Differentiation of Trichophyton rubrum clinical isolates from Japanese and Chinese patients by randomly amplified polymorphic DNA and DNA sequence analysis of the non-transcribed spacer region of the rRNA gene

Dermatophytoses in domesticated animals

Dermatophytes are among the most frequent causes of ringworm infections in domesticated animals. They are known to serve as reservoirs of the zoophilic dermatophytes and these infections have important zoonotic implication. In Nigeria and probably West Africa, there are not many studies on the incidence of dermatophytosis in domesticated animals. In the current study, 538 domesticated animals with clinically suggestive lesions were investigated for dermatophytes. Identification of dermatophyte species was performed by macro- and micro morphological examination of colonies and by biochemical methods. In the cases of isolates that had atypical morphology and/or biochemical test results, the rDNA internal transcribed spacer region 2 (ITS 2) sequencing was performed. Out of this number, 214 (39.8%) were found to be colonized by a variety of ten species of dermatophytes. M. canis was the most frequently isolated species (37.4%), followed by T. mentagrophytes (22.9%) and T. verrucosum (15.9%). M. persicolor and T. gallinae were jointly the least species isolated with a frequency of 0.55% respectively. The recovery of dermatophyte isolates previously shown to be common etiological agents of dermatophytosis especially from children in the same region suggests that animal to human transmission may be common. Possible implications and recommendations are discussed.

Identification and differentiation of Trichophyton rubrum clinical isolates using PCR-RFLP and RAPD methods

Trichophyton rubrum represents the most frequently isolated causative agent of superficial dermatophyte infections. Several genotyping methods have recently been introduced to improve the delineation between pathogenic fungi at both the species and the strain levels. The purpose of this study was to apply selected DNA fingerprinting methods to the identification and strain discrimination of T. rubrum clinical isolates. Fifty-seven isolates from as many tinea patients were subjected to species identification by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis and strain differentiation using a randomly amplified polymorphic DNA (RAPD) method, with two primers designated 1 and 6. Using PCR-RFLP, 55 of the isolates studied were confirmed to be T. rubrum. Among those, a total of 40 and five distinct profiles were obtained by RAPD with primers 1 and 6, respectively. The combination of profiles from both RAPD assays resulted in 47 genotypes and an overall genotypic diversity rate of 85.4%. A dendrogram analysis performed on the profiles generated by RAPD with primer 1 showed most of the isolates (87.3%) to be genetically related. PCR-RFLP serves as a rapid and reliable method for the identification of T. rubrum species, while the RAPD analysis is rather a disadvantageous tool for T. rubrum strain typing.

Trichophyton rubrum and Trichophyton interdigitale: genetic diversity among species and strains by random amplified polymorphic DNA method

Onychomycosis is a common condition that represents up to 50% of all nail problems and 30% of all cases of dermatophytoses. Trichophyton rubrum and Trichophyton interdigitale are the most common agents involved in this condition. In cases of recurrent post-treatment onychomycosis, strain fingerprinting could reveal whether the original isolate is responsible, a new strain has been acquired or if multiple strains are involved. The aim of this study was to evaluate the efficacy of the RAPD method for species and strain differentiation of T. rubrum and T. interdigitale obtained from patients with subungeal distal-lateral onychomycosis. A set of 86 strains of onychomycosis causative dermatophytes were submitted to species differentiation and strain typing by RAPD method with two previously described primers. Both primers proved capable of strain differentiation when tested for each species. Nineteen molecular profiles were configured for T. rubrum isolates with primers 1 and 6. For T. mentagrophytes, ten molecular profiles were configured with primer 1 and twenty-one with primer 6. We found that T. interdigitale and T. rubrum species were grouped in different clusters when both primers were analyzed together. This study shows that these primers are valuable tools for strain differentiation with T. rubrum and T. intedigitale.