients failing conventional amphotericin B or with renal impairment. Liposomal amphotericin B is also indicated for empirical therapy of suspected fungal infections in febrile neutropenic patients giving this compound an advantage over the two other formulations. Lipid formulations of amphotericin B are extremely expensive. Whether the increase in cost translates into a long-term benefit for the patient is still unknown.

Recommendations for the treatment of fungal pneumonias

Incidences of fungal pneumonias have increased in immunocompromised patients with HIV infection or receiving bone marrow replacement or solid organ transplantation. Fungal pneumonias including aspergillosis, cryptococcosis, candidiasis, coccidioidomycosis, histoplasmosis and blastomycosis are one of the major causes of morbidity and mortality among the immunosuppressed hosts. Therefore, clinicians should consider the most appropriate and aggressive treatment of fungal pneumonias in this population. This report outlines the state of the art in the treatment of fungal pneumonias and discusses recent advances in antifungal therapy. Practice guidelines for the treatment with commonly used antifungal agents including amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine, are very useful for clinicians to manage the diseases appropriately. Echinocandins and second-generation triazoles will hopefully help clinicians to overcome the limitations of the current therapy.

Antifungal susceptibility of clinical and environmental isolates of Cryptococcus neoformans to four antifungal drugs determined by two techniques

A total of 64 Cryptococcus neoformans strains, including clinical and environmental Brazilian isolates var. neoformans and var. gattii, were tested for susceptibility to amphotericin B, 5-flucytosine, fluconazole and itraconazole. The tests were performed according to the recommendations of National Committee of Clinical Laboratory Standards and the method of macrodilution in liquid medium of Shadomy et al. [Manual de Microbiologia Clínica, 4th ed. Buenos Aires: Editorial Medica Panamericana, 1987: 1229-38]. For most drugs there was a significant difference between the readings taken at 24 and 48 h with both methods. When the minimum inhibitory concentrations obtained by the two techniques were compared, significant differences were observed for amphotericin B and fluconazole. Overall, differences in drug susceptibility with respect to the origin of the isolates or the variety of the fungus were not observed. As an exception, the gattii variety exhibited a high resistance rate to amphotericin B when the technique of Shadomy et al. was applied, a fact possibly related to the greater difficulty for treatment of the disease caused by this fungal variety.

Inhibition of human pathogenic fungi by ethnobotanically selected plant extracts

In this study, 36 extracts derived from 29 plant species selected using an ethnobotanical approach were tested for antifungal activity against a taxonomically diverse group of 13 human pathogenic fungi. We compared the inhibitory characteristics of these plant extracts with those of the commonly used antifungals, amphotericin B and ketoconazole, and the plant-derived antifungal, berberine. Several plant extracts, notably those from Zingiber officinale (ginger) and Juglans cinerea (butternut), had pronounced antifungal activity against a wide variety of fungi, including strains that were highly resistant to amphotericin B and ketoconazole. Further exploration of Z. officinale as an antifungal is warranted as this species is generally regarded as safe for human consumption.

[Susceptibility to antifungal agents of Cryptococcus species of clinical interest]

BACKGROUND

Studies on the susceptability of Cryptococcus species to antifungal agents are scarce.

METHOD

We investigate the susceptibility of 54 clinical and environmental strains from six different species using the Sensititre and the NCCLS methods.

RESULTS

Environmental strains were less susceptible than clinical strains. We found MICs >= 64 mg/l for fluconazole, MICs >= 1 mg/l for itraconazole and MICs >= 32 mg/l for 5-fluorocytosine in C. albidus, C. neoformans and C. uniguttulatus.

CONCLUSIONS

These findings point at the importance of determining the antifungal susceptibility of Cryptococcus species.

In vitro susceptibility to antifungal agents of clinical and environmental Cryptococcus neoformans isolated in Southern of Brazil

The purpose of the present study was to compare the susceptibility to four antifungal agents of 69 Cryptococcus neoformans strains isolated from AIDS patients with that of 13 C. neoformans strains isolated from the environment. Based on the NCCLS M27-A methodology the Minimal Inhibitory Concentrations (MICs) obtained for amphotericin B, itraconazole and ketoconazole were very similar for clinical and environmental isolates. Clinical isolates were less susceptible to fluconazole than environmental isolates. The significance of these findings and aspects concerning the importance, role and difficulties of C. neoformans susceptibility testing are also discussed.

Antifungal susceptibilities, varieties, and electrophoretic karyotypes of clinical isolates of Cryptococcus neoformans from Brazil, Chile, and Venezuela

One hundred clinical isolates of Cryptococcus neoformans from human immunodeficiency virus (HIV)-infected and non-HIV-infected patients from Brazil, Chile, and Venezuela were separated according to varieties and tested for antifungal susceptibility. A high susceptibility to antifungal agents was observed among all the isolates. The electrophoretic karyotyping of 51 strains revealed good discrimination among Cryptococcus neoformans var. neoformans strains.

Correlation of fluconazole MICs with clinical outcome in cryptococcal infection

We have correlated the in vitro results of testing the susceptibility of Cryptococcus neoformans to fluconazole with the clinical outcome after fluconazole maintenance therapy in patients with AIDS-associated cryptococcal disease. A total of 28 isolates of C. neoformans from 25 patients (24 AIDS patients) were tested. The MICs were determined by the broth microdilution technique by following the modified guidelines described in National Committee for Clinical Standards (NCCLS) document M27-A, e.g., use of yeast nitrogen base medium and a final inoculum of 10(4) CFU/ml. The fluconazole MIC at which 50% of isolates are inhibited (MIC(50)) and MIC(90), obtained spectrophotometrically after 48 h of incubation, were 4 and 16 microg/ml, respectively. Of the 25 patients studied, 4 died of active cryptococcal disease and 2 died of other causes. Therapeutic failure was observed in five patients who were infected with isolates for which fluconazole MICs were > or =16 microg/ml. Four of these patients had previously had oropharyngeal candidiasis (OPC); three had previously had episodes of cryptococcal infection, and all five treatment failure patients had high cryptococcal antigen titers in either serum or cerebrospinal fluid (titers, >1:4,000). Although 14 of the 18 patients who responded to fluconazole therapy had previously had OPC infections, they each had only a single episode of cryptococcal infection. It appears that the clinical outcome after fluconazole maintenance therapy may be better when the infecting C. neoformans strain is inhibited by lower concentrations of fluconazole for eradication (MICs, <16 microg/ml) than when the patients are infected with strains that require higher fluconazole concentrations (MICs, > or =16 microg/ml). These findings also suggest that the MICs determined by the modified NCCLS microdilution method can be potential predictors of the clinical response to fluconazole therapy and may aid in the identification of patients who will not respond to fluconazole therapy.

Clinical features and in vitro susceptibilities of two varieties of Cryptococcus neoformans in Taiwan

One hundred years after introduction of the Eucalyptus tree to Taiwan, a predominantly subtropical island, we analyzed clinical and microbiological data of 59 patients with Cryptococcus neoformans infection hospitalized at National Taiwan University Hospital during 1982 to 1997. There were 38 (64.4%) cases of cryptococcosis caused by the var. neoformans and 21 (35.6%) caused by the var. gattii. Thirty-three patients (55.9%) had impaired T cell function, which included 12 patients with acquired immunodeficiency syndrome (AIDS). Eleven of the 12 patients with AIDS were diagnosed after 1995, and 11 cases were caused by var. neoformans. Minimum inhibitory concentrations (MICs) determined by the NCCLS broth microdilution method using antibiotic medium 3 improved the discrimination of in vitro susceptibility against amphotericin B and demonstrated that var. gattii isolates were less susceptible (geometric means 0.25 microg/ml versus 0.64 microg/ml, P < 0.001). In addition, a higher proportion of var. gattii were less susceptible to flucytosine as compared with var. neoformans (35.0% versus 64.9%, P = 0.030). There was no seasonal clustering for isolation of var. neoformans, though infections caused by var. gattii peaked in July and August. Compared with the first study of cryptococcosis (1957-1972) at NTUH, this study demonstrated the increase in immunocompromised and elderly patients, as well as a higher proportion of Cryptococcus isolated from blood or bone marrow. Facing the increasing adaptive plantation of Eucalyptus in Taiwan, the importance of field study regarding the role of Eucalyptus plantations in Taiwan and occurrence of cryptococcosis in human beings cannot be over-emphasized.

Amphotericin B and its new formulations: pharmacologic characteristics, clinical efficacy, and tolerability

Amphotericin B (amB) remains the gold standard for the treatment of invasive fungal infections. However, the efficacy is limited, with response rates from 10% to 80%. Moreover, amB is toxic, especially for the kidneys. New formulations have been developed in an attempt to improve both efficacy and tolerability. In an attempt to reduce toxicity, a number of investigators have reconstituted amB in a lipid emulsion, but few data are available on efficacy in documented infections. An improvement in immediate and renal tolerance was obtained with equivalent daily dose regimens, but the therapeutic index does not appear to be improved. This approach cannot be recommended at present. Three lipid formulations have been developed and are now available in most countries: amB colloidal dispersion (ABCD), amB lipid complex (ABLC), and liposomal amB (AmBisome). The efficacy of ABCD on various fungal infections has been assessed in open trials, with a response rate of 49% in aspergillosis, 70% in candidiasis, and 67% in mucormycosis. In two randomized trials comparing ABCD with amB in invasive aspergillosis and in persistent febrile neutropenia, the response rates were equivalent. ABCD was less nephrotoxic. In contrast, immediate reactions to ABCD were as frequent and severe as with amB. These immediate effects are more frequent during the first infusions and lessen as treatment continues. The recommended dose is 3-4 mg/kg/day. ABLC appeared to be effective as rescue therapy in various types of invasive mycoses, with a response rate of 42% in aspergillosis, 67% in candidiasis, and 82% in fusariosis. Efficacy identical to that of amB was demonstrated in a comparative randomized trial involving patients with invasive candidiasis. General and renal tolerability is improved compared with amB. The recommended dose regimen is 5 mg/kg/day. Liposomal amB (AmBisome) is the only truly liposomal formulation. The response rates in preliminary trials were 66% in aspergillosis and 81% in candidiasis. Several comparative studies have confirmed that this formulation has similar or superior efficacy relative to amB in various fungal infections and also in the empirical treatment of febrile neutropenia. Renal and general tolerability is excellent. The optimal dosing remains unclear but is generally between 3 and 5 mg/kg/day. A double-blind trial comparing the tolerance of liposomal amB and ABLC demonstrated that both infusion-related events and nephrotoxicity were significantly lower for liposomal amB. In sum, the new lipid formulations of amB are effective in various invasive fungal infections. The three formulations exhibit reduced nephrotoxicity compared with conventional amB. Large-scale comparative clinical trials may clarify issues of relative efficacy in various forms of mycotic infections.

Molecular epidemiology and antifungal susceptibility of Cryptococcus neoformans isolates from Ugandan AIDS patients

Little is known of the antifungal susceptibility patterns and molecular epidemiology of Cryptococcus neoformans from tropical regions. We studied 164 clinical isolates of C. neofomans from 120 Ugandan AIDS patients with cryptococcal meningitis by analyzing their electrophoretic karyotypes and antifungal susceptibility profiles. Computer-assisted analysis of karyotype patterns was performed to generate dendrograms. MICs of fluconazole and flucytosine were determined by reference methods. A total of 43 distinguishable DNA types were identified among the 164 isolates. Only 30 patients (25%) were infected with their own unique strain of c. neoformans, whereas 75% of the patients shared their infecting strain with at least one other patient. Among 17 patients with more than one CSF isolate of C. neoformans, sequential isolates were identical or highly related in 12 (71%) and were different in five patients (29%). The isolates were susceptible to both fluconazole and flucytosine and there were no instances in which a stepwise increase in either fluconazole or flucytosine MICs was observed among serial isolates. These findings suggest that the epidemiology of cryptococcal disease in AIDS patients from tropical regions may be somewhat different from that observed in more temperate climates.

Detection of resistance to amphotericin B among Cryptococcus neoformans clinical isolates: performances of three different media assessed by using E-test and National Committee for Clinical Laboratory Standards M27-A methodologies

Although reliable detection of resistance in vitro is critical to the overall performance of any susceptibility testing method, the recently released National Committee for Clinical Laboratory Standards M27-A methodology for susceptibility testing of yeasts discriminates poorly between resistant and susceptible isolates of Candida spp. We have previously shown that both substitution of antibiotic medium 3 for RPMI 1640 medium in the microdilution variant of the M27-A method and use of the E-test agar diffusion methodology permit detection of amphotericin B-resistant Candida isolates. To determine the relevance of these observations to Cryptococcus neoformans, we have evaluated the performances of both the M27-A and the E-test methodologies with this yeast using three different media (RPMI 1640 medium, antibiotic medium 3, and yeast nitrogen base). As with Candida, we found that only antibiotic medium 3 permitted consistent detection of resistant isolates when testing was performed in broth by the M27-A method. When testing was performed by the E-test agar diffusion method, both RPMI 1640 medium and antibiotic medium 3 agar permitted ready detection of the resistant isolates. Reading of the results after 48 h of incubation was required for testing in broth by the M27-A method, while the MIC could be determined after either 48 or 72 h when the agar diffusion method was used.

Amphotericin-B colloidal dispersion. A review of its use against systemic fungal infections and visceral leishmaniasis

Formulation of amphotericin B with sodium cholesteryl sulphate alters the pharmacokinetic properties of the drug, particularly reducing its distribution to the kidneys. The antifungal activity in vitro of amphotericin B colloidal dispersion (ABCD) is similar to that of conventional amphotericin B (C-AmB) against true pathogenic organisms including Blastomyces, Coccidioides, Histoplasma and Paracoccidioides species and the opportunistic organisms such as Candida and Cryptococcus species. In animal models, ABCD was generally less effective than an identical dose of C-AmB, but overall was more effective because of its improved therapeutic index. Although ABCD appeared to be more effective than C-AmB in resolving infection and improving survival in patients with proven or probable invasive aspergillosis, the retrospective design of the study and the greater prevalence of neutropenia in patients treated with the conventional formulation necessitate cautious interpretation of the results. ABCD has been effective and seldom caused nephrotoxicity in patients with fungal infection who had previously failed to adequately respond or had developed renal toxicity with C-AmB. Similarly, ABCD was effective in patients with proven or suspected fungal infection after bone marrow transplantation. Preliminary results from a pilot study comparing ABCD and C-AmB in patients with neutropenia and persistent fever reported similar response rates with both formulations. ABCD is an effective treatment for visceral leishmaniasis in immunocompetent patients. In 1 study, about 12% of ABCD recipients discontinued the drug because of adverse events; infusion-related events were the most common cause of discontinuation. The renal tolerability of ABCD is better than that of C-AmB. ABCD appears to be an effective alternative to conventional amphotericin B in patients with invasive aspergillosis or visceral leishmaniasis and in those with proven or suspected systemic fungal infection who are intolerant of the conventional formulation or have pre-existing renal impairment. Preliminary data also suggest that ABCD is an alternative to C-AmB when used empirically in patients with neutropenia and fever. Nevertheless, the efficacy of ABCD compared with that of the conventional formulation has yet to be adequately demonstrated and the role of ABCD relative to that of liposomal and other lipid-based formulations has not been determined.

CONCLUSIONS

ABCD, like other lipid-based and liposomal formulations of amphotericin B, has been designed to deliver the active drug to the target site, while reducing renal toxicity. The aim of increasing the therapeutic index compared with C-AmB has been achieved.

Development of secondary resistance to fluconazole in Cryptococcus neoformans isolated from a patient with AIDS

Cryptococcus neoformans is the fifth most common opportunistic agent of infection in patients with AIDS in the USA, exceeded only by Candida species, Pneumocystis carinii, cytomegalovirus and Mycobacterium avium1, 2, 6, 10, 11. In Brazil is the sixth, exceeded by Candida species, P. carinii, Mycobacterium species, Toxoplasma gondii, and herpes simplex virus (AIDS, Boletim Epidemiológico, set/nov 96, Ministério da Saúde, Brasil). During 30 years, the treatment of C. neoformans meningitis was based on the use of amphotericin B with or without flucytosine13. Nowadays, with the immunodepression caused by human immunodeficiency virus (HIV) infection and the availability of new antifungal drugs as the triazoles, the concept related to cure and relapses of cryptococcosis has been altered7, 20. Patients are treated with amphotericin B with or without flucytosine as initial therapy, but maintenance therapy is always necessary in AIDS patients with C. neoformans infections

Molecular epidemiology of Cryptococcus neoformans in Brazil and the United States: evidence for both local genetic differences and a global clonal population structure

Little is known about the global molecular epidemiology of the human pathogenic fungus Cryptococcus neoformans. We studied 51 clinical and environmental (pigeon excreta) isolates from two cities in Brazil (Belo Horizonte and Rio de Janeiro) by analyzing their carbon assimilation patterns, electrophoretic karyotypes, restriction fragment length polymorphisms (RFLPs) with the C. neoformans repetitive element-1 (CNRE-1), and URA5 sequences. Results were compared to those previously obtained for isolates from New York City by the same DNA typing methods. Computer-assisted analysis of RFLPs and contour-clamped homogeneous electrophoresis (CHEF) patterns and URA5 sequences was performed to generate dendrograms. Some environmental and clinical isolates were found to be indistinguishable by CHEF, CNRE-1 RFLP, and URA5 sequence analyses. Similarly, some isolates from Rio de Janeiro and Belo Horizonte were indistinguishable by the three DNA typing techniques. Overall, Brazilian isolates appeared to be less heterogeneous by DNA analysis than isolates from other regions. Several Brazilian isolates were highly related to New York City isolates. Phylogenetic analysis of the sequences obtained for the Brazilian isolates and those obtained for New York City isolates was congruent with the dendrogram generated from the CNRE-1 RFLP data. In summary our results indicate (i) that the discriminatory power of the DNA typing method differs for Brazilian and New York City strains, with the order being CNRE-1 RFLP analysis > URA5 sequence analysis > CHEF analysis and CHEF analysis > URA5 sequence analysis > CNRE-1 RFLP analysis, respectively; (ii) that there are differences in local genetic diversity for Brazilian and New York City isolates; (iii) that there is additional evidence linking clinical isolates to those in pigeon excreta; and (iv) that some isolates from Brazil and New York City are closely related, consistent with the global dispersal of certain pathogenic strains.