Biomedical subjects
Publications and source records attributed to F Fanti.
Cladophialophora bantiana is an uncommon fungus related to the black yeasts which causes, if untreated, mostly fatal cerebral infections in immunosuppressed and competent patients. We report a case of a patient who survived a recurrent cerebral abscess caused by C. bantiana despite delayed and apparently inappropriate therapy.
Susceptibility of Mycobacterium bovis strains to antituberculous drugs (isoniazid and rifampin) was detected by radiometric BACTEC 460TB system. M.bovis strains were isolated from tissue samples showing tuberculous lesions collected at an abbattoir from cattle belonging to 47 tuberculosis outbreaks occurring in Northern Italy in 1995-1999. Forty-six out of 61 strains (75.4%) resulted susceptible to both isoniazid and rifampin. Thirteen strains (21.3%) were resistant to isoniazid only. No strains showed resistance to rifampin only. Two strains (3.3%) resulted resistant to both drugs, showing antituberculous multidrug-resistance. Given the compulsory eradication program of bovine tuberculosis by elimination of infected animals and the ban on antituberculous drug treatments in animals, detection of resistant M. bovis strains appears of great interest.
Onychocola canadensis is a non-dermatophytic mould that has been associated with onychomycosis particularly in temperate climates. Until now, O. canadensis has been isolated from patients in Canada (14 cases), New Zealand (three), France (nine), UK (four) and Spain (two). We describe the first Italian case of onychomycosis caused by this fungus.
Fluconazole susceptibility among 800 clinical Candida isolates (60% C. albicans) and two control strains (C. krusei ATCC 6258 and C. parapsilosis ATCC 22019) was tested with the NCCLS M27-A method (gold standard) and six commercial products (Candifast, disk, Etest, Fungitest, Integral System Yeasts, and Sensititre YeastOne). Results were classified as susceptible, susceptible-dose dependent, or resistant using M27-A breakpoints or, for Fungitest, Integral System Yeasts, and Candifast, as susceptible, intermediate, or resistant, according to the manufacturers' instructions. Concordance with NCCLS M27-A results was analyzed with the chi(2) test. Intra- and interlaboratory reproducibility was also evaluated. NCCLS M27-A (90.1%), Etest (93.1%), Sensititre YeastOne (93.1%), disk (96.7%), Fungitest (92.6%), Integral System Yeasts (40.6%), and Candifast (6.0%) classified the indicated percentages of C. albicans isolates as susceptible. Among non-C. albicans strains, the percentages of susceptible isolates were as follows: NCCLS M27-A, 74.0%; Etest, 83.8%; Sensititre YeastOne, 64.1%; disk, 60.6%; Fungitest, 76.6%; Integral System Yeasts, 28.3%; and Candifast, 27.4%. All methods except Candifast and Integral System Yeasts showed good agreement with NCCLS M27-A results for both C albicans and non-C. albicans isolates. Intralaboratory reproducibility was excellent for NCCLS M27-A, Etest, Sensititre YeastOne, disk, and Fungitest (88 to 91%). Similar results emerged from the interlaboratory reproducibility evaluation. Our findings indicate that some commercial methods can be useful for fluconazole susceptibility testing of clinical Candida isolates. Those characterized by a lack of medium standardization and/or objective interpretative criteria should be avoided. Particular caution is necessary when testing is being done for clinical and epidemiological purposes.
Fusapyrone (1) and deoxyfusapyrone (2), two alpha-pyrones originally isolated from rice cultures of Fusarium semitectum, were tested in several biological assays. Compounds 1 and 2 showed considerable antifungal activity against several plant pathogenic and/or mycotoxigenic filamentous fungi, although they were inactive toward yeasts isolated from plants and the Gram-positive bacterium Bacillus megaterium in disk diffusion assays. Compound 1 was consistently more active than 2. Among the tested fungi, Fusarium species were the least sensitive to the two pyrones, while Alternaria alternata, Ascochyta rabiei, Aspergillusflavus, Botrytis cinerea, Cladosporium cucumerinum, Phoma tracheiphila, and Penicillium verrucosum were the most sensitive. Compounds 1 and 2 also showed good inhibitory activity toward agents of human mycoses. Aspergilli were the most sensitive, while some species-specific variability was found among the Candida spp. In an Artemia salina larvae bioassay, 1 was not toxic at the highest concentration tested (500 microM), whereas the LC(50) of 2 was 37.1 microM (21.8 microg/mL). Neither 1 nor 2 was phytotoxic in a panel of assays that monitored plant-cell toxicity, as well as wilt-, chlorosis-, and necrosis-inducing activity. Moreover, 2 stimulated the root elongation of tomato seedlings at doses of 10 and 100 microM. In consideration of the biological activities evidenced in this study, 1 and 2 appear to be potential candidates for biotechnological applications, as well as good models for studies on mechanism(s) of action and structure-activity relationships.
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A ligase chain reaction (LCR) DNA amplification method for the molecular diagnosis of Mycobacterium tuberculosis complex (Abbott LCx MTB) was evaluated in comparison with solid (Lowenstein Jensen), liquid (7H12, Bactec 460 system) phase culture and microscopic examination (ME) on 86 tissue samples collected from 86 intradermal tuberculin positive cattle and one pool from 4 guinea pigs experimentally infected with M. bovis. Overall, 48 samples (58.81%) were culturally positive for mycobacteria, and on the basis of biochemical characters, all the isolates were identified as M. bovis. Sensitivity was 83.92% for LCx, 53.57% for LJ, 85.71% for Bactec and 41.07% for ME. In 3 out of 25 "no visible lesion" tissue samples, M. bovis was detected only by LCx and Bactec but not by LJ and ME. The concordance in the determination of positives and negatives among the methods observed in pairs was calculated according to Cohen's K concordance coefficient and showed 81.1% of concordance of LCx vs Bactec, 68.8% LCx vs LJ, 72.2% LCx vs ME, 80.0% Bactec vs LJ, 66.7% Bactec vs ME, 85.5% LJ vs ME. Despite a certain variability in concordance rates, both Cohen's K concordance coefficients or standardized (Zk) values were statistically significant. Both LCx and Bactec appear not alternative but subsidiary to the other methods traditionally applied for direct diagnosis of bovine tuberculosis on tissue samples from cattle reacting to intradermal tuberculin test.
Human natural (KTAb), murine monoclonal (KTMAb), and single-chain recombinant (KTScFv) candidacidal antibodies representing the internal image of a killer toxin from the yeast Pichia anomala (KT), characterized by a wide spectrum of antibiotic activity, exerted a lethal effect against a KT-sensitive multidrug-resistant isolate of Mycobacterium tuberculosis. KTMAb and KTScFv were produced by the hybridoma and DNA technologies, respectively, from the spleen lymphocytes of animals immunized with the idiotype of a KT-neutralizing MAb (MAb KT4), while KTAb were purified against MAb KT4 from the vaginal fluid of women infected with Candida albicans cells bearing an idiotype-like KT cell wall receptor. Mycobactericidal activity was related to the binding of KTAb, KTMAb, and KTScFv to the cell surface of KT-sensitive bacterial cells and was prevented by specific absorption of KT-like antibodies onto MAb KT4. These data identify a novel potentially useful immunotherapeutic approach to tuberculosis.
A ligase chain reaction (LCR) DNA amplification method for the molecular diagnosis of Mycobacterium tuberculosis (Abbott LCx MTB) was evaluated in comparison with solid and liquid phase culture on 622 selected samples collected in two large Italian hospitals, of which 310 obtained from HIV-1 positive patients and 312 from HIV-negative individuals. The overall prevalence of mycobacteria by culture was 22% (137/622), and the apparent sensitivity and specificity of LCx vs. culture were 87.6% and 98.2%. Of the 26 culture positive/LCx negative samples, 22 were positive for MOTT and 4 for M. tuberculosis. All 9 samples positive by LCx and negative by culture were classified as true positive by clinical criteria. The final values of sensitivity, specificity, positive predictive value and negative predictive value for LCx rose to 96.8%, 100%, 100% and 99.2%, respectively. The adjusted sensitivity of culture methods was 89.5% for solid phase and 92.7% for Bactec. In view of the high sensitivity on both smear-positive (100%) and smear-negative (92.4%) samples and of the high negative predictive value, the LCR-based amplification method appears suitable as a routine screening method for the rapid diagnosis of M. tuberculosis in high-risk patients.
Two patients seropositive for human immunodeficiency virus (HIV) and with no previous acquired immunodeficiency syndrome-defining conditions developed cavitary pneumonia and pleural disease caused by Rhodococcus equi. R. equi was isolated from these patients' sputum and lung biopsy specimens, respectively, but the microorganism was initially considered to be a contaminant (patient 1) or misidentified as a nontuberculous mycobacterium (patient 2). The R. equi infection was fatal in one patient, who died after 4 months without specific antimicrobial therapy; the second patient was unresponsive to combination therapy with various antimicrobial agents. R. equi may cause life-threatening infections in HIV-infected patients. Microbiology laboratories should be cognizant of the need to exclude R. equi as a cause of infection in highly immunosuppressed patients.
Yeast killer toxin cell wall receptors of Candida albicans were observed by indirect immunofluorescence using an affinity purified rabbit anti-idiotypic antiserum. The antiserum had been raised against a monoclonal antibody neutralizing the in vitro activity of a killer toxin produced by a selected strain of Hansenula anomala UCSC 25F. This simple procedure permitted the location of killer toxin cell wall receptors in various morphological phases of the yeast cells. The use of the indirect immunofluorescence technique with anti-idiotypic antibodies may have potential value in determining the occurrence of killer toxin receptors in other microbial systems.
Forty-four presumptive killer yeasts were tested against bacterial isolates, including rapid-growing gram-positive and gram-negative bacteria, as well as slow-growing bacteria, such as the mycobacteria. A killer system, based on the patterns of bacterial susceptibility to the action of nine selected killer yeasts, was developed for epidemiological purposes. The killer system, previously standardized for yeasts and hyphomycetes, was adapted to the specific growth conditions of the bacterial isolates. The results obtained confirm that susceptibility to the yeast killer phenomenon is widespread among microorganisms unrelated to yeasts and that it could form the basis for a convenient and adaptable biotyping method in microbiological laboratories.
The impact of the airborne opportunistic fungus pathogen, Aspergillus fumigatus in patients hospitalized at the university hospital of Parma, Italy, and its outpatients was investigated during a period of six months. Sputum and bronchial washings were collected from 986 patients. The 2,437 specimens were culturally examined for the presence of A. fumigatus regardless of the patient's clinical diagnosis. This fungus was isolated from 32 patients (3.2%). Subsequently, immunological tests for aspergillosis were performed on 22 of these culture-positive patients. Eight of these patients (36.4%) were serologically proven to be affected by aspergillosis. The 32 A. fumigatus isolates were epidemiologically investigated by the killer system to determine the mode of spread of these infections. Among the patients, fifteen different biotypes were differentiated, and their value in studying the epidemiology of aspergillosis in the hospital environment was investigated.
The differential action of four selected yeast killer toxins on the mycelial and yeast forms of four isolates of the dimorphic fungus Sporothrix schenckii was comparatively evaluated. The results confirmed that the yeast killer phenomenon is present among hyphomycetes and yeasts and that both morphological forms of S. schenckii are susceptible to the action of the same yeast killer toxin. Quantitative differences in the response to the killer action of the mycelial and yeast forms in individual strains were also observed. To avoid retroconversion of the dimorphic forms, we used a modification of the conventional killer system.
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During the period June 1983-May 1984, faecal specimens from 797 patients with acute enteritis were examined for the presence of bacterial, viral and parasitic agents; 209 (26.2%) enteritic pathogens were identified, of whom 118 (35.4%) in 333 samples from the pediatrics wards. Bacterial agents were detected in 122 (15.3%), viruses in 63 (7.9%) and parasites in 25 (3.1%) of the 797 specimens. LT-producing E. coli, Salmonella and Rotavirus were the most frequent pathogens. Bacterial agents occurred most frequently in the summer and autumnal months, whereas viruses showed two peaks, the first one in summer due to cultivable agents, the second in winter to Rotavirus mainly.