Agrobacterium tumefaciens-mediated transformation of Guignardia citricarpa

Guignardia citricarpa, the causal agent of Citrus Black Spot, was successfully transformed via Agrobacterium tumefaciens with cassettes for gfp and bar expression. Transformation is essential to understand the role of genes during interaction between plants and its pathogens. Using a binary plasmid vector based in the pPZP201BK, both germinated conidia and physically fragmented hyphae of G. citricarpa were transformed. Eight independent transformants of G. citricarpa resistant to ammonium glifosinate displayed GFP fluorescence. The majority (93.75%) of the G. citricarpa transformants was mitotically stable and contained a single T-DNA copy ectopically integrated to the chromosome. This is the first report of G. citricarpa transformation and will allow future work on virulence determinants of the fungus and possibly its control.

Development of a simple and rapid Agrobacterium tumefaciens-mediated transformation system for the entomopathogenic fungus Metarhizium anisopliae var. acridum

AIMS

To examine the ability of Agrobacterium to attach to Metarhizium anisopliae var. acridum strain CG423 under co-cultivation and to develop an Agrobacterium-mediated method of gene delivery into strain CG423, a promising agent for biological control of grasshoppers.

METHODS AND RESULTS

The co-cultivation of Agrobacterium tumefaciens and M. anisopliae var. acridum was analysed under scanning electron microscopy. We observed that Agrobacterium attached to and formed aggregates around Metarhizium conidia and germ tubes. We also observed the occurrence of fibril-like structures connecting neighbouring bacterial-fungal cells. The Agrobacterium-mediated transformation was applied using two binary vectors carrying a benomyl resistance gene as a selection marker. The efficiency of transformation was up to 53 transformants per 10(5) target conidia. High mitotic stability of the transformants (89-97%) was demonstrated after five successive transfers on non-selective media. Molecular analysis revealed the occurrence of high frequency of gene conversion.

CONCLUSIONS

In our study, we report that A. tumefaciens strain AGL-1 attaches to and genetically transforms the entomopathogenic fungus Metarhizium anisopliae var. acridum.

SIGNIFICANCE AND IMPACT OF THE STUDY

We report for the first time, the attachment of Agrobacterium to fungal cells opening new avenues for the study of this essential step of the T-DNA transfer process. Considering the efficiency of the transformation protocol herein described, this is a useful tool for gene disruption in M. anisopliae var. acridum.

Epidemiological aspects of clinical and environmental Cryptococcus neoformans isolates in the Brazilian state Rio Grande do Sul

Cryptococcus neoformans is a pathogenic fungus that causes life-threatening meningoencephalitis in immunocompromised patients (HIV-positive patients), and lymphoproliferative disorders in patients subjected to organ transplantation and other immunosuppressive therapies. This fungus is commonly found in soil and avian excreta, mainly from pigeon and turkey. We describe the isolation and characterization of 17 clinical and 10 environmental (pigeon excreta) isolates from the Brazilian state Rio Grande do Sul. We analyzed capsule formation, carbon assimilation pattern, canavanine-glycine-bromothymol blue (CGB) reaction, and nitrate and urease tests, as well as susceptibility to antifungal drugs. The genetic variability among C. neoformans isolates was studied using randomly amplified polymorphic DNA (RAPD) analysis. Eight of 22 arbitrary polymerase chain reaction primers used confirmed genetic polymorphism among the environmental isolates tested, suggesting that it remains feasible to use RAPD analysis as a typing method. Three of the selected primers yielded 10 molecular subclasses. The majority of the clinical isolates were assigned to the molecular subclass F. The RAPD data obtained reinforce the developing consensus about the population structure of this fungus.

The efficacy of a topical application of terbinafine 1% solution in subjects with pityriasis versicolor: a placebo-controlled study

A prospective randomised placebo-controlled double-blind study was designed to investigate whether topical terbinafine 1% solution is an effective treatment for subjects with pityriasis versicolor. The intention-to-treat population consisted of 110 subjects. The number of subjects who received terbinafine 1% solution was 76 and the number who received placebo was 34; treatments were given twice a day for 1 week. The primary efficacy variables were categorised at weeks 1, 2, 4 and 8. Eight weeks after the start of therapy, 81% of the subjects using terbinafine solution and 41% of those receiving placebo had a negative mycological examination (p < 0.001). A clinical effect of treatment was recorded in 72% of the subjects using terbinafine 1% solution and 26% of those receiving placebo (p < 0.001). We conclude that terbinafine 1% solution is an effective and safe local treatment modality for pityriasis versicolor.

[Terbinafine versus miconazole in patients with tinea pedis]

OBJECTIVE

To compare the efficacy of terbinafine cream during 1 week with the efficacy of miconazole cream during 4 weeks in the treatment of tinea pedis.

DESIGN

Prospective randomised double-blind study.

SETTING

Department of dermatology, Academic Hospital Leiden, the Netherlands.

METHODS

Patients who visited the general practitioner for tinea pedis and who had a positive KOH preparation were treated with terbinafine cream during 1 week and placebo during 3 weeks, or with miconazole cream during 4 weeks. Evaluation was done 1, 2, 3, 4 and 6 weeks after the start of the treatment. Mycological cure was defined as presence of a positive KOH preparation and a positive culture before treatment, and a negative result for both after treatment. Clinical efficacy was defined as mycological cure and presence of at most two minor symptoms (erythema, vesicles, squamae, itching) of the previously most serious skin lesion. Evaluation was done of all patients with a positive KOH preparation and of all patients with a positive KOH and a positive culture.

RESULTS

263 patients were included. Of these 207 had a positive culture; 56 patients had a positive KOH preparation but a negative culture. The group of patients treated with terbinafine and placebo consisted of 129 patients, the miconazole group of 134 patients. Both groups had an equal distribution as to age, sex, race, duration and seriousness of the fungal infection and previous treatment. Mycological cure and clinical efficacy throughout the evaluation were similar in both treatment groups, in both patients with positive KOH preparation and in patients with a positive KOH preparation and a positive culture. After 6 weeks mycological cure was seen in about 95% and clinical efficacy in about 87%.

CONCLUSION

In the treatment of tinea pedis local application of terbinafine cream during 1 week is as good as treatment with miconazole cream during 4 weeks.

Fungal infections in the Netherlands. Prevailing fungi and pattern of infection

BACKGROUND

Species of fungi have specific characteristics in geographic distribution, and they have a predilection for certain body areas.

OBJECTIVE

To obtain information about the prevailing fungi and their pattern of infection in the Netherlands.

METHODS

An analysis was made of the results of mycological examinations carried out in subjects referred to the mycological laboratory of the Department of Dermatology, University Hospital Leiden, the Netherlands, in the period of 1972-1992.

RESULTS

The feet, extremities and groin were most commonly infected. The feet and extremities were mainly infected with dermatophytes (Trichophyton rubrum), but in the groin Candida albicans accounted for 49.9% of the fungal infections. Onychomycosis ranked third in prevalence (17.3% of all fungal infections). The main etiologic agent in the toenails was T. rubrum, but in fingernails C. albicans seems to be at least as important as T. rubrum. On the trunk (mainly the chest, especially in women) and buttocks C. albicans was again the main etiologic agent for fungal infections. Dermatophytes accounted for only 32.4% and 14.2% of the fungal infections on the buttock and trunk, respectively. On the buttock and trunk T. rubrum was the main etiologic agent as far as dermatophytes are concerned. On the trunk, Microsporum canis and M. ferrugineum were of some importance as well. The prevalence of tinea capitis was very low and accounted for only 0.7% of all fungal infections.

CONCLUSION

Cutaneous candidosis accounted for 30.3% of all fungal infections and is therefore important. On the chest, buttocks, groin and finger-nails, the prevalence of C. albicans is higher than that of dermatophytes.

[Swimmer's eczema: intertrigo, erythrasma or a yeast or fungus infection?]

OBJECTIVE

To determine the proportional contributions of tinea pedis, intertrigo, erythrasma and Candida to 'swimmer's eczema.'

DESIGN

Descriptive.

SETTING

Department of Dermatology, University Hospital Leiden, the Netherlands.

METHOD

General practitioners were encouraged to refer every patient with clinical signs of foot mycosis. Mycological tests (culture and microscopy) were performed.

RESULTS

A total of 296 patients with interdigital mycosis and 30 with tinea pedis of the moccasin type were included. In 56% of the patients with swimmer's eczema dermatophytes were recognised, 10% showed erythrasma and in 30% no cause could be found. Candida only played a minor role. Trichophyton mentagrophytes was found more often in swimmer's eczema than in tinea pedis of the moccasin type.

CONCLUSION

Swimmer's eczema has several causes, which can be determined with mycological tests. Microscopy is the most sensitive method in regard to demonstrating dermatophytes and erythrasma.

[Fungi causing onychomycoses in The Netherlands]

OBJECTIVE

To obtain information about prevalences of fungi responsible for onychomycosis in the Netherlands.

DESIGN

Retrospective.

SETTING

Mycological laboratory of the Dermatological department, University Hospital, Leiden, the Netherlands.

METHODS

The results of mycological tests of nail samples collected in the period of 1987-1992 were analysed. If the culture was positive, the nature of the yeast or dermatophyte was determined.

RESULTS

Nail samples were obtained from 861 patients (22% fingernails, 78% toenails). No mycological confirmation of clinical diagnosis could be obtained in 60% of fingernail samples and 45% of toenail samples. Of the mycologically confirmed finger onychomycoses 77.5% were caused by yeasts, the remaining part by Trichophyton rubrum. Toenail onychomycosis in 9.9% of the cases was caused by yeasts, in 11.8% by T. mentagrophytes, in 1.2% by Epidermophyton floccosum, and in under 1% by non-dermatophytes. Just as in fingernail onychomycosis, the major cause of toenail onychomycosis is T. rubrum.

CONCLUSION

Onychomycosis cannot be diagnosed on clinical grounds, without mycological testing. Since antimycotic treatment is not always effective in onychomycosis caused by yeasts and non-dermatophytes, mycological diagnosis is necessary.