Epidemiology, Clinical Manifestations, and Therapy of Infections Caused by Dematiaceous Fungi

The dematiaceous (brown-pigmented) fungi are a large and heterogenous group of moulds that cause a wide range of diseases including phaeohyphomycosis, chromoblastomycosis, and eumycotic mycetoma. Among the more important human pathogens are Alternaria species, Bipolaris species, Cladophialophora bantiana, Curvularia species, Exophiala species, Fonsecaea pedrosoi, Madurella species, Phialophora species, Scedosporium prolificans, Scytalidium dimidiatum, and Wangiella dermatitidis. These organisms are widespread in the environment, being found in soil, wood, and decomposing plant debris. Cutaneous, subcutaneous, and corneal infections with dematiaceous fungi occur worldwide, but are more common in tropical and subtropical climates. Infection results from traumatic implantation. Most cases occur in immunocompetent individuals. Dematiaceous moulds are also important causes of invasive sinusitis and allergic fungal sinusitis. Infection is thought to follow inhalation. Although cerebral infection is the commonest form of systemic phaeohyphomycosis, other localized deep forms of the disease, such as arthritis, and endocarditis, have been reported. Disseminated infection is uncommon, but its incidence is increasing, particularly among immunocompromised individuals. Scedosporium prolificans is the most frequent cause. A number of dematiaceous fungi are neurotropic, including Cladophialophora bantiana, Ramichloridium mackenziei, and Wangiella dermatitidis. Although cases have occurred in immunocompromised persons, cerebral phaeohyphomycosis is most common in immunocompetent individuals with no obvious risk factors. Most forms of disease caused by dematiaceous fungi require both surgical and medical treatment. Itraconazole is currently the most effective antifungal agent for chromoblastomycosis and subcutaneous phaeohyphomycosis, while ketoconazole remains useful for mycetoma. Extensive surgical debridement combined with amphotericin B treatment is recommended for chronic invasive sinusitis. Long-term treatment with itraconazole has led to improvement or remission in some patients that had failed to respond to amphotericin B. Allergic fungal sinusitis requires surgical removal of impacted mucin combined with postoperative oral corticosteroids. Antifungal treatment is not usually of benefit, but post-operative itraconazole may reduce the need for reoperation. The clinical outcome of cerebral and other deep-seated forms of phaeohyphomycosis is dismal, with long-term survival being reported only when complete surgical resection of discrete lesions is possible. The development of new antifungal agents and combination treatment may help to improve the management of these infections.

Correlation of MIC with outcome for Candida species tested against voriconazole: analysis and proposal for interpretive breakpoints

Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between the in vitro activity and outcome from both in vivo and clinical studies. Using data generated by standardized broth microdilution and disk diffusion test methods, the Antifungal Susceptibility Subcommittee of the Clinical and Laboratory Standards Institute has now proposed interpretive breakpoints for voriconazole and Candida species. The MIC distribution for voriconazole was determined using a collection of 8,702 clinical isolates. The overall MIC90 was 0.25 microg/ml and 99% of the isolates were inhibited at < or = 1 microg/ml of voriconazole. Similar results were obtained for 1,681 Candida isolates (16 species) from the phase III clinical trials. Analysis of the available data for 249 patients from six phase III voriconazole clinical trials demonstrated a statistically significant correlation (P = 0.021) between MIC and investigator end-of-treatment assessment of outcome. Consistent with parallel pharmacodynamic analyses, these data support the following MIC breakpoints for voriconazole and Candida species: susceptible (S), < or = 1 microg/ml; susceptible dose dependent (SDD), 2 microg/ml; and resistant (R), > or = 4 microg/ml. The corresponding disk test breakpoints are as follows: S, > or = 17 mm; SDD, 14 to 16 mm; and R, < or = 13 mm.

Incidence of invasive aspergillosis following hematopoietic stem cell and solid organ transplantation: interim results of a prospective multicenter surveillance program

The incidence of invasive aspergillosis was estimated among 4621 hematopoietic stem cell transplants (HSCT) and 4110 solid organ transplants (SOT) at 19 sites dispersed throughout the United States, during a 22 month period from 1 March 2001 through 31 December 2002. Cases were identified using the consensus definitions for proven and probable infection developed by the Invasive Fungal Infections Cooperative Group of the European Organization for Research and Treatment of Cancer and the Mycoses Study Group of the National Institute of Allergy and Infectious Diseases. The cumulative incidence (CI) of aspergillosis was calculated for the first episode of the infection that occurred within the specified time period after transplantation. To obtain an aggregate CI for each type of transplant, data from participating sites were weighted according to the proportion of transplants followed-up for specified time periods (four and 12 months for HSCT; six and 12 months for SOT). The aggregate CI of aspergillosis at 12 months was 0.5% after autologous HSCT, 2.3% after allogeneic HSCT from an HLA-matched related donor, 3.2% after transplantation from an HLA-mismatched related donor, and 3.9% after transplantation from an unrelated donor. The aggregate CI at 12 months was similar following myeloablative or non-myeloablative conditioning before allogeneic HSCT (3.1 vs. 3.3%). After HSCT, mortality at 3 months following diagnosis of aspergillosis ranged from 53.8% of autologous transplants to 84.6% of unrelated-donor transplants. The aggregate CI of aspergillosis at 12 months was 2.4% after lung transplantation, 0.8% after heart transplantation, 0.3% after liver transplantation, and 0.1% after kidney transplantation. After SOT, mortality at three months after diagnosis of aspergillosis ranged from 20% for lung transplants to 66.7% for heart and kidney transplants. The Aspergillus spp. associated with infections after HSCT included A. fumigatus (56%), A. flavus (18.7%), A. terreus (16%), A. niger (8%), and A. versicolor (1.3%). Those associated with infections after SOT included A. fumigatus (76.4%), A. flavus (11.8%), and A. terreus (11.8%). In conclusion, we found that invasive aspergillosis is an uncommon complication of HSCT and SOT, but one that continues to be associated with poor outcomes. Our CI figures are lower compared to those of previous reports. The reasons for this are unclear, but may be related to changes in transplantation practices, diagnostic methods, and supportive care.

Intra- and interlaboratory study of a method for testing the antifungal susceptibilities of dermatophytes

The National Committee for Clinical Laboratory Standards (NCCLS) M38-A standard for the susceptibility testing of conidium-forming filamentous fungi does not explicitly address the testing of dermatophytes. This multicenter study, involving six laboratories, investigated the MIC reproducibility of seven antifungal agents tested against 25 dermatophyte isolates (5 blinded pairs of five dermatophyte species per site for a total of 300 tests), using the method of dermatophyte testing developed at the Center for Medical Mycology, Cleveland, Ohio. The dermatophytes tested included Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton tonsurans, Epidermophyton floccosum, and Microsporum canis. Seven antifungals with activity against dermatophytes were tested, including ciclopirox, fluconazole, griseofulvin, itraconazole, posaconazole, terbinafine, and voriconazole. Interlaboratory MICs for all isolates were in 92 to 100% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 88 to 99% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Intralaboratory MICs between blinded pairs were in 97% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 96% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Data from this study support consideration of this method as an amendment to the NCCLS M38-A standard for the testing of dermatophytes.

Population-based surveillance and a case-control study of risk factors for endemic lymphocutaneous sporotrichosis in Peru

Population-based surveillance and a case-control study were conducted in Abancay, Peru, to estimate the burden of disease and to determine risk factors for sporadic lymphocutaneous sporotrichosis (LS). Laboratory records from local hospitals were reviewed for the years of 1997 and 1998, and prospective surveillance was conducted for the period of September 1998 through September 1999. A case-control study was conducted with 2 matched control subjects per case patient. The mean annual incidence was 98 cases per 100,000 persons. Children had an incidence 3 times higher than that for adults and were more likely to have LS lesions on the face and neck. Identified risk factors included owning a cat, playing in crop fields, having a dirt floor in the house, working mainly outdoors, and having a ceiling made of raw wood or conditions associated with a lower socioeconomic status. Decreased environmental exposure, such wearing protective clothing during construction activities for adults or limiting contact with cats and soil for children, and improvements in living spaces may decrease the incidence of LS.

Coccidioidomycosis in India: report of a second imported case

We describe a fatal case of imported coccidioidomycosis in India in a 22-year-old male who worked in Tucson, Arizona, approximately four years prior to his illness. The diagnosis was based on the presence of characteristic spherules with endospores in biopsy tissue of lymph nodes, bone and pus from a chronic discharging sinus in the left gluteal region and isolation of Coccidioides immitis in culture. C. immitis is one of the most infectious and virulent fungal pathogens and poses a serious occupational hazard for laboratory personnel, especially in areas where the disease is not endemic. To reduce the role of laboratory-acquired infection, all procedures that involve manipulation of cultures of C. immitis should, whenever possible, be conducted in a biological safety cabinet.

Counterpoint: invasive aspergillosis and the environment--rethinking our approach to prevention

Preventive measures are important in the control of invasive aspergillosis (IA) because diagnosis is difficult and the outcome of treatment is poor. If effective strategies are to be devised, it will be essential to have a clearer understanding of the sources and routes of transmission of Aspergillus species. Nosocomial outbreaks of IA highlight the fact that Aspergillus spores are common in the hospital environment. However, in general, such outbreaks are uncommon. Most cases of IA are sporadic in nature, and many of them are now being acquired outside of the hospital setting. Housing patients in high-energy particulate air-filtered hospital rooms helps prevent IA, but it is feasible and cost-effective only for the highest-risk groups and for limited periods. Control measures, which are designed to protect patients from exposure to spores outside the hospital, are even more difficult. Nevertheless, now that high-risk patients are spending more time outside of the hospital, the cost benefits of antifungal prophylaxis and other preventive measures require careful evaluation.

Trends in antifungal drug susceptibility of Cryptococcus neoformans isolates in the United States: 1992 to 1994 and 1996 to 1998

The antifungal drug susceptibilities of two collections of Cryptococcus neoformans isolates obtained through active laboratory-based surveillance from 1992 to 1994 (368 isolates) and 1996 to 1998 (364 isolates) were determined. The MICs of fluconazole, itraconazole, and flucytosine were determined by the National Committee for Clinical Laboratory Standards broth microdilution method; amphotericin B MICs were determined by the E-test. Our results showed that the MIC ranges, the MICs at which 50% of isolates are inhibited (MIC(50)s), and the MIC(90)s of these four antifungal agents did not change from 1992 to 1998. In addition, very small numbers of isolates showed elevated MICs suggestive of in vitro resistance. The MICs of amphotericin B were elevated (>or=2 microg/ml) for 2 isolates, and the MICs of flucytosine were elevated (>or=32 microg/ml) for 14 isolates. Among the azoles, the fluconazole MIC was elevated (>or=64 microg/ml) for 8 isolates and the itraconazole MIC (>or=1 microg/ml) was elevated for 45 isolates. Analysis of 172 serial isolates from 71 patients showed little change in the fluconazole MIC over time. For isolates from 58 patients (82% of serial cases) there was either no change or a twofold change in the fluconazole MIC. In contrast, for isolates from seven patients (12% of serial cases) the increase in the MIC was at least fourfold. For isolates from another patient there was a 32-fold decrease in the fluconazole MIC over a 1-month period. We conclude that in vitro resistance to antifungal agents remains uncommon in C. neoformans and has not significantly changed with time during the past decade.

Antifungal susceptibility testing: practical aspects and current challenges

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

Trends in mortality due to invasive mycotic diseases in the United States, 1980-1997

To determine national trends in mortality due to invasive mycoses, we analyzed National Center for Health Statistics multiple-cause-of-death record tapes for the years 1980 through 1997, with use of their specific codes in the International Classification of Diseases, Ninth Revision (ICD-9 codes 112.4-118 and 136.3). In the United States, of deaths in which an infectious disease was the underlying cause, those due to mycoses increased from the tenth most common in 1980 to the seventh most common in 1997. From 1980 through 1997, the annual number of deaths in which an invasive mycosis was listed on the death certificate (multiple-cause [MC] mortality) increased from 1557 to 6534. In addition, rates of MC mortality for the different mycoses varied markedly according to human immunodeficiency virus (HIV) status but were consistently higher among males, blacks, and persons > or =65 years of age. These data highlight the public health importance of mycotic diseases and emphasize the need for continuing surveillance.

Molecular epidemiology of Candida albicans strains isolated from the oropharynx of HIV-positive patients at successive clinic visits

Candida albicans strain diversity and fluconazole resistance were prospectively analyzed in oral strains from 29 adult human immunodeficiency virus (HIV)-positive patients followed for > 1 year who had five or more culture-positive clinic visits. Molecular typing consisted of genomic blots probed with the Ca3 repetitive element. Sixteen patients had one or more episodes of oropharyngeal candidiasis (OPC), 12 (75%) maintained the original genotype, whereas the remaining four patients had a succession of 2-3 genotypes. The original genotype, either alone or mixed with another strain or with non-C. albicans Candida spp., was recovered from oral lesions in 13 of 15 evaluable (86.7%) patients. C. dubliniensis was the infecting yeast in the remaining two patients. Different patterns of fluconazole resistance occurred in three OPC patients. One patient's infecting strain became less susceptible. A second patient was infected with a resistant genotype and a progressively more susceptible minor genotype variant. C. dubliniensis isolates from the third patient varied in susceptibility. Thirteen colonized patients who never developed OPC harbored a greater variety of C. albicans genotypes (2-6) than their infected counterparts (P = 0.35). OPC patients maintained their original endogenous C. albicans strains for prolonged periods, whether or not they demonstrated decreased in vitro susceptibility to fluconazole. The adaptation and maintenance of an endogenous C. albicans strain within its host may be linked to as yet uncharacterized factors.

Sporothrix schenckii sensitivity to voriconazole, itraconazole and amphotericin B

One hundred clinical isolates of Sporothrix schenckii were tested against voriconazole, itraconazole and amphotericin B using a modification of the NCCLS M27-A in vitro yeast susceptibility testing procedure. NCCLS M38-P for moulds was not used because yeast forms may have been present when the test isolates were incubated at 35 +/- 1 degrees C. The minimum inhibitory concentration (MIC) values were: voriconazole 0.5-8 (geometric mean titer 6.50) microg ml(-1) ; itraconazole 0.03-8 (geometric mean titer 1.56) microg ml(-1); and amphotericin B 0.25-2 (geometric mean titer 1.23) microg ml(-1). The minimum fungicidal concentration (MFC) values were: voriconazole 2-8 (geometric mean titer 7.67) microg ml(-1); itraconazole 0.125-8 (geometric mean titer 7.41) microg ml(-1); and amphotericin B 0.125-2 (geometric mean titer 1.53) microg ml(-1). Based upon MIC values, sensitivity to amphotericin B is strain-dependent. S. schenckii is more sensitive to itraconazole than voriconazole based upon a comparison of MIC geometric means, even though the MIC ranges were essentially the same.

In vitro antifungal susceptibility methods and clinical implications of antifungal resistance

As new antifungal agents are introduced for the treatment of infections caused by yeasts and filamentous fungi (moulds), it is important that reliable methods are available for the in vitro testing of both new and established agents. The ultimate goal of in vitro testing is the prediction of the clinical outcome of therapy. The use of the M27-A procedures that were developed by the US National Committee for Clinical Laboratory Standards (NCCLS) has led to increased interlaboratory agreement of minimum inhibitory concentrations (MICs) for yeasts and has facilitated the establishment of interpretive breakpoints for fluconazole and itraconazole. The clinical relevance and limitations of these breakpoints are discussed elsewhere. The focus of this paper is to review the advantages and disadvantages of the available methods for antifungal susceptibility testing of yeasts and moulds as well as the clinical implications of in vitro antifungal resistance.

Gastrointestinal basidiobolomycosis in Arizona: clinical and epidemiological characteristics and review of the literature

Gastrointestinal basidiobolomycosis (GIB) is an unusual fungal infection that is rarely reported in the medical literature. From April 1994 through May 1999, 7 cases of GIB occurred in Arizona, 4 from December 1998 through May 1999. We reviewed the clinical characteristics of the patients and conducted a case-control study to generate hypotheses about potential risk factors. All patients had histopathologic signs characteristic of basidiobolomycosis. Five patients were male (median age, 52 years; range, 37--59 years) and had a history of diabetes mellitus (in 3 patients), peptic ulcer disease (in 2), or pica (in 1). All patients underwent partial or complete surgical resection of the infected portions of their gastrointestinal tracts, and all received itraconazole postoperatively for a median of 10 months (range, 3--19 months). Potential risk factors included prior ranitidine use and longer residence in Arizona. GIB is a newly emerging infection that causes substantial morbidity and diagnostic confusion. Further studies are needed to better define its risk factors and treatment.

Use of a repetitive DNA probe to type clinical and environmental isolates of Aspergillus flavus from a cluster of cutaneous infections in a neonatal intensive care unit

Aspergillus flavus is second to A. fumigatus as a cause of invasive aspergillosis, but no standard method exists for molecular typing of strains from human sources. A repetitive DNA sequence cloned from A. flavus and subcloned into a pUC19 vector, pAF28, was used to type 18 isolates from diverse clinical, environmental, and geographic sources. The restriction fragment length polymorphisms generated with EcoRI- or PstI-digested genomic DNA and probed with digoxigenin-labeled pAF28 revealed complete concordance between patterns. Eighteen distinct fingerprints were observed. The probe was used to investigate two cases of cutaneous A. flavus infection in low-birth-weight infants in a neonatal intensive care unit (NICU). Both infants were transported by the same ambulance and crew to the NICU on the same day. A. flavus strains of the same genotype were isolated from both infants, from a roll of tape used to fasten their umbilical catheters, from a canvas bag used to store the tape in the ambulance, and from the tape tray in the ambulance isolette. These cases highlight the need to consider exposures in critically ill neonates that might occur during their transport to the NICU and for stringent infection control practices. The hybridization profiles of strains from a second cluster of invasive A. flavus infections in two pediatric hematology-oncology patients revealed a genotype common to strains from a definite case patient and a health care worker. A probable case patient was infected with a strain with a genotype different from that of the strain from the definite case patient but highly related to that of an environmental isolate. The high degree of discrimination and reproducibility obtained with the pAF28 probe underscores its utility for typing clinical and environmental isolates of A. flavus.

Quantitation of Candida albicans ergosterol content improves the correlation between in vitro antifungal susceptibility test results and in vivo outcome after fluconazole treatment in a murine model of invasive candidiasis

MIC end point determination for the most commonly prescribed azole antifungal drug, fluconazole, can be complicated by "trailing" growth of the organism during susceptibility testing by the National Committee for Clinical Laboratory Standards approved M27-A broth macrodilution method and its modified broth microdilution format. To address this problem, we previously developed the sterol quantitation method (SQM) for in vitro determination of fluconazole susceptibility, which measures cellular ergosterol content rather than growth inhibition after exposure to fluconazole. To determine if SQM MICs of fluconazole correlated better with in vivo outcome than M27-A MICs, we used a murine model of invasive candidiasis and analyzed the capacity of fluconazole to treat infections caused by C. albicans isolates which were trailers (M27-A MICs at 24 and 48 h, </=1.0 and >/=64 microg/ml, respectively; SQM MIC, </=1.0 microg/ml), as well as those which were fluconazole sensitive (M27-A and SQM MIC, </=1.0 microg/ml) and fluconazole resistant (M27-A MIC, >/=64 microg/ml; SQM MIC, 54 microg/ml). Compared with the untreated controls, fluconazole therapy increased the survival of mice infected with a sensitive isolate and both trailing isolates but did not increase the survival of mice infected with a resistant isolate. These results indicate that the SQM is more predictive of in vivo outcome than the M27-A method for isolates that give unclear MIC end points due to trailing growth in fluconazole.

In vitro activities of voriconazole, itraconazole, and amphotericin B against Blastomyces dermatitidis, Coccidioides immitis, and Histoplasma capsulatum

The in vitro activity of voriconazole was compared to those of itraconazole and amphotericin B against the mold forms of 304 isolates of three dimorphic fungi, Blastomyces dermatitidis, Coccidioides immitis, and Histoplasma capsulatum. MICs were determined by a broth microdilution adaptation of the National Committee for Clinical Laboratory Standards M27-A procedure. RPMI 1640 medium was used for tests with voriconazole and itraconazole, whereas Antibiotic Medium 3 with 2% glucose was used for amphotericin B. Minimum fungicidal concentrations (MFCs) were also determined. Amphotericin B was active against all three dimorphic fungi, with MICs at which 90% of the isolates tested are inhibited (MIC(90)s) of 0.5 to 1 microg/ml. Itraconazole had MIC(90)s of 0.06 microg/ml for H. capsulatum, 0.125 microg/ml for B. dermatitidis, and 1 microg/ml for C. immitis. The MIC(90)s of voriconazole were 0.25 microg/ml for all three fungi. Amphotericin B was fungicidal for B. dermatitidis and H. capsulatum with MFCs at which 90% of strains tested are killed (MFC(90)s) of 0.5 and 2 microg/ml, respectively. It was less active against C. immitis, with MFCs ranging from 0.5 to >16 microg/ml. Voriconazole and itraconazole were lethal for most isolates of B. dermatitidis, with MFC(50)s and MFC(90)s of 0.125 and 4 microg/ml, respectively. Both azoles were fungicidal for some isolates of H. capsulatum, with MFC(50)s of 2 and 8 microg/ml for itraconazole and voriconazole, respectively; neither had a lethal effect upon C. immitis. Our results suggest that voriconazole possesses promising activity against these important human pathogens.

Comparative evaluation of PASCO and national committee for clinical laboratory standards M27-A broth microdilution methods for antifungal drug susceptibility testing of yeasts

The PASCO antifungal susceptibility test system, developed in collaboration with a commercial company, is a broth microdilution assay which is faster and easier to use than the reference broth microdilution test performed according to the National Committee for Clinical Laboratory Standards (NCCLS) document M27-A guidelines. Advantages of the PASCO system include the system's inclusion of quality-controlled, premade antifungal panels containing 10, twofold serial dilutions of drugs and a one-step inoculation system whereby all wells are simultaneously inoculated in a single step. For the prototype panel, we chose eight antifungal agents for in vitro testing (amphotericin B, flucytosine, fluconazole, ketoconazole, itraconazole, clotrimazole, miconazole, and terconazole) and compared the results with those of the NCCLS method for testing 74 yeast isolates (14 Candida albicans, 10 Candida glabrata, 10 Candida tropicalis, 10 Candida krusei, 10 Candida dubliniensis, 10 Candida parapsilosis, and 10 Cryptococcus neoformans isolates). The overall agreements between the methods were 91% for fluconazole, 89% for amphotericin B and ketoconazole, 85% for itraconazole, 80% for flucytosine, 77% for terconazole, 66% for miconazole, and 53% for clotrimazole. In contrast to the M27-A reference method, the PASCO method classified as resistant seven itraconazole-susceptible isolates (9%), two fluconazole-susceptible isolates (3%), and three flucytosine-susceptible isolates (4%), representing 12 major errors. In addition, it classified two fluconazole-resistant isolates (3%) and one flucytosine-resistant isolate (1%) as susceptible, representing three very major errors. Overall, the agreement between the methods was greater than or equal to 80% for four of the seven species tested (C. dubliniensis, C. glabrata, C. krusei, and C. neoformans). The lowest agreement between methods was observed for miconazole and clotrimazole and for C. krusei isolates tested against terconazole. When the data for miconazole and clotrimazole were removed from the analysis, agreement was >/=80% for all seven species tested. Therefore, the PASCO method is a suitable alternative procedure for the testing of the antifungal susceptibilities of the medically important Candida spp. and C. neoformans against a range of antifungal agents with the exceptions only of miconazole and clotrimazole and of terconazole against C. krusei isolates.

Aspergillus antigen testing in bone marrow transplant recipients

AIMS

To assess the clinical usefulness of a commercial aspergillus antigen enzyme linked immunosorbent assay (ELISA) in the diagnosis of invasive aspergillosis (IA) in bone marrow transplant recipients, and to compare it with a commercial latex agglutination (LA) test.

METHODS

In total, 2026 serum samples from 104 bone marrow transplant recipients were tested. These comprised 67 sera from seven patients who had died with confirmed IA, 268 sera from nine patients who had died with suspected IA, and 1691 sera from 88 patients with no clinical, radiological, or microbiological signs of IA.

RESULTS

The ELISA was more sensitive than the LA test. All patients who were ELISA positive were also LA positive, and a positive LA result never preceded a positive ELISA. Twelve of 16 patients with confirmed or suspected IA were ELISA positive on two or more occasions, compared with 10 of 15 who were LA positive. ELISA was positive before LA in five patients (range, 2-14 days), and became positive on the same day in the remainder. Aspergillus antigen was detected by ELISA a median of 15 days before death (range, 4-233). Clinical and/or radiological evidence of IA was noted in all patients, and a positive ELISA was never the sole criterion for introduction of antifungal treatment. Two samples (one from each of two patients without IA) gave false positive results.

CONCLUSIONS

The aspergillus ELISA is a specific indicator of invasive aspergillosis if the criterion of two positive samples is required to confirm the diagnosis. However, the test is insufficiently sensitive to diagnose aspergillosis before other symptoms or signs are apparent, and hence is unlikely to lead to earlier initiation of antifungal treatment. It is therefore unsuitable for screening of asymptomatic patients at risk of invasive aspergillosis, but does have a useful role in confirming the diagnosis in symptomatic patients.

Report of the first human case of lobomycosis in the United States

We describe the first human case of lobomycosis caused by Lacazia loboi in a 42-year-old white male resident of Georgia. The patient had traveled to Venezuela 7 years earlier, where he had planned to rappel down Angel Falls in Canaima. Although he never actually rappelled the falls, he did walk under the falls at least three times, exposing himself to the high water pressures of the falls. He noticed a small pustule with surrounding erythema developing on the skin of his right chest wall. The lesion gradually increased in size and had an appearance of a keloid. For cosmetic reasons, the patient sought medical treatment to remove the lesion. After an uncomplicated excision of the lesion, the patient recovered completely. The excised tissue was fixed in formalin for pathologic examination. Tissue sections stained by hematoxylin and eosin, periodic acid-Schiff stain, and Gomori methenamine silver stain procedures showed numerous histiocytes, multinucleated giant cells, and numerous globose or subglobose, lemon-shaped cells producing multiple blastoconidia connected by narrow tube-like connectors and catenate chains of various lengths characteristic of L. loboi.

Lack of correlation of in vitro amphotericin B susceptibility testing with outcome in a murine model of Aspergillus infection

Amphotericin B has been the standard therapy for invasive aspergillosis since its introduction in 1957. It is only moderately effective. Many susceptibility tests have been used but little variation has been noted between strains. We have studied three strains of Aspergillus fumigatusand one of Aspergillus terreusin a neutropenic mouse model of invasive aspergillosis and attempted to correlate the variable efficacy in vivowith MICs generated by over 30 different susceptibility test formats. One strain of A. fumigatus(AF65) and the strain of A. terreus(AT49) were 'resistant' and the remaining two strains of A. fumigatus(AF210 and AF294) were 'susceptible' in vivo. Only AT49 had elevated MICs of amphotericin (MIC 2 mg/L) by 41 of 54 in vitrotesting systems. With each test format, including Etest, there was no distinction between MICs obtained for AF65, AF210 and AF294 (MICs 0.125-64 mg/L depending on the test). Thus despite extensive efforts we have been unable to correlate susceptible test results with in vivooutcome in A. fumigatusbut we have with A. terreus, with some test formats. This suggests that, at present, amphotericin B susceptibility testing of A. fumigatus is of limited clinical value and further work needs to be done to find testing systems that can identify the 'resistance' documented in vivo.

Candida dubliniensis fungemia: the first four cases in North America

We report the first four North American cases of Candida dubliniensis fungemia, including the first isolation of this organism from the bloodstream of an HIV-infected person. All isolates were susceptible in vitro to commonly used antifungal drugs. This report demonstrates that C. dubliniensis can cause bloodstream infection; however, the incidence of disease is not known.

A randomized controlled trial of itraconazole versus fluconazole for the prevention of fungal infections in patients with haematological malignancies. U.K. Multicentre Antifungal Prophylaxis Study Group

Fluconazole is widely used as antifungal prophylaxis but it is ineffective against Aspergillus. Itraconazole has a broader spectrum of activity but the capsules give erratic bioavailability in neutropenic patients. We compared itraconazole oral solution (which has an improved pharmacokinetic profile) with fluconazole for antifungal prophylaxis. Adults with haematological malignancies receiving chemotherapy or bone marrow transplants were randomly allocated 5 mg/kg/d itraconazole (itra) solution (288 episodes) or 100 mg fluconazole suspension (flu) (293 episodes) from before the onset of neutropenia until neutrophil recovery or suspected fungal infection. Outcomes were assessed by independent reviewers unaware of the prophylaxis allocation. More proven systemic fungal infections occurred in flu (Aspergillus four, Candida tropicalis one, C. krusei one) than itra (C. albicans one) and more of these were fatal (four versus nil). This difference reached statistical significance when first study episodes were considered separately (six flu versus nil itra, P = 0.03). Significantly more deaths of presumed fungal origin occurred in flu than itra (seven versus nil, P = 0.024). There were significantly more cases of proven aspergillosis in flu than itra (six versus nil, P = 0.038, 5/6 cases were fatal) if those occurring outside the study period are included. Significantly more patients receiving flu required amphotericin B (58 v 39, P = 0.043) but this may have been affected by the fact that the study was not blinded. There were 11 proven mucosal candidal infections in flu and four in itra. Itraconazole solution and fluconazole provide effective prophylaxis against Candida but itraconazole affords greater protection against fatal aspergillosis.

Comparison of E-test and broth microdilution methods for antifungal drug susceptibility testing of molds

We compared the E test with a broth microdilution method, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 90 isolates of pathogenic molds (10 Absidia corymbifera, 10 Aspergillus flavus, 10 Aspergillus fumigatus, 10 Aspergillus niger, 10 Aspergillus terreus, 10 Exophiala dermatitidis, 10 Fusarium solani, 10 Scedosporium apiospermum, 5 Scedosporium prolificans, and 5 Scopulariopsis brevicaulis). Overall, there was 71% agreement between the results of the two methods for amphotericin B (E-test MICs within +/-2 log2 dilutions of broth microdilution MICs) and 88% agreement with the results for itraconazole. The overall levels of agreement (within +/-2 log2 dilutions) were >/=80% for 5 of the 10 species tested against amphotericin B and 8 of the 10 species tested against itraconazole. The best agreement between the results was seen with A. fumigatus and A. terreus (100% of results for both agents within +/-2 log2 dilutions). The poorest agreement was seen with S. apiospermum, S. prolificans, and S. brevicaulis tested against amphotericin B (20% of results within +/-2 log2 dilutions). In every instance, this low level of agreement was due to isolates for which the broth microdilution MICs were low but for which the E-test MICs were much higher. The E test appears to be a suitable alternative procedure for testing the susceptibility of Aspergillus spp. and some other molds to amphotericin B or itraconazole.

Bioassays for itraconazole blood levels: an interlaboratory collaborative study

Duplicate bioassays for itraconazole and hydroxy-itraconazole were run with 30 serum samples in five laboratories, each using a different method. Both itraconazole and hydroxy-itraconazole were used as standards. Despite quantitative variations, the results of the bioassays correlated sufficiently to indicate the relative level of antifungal activity in the test samples.

In vitro activity of Syn-2869, a novel triazole agent, against emerging and less common mold pathogens

The in vitro activity of Syn-2869 was compared with that of amphotericin B and itraconazole. MICs for 100 isolates of pathogenic molds belonging to 12 species were determined by a broth microdilution adaptation of the method recommended by the National Committee for Clinical Laboratory Standards. Syn-2869 and itraconazole showed comparable, good activity against the dematiaceous molds Cladophialophora bantiana, Cladophialophora carrionii, Exophiala dermatitidis, Fonsecaea pedrosoi, Phialophora parasitica, and Ramichloridium mackenziei. Neither of the azole agents was active against the hyaline molds Fusarium solani, Scedosporium prolificans, and Scopulariopsis brevicaulis, but both were more active than amphotericin B against Scedosporium apiospermum. The MICs of the three agents were comparable for the mucoraceous mold Absidia corymbifera, but Syn-2869 appeared to be the least active against the dimorphic mold Sporothrix schenckii. Our results suggest that Syn-2869 could be effective against a range of mold infections in humans.

Comparison of the API Candida system with the AUXACOLOR system for identification of common yeast pathogens

Two commercial systems for the identification of yeasts were evaluated by using 159 clinical isolates that had also been identified by conventional biochemical and morphological methods. The API Candida system correctly identified 146 isolates (91.8%), and the AUXACOLOR system correctly identified 145 isolates (91.2%). However, of the 146 isolates identified by the API Candida system, 23 required supplemental biochemical tests or morphological assessment to obtain the correct identification. The AUXACOLOR system gave no identification in 13 cases (8.2%), while the API Candida system gave an unreadable profile in only one case. Incorrect identifications were more common with the API Candida system (12 isolates; 7.5%) than with the AUXACOLOR system (1 isolate; 0.6%).

Infections in adults undergoing unrelated donor bone marrow transplantation

This study retrospectively reviews infections over a 7-year period in 60 consecutive adults (median age 25 years) undergoing their first unrelated donor bone marrow transplant (UD-BMT). T-cell depletion was employed in 93%. More than half the patients had one or more severe, potentially life-threatening, infections. There was a high incidence of invasive fungal infections (Aspergillus 17, Candida four), despite the use of itraconazole or amphotericin prophylaxis. Ten Aspergillus infections occurred beyond 100 d. Two patients (11%) with invasive aspergillosis survived. Clustering of infections was noted, with invasive fungal infections significantly associated with bacteraemias (OR 3.73, P=0.06) and multiple viral infections (OR 4.25, P=0.05). There were 21 severe viral infections in 16 patients, with CMV disease occurring in four patients only; viral pneumonitis was predominantly due to 'community respiratory' viruses. Most early bacteraemias (68%) were due to Gram-positive organisms. The majority of episodes of Gram-negative sepsis were caused by non-fastidious non-fermentative bacteria, such as Pseudomonas spp. and Acinetobacter spp., historically regarded as organisms of low pathogenicity. In patients with successful engraftment and minimal graft-versus-host disease, late infections suggestive of continued immune dysfunction (shingles, recurrent lower respiratory infections, Salmonella enteritis and extensive warts) were common.

Imported mycoses in Europe

This article reviews the clinical manifestations, diagnosis and management of some of the more important systemic infections that are now being imported into Europe. It also considers the risks some of the causal organisms pose to European laboratory workers, many of whom are unfamiliar with the precautions that should be taken when handling these pathogens.

In-vitro activity of voriconazole, itraconazole and amphotericin B against filamentous fungi

The in-vitro fungistatic and fungicidal activities of voriconazole were compared with those of itraconazole and amphotericin B. MICs for 110 isolates belonging to 11 species of filamentous fungi were determined by a broth microdilution adaptation of the method recommended by the National Committee for Clinical Laboratory Standards. Minimum lethal concentrations (MLCs) of the three antifungal agents were also determined. The MIC ranges of the three compounds were comparable for Aspergillus flavus, Aspergillus fumigatus, Cladophialophora bantiana and Exophiala dermatitidis. Voriconazole and itraconazole were more active than amphotericin B against Fonsecaea pedrosoi, but the two azole agents were less active against Sporothrix schenckii. Voriconazole was more active than itraconazole or amphotericin B against Scedosporium apiospermum, but less active than the other two agents against two mucoraceous moulds, Absidia corymbifera and Rhizopus arrhizus. Voriconazole and amphotericin B were more active than itraconazole against Fusarium solani. With the exception of S. apiospermum, all the moulds tested had MLC50 values of < or =2 mg/L and MLC90 values of < or =4 mg/L against amphotericin B. Voriconazole and itraconazole showed fungicidal effects against five of the 1 1 moulds tested (A. flavus, A. fumigatus, C. bantiana, E. dermatitidis and F. pedrosoi) with MLC90 values of < or =2 mg/L. In addition, voriconazole was fungicidal for Phialophora parasitica. Our results suggest that voriconazole could be effective against a wide range of mould infections in humans.

Comparison of a new commercial colorimetric microdilution method with a standard method for in-vitro susceptibility testing of Candida spp. and Cryptococcus neoformans

The Sensititre Yeast One method (AccuMed International Ltd, East Grinstead, UK) is a microplate-based procedure that incorporates an oxidation-reduction indicator, Alamar Blue, for the in-vitro testing of five antifungal agents (amphotericin B, fluconazole, itraconazole, ketoconazole and flucytosine). We compared this colorimetric method with a standard broth microdilution test, performed according to US National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in-vitro susceptibilities of 180 isolates of Candida spp. (50 Candida albicans, 50 Candida glabrata, ten Candida kefyr, 20 Candida krusei, ten Candida lusitaniae, 20 Candida parapsilosis and 20 Candida tropicalis) and 20 isolates of Cryptococcus neoformans. The overall agreement between the results of the two methods (colorimetric MICs within +/- two log2 dilutions of standard MICs) were 99% for amphotericin B, 96.5% for flucytosine, 93% for itraconazole, 91.5% for fluconazole and 85.5% for ketoconazole. The overall levels of agreement between the two methods were > or = 94% for six of the eight species tested, the exceptions being C. neoformans and C. tropicalis where the overall agreement was 89% and 80% respectively. The poorest agreement between the results for individual agents was seen with C. tropicalis and the three azole agents (60-75% of colorimetric MICs within +/- two log2 dilutions of standard MICs), and C. neoformans for ketoconazole (50%). The Yeast One method appears to be a suitable alternative procedure for routine antifungal susceptibility testing of Candida spp. and C. neoformans.

Multi-centre evaluation of the Etest method for antifungal drug susceptibility testing of Candida spp. and Cryptococcus neoformans. BSAC Working Party on Antifungal Chemotherapy

Ten laboratories tested 18 isolates of Candida spp. and two of Cryptococcus neoformans against amphotericin B, flucytosine, fluconazole and itraconazole on two occasions by the Etest method. Two individuals read each set of results. Of the 18 isolates of Candida spp., five were duplicated, but the participants were not told this. In 40 of the 60 drug-organism combinations studied, at least 80% of the Etest MICs fell within a five-concentration range corresponding to the modal MIC +/- 1 log2 dilution. In five combinations, >50% of the Etest MICs fell outside this five-concentration range. In 17 (85%) of the 20 drug-organism combinations tested in duplicate, at least 80% of the paired Etest results fell within two concentrations of each other (corresponding to one log2 dilution). Overall, 88.5% of the paired Etest results for amphotericin B agreed to within two concentrations, as did 94% of results for flucytosine, 92% for fluconazole and 79% for itraconazole. The broth microdilution MICs of the four antifungal agents for the 15 isolates were measured on five occasions in the Mycology Reference Laboratory, Bristol. In each case, the results fell within a three log2 concentration range. In 24 (40%) of the 60 drug-organism combinations tested, at least 80% of the Etest results fell within the broth microdilution test MIC range, but 27 (45%) showed <50% exact agreement. In 33 (73%) of 45 drug-organism combinations involving flucytosine, fluconazole or itraconazole, at least 80% of the Etest results fell within the same class (susceptible, resistant, or susceptible dependent upon dose) as the broth microdilution results. With fluconazole, the Etest method misclassified three susceptible isolates of Candida spp. as resistant in 1.5-15% of tests. With itraconazole, the Etest misclassified seven susceptible isolates of Candida spp. as resistant in 5-62.5% of tests. The Etest also misclassified both C. neoformans isolates as resistant to flucytosine, fluconazole and itraconazole in 7.5-65% of tests. Our results suggest that the Etest is suitable for routine use with Candida spp. and amphotericin B or flucytosine. It is less reliable for the azoles, and isolates that appear to demonstrate acquired resistance should be retested with well-established reference methods.

In-vitro susceptibility of Cryptococcus neoformans isolates to fluconazole and itraconazole

The in-vitro susceptibilities of 143 isolates of Cryptococcus neoformans, collected from British patients between 1994 and 1996, to fluconazole and itraconazole were compared with those of 36 isolates collected between 1971 and 1985, 41 isolates collected between 1986 and 1989, and 43 Ugandan isolates collected in 1996. Testing was done with a broth microdilution method in YNB medium supplemented with glucose, incubation at 30 degrees C for 72 h, and an endpoint of 50% inhibition. The results showed that the MIC ranges, MIC50s and MIC90s of fluconazole and itraconazole for C. neoformans isolates from the UK have remained unchanged despite the recent widespread use of triazoles for long-term maintenance of patients with AIDS-associated cryptococcal meningitis. The MIC ranges, MIC50s and MIC90s of the 43 isolates from untreated Ugandan patients with AIDS were similar to those of the British isolates. Examination of our records for 1994-96 revealed six cases in which a four-fold or greater rise in the MIC of fluconazole was associated with relapsed cryptococcal meningitis.

Fungal infections in neutropenia: current problems and chemotherapeutic control

Invasive fungal infection is a significant problem in neutropenic individuals. The commonest causes of infection are Aspergillus and Candida spp., although a growing number of other organisms (including species of Fusarium and Trichosporon) have been implicated. The clinical manifestations of these infections are described here, and diagnostic problems are discussed. The role of lipid-based formulations of amphotericin B, and of the triazole compounds, itraconazole and fluconazole, in the treatment and prevention of fungal infection is discussed.

Comparison of in vitro antifungal activities of free and liposome-encapsulated nystatin with those of four amphotericin B formulations

The in vitro activity of a multilamellar liposomal formulation of nystatin (Nyotran) was compared with those of free nystatin and four pharmaceutical preparations of amphotericin B. MICs for 200 isolates of two Aspergillus spp., seven Candida spp., and Cryptococcus neoformans were determined by a broth microdilution adaptation of the method recommended by the National Committee for Clinical Laboratory Standards. Minimum lethal concentrations (MLCs) of the six antifungal preparations were also determined. Both nystatin formulations possessed fungistatic and fungicidal activities against the 10 species tested. Liposomal nystatin appeared to be as active as free nystatin, with MICs and MLCs that were similar to, or lower than, those of the latter. Neither formulation of nystatin was as active as amphotericin B deoxycholate (Fungizone) or amphotericin B lipid complex (Abelcet), but both were more effective than liposomal amphotericin B (AmBisome). Our results suggest that further evaluation of liposomal nystatin is justified.

Molecular epidemiological study of Aspergillus fumigatus in a bone marrow transplantation unit by PCR amplification of ribosomal intergenic spacer sequences

We have developed a PCR-based method for the subspecific discrimination of Aspergillus fumigatus types by using two primers designed to amplify the intergenic spacer regions between ribosomal DNA transcription units. The method permitted the reproducible discrimination of 11 distinct DNA types among a total of 119 isolates of A. fumigatus collected from patients and from the environment of a bone marrow transplantation (BMT) unit over a three-year period. Ten DNA types of A. fumigatus were isolated from patients in the BMT unit; eight of these types were also found in the hospital environment, and six of these were present in the unit itself. Thirteen BMT patients developed infection with one of three DNA types some months after these had first been found in the environment of the unit. In other instances, the same DNA types of A. fumigatus were isolated from BMT patients that were later recovered from the environment of the unit. Several DNA types of A. fumigatus were found in the hospital environment over an 18-month period. Molecular typing of multiple isolates of A. fumigatus, obtained from postmortem tissue samples, showed that one patient was infected with a single DNA type, but two others had up to three different DNA types. Our findings suggest that A. fumigatus infection in BMT recipients may be nosocomial in origin and underline the need for careful environmental monitoring of units in which high-risk patients are housed.

Comparative evaluation of FUNGITEST and broth microdilution methods for antifungal drug susceptibility testing of Candida species and Cryptococcus neoformans

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates of Candida spp. (50 C. albicans, 50 C. glabrata, 10 C. kefyr, 20 C. krusei, 10 C. lusitaniae, 20 C. parapsilosis, and 20 C. tropicalis isolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception of C. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.

Itraconazole pulse: an overview of current use

Traditionally, fungal infections of the fingernails and toenails have been difficult to treat. Itraconazole is an orally administered triazole antifungal agent with a wide spectrum of activity against dermatophytes, yeasts and some moulds. Pulse therapy with itraconazole is an effective new treatment which offers the shortest treatment course with the least total number of treatment days and lowest total dose.

Rhizopus microsporus in wooden tongue depressors: a major threat or minor inconvenience?

The investigation and management of an apparent outbreak of Rhizopus spp. in a London paediatric referral centre between September 1995 and April 1996 is described. The organism was identified in microbiological surveillance samples from 23 patients nursed in four hospital areas. Investigations revealed the presence of the organism in spatulae from all ward areas investigated and from closed boxed containers held in the central hospital stores obtained from a new supplier. In contrast, culture of spatulae from the initial supplier failed to yield any fungal isolates. The incident was reported to the Medical Device Agency (MDA), the Central Public Health Laboratory Service (CPHLS) and the Birmingham PHLS. A statement was prepared for the weekly Communicable Disease Report and a hazard warning issued by the MDA. The spatulae were withdrawn from use and the contract with the original supplier was re-established. This incident resulted in contamination of samples only and no patient involvement. It highlights the problems which may follow use of equipment for unintended purposes and the need for good manufacturing practice guidelines to be applied to non-sterile equipment used in direct patient care.

Nail infection caused by Onychocola canadensis: report of the first four British cases

Onychocola canadensis is a recently recognized cause of human nail infection. We present the first four cases of onychomycosis caused by this organism among patients resident in the UK.

Molecular biological characterization of an azole-resistant Candida glabrata isolate

Two isolates of Candida glabrata, one susceptible and one resistant to azole antifungals, were previously shown to differ in quantity and activity of the cytochrome P-450 14alpha-lanosterol demethylase which is the target for azole antifungals. The resistant isolate also had a lower intracellular level of fluconazole, but not of ketoconazole or itraconazole, than the susceptible isolate. In the present study a 3.7-fold increase in the copy number of the CYP51 gene, encoding the 14alpha-lanosterol demethylase, was found. The amount of CYP51 mRNA transcript in the resistant isolate was eight times greater than it was in the susceptible isolate. Hybridization experiments on chromosomal blots indicated that this increase in copy number was due to duplication of the entire chromosome containing the CYP51 gene. The phenotypic instability of the resistant isolate was demonstrated genotypically: a gradual loss of the duplicated chromosome was seen in successive subcultures of the isolate in fluconazole-free medium and correlated with reversion to susceptibility. The greater abundance of the amplified chromosome induced pronounced differences in the protein patterns of the susceptible and revertant isolates versus that of the resistant isolate, as demonstrated by two-dimensional gel electrophoresis (2D-GE). Densitometry of the 2D-GE product indicated upregulation of at least 25 proteins and downregulation of at least 76 proteins in the resistant isolate.