Irene Weitzman

Non-keratinous agar media as substrates for the ascigerous state in certain members of the gymnoascaceae pathogenic for man and animals

Agar media containing oatmeal with and without tomato paste served as non-keratinous, soil-free substrates for the abundant production of fertile cleistothecia by several Nannizzia and Arthroderma species and by 2 homothallic isolates of Histoplasma capsulatum capable of producing the perfect form.

Variation in Microsporum gypseum. I. A genetic study of pleomorphism

Studies on the nature of pleomorphism were made possible by the rediscovery of sexual reproduction in the dermatophyte, Microsporum gypseum (Bodin) Guiart & Grigorakis. Ascus analysis of progeny resulting from crosses between certain pleomorphic cultures and wild-type revealed a 1:1 segregation of mutant to wild-type. Several other variants not considered pleomorphic by conventional definition, showed a similar segregation pattern. Crosses between mutant cultures revealed linkages among several loci. Most of the white, fluffy, aconidial cultures were sexually sterile; however, five such cultures capable of crossing with wild-type were found to have resulted from two gene mutations. Ascus analysis of crosses between these double mutants and wild-type have indicated loose linkage between the two mutant loci in one culture, and the absence of linkage in the other four cultures. Pleomorphism is thus shown to be the result of one or more gene mutations. It is suggested that the term pleomorphism be discarded i...

Dermatophytes : gross and microscopic

Dermatophytes, members of the anamorphic genera Epidermophyton, Microsporum, and Trichophyton, are capable of invading keratinous tissue, causing cutaneous infection referred to as dermatophytosis. These species may be anthropophilic, zoophilic, or geophilic based on host preference and natural habitat. These groupings are epidemiologically significant. This article provides a description of the genera and species of the dermatophytes--gross and microscopic--and the tests that may be necessary to confirm their identification.

Differentiation of Nocardia from rapidly growing Mycobacterium species by PCR-RFLP analysis

The nucleotide sequences from a region of the groEL gene from one Nocardia asteroides and from several species of Mycobacterium were determined and found to be highly homologous. Based on these homologies, we developed a rapid method capable of differentiating between these two genera. The method is based on restriction fragment-length polymorphism (RFLP) analysis of DNA amplified from the groEL gene that is highly conserved between mycobacteria and nocardiae. When the groEL gene from species of these genera is enzymatically amplified by the polymerase chain reaction (PCR), a 422-bp fragment is generated. Correlation of the restriction endonuclease digestion patterns of the amplification products with reference and/or biochemically characterized clinical samples enabled us to establish RFLP profiles for ten species of Mycobacterium and five species of Nocardia. When a portion of the groEL gene from each of these organisms is digested with the restriction endonuclease Hae III, that organism is readily assigned to one of these two genera on the basis of the derived RFLP patterns. The utility of this approach was examined by testing 105 pure cultures from samples previously identified by routine culture techniques for the presence of groEL DNA sequences of mycobacterial or nocardial origin. This analysis correctly identified the organism in all samples tested. In summary, PCR-RFLP analysis provides a rapid and sensitive method for the differentiation of Nocardia species from rapidly growing Mycobacterium species.

Phialophora parasitica, an emerging pathogen

Monoconidial cultures derived from 12 clinical and environmental isolates of Phialophora parasitica were compared with respect to morphologic and physiologic characteristics and response to antifungal agents. No yeast cells were seen in 1- and 3-week-old slide culture preparations. Also, not all of the distinguishing characteristics of this species were displayed by all isolates on all media examined. Although the isolates grew on Sabouraud agar with chloramphenicol and cycloheximide, some inhibition was observed. All cultures were strongly urease-positive and hydrolyzed casein and starch; most decomposed tyrosine but not gelatin. All but one environmental isolate grew well at both 23 and 37 degrees C, but none grew at 40 degrees C. In the sensitivity testing the isolates did not vary much in their response to each drug, although some anomalies were observed. Amphotericin B and miconazole had minimum inhibitory concentrations in the low sensitivity range (2.0-8.0 and 2.5-10 micrograms m-1 respectively), for most isolates, and most isolates were resistant to both 5-fluorocytosine and ketoconazole. Limited observations were made on three other Phialophora species which might be confused with P. parasitica.

A comparison between Dactylaria gallopava and Scoleocobasidium humicola: first report of an infection in a tortoise caused by S. humicola

Scolecobasidium humicola, a soil fungus and etiologic agent of phaeohyphomycosis in fish, is herein reported to cause cutaneous lesions in a tortoise, Terrapine carolina var. carolina. S. humicola was isolated from lesions on the foot and dematiaceous hyphae were observed in KOH preparations of the biopsy and in stained preparations. This isolate and others were compared morphologically and physiologically with isolates of Dactylaria gallopava which it resembles. As a result of this investigation, we concluded that D. gallopava may be differentiated from S. humicola macroscopically, by the production in D. gallopava of an extensive diffusible purplish-red to reddish-brown pigment when cultured on Sabouraud dextrose agar; microscopically, by the presence and usually predominance of conidia, whose apical cell is markedly wider than the basal cell, and usually constricted at the septum; and physiologically, by the ability to grow on media containing cycloheximide and by the ability to grow well at 36-45 degrees C. In contrast, S. humicola does not usually produce a diffusible pigment on Sabourauds dextrose agar or if present, is not extensive; it lacks the wider upper cell; is less constricted or non-constricted at the central septum; grows on media containing cycloheximide, although some inhibition may occur and lastly, does not grow at 36 degrees C or higher. Both species were urease positive, hydrolysed tyrosine but not casein, xanthine, or gelatin.

Subcutaneous infection with Phialophora richardsiae and its susceptibility to 5-fluorocytosine, amphotericin B and miconazole

Two patients are described with subcutaneous infections due to Phialophora richardsiae. Both were diabetics and originally came from subtropical areas. One of the patients had a cystic lesion which was well encapsulated while the other had a large ulcerating lesion with draining sinus tracts. The organisms were found to be susceptible to cycloheximide but resistant to 5-fluorocytosine, miconazole and amphotericin B. There was some variability in the degree of resistance depending upon whether the primary or secondary phialoconidia were tested. While simple excision appears curative for the solitary cystic type of lesion, therapy of the ulcerating form of the disease remains problematic.

A comparison of the pathogenicity of three members of the Microsporum gypseum complex

A comparison of the pathogenicity for guinea pigs and rabbits of the 3 members of the M. gypseum complex (N. incurvata, N. gypsea and N. fulva), was accomplished by intradermal multiple puncture inoculation. No notable difference in pathogenicity was observed between N. gypsea and N. incurvata. The local reactions of the animals ranged from negative to inflammatory and many lesions exhibited crust formation. In contrast, N. fulva appeared to be much less virulent.Nineteen of 21 isolates of M. gypseum recovered from spontaneous human and animal lesions were identified as N. gypsea, the remaining 2 as N. incurvata.The results of the animal inoculations and the identification of the perfect form of clinical isolates point to N. fulva as the least virulent member of the M. gypseum complex.

Studies with clinical isolates of Cunninghamella. I. Mating behavior.

Six clinical isolates of Cunninghamella, including two which had been described in the literature as C. elegans, were paired with tester strains of C. bertholletiae, C. elegans and with two isolates of C. polymorpha. These tester strains were in turn paired with each other in all combinations. Zygospores were produced in intraspecific crosses including pairings between cultures of C. polymorpha which had not been previously reported to produce zygospores. Five of the six clinical isolates produced zygospores in matings with C. polymorpha and zygospore formation also occurred when all six of the human isolates were paired with C. bertholletiae. None mated with C. elegans. One culture of C. bertholletiae produced numerous zygospores in crosses with C. polymorpha. As the result of our studies on mating behavior we conclude that: all six clinical isolates should be identified as C. bertholletiae not C. elegans, C. bertholletiae is a distinct species and not a synonym of C. elegans and C. polymorpha, as redescribed by Samson and represented by his designated neotype strain, is not a valid species.

Studies with clinical isolates of Cunninghamella II. Physiological and morphological studies.

Studies were made to determine whether distinctions between Cunninghamella elegans and C. bertholletiae, and between clinical and saprophytic isolates of C. bertholletiae, can be made on a physiologic and/or morphologic basis. Results indicate that temperature tolerance is the key differential feature for C. elegans, which does not grow at 40 C. Strains of C. bertholletiae were variable with respect to temperature tolerance. All of the clinical isolates of the latter, but only five of seven saprophytic strains, grew well at 40-45 C. As a group, however, clinical and saprophytic isolates of C. bertholletiae could not be differentiated. Temperature tolerance may also be a key differential feature in identifying neutral isolates of Cunninghamella which lack conidia with long echinulations. One of the clinical isolates of C. bertholletiac which failed to produce zygospores when paired with both (+) and (-) mating types of C. elegans and C. bertholletiae was identified on the basis of growth at 40 C and minor characteristics common to other clinical isolates.