Multicenter comparison of the ISO standard 20776-1 and the serial 2-fold dilution procedures to dilute hydrophilic and hydrophobic antifungal agents for susceptibility testing

A multicenter study was conducted to assess the accuracy of the ISO standard 20776-1 and the serial 2-fold dilution procedures for antifungal susceptibility testing. Fluconazole trays can be accurately prepared by following ISO and serial dilution schemes. However, itraconazole trays showed a significant lack of reproducibility that was independent of which method was followed.

Development of azole resistance in Aspergillus fumigatus during azole therapy associated with change in virulence

Four sequential Aspergillus fumigatus isolates from a patient with chronic granulomatous disease (CGD) eventually failing azole-echinocandin combination therapy were investigated. The first two isolates (1 and 2) were susceptible to antifungal azoles, but increased itraconazole, voriconazole and posaconazole MICs were found for the last two isolates (3 and 4). Microsatellite typing showed that the 4 isolates were isogenic, suggesting that resistance had been acquired during azole treatment of the patient. An immunocompromised mouse model confirmed that the in vitro resistance corresponded with treatment failure. Mice challenged with the resistant isolate 4 failed to respond to posaconazole therapy, while those infected by susceptible isolate 2 responded. Posaconazole-anidulafungin combination therapy was effective in mice challenged with isolate 4. No mutations were found in the Cyp51A gene of the four isolates. However, expression experiments of the Cyp51A showed that the expression was increased in the resistant isolates, compared to the azole-susceptible isolates. The microscopic morphology of the four isolates was similar, but a clear alteration in radial growth and a significantly reduced growth rate of the resistant isolates on solid and in broth medium was observed compared to isolates 1 and 2 and to unrelated wild-type controls. In the mouse model the virulence of isolates 3 and 4 was reduced compared to the susceptible ones and to wild-type controls. For the first time, the acquisition of azole resistance despite azole-echinocandin combination therapy is described in a CGD patient and the resistance demonstrated to be directly associated with significant change of virulence.

Molecular screening for Candida orthopsilosis and Candida metapsilosis among Danish Candida parapsilosis group blood culture isolates: proposal of a new RFLP profile for differentiation

Candida orthopsilosis and Candida metapsilosis are recently described species phenotypically indistinguishable from Candida parapsilosis . We evaluated phenotyping and molecular methods for the detection of these species among 79 unique blood culture isolates of the C. parapsilosis group obtained during the years 2004-2008. The isolates were screened by PCR amplification of the secondary alcohol dehydrogenase-encoding gene ( SADH) followed by digestion with the restriction enzyme Ban I, using C. parapsilosis ATCC 22019, C. orthopsilosis ATCC 96139 and C. metapsilosis ATCC 96144 as controls. Isolates with RFLP patterns distinct from C. parapsilosis were characterized by sequence analysis of the ITS1-ITS2, 26S rRNA (D1/D2) and SADH regions. Restriction patterns for the 3 species with each of 610 restriction enzymes were predicted in silico using 12 available sequences. By PCR-RFLP of the SADH gene alone, four isolates (5.1 %) had a pattern identical to the C. orthopsilosis reference strain. Sequence analysis of SADH and ITS (internal transcribed spacer) regions identified two of these isolates as C. metapsilosis. These results were confirmed by creating a phylogenetic tree based on concatenated sequences of SADH, ITS and 26S rRNA gene sequence regions. Optimal differentiation between C. parapsilosis, C. metapsilosis and C. orthopsilosis was predicted using digestion with NlaIII, producing discriminatory band sizes of: 131 and 505 bp; 74, 288 and 348 bp; and 131, 217 and 288 bp, respectively. This was confirmed using the reference strains and 79 clinical isolates. In conclusion, reliable discrimination was obtained by PCR-RFLP profile analysis of the SADH gene after digestion with NlaIII but not with BanI. C. metapsilosis and C. orthopsilosis are involved in a small but significant number of invasive infections in Denmark.

Echinocandin susceptibility testing of Candida species: comparison of EUCAST EDef 7.1, CLSI M27-A3, Etest, disk diffusion, and agar dilution methods with RPMI and isosensitest media

This study compared nine susceptibility testing methods and 12 endpoints for anidulafungin, caspofungin, and micafungin with the same collection of blinded FKS hot spot mutant (n = 29) and wild-type isolates (n = 94). The susceptibility tests included EUCAST Edef 7.1, agar dilution, Etest, and disk diffusion with RPMI-1640 plus 2% glucose (2G) and IsoSensitest-2G media and CLSI M27A-3. Microdilution plates were read after 24 and 48 h. The following test parameters were evaluated: fks hot spot mutants overlapping the wild-type distribution, distance between the two populations, number of very major errors (VMEs; fks mutants misclassified as susceptible), and major errors (MEs; wild-type isolates classified as resistant) using a wild-type-upper-limit value (WT-UL) (two twofold-dilutions higher than the MIC(50)) as the susceptibility breakpoint. The methods with the lowest number of errors (given as VMEs/MEs) across the three echinocandins were CLSI (12%/1%), agar dilution with RPMI-2G medium (14%/0%), and Etest with RPMI-2G medium (8%/3%). The fewest errors overall were observed for anidulafungin (4%/1% for EUCAST, 4%/3% for CLSI, and 3%/9% for Etest with RPMI-2G). For micafungin, VME rates of 10 to 71% were observed. For caspofungin, agar dilution with either medium was superior (VMEs/MEs of 0%/1%), while CLSI, EUCAST with IsoSensitest-2G medium, and Etest were less optimal (VMEs of 7%, 10%, and 10%, respectively). Applying the CLSI breakpoint (S Collapse

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MESH Headings

• Anidulafungin
• Antifungal Agents/pharmacology
• Candida/drug effects
• Candida/genetics
• Candidiasis/microbiology
• Caspofungin
• Culture Media
• Echinocandins/pharmacology
• Indicator Dilution Techniques
• Lipopeptides/pharmacology
• Micafungin
• Microbial Sensitivity Tests/methods
• Microbial Sensitivity Tests/standards
• Reference Standards

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Grants

• R01 AI069397 NIAID NIH HHS
• AI069397 NIAID NIH HHS

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Invasive fungal infections in the paediatric and neonatal population: diagnostics and management issues

Invasive fungal infections in children appear to have increased over the past few decades. Especially neonates and children with primary and secondary immunodeficiencies are at risk. Candida and Aspergillus spp. are the most commonly isolated organisms. In addition, Malassezia may cause systemic infections in newborns and zygomycosis is important because of its rising incidence and high case fatality rate. Timely diagnosis and initiation of appropriate antifungal therapy is imperative for improving outcomes. However, traditional techniques are time-consuming and representative sample material, using invasive procedures, may be difficult to obtain in the paediatric setting. This review provides an overview of the advances in detection and rapid species identification, with a focus on issues relevant in these settings. Subsequently, the current antifungal treatment options for neonates and children are discussed in light of the antifungal spectrum of the available agents and the specific pharmacokinetic properties in different age groups. Although a multitude of newer antifungal compounds have become available within the last decade, further studies are necessary to clearly establish the role for each of these agents among neonates and children.

[Blastocystis--an enigmatic parasite]

Blastocystis can be isolated from roughly 25% of patients suspected of intestinal parasitosis. At least ten subtypes (STs) have been isolated from humans and animals, and recent data demonstrate that the pathogenicity of the parasite is subtype-dependent. For instance, ST1 and ST7 are more prevalent among patients with symptoms than healthy individuals, whereas ST3 predominates among healthy carriers. The article sums up basic aspects of the parasite and gives an introduction to new data and points of criticism of previous studies seeking to unravel the pathogenicity of the parasite.

Disseminated Penicillium marneffei Sepsis in a HIV-positive Thai Woman in Denmark

We report the first case of disseminated Penicillium marneffei infection, in a 32-y-old HIV positive Thai woman, in Denmark. Untreated it is a life-threatening infection. Therefore it is extremely important to consider P. marneffei in patients who are immunocompromized and who have been travelling to Southeast Asia or China.

Diagnostics of fungal infections in the Nordic countries: We still need to improve!

A Nordic External Quality Assessment programme in medical mycology was established in 2005. In order to monitor not 'best practice' but the level of routine diagnostics, specimens were designed to resemble clinical samples and laboratories were asked to handle the samples like routine samples. Five simulated clinical samples were distributed to 59 participating Nordic laboratories of clinical microbiology. The specimens contained the following microorganisms: 1) Candida glabrata and C. albicans in a ratio of 1:20; 2) Cryptococcus neoformans; 3) Aspergillus fumigatus, C. albicans and Enterobacter cloacae; 4) C. tropicalis, Klebsiella pneumonia and Enterococcus faecium; 5) None. 66% of the laboratories failed to detect the C. glabrata isolate in sample no. 1. 34% of the laboratories reporting susceptibility results incorrectly reported the Cryptococcus neoformans isolate as fluconazole susceptible. 24% of the laboratories failed to detect Aspergillus fumigatus in specimen no. 3 despite the accompanying clinical information notifying that it was a BAL sample from a neutropenic patient in an ICU. In conclusion, this distribution of simulated clinical samples illustrates that the traditional quality assessment programmes may give a false sense of satisfactory performance, that mycological diagnosis is difficult, and that there is a need of further improvement and attention.

Semi-national surveillance of fungaemia in Denmark 2004-2006: increasing incidence of fungaemia and numbers of isolates with reduced azole susceptibility

A semi-national laboratory-based surveillance programme for fungaemia was initiated in 2003 that now covers c. 3.5 million inhabitants (64%) of the Danish population. In total, 1089 episodes of fungaemia were recorded during 2004-2006, corresponding to an annual incidence of 10.4/100 000 inhabitants. The annual number of episodes increased by 17% during the study period. Candida spp. accounted for 98% of the fungal pathogens. Although Candida albicans remained predominant, the proportion of C. albicans decreased from 66.1% in 2004 to 53.8% in 2006 (p <0.01), and varied considerably among participating departments, e.g., from 51.1% at a university hospital in Copenhagen to 67.6% in North Jutland County. Candida glabrata ranked second, and increased in proportion from 16.7% to 22.7% (p 0.04). Candida krusei was isolated rarely (4.1%), but the proportion doubled during the study period from 3.2% to 6.4% (p 0.06). MIC distributions of amphotericin B and caspofungin were in close agreement with the patterns predicted by species identification; however, decreased susceptibility to voriconazole, defined as an MIC of >1 mg/L, was detected in one (2.5%) C. glabrata isolate in 2004 and in 12 (14.0%) isolates in 2006 (p 0.03). Overall, the proportion of isolates with decreased susceptibility to fluconazole exceeded 30% in 2006. The incidence of fungaemia in Denmark was three-fold higher than that reported from other Nordic countries and is increasing. Decreased susceptibility to fluconazole is frequent, and a new trend towards C. glabrata isolates with elevated voriconazole MICs was observed.

Multicentre determination of quality control strains and quality control ranges for antifungal susceptibility testing of yeasts and filamentous fungi using the methods of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antimicrobial Susceptibility Testing (AFST-EUCAST)

A multicentre study involving seven laboratories was performed using techniques recommended by the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antimicrobial Susceptibility Testing (AFST-EUCAST) to evaluate and propose quality control ranges and strains for susceptibility testing of fermentative yeasts and filamentous fungi. Participating laboratories tested the susceptibilities of a panel of 12 encoded isolates to amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole and posaconazole. In total, 15 lots of assay medium were tested, with one lot being common to all laboratories, and 18 144 MIC values were determined. Intra- and inter-laboratory agreements and intra-class correlation coefficients (ICCs) of the results for each drug/strain/lot combination were calculated. An average value of 85% agreement was selected for validation purposes. The average percentage of intra-laboratory agreement was 90-95%, with ICC values of 0.90-0.95 (p <0.01). Inter-laboratory reproducibility was also high, with 92% agreement and an ICC of 0.97 (p <0.01). The reproducibility was somewhat better with the common lot of assay medium (96% agreement) than with the different lots (91% agreement), but this difference was not significant. Two isolates that showed trailing growth had agreement percentages below the 85% limit selected for validation purposes and were therefore excluded from the panel of quality control strains. The recommended EUCAST methodologies were found to be highly reproducible and reliable for susceptibility testing of yeasts and filamentous fungi. Ten isolates are proposed for use as quality control strains with these EUCAST procedures.

The prevalence of Dientamoeba fragilis in patients with suspected enteroparasitic disease in a metropolitan area in Denmark

The prevalence of Dientamoeba fragilis in patients from a metropolitan area in Denmark was determined by examination of paired stool samples using two techniques: a formol ethyl-acetate concentration technique with unpreserved faeces and a permanent staining technique on faeces preserved with sodium acetate-acetic acid-formalin (SAF). Using the SAF permanent staining technique and the formol ethyl-acetate concentration technique, 25% and 15% of the specimens, respectively, were parasite-positive. D. fragilis was detected in 12 of the 103 patients, only two of whom harboured other recognised pathogenic parasites. Overall, D. fragilis had a remarkably high prevalence in the metropolitan area of Denmark investigated.

In vivo efficacy and pharmacokinetics of voriconazole in an animal model of dermatophytosis

The standard treatment for tinea capitis caused by Microsporum species for many years has been oral griseofulvin, which is no longer universally marketed. Voriconazole has been demonstrated to inhibit growth of Microsporum canis in vitro. We evaluated the efficacy and tissue pharmacokinetics of oral voriconazole in a guinea pig model of dermatophytosis. Guinea pigs (n = 16) were inoculated with M. canis conidia on razed skin. Voriconazole was dosed orally at 20 mg/kg/day for 12 days (days 3 to 14). The guinea pigs were scored clinically (redness and lesion severity) and mycologically (microscopy and culture) until day 17. Voriconazole concentrations were measured day 14 in blood, skin biopsy specimens, and interstitial fluid obtained by microdialysis in selected animals. Clinically, the voriconazole-treated animals had significantly less redness and lower lesion scores than untreated animals from days 7 and 10, respectively (P < 0.05). Skin scrapings from seven of eight animals in the voriconazole-treated group were microscopy and culture negative in contrast to zero of eight animals from the untreated group at day 14. The colony counts per specimen were significantly higher in samples from untreated animals (mean colony count of 28) than in the voriconazole-treated animals (<1 in the voriconazole group [P < 0.0001]). The voriconazole concentration in microdialysate (unbound) ranged from 0.9 to 2.0 microg/ml and in the skin biopsy specimens total from 9.1 to 35.9 microg/g. In conclusion, orally administered voriconazole leads to skin concentrations greater than the necessary MICs for Microsporum and was shown to be highly efficacious in an animal model of dermatophytosis. Voriconazole may be a future alternative for treatment of tinea capitis in humans.

Five-hour diagnosis of dermatophyte nail infections with specific detection of Trichophyton rubrum

A rapid two-step DNA extraction method and a multiplex PCR for the detection of dermatophytes in general and Trichophyton rubrum specifically were developed and evaluated with DNA extracted from pure cultures and from clinically diseased nails. DNA from the following dermatophytes was used: Epidermophyton floccosum, Microsporum audouinii, Microsporum canis, Microsporum gypseum, Microsporum nanum, Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton schoenleinii, Trichophyton soudanense, Trichophyton terrestre, Trichophyton tonsurans, Trichophyton verrucosum, and Trichophyton violaceum. Human DNA and DNA from the following nondermatophyte fungi were included as controls: Alternaria, Aspergillus niger, Candida albicans, Candida glabrata, Candida krusei, Malassezia furfur, Saccharomyces cerevisiae, and Scopulariopsis brevicaulis. A total of 118 nail samples received for routine microscopy and culture for dermatophytes were subsequently tested by the two PCRs separately and in a multiplex format. Using DNA extracted from pure cultures and the pan-dermatophyte PCR, the T. rubrum-specific PCR sequentially and in a multiplex format correctly detected all dermatophytes and additionally correctly identified T. rubrum. Comparison of the traditional diagnostic evaluation (microscopy and culture) of nail samples with PCR on DNA directly extracted from the nails showed excellent agreement between PCR and microscopy, but the number of samples with dermatophyte species identification was increased considerably from 22.9% to 41.5%, mainly due to the identification of T. rubrum by PCR in microscopy-positive but culture-negative samples. In conclusion, this 5-hour diagnostic test was shown to increase not only the speed but also the sensitivity of investigation for nail dermatophytosis.

Acute pulmonary aspergillosis in immunocompetent subjects after exposure to bark chippings

We describe 2 cases of immunocompetent males with acute community-acquired invasive pulmonary aspergillosis developing shortly after spreading bark chippings. One patient with a fatal outcome was initially diagnosed as allergic alveolitis rather than infection and received steroid treatment illustrating the obvious challenges in the differential diagnosis between these disease entities.

DETECTION OF BLASTOCYSTIS HOMINIS IN UNPRESERVED STOOL SPECIMENS BY USING POLYMERASE CHAIN REACTION

Blastocystis hominis is a common enteric parasite of worldwide distribution. Its pathogenetic potential has not yet been established, although numerous case reports suggest that B. hominis may cause the development of various gastrointestinal symptoms and disorders. The detection of the parasite in stool specimens is conventionally done by microscopy of direct smears, fecal concentrates, or permanently stained smears; however, morphology-based diagnosis is problematic. The aim of this study was to develop and evaluate a polymerase chain reaction (PCR) technique for the direct detection of B. hominis in human stool samples. Primers were based on small subunit ribosomal DNA and able to detect > or =32 parasites/200 mg stool artificially spiked with cultured B. hominis. In the evaluation of 43 clinical specimens, the PCR was tested against the formol ethyl acetate concentration technique (FECT) and a culture technique, proving 100% test specificity and a significantly higher sensitivity than the FECT. The PCR method is recommended for screening clinical specimens for B. hominis infection and for use in prevalence studies.

Amphotericin B and Caspofungin Resistance in Candida glabrata Isolates Recovered from a Critically Ill Patient

BACKGROUND

Consecutive Candida glabrata isolates recovered from a patient in an intensive care unit were resistant to amphotericin B (minimum inhibitory concentration, up to 32 mu g/mL; determined by Etest [AB Biodisk]). Analyses at the national reference laboratory showed that some isolates were also resistant to azoles and caspofungin. In this study, 4 isolates were studied thoroughly using susceptibility assays and a mouse model and to determine clonality.

METHODS

Different broth microdilution tests, Etests, and time-kill studies for antifungals were performed in different media. Three of the 4 isolates were examined in an in vivo experiment, in which mice were challenged intravenously with 1 of 3 isolates and treated daily with amphotericin B, caspofungin, or saline. For the clonality studies, arbitrarily primed polymerase chain reaction (PCR) was performed with the 4 isolates, 8 isolates obtained from nonrelated patients, and a reference strain.

RESULTS

The murine model indicated that 1 isolate was resistant to amphotericin B, 1 had intermediate susceptibility, and 1 was fully susceptible. Two of the 3 isolates were resistant to caspofungin. Microdilution methods did not reliably differentiate between amphotericin B-susceptible and -resistant isolates. All assays identified caspofungin-susceptible and -resistant isolates. Arbitrarily primed PCR showed that the 4 isolates probably were of clonal origin.

CONCLUSIONS

We have documented the emergence of amphotericin B-resistant and caspofungin-resistant C. glabrata isolates during treatment of a critically ill liver transplant recipient. Only the Etest predicted amphotericin B resistance in the isolates. We recommend that important fungal strains recovered from patients who are receiving antifungal therapy should be tested for susceptibility to the antifungal drug used, because resistance can be present initially or may occur during treatment.

Four cases of Candida albicans infections with isolates developing pink colonies on CHROMagar Candida plates

Candida albicans, the most commonly isolated yeast species, is typically identified by its green colony-colour on CHROMagar Candida plates. We here report four cases of Candida albicans infections, in which the initial identification was non-albicans isolates due to a clear pink colour of the colonies on CHROMagar Candida plates. However, classical phenotypic criteria, biochemical assimilation pattern and molecular characterisation identified all four isolates as C. albicans isolates.

Seminational surveillance of fungemia in Denmark: notably high rates of fungemia and numbers of isolates with reduced azole susceptibility

The aim of this study was to present the first set of comprehensive data on fungemia in Denmark including the distribution of species and range of susceptibility to major antifungal compounds based on a seminational surveillance study initiated in 2003. The catchment area of the participating hospitals had a population of 2.8 million, or 53% of the Danish population. A total of 303 episodes of fungemia were registered (annual rate, 11 of 100,000 people or 0.49 of 1,000 hospital discharges). Candida species accounted for 97.4% of the fungal pathogens. C. albicans was the predominant species (63%), but the proportion varied from 57% to 72% among participating departments of clinical microbiology. C. glabrata was the second most frequent species (20%; range, 8% to 32%). C. krusei was a rare isolate (3%) and occurred only at two of the participating hospitals. Retrospective data retrieved from the Danish laboratory systems documented a continuous increase of candidemia cases since the early 1990s. For the 272 susceptibility-tested isolates, MICs of amphotericin B and caspofungin were within the limits expected for the species or genus. However, decreased azole susceptibility, defined as a fluconazole MIC of >8 microg/ml and/or itraconazole MIC of >0.125 microg/ml, was detected for 11 Candida isolates that were neither C. glabrata nor C. krusei. Including intrinsically resistant fungi, we detected decreased susceptibility to fluconazole and/or itraconazole in 87 (32%) current Danish bloodstream fungal isolates. We showed a continuous increase of fungemia in Denmark and an annual rate in 2003 to 2004 higher than in most other countries. The proportion of bloodstream fungal isolates with reduced susceptibility to fluconazole and/or itraconazole was also notably high.