[Disk diffusion method for fluconazole susceptibility testing of Candida spp. isolates]

In order to standardize and evaluate a disk diffusion method with visual reading to detect in vitro fluconazole susceptibility of yeast, 1193 clinical isolates were tested. These included 584 Candida albicans, 196 Candida parapsilosis, 200 Candida tropicalis, 113 Candida glabrata, 50 Candida krusei and 50 Candida spp. and other opportunistic yeasts. The disks were manufactured in the INEI-ANLIS "Dr. Carlos G. Malbrán. The disk diffusion method results were compared to MIC results obtained by the reference CLSI M27-A2 broth microdilution method modified by EUCAST. The interpretative breakpoints for in vitro susceptibility testing of fluconazole were established at: zone diameter > or =16 mm for MIC < or =8 microg/ml (susceptible isolates), between 9 and 15 mm for MIC = 16-32 microg/ml (susceptible dose-dependent isolates), and < or =8 mm for MIC > or =64 microg/ml (resistant isolates). Overall agreement between the two methods was 94.7%, with 0.2% very major errors, and 0.3% major errors. Inter - and intralaboratory agreement was good. The disk diffusion method for drug susceptibility testing of Candida spp. isolates is inexpensive, reliable and reproducible. However, when the inhibition zone diameter is < or =15 mm, it is advisable to test the isolate by the reference microdilution method.

[Multicenter study of fungemia due to yeasts in Argentina]

The incidence of candidemia has increased approximately 500% in high-complexity hospitals. A change in the spectrum of Candida infections due to species other than Candida albicans has also been detected. Between April 1999 and April 2000 a multicenter study was performed in order to determine the species distribution associated to candidemias in Argentina and the susceptibility profile of the isolates to the current antifungal drugs. Thirty six institutions have participated. All the 265 yeast strains isolated from blood cultures were identified by morphological, physiological, and biochemical tests. The antifungal susceptibility testing of isolates was performed based on the reference NCCLS procedure. The distribution of species was: Candida albicans (40.75%), Candida parapsilosis (28.67%), Candida tropicalis (15.84%), Candida famata (3.77%), Cryptococcus neoformans (3.77%), Candida glabrata (2.64%), and others (4.53%). Most of the isolates were susceptible to amphotericin B, fluconazole and itraconazole. Mortality associated to the fungemia by yeasts episodes (n=265) was 30%, lower than results previously determined (33-54%). The mortality percentage in patients who received antifungal therapy versus patients without treatment was 26.3% and 47%, respectively.

[Immunodiagnosis of endemic mycoses and bronchopulmonary aspergillosis: a multicenter study in Argentina]

In order to contribute to the knowledge of the relative frequency of chronic fungal diseases and assess the performance of diagnostic laboratories in Argentina, a multicenter study was performed with the participation of 25 medical centers located in 12 different provinces and Buenos Aires City. Between 04-01-2000 and 03-30-2001, 965 serum specimens from patients clinically suspected of having histoplasmosis (HP), paracoccidioidomycosis (PCM), coccidioidomycosis (CM) or aspergilosis were analyzed. Agar immunodiffusion tests (IDD) were done locally. All positive and 35% of negative sera were retested in the reference center. Results of laboratories of origin showed 98.8% concordance with those of reference center. Antibodies against any of the etiological agents were detected in 120 specimens from 98 patients. Endemic mycoses (HP, PCM and CM) were diagnosed in 70 patients (71.4%) and aspergilosis in 28 (28.6%). The frequencies of the different mycoses in decreasing order were PCM 47 patients (47.9%), aspergilosis 28 patients (28.6%), HP 13 patients (13.3%) and CM 10 patients (10.2%). The study was carried out on a voluntary basis and some areas of the country were not represented. However, the frequencies were in range with the expected rates in the population under study.

Antimicrobial activity of aqueous extracts and of berberine isolated from Berberis heterophylla

The antimicrobial activity of Berberis heterophylla leaves, stems and root aqueous extracts was studied in vitro on Gram-positive and Gram-negative bacteria and fungi. The in vitro antifungal activity of berberine isolated from the same source against different Candida species was also investigated.

[Buttock mass and malignant sciatic nerve tumor]

Malignant peripheral nerve sheath tumors (MPNST) are rare. We report a case of a MPNST of the proximal sciatic nerve in the thigh, unassociated with pre-existing type 1 neurofibromatosis or history of radiation therapy. A 71-year-old man had a 6 month history of constant, severe, burning pain affecting the sole of the left foot. One month after the onset, the pain radiated to the left calf, posterior aspect of the thigh and buttock, and distal leg weakness followed. Three months prior to admission, the patient developed a large and painful mass in the buttock, that occupied the entire left gluteal region on examination. There was severe weakness of ankle and toe dorsiflexion and plantarflexion, decreased sensation on the lateral and posterior aspect of the left leg as well as on the dorsal and plantar surfaces of the foot, and absent ankle jerk. EMG showed denervation and motor unit loss in the short head of biceps femoris and muscles supplied by tibial and peroneal nerves on the left side. Magnetic resonance imaging revealed a 10-cm enhancing mass of the left sciatic nerve from the upper thigh to the greater sciatic notch. In surgery, a large MPNST with a high Ki67 labeling index (> 60 %) was subtotally removed from the sciatic nerve, and adjuvant radiation therapy was administered. In the ensuing months the tumor invaded the entire pelvic region. A high sciatic malignant tumor can present with a rapidly growing buttock mass and unilateral, neuropathic foot pain imitating the tarsal tunnel syndrome.

[Malassezia species isolated from skin diseases in a care center in the city of Buenos Aires, Argentina]

The epidemiology of Malassezia genus is poorly understood; geographical and population factors might have influence on the species distribution. The aim of this work was to determine the frequency of Malassezia species involved in skin diseases in a diagnostic center at Buenos Aires City. From 02/01/1999 to 10/31/2001, 456 skin specimens from 447 patients diagnosed as pityriasis versicolor, seborrheic dermatitis, foliculitis and atopic dermatitis, were analyzed by microscopic examination and culture. Malassezia spp was evidenced in 255 skin samples (55.9%) by microscopic analysis but it could be recovered from only 99 (38.8%) specimens. Malassezia species were isolated from 10 (3.9%) scarring lesions that were negative by microscopy. Among 109 isolates, M. sympodialis (58.7%) was the most frequent, followed by M. globosa and M. furfur (18.3% and 9.2%). Unique isolates (0.9%) of M. obtusa, M. slooffiae and M. restricta were recovered. Eleven isolates (10.1%) could not be identified because they had lost viability in the culture. This is the first study on Malassezia species associated to skin diseases in Argentina; further screening including other geographic regions of the country is necessary in order to confirm these results.

[1st environmental isolation of Cryptococcus neoformans var. gattii in Argentina]

Two strains of C. neoformans var. gattii serotype B were isolated from a park in Buenos Aires city, Argentina. Samples were collected in spring, rubbing with swabs on the inner hollow of Eucalyptus spp. and other trees, which were not identified at the collection moment. Samples were swabbed directly onto cafeic acid with antibiotic agar, then incubated at 28 degrees C and observed daily for a week. Isolates were recovered from cafeic acid medium showing characteristic colonies of the species that allowed differentiation from other microorganisms of the sample. Identification was performed using carbohydrate fermentation, assimilation of nitrogen and carbon sources, and urease and phenoloxidase detection. Strain variety was determined with canavanine-glicine-bromotimol blue agar medium (CGB). Genotypic characterization using AP-PCR with (GACA)4 aleatory primer showed that both band profiles could be differentiated by only one band. These two strains were isolated from tree species different from Eucalyptus spp. These isolates from natural sources demonstrate that C. neoformans var. gattii efosts in Buenos Aires city environment and that it is not necessarily associated with Eucalyptus spp. The presence of C. neoformansvar. gattii in the environment, detected for the first time in Argentina, may explain its sporadic association with human infections in the local population.

[Distribution of Cryptococcus neoformans serotypes associated with human infections in Argentina]

C. neoformans (Cn) causes severe meningitis in immunocompromised patients, particularly those with AIDS. Little is known about Cn serotypes associated with human infections in Argentina due to the lack of antisera availability. The aim of this study was to produce these antisera, to serotype the Argentinean clinical isolates of Cn received at our laboratory from 1984 to 2001 and to evaluate the agreement of these results with the variety differentiation obtained with Canavanine-Glycine-Bromothymol Blue agar (CGB) medium. We studied 123 isolates recovered from first episodes of cryptococcosis from HIV-infected patients (85), non HIV-infected patients (6) and from other non specified patients (32). Of the isolates, 89% (110/123) were serotype A, 4% (5/123) corresponded to serotype D, 3% (3/129) were serotype AD, 3 isolates were untypable and 2 corresponded to serotype B. All the serotyped isolates agreed with the variety determined by CGB medium. These results indicate that, in our country, most cryptococcal infections in patients with AIDS are associated with serotype A (77/85), which agrees with international studies. In patients with other immunosuppressions, this serotype may be also predominant, although a low number of isolates were tested (4/6). Recovery of Cn serotype B in these clinical isolates suggests that studying the variety and their serotypes might be important to detect a probable epidemiological alteration.

[Electrophoretic karyotypes and genomic DNA restriction fragment analysis: their usefulness as tools in the epidemiological study of Candid parapsilosis]

During the past decades, several studies have reported an increase in the incidence of nosocomial candidosis. In a prospective study, performed at the Departamento de Micología, INEI, ANLIS Dr. C. G. Malbrán and the Servicio de Neonatología and Microbiología, Hospital de Niños Sor María Ludovica, from October 1995 to December 1996, 167 patients with candidosis were detected. Candida species isolated were C. albicans (53.1%), C. parapsilosis (26.5%) and C. tropicalis (14.8%). The aim of this work was to characterize the clinical C. parapsilosis isolates from pediatric patients hospitalized in two neonatal intensive care units from the same hospital and to evaluate the usefulness of electrophoretic karyotype (EK) and restriction endonuclease analysis of genomic DNA (REAG) using a low frequency digestion enzyme. EK of all isolates disclosed 12 banding patterns and REAG with endonuclease Sfi I showed only 5 groups. However, isolates from the control group could not be separated from the clinical isolates. The isolates within each dendogram group for EK or REAG were apparently unrelated. Our results show that EK yields better results than REAG, but that it falls short of the desired discrimination, which suggests that these techniques do not seem to be useful for studying nosocomial C. parapsilosis outbreaks.

[Vaginal candidiasis: etiology and sensitivity profile to antifungal agents in clinical use]

Candida vaginitis is one of the most frequent infection of the female genital tract with a high incidence. Approximately 75% of sexually active women suffer at least one episode of Candida vaginitis and 10% of them have recurrent episodes. Pregnancy, diabetes mellitus and antibiotic treatment are the most common predisposing factors, C. albicans is the etiologic agent most frequently found. The widespread reports of fluconazole resistance in Candida species and the selection of non Candida albicans prompted the study of species distribution of vulvovaginal candidiasis and their in vitro susceptibility against current antifungal agents. A total of 314 women with vaginal infection were studied. Yeasts were isolated from 104 patients with vulvovaginal candidiasis. The following species were identified: C. albicans 87.5%, C. glabrata 8.6% and 3.9% included C. krusei, C. famata, C. tropicalis and S. cerevisiae. The minimal inhibitory concentration (MIC) was determined for nystatin, isoconazole, fluconazole and ketoconazole, using a broth microdilution method based on NCCLS procedure. Although most of the isolates were C. albicans, the high percentage of C. glabrata recovered suggests the need to identify the yeasts isolated. Fluconazole resistant C. albicans were isolated in 13.46% of the cases. Thus, further studies are required to correlate the possible role of these strains in recurrent vulvovaginal candidiasis.

[Molecular characterization of autochthonous clinical isolates of Histoplasma capsulatum var. capsulatum using RAPD-PCR]

The aim of our work was to determine the genotypic relatedness among H. capsulatum isolates from Argentinian patients with or without AIDS and isolates from other sources and geographic origins. We analyzed band patterns of 16 isolates obtained by RAPD-PCR, 11 Argentinian clinical isolates (8 from patients with AIDS and 3 from patients without AIDS), 2 strains from the CDC, 2 isolates from Mexico and one isolate from Uruguay. With the band patterns obtained, we built a dendrogram, which showed 3 major groups. Group I contained 2 isolates from Mexico, group II 1 strain from CDC and group III included 13 isolates, and was divided into 4 subgroups. Subgroup IIIa contained 2 isolates from patients with and without AIDS. Subgroup IIIb included isolates from patients without AIDS from Chaco. Subgroup IIIc contained 7 isolates from Argentina (from Buenos Aires province) and the Uruguayan isolate (6 isolates from patients with AIDS). Subgroup IIId included only one strain from CDC. All the Argentinian and the Uruguayan isolates went into group III, subgroups IIIa, IIIb and IIIc. This is a preliminary study; however, a relatedness of the RAPD-PCR band patterns and the geographic origin was observed. Although there might be a probable association between immunocompromised patients with AIDS and infective capability of some H. capsulatum isolates, further studies with a larger number of isolates from different sources and geographic origins are necessary to confirm these results.

Maxillary sinusitis caused by Actinomucor elegans

We report the first case of maxillary sinusitis caused by Actinomucor elegans in an 11-year-old patient. Histopathological and mycological examinations of surgical maxillary sinuses samples showed coenocytic hyphae characteristic of mucoraceous fungi. The fungi recovered had stolons and rhizoids, nonapophyseal and globose sporangia, and whorled branched sporangiophores and was identified as A. elegans. After surgical cleaning and chemotherapy with amphotericin B administered intravenously and by irrigation, the patient became asymptomatic and the mycological study results were negative.

[Nosocomial transmission of Candida albicans in newborn infants]

Candida spp. colonization in neonates occurs due to vertical or horizontal transmission. Preliminary studies determined that Candida albicans is the principal agent of these infections. In order to establish nosocomial transmission, 26 Candida albicans strains isolated from patients with candidosis hospitalized during a 18-month period in 2 neonatal intensive care units (NICU) from a pediatric hospital were studied. Fourteen isolates from patients and health care workers, involved in possible outbreaks of an intensive care unit (UCI) and a NICU from another pediatric hospital were also studied. All Candida albicans strains were genotyped by Southern blot hybridization with 27A. Isolates for outbreak confirmation were also hybridized with another specific Candida albicans probe, Ca3. Hybridization patterns demonstrated horizontal transmission in all the units studied. In a NICU, transmission among 4 patients during a 10-month period could be established and in the other NICU, 3 cases of transmission among 2 patients each were demonstrated in periods of 2 to 20 days. The outbreak studies showed the same strain isolated from 2 nurses and from one patient at the NICU and at the ICU identical strains were found in 3 patients. In this study, hybridization with Ca3 in addition to 27A probe did not increase discrimination power among isolates. Genotypic analysis allows, not only, determination of transmission and persistence of strains during prolonged periods or in sporadic outbreaks, but also facilitates necessary epidemiological decisions for optimizing nosocomial fungal infection control measures.

[In vitro infection by different strains of Paracoccidioides brasiliensis]

We analyzed the in vitro infection process by P. brasiliensis and the effect of extracellular factor(s) produced on monolayers of mammalian Vero cell lines. The yeast phase of four strains was studied: B339 (avirulent or slightly virulent), U, (intermediate virulence), 93745 and 63265 (both highly virulent). Strains of intermediate and high virulence had higher adherence at first contact (about 16%). Strain B339 had a slower adherence at first contact (8%) than the others during the same period. The production of extracellular proteases, soluble extracellular factor(s) and extracellular antigen gP43 showed no correlation with the in vitro physiopathogenicity of the analyzed strains. We demonstrate that the Vero model presented in this paper is a suitable system to study infection and virulence in vitro. We are currently assessing its usefulness as a tool for the analysis of the interaction between pathogen, host and antifungal agents.

Timed-kill curves for Cryptococcus neoformans isolated from patients with AIDS

Infection with Cryptococcus neoformans is an increasing problem in immunocompromised patients, particularly those with acquired immune deficiency syndrome (AIDS). Amphotericin B and fluconazole are currently acceptable therapies for cryptococcal meningitis; however, their effects remain suboptimal and recurrence or treatment failure is still a problem. Antifungal susceptibility testing may be an important tool for guiding therapy, but for C. neoformans, a reliable method is still not available. This retrospective study evaluated minimal inhibitory concentration (MIC) for amphotericin B and fluconazole, and minimal fungicidal concentration (MFC) and timed-kill curves for amphotericin B against 16 clinical isolates of C. neoformans obtained from AIDS patients with cryptococcal meningitis. No correlation between clinical outcome and MIC was observed for amphotericin B. In selected cases, the MFC seemed to be a better predictor of outcome than MIC. In this study, amphotericin B timed-kill curves appeared to show a correlation with clinical outcome of the 16 patients with AIDS-associated cryptococcal meningitis. These in vitro tests must be further evaluated in prospective studies to confirm their potential usefulness for guiding cryptococcal meningitis therapy.

In vitro susceptibility studies of Cryptococcus neoformans isolated from patients with no clinical response to amphotericin B therapy

The in vitro activities of three antifungal drugs alone and in combination were evaluated against five isolates of Cryptococcus neoformans using time-kill curves (TKC). The isolates were from AIDS patients who had either died or had failed to show a clinical response during amphotericin B (AMB) treatment. AMB, fluconazole (FCZ) and flucytosine (5FC), and combinations of the drugs (AMB plus 5FC, AMB plus rifampicin (RIF) and FCZ plus 5FC), were evaluated. With all five isolates AMB did not show fungicidal activity; instead, a persistent or tolerant effect was observed. Combinations of AMB plus 5FC and AMB plus RIF showed a clear synergic effect, except for one isolate tested with AMB plus RIF. In contrast, the FCZ plus 5FC combination did not inhibit growth of any isolate.

Influence of shaking on antifungal susceptibility testing of Cryptococcus neoformans: a comparison of the NCCLS standard M27A medium, buffered yeast nitrogen base, and RPMI-2% glucose

Cryptococcus neoformans is a nonfermentative yeast that requires oxygen for growth. The shaking of culture media achieves good oxygenation, promoting the growth of cryptococci. In this study, three test media (RPMI 1640, RPMI 1640-2% glucose, and buffered yeast nitrogen base ¿BYNB) recommended in the National Committee for Clinical Laboratory Standards M27A standard were examined. Growth abilities and minimum inhibitory concentrations (MICs) in microplates incubated at 35 degrees C for 48 h were determined. The results indicated that shaking and an inoculum size of 10(5) CFU/ml yielded optimal growth of this yeast. Compared to RPMI 1640, supplementation of RPMI 1640 with 2% glucose did not significantly improve growth of C. neoformans and resulted in an 8.7-h delay of exponential growth. Cryptococcal growth in RPMI 1640 at 24 h was notably better than that in RPMI-2% glucose, although by 48 h the growths were comparable. The MIC range of amphotericin B observed for the C. neoformans strains grown in RPMI 1640 with or without glucose was too narrow to allow the separation of susceptible and resistant strains based on clinical outcome. The widest ranges of MICs of flucytosine and fluconazole were obtained with BYNB. This work demonstrates the need for a new antifungal susceptibility test for C. neoformans.

[Multicenter study of superficial mycoses in Argentina. EMMS Group]

Dermatomycoses are an important sanitary problem. Our country counts with partial epidemiological data only referred to a few geographical areas. The aim of our work was to perform a multicenter study with the participation of 15 medical centers located at the Capital City and in 11 Provinces of Argentina with different socioeconomical and cultural characteristics. Between October and December 1998, 851 ambulatory patients of both sexes (58% female, 42% male) with lesions compatible with mycoses in skin, nails or scalp were studied. Only 51.6% of the patients had mycoses confirmed by direct microscopic examination and/ or culture. Dermatophytes caused 69.3% of the diagnosticated infections, yeast 12.2% and Malassezia furfur 13.3%. Agents of dermatomycoses most frequently isolated were T. rubrum (52.7%), T. mentagrophytes (19.2%) and M. canis (14.2%). C. albicans was the predominant causative agent of yeast infections (44.4%). In children below 11 years old, the most frequent infections were tinea capitis 55.4% (M. canis 60%, T. tonsurans and M. gypseum 8.3%) and tinea corporis 20% (M. canis 46%, T. mentagrophytes 30%). The most frequent localizations in adult were toenail and feet (63%) (T. rubrum 47.3% and 45.7%, T. mentagrophytes 9.5% and 23.4%, respectively), fingernail 15.6% (C. albicans 25% and T. rubrum 8.3%) and trunk and extremities 12.2% (M. furfur 57.5% and T. mentagrophytes 14.9%). Direct examination allowed the diagnosis of 94.66% of all positive samples and 91.74% of the cases with positive isolation.

[Multicenter study on nosocomial candidiasis in the Republic of Argentina]

A multicenter study was performed between April and September 1998 with the participation of 12 medical centers located in 8 different provinces and in the capital city of Argentina. The aim of this study was to determine the species distribution and the antifungal susceptibility profile of isolates causing nosocomial fungal infections. All the fungal isolates obtained were sent to the Mycology Department for reference identification and antifungal susceptibility testing. Eighty-nine isolates were received from different clinical specimens. The distribution of species obtained was C. albicans (50.6%), C. tropicalis (22.5%), C. parapsilosis (20.2%), C. krusei (3.4%), C. glabrata (2.2%) and Debaryomyces hansenii (1.1%). Most of the isolates (85/88) had MICs for amphotericin B < or = 1 microgram/ml, C. krusei showed resistance to fluconazole but was dose dependent susceptible to itraconazole, C. glabrata (2/2) were resistant against both drugs, most of the isolates of C. albicans, C. tropicalis and C. parapsilosis were susceptible to these triazole drugs. These data showed a different distribution of Candida species compared with results obtained in other countries. The low frequency of appearance of C. krusei and C. glabrata in our country suggests a reduced selective pressure by triazoles.

[In vitro sensitivity of Paracoccidioides brasiliensis to systemically used antifungal agents]

In 1992, the NCCLS proposed a broth macrodilution method for determining the in vitro susceptibility of yeast. However, for dimorphic fungi no standardised method is available. The aim of our study was to evaluate the reference broth macrodilution method with isolates of Paracoccidioides brasiliensis. The in vitro susceptibility of two ATCC strains (32069 and 36324) and nine clinical isolates were determined against serial dilutions of amphotericin B (AMB), ketoconazole (KTZ), and itraconazole (ITZ) from 0.02 to 20 mg/l and fluconazole (FCZ) from 0.1 to 100 mg/l. The inoculum used was 0.5 x 10(4)-2.5 x 10(5) CFU/ml, employing the yeast phase in order to obtain homogeneous growth. The test was incubated with agitation in a rotating shaker at 35 degrees C, and 7 days was the optimal time for MIC final reading. Average MIC50/MIC90 (mg/l) for the eleven isolates tested were the following: AMB: < 0.02/0.16, FCZ: 1.6/6.2, KTZ: 0.08/0.31, ITZ: 0.31/1.3. One clinical isolate showed high MIC for azole drugs (KTZ: 1.3 mg/ml, FCZ: 100 mg/l and ITZ 5 mg/l). Although further studies are necessary to evaluate the usefulness of this methodology for P. brasiliensis, the latter may be clinically useful to predict the development of resistance.

[Specific fungal antisera production in rabbits]

A method for fungic antisera production against Aspergillus fumigatus, Histoplasma capsulatum, Paracoccidioides brasiliensis and Coccidioides immitis in rabbits was evaluated. Intradermic via and antigen in the dilution used for routine tests (UD) were employed to produce positive control serum for immunodiffusion test in agar gel. A. fumigatus, H. capsulatum and C. immitis antigens were prepared as described in CDC's Procedure Manual, P. brasiliensis antigen was prepared as previously described by Pires de Camargo. All rabbits produced antibodies against the different specific antigens in the primary response peak and after each booster. The titer obtained in secondary response was similar or smaller than the primary response in all cases. However, bands of similar quality and intensity were obtained by immunoprecipitation in agar gel tests. Although the antibody titers proved to be similar, higher or lower concentration of antigen used in the primary immunization produced fewer and smeared bands, respectively. This effect was evaluated in A. fumigatus only. Specific antisera production with this method proved to be easy and yielded high quality antisera. The major advantages of this method are: a) reduced number of inoculations, b) fast and simple standardisation of the antigen needed, c) equally useful for all the fungal species used so far. Therefore we strongly recommend this method.

[Candida dubliniensis: 1st isolation in Argentina]

We report the first isolation of Candida dubliniensis in Argentina. This strain was isolated from an oral lesion of an adult patient with AIDS during one recurrent episode of a previously treated oropharingeal candidosis. Phenotypic and genotypic characteristics coincided with those described by Sullivan et al., who was the first to study this new species.

Widespread geographic distribution of oral Candida dubliniensis strains in human immunodeficiency virus-infected individuals

Candida dubliniensis is a recently identified chlamydospore-positive yeast species associated with oral candidiasis in human immunodeficiency virus (HIV)-infected (HIV+) patients and is closely related to Candida albicans. Several recent reports have described atypical oral Candida isolates with phenotypic and genetic properties similar to those of C. dubliniensis. In this study 10 atypical chlamydospore-positive oral isolates from HIV+ patients in Switzerland, the United Kingdom, and Argentina and 1 isolate from an HIV-negative Irish subject were compared to reference strains of C. albicans and Candida stellatoidea and reference strains of C. dubliniensis recovered from Irish and Australian HIV+ individuals. All 11 isolates were phenotypically and genetically similar to and phylogenetically identical to C. dubliniensis. These findings demonstrate that the geographical distribution of C. dubliniensis is widespread, and it is likely that it is a significant constituent of the normal oral flora with the potential to cause oral candidiasis, particularly in immunocompromised patients.

[Yeast infections: causative agents and their antifungal resistance in hospitalized pediatric patients and HIV-positive adults]

Candidiasis has increased its frequency over the last decade, particularly among hospitalized patients where it is accompanied with high rates of mortality, and in patients with AIDS who are predisposed to oropharyngeal or esophageal candidiasis. The aim of this study was to determine the frequency of appearance of different yeast species and the resistance profile to current antifungal drugs in hospitalized pediatric patients and adult HIV patients from 5 institutions of Buenos Aires City and suburbs, and La Plata City, during the period 1993-1995, in order to obtain local and updated information. Candida albicans was the etiologic agent recovered in 87% of the 214 HIV positive patients with oropharyngeal candidosis, and in 50% of the 209 hospitalized pediatric patients. In the latter group 28% of these infections were due to Candida parapsilosis and 18% to Candida tropicalis, but only 2% and 4% of oral candidosis were caused by these organisms. Detection of Malassezia furfur and Hansenula anomala, responsible of systemic infections, and Trichosporon beigelii, isolated from a burn patient, were considered remarkable since these organisms appear to be emerging pathogens. Azole resistant species as Candida krusei and C. glabrata were mostly recovered from HIV positive patients, exposed to fluconazole treatment. A very low number of amfotericin B "resistant" yeasts (n = 9) were observed in both groups. However, resistance to azole drugs, particularly to fluconazole, was found in pediatric patients (13%) and in HIV infected adults (34%).

A rapid urease test for presumptive identification of Cryptococcus neoformans

A rapid method to evidence urease activity is described. Urea hydrolysis and consequent production ammonia are detected by a chemical reaction producing a blue phenol compound (indophenol blue). Three hundred and three yeast were tested. Out of 107 urease-positive organisms detected by Christensen's Urea Agar Test (CUAT) 102 were positive by our method. No false negatives were observed by this method when testing 87 Cryptococcus strains. Ths practical screening test for presumptive identification of Cryptococcus neoformans is simple, unaffected by pH changes and requires 15 minutes to be performed.