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Infections caused by biofilm-forming agents have important implications for world health. Mixed infections, caused by more than one etiological agent, are also an emerging problem, especially regarding the standardization of effective diagnosis and treatment methods. Cases of mixed onychomycosis (OM) have been reported; however, studies on the microbial interactions between the different fungi in biofilms formed on nails are still scarce. We describe a case of mixed OM caused by the dermatophyte Trichophyton rubrum and the black yeast-like fungus Rhinocladiella similis. Identical growths of both fungi were observed in more than 50 cultures from different nail samples. Additionally, both species were able to form organized single and mixed biofilms, reinforcing the participation of both fungi in the etiology of this OM case. R. similis seemed to grow faster during the process, suggesting that T. rubrum benefits from biofilm development when in combination. Moreover, the biofilm of the Rhinocladiella isolate exhibited exacerbated production of the extracellular matrix, which was not observed with that of a Rhinocladiella reference strain, suggesting that the isolate had natural abilities that were possibly perfected during development in the nail of the patient.

BACKGROUND: Human dermatophytoses are the most widespread infections caused by fungi. These are capable of invading the keratin-containing tissues of animals. Nannizzia nana (N. nana) can cause ringworm in pigs and rarely cause infections in humans.
METHODS: We conducted a search using PUBMED for articles published from January 1, 1990 to March 31, 2022 to identify additional cases. The search terms used were \"Microsporum nanum\" and \"Nannizzia nana\".
RESULTS: After reviewing the literature, we identified a total of 16 cases of dermatophytosis due to N. nana since 1990. In most of the patients, the clinical diagnosis was tinea corporis and the most widely used antifungals were: terbinafine and griseofulvin.
CONCLUSIONS: N. nana is a dermatophyte species isolated infrequently in humans, but it represents a potential source of dermatophytosis in people who come into direct or indirect contact with animals and soil.

Microsporum canis is a dermatophyte known to cause superficial skin infections. In immunocompromised patients, it can lead to invasive dermatophytosis. We present a case of biopsy-proven left knee mycetoma caused by M canis in a renal transplant patient. Identification of M canis was achieved via sequencing of the internal transcribed spacer regions. Treatment involved surgical debridement, oral posaconazole, and reduction in immunosuppression. In addition, we provide a review of current literature on invasive M canis infections.

Tinea is a superficial fungal infection of the skin. Gyrate erythemas are reactive conditions that present as annular red lesions. A 61-year-old woman was diagnosed with tinea corporis whose skin lesions morphologically mimicked a gyrate erythema. She presented with diffuse annular plaques affecting the left side of her chest and abdomen that did not respond to a combination antifungal-corticosteroid cream for six-month duration. The appearance and clinical differential diagnosis included a gyrate erythema. Initial evaluation of the skin biopsy from the lesion\'s edge demonstrated a spongiotic dermatitis, and staining for fungal organisms was negative. However, deeper sections and a different fungal stain revealed hyphae in the stratum corneum and established a diagnosis of tinea corporis. The PubMed database was used to review the following terms: tinea corporis, gyrate erythema, and tinea incognito. Relevant papers and references cited in those papers that were generated by the search were used. Tinea corporis, especially if previously treated with topical corticosteroids, can masquerade as other dermatoses including a gyrate erythema. Correlation of clinical presentation and pathology findings is essential, especially if the biopsy results do not confirm the suspected clinical diagnosis. Consideration to perform deeper sections or additional special stains or both should also be entertained when the initial pathology observations do not support the presumptive diagnosis based on clinical morphology and history.

Erythroderma presents as generalized skin redness. The features of a 39-year-old man who presented with erythroderma are described. His skin biopsy revealed hyphae in the stratum corneum, which established the diagnosis of tinea corporis. His erythroderma resolved following treatment with an oral antifungal agent. Several conditions can be associated with erythroderma. Common etiologies for erythroderma include medications, neoplasms, and papulosquamous disorders. Superficial dermatophyte-associated erythroderma is rare. However, although erythroderma caused by generalized superficial mycosis is infrequently encountered, tinea corporis should be included in the new-onset or chronic erythroderma. The detection of fungal hyphae in the stratum corneum of a biopsy of the erythrodermic skin can not only establish dermatophyte infection as the underlying cause of the individual\'s erythroderma but also an alternative cause of erythroderma.

A novel dermatophyte was isolated from skin scales of a female patient presenting with tinea corporis of the wrist and arm. Her principal risk factor was long-term corticosteroid use for underlying Lupus autoimmune syndrome. Microscopic examination of skin scales from lesions revealed hyphae consistent with dermatophyte infection, and a morphologically identical fungus grew in pure culture on all cultures of skin scales. Repeat isolation of the same organism from persistent lesions five months later confirmed the novel species as the causative agent. Microscopic examination revealed predominantly smooth, thin-walled macroconidia, with large numbers of unicellular aleuriospores of varied shapes and sizes. Since the isolate exhibited considerable microscopic pleomorphism, sharing morphological features consistent with several dermatophyte genera, it was subjected to multi-locus phylogenetic analyses employing a total of six different loci. Sequence analyses of all loci revealed that the isolate clustered with species within Nannizzia but diverged from all known members of the genus by 2 to 13% depending on locus analyzed. The isolate exhibited high minimum inhibitory concentrations for terbinafine in vitro, which might explain why the infection had failed to respond to two cycles of oral treatment with this antifungal agent. Interestingly, sequences in GenBank of an unnamed \"Microsporum sp\" isolated from leg skin of a patient in the Czech Republic showed greater than 99% identity across all of the loci analysed in common, indicating that this novel organism, which we describe here as Nannizzia perplicata sp. nov., is likely not restricted to the UK.

BACKGROUND: Trichophyton tonsurans is an anthropophilic dermatophyte, frequent in the USA and in Asia where it is responsible for causing tinea capitis. At present, we attend an emergence of this species in certain regions where it was not or little met. Here, we report a case of onychomycosis of the hand due to T. tonsurans associated with non-albicans Candida species at an adult woman.
METHODS: The patient is a 62-year-old woman, with hypertension and diabetes. She reports the rather frequent use of chemical cleaners for the housework. She presented one year previously a distal onycholysis of the last four fingers of the left hand. The clinical examination objectified a presence of intertrigo in the second interdigital space. The mycological examination showed at the direct examination mycelial elements and the culture allowed the isolation of T. tonsurans associated with non-albicans Candida species.
CONCLUSIONS: Our observation highlights especially the identification of a species, which has been described only once in Morocco about a case with onychomycosis of the feet. A possible emergence of this species in our country is not far from being possible.

Trichophyton usually causes a superficial skin infection, affecting the outermost layer of the epidermis, the stratum corneum. In immunocompromised patients, deeper invasion into the dermis and even severe systemic infection with distant organ involvement can occur. Most cases of deeper dermal dermatophytosis described in the literature so far involved pre-existing superficial dermatophytosis.
We report a 68-year-old woman presented to our clinic with a 3-month history of palpable nodules on the right ankle without pre-existing superficial dermatophytosis. Magnetic resonance imaging showed multiple, well-demarcated, cystic lesions around the lateral malleolus, located in the subcutaneous or dermal layers. The sizes varied from 0.5 cm to 4 cm in diameter. The patient underwent complete excision of the lesions. Fungal culture yielded Trichophyton rubrum on Sabouraud dextrose agar. Histopathology showed organizing abscesses with degenerated fungal hyphae. After the 12-week oral itraconazole therapy, the lesions were completely resolved.
Dermatophytes should be considered as a possible cause of deep soft tissue abscesses in immunocompromised patients, even though there is no superficial dermatophytosis lesion.

Recently, an increasing prevalence of nondermatophyte mold onychomycosis was observed, in which Chaetomium globosum was rarely involved as primary pathogenic agent. Besides this, reports of mixed infection associating a dermatophyte and a nondermatophyte mold have become more frequent. Here, we present a clinical case of a mixed onychomycosis infection of a toenail caused by Chaetomium globosum and Trichophyton mentagrophytes. To our knowledge, this specific association is reported for the first time in Canada.