Canis Dermatophytosis Research Articles

A Household Microsporum canis Dermatophytosis Suggested by Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry Analysis

Case seriesPatients: Female, 4-year-old • her family (father, mother, sister)Final Diagnosis: Microsporum canis dermatophytosisSymptoms: ItichingMedication: —Clinical Procedure: Time-of-flight mass spectrometry (TOF-MS)Specialty: Infectious DiseasesObjective:Unknown ethiologyBackground:Microsporum canis is a pathogenic dermatophyte that usually colonizes animals, and secondary infection of humans comes from pets. The infected patients show hair loss with erythema and are diagnosed as having dermatophytosis, but the transmission routes of M. canis from animals to others are sometimes unclear, although they are critical to the treatment of patients and infection control. To identify the pathogens and the transmission routes, morphological observations by microscopes and conventional polymerase chain reaction (PCR) have been used; however, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has recently become a useful tool.Case Reports:A 4-year-old girl presented with pruritic, erythematous lesions on the head with alopecia. The dermatologists diagnosed dermatophytosis caused by fungal infection, and M. canis was suspected as the pathogen because of the morphologic characteristics. All of her family members subsequently showed similar hair findings and symptoms. The growth of M. canis was also observed in serial cultures, and all strains were confirmed to be identical, but different from the standard strain on MALDI-TOF MS. In this household infection case, abandoned cats were considered to be the origin of M. canis transmission, and the family members finally improved following oral administration of antifungal agents.Conclusions:M. canis should be carefully investigated as the causative pathogen of dermatophytosis secondary to household infection. MALDI-TOF MS appears to be an excellent tool to confirm the transmission routes of the fungal pathogens among infected patients.

Trichophyton species and Microsporum gypseum infection and fomite carriage in cats from three animal shelters: a retrospective case series.

The goal of this retrospective case series was to report on the clinical aspects of confirmed Trichophyton species and Microsporum gypseum infections in cats from three animal shelters. This was an observational retrospective study. Fungal culture and treatment data from three animal shelters was retrospectively reviewed to identify cats with dermatophytosis caused by Trichophyton species or M gypseum. Among the three shelters only four cats were diagnosed with M gypseum dermatophytosis. With respect to Trichophyton species infections, there were six cases identified and treated in a 1 year period in one shelter, 13 cases over 13 years in the second shelter and 27 cases over 5 years in the third shelter. Four cases of M gypseum dermatophytosis were treated in the third shelter. Young cats were most commonly infected and the disease was most commonly diagnosed in the fall and winter months. Lesions were inflammatory and found predominantly on the head and neck. There was a rapid response to treatment in all cases; mean (n = 20) and median (n = 17) days to mycological cure were calculated from available data. Fungal culture data revealed fomite carriage without clinical evidence of infection for Trichophyton species (n = 43) cats and M gypseum (n = 37) cats. There is a paucity of clinical information about non-Microsporum canis dermatophytosis in shelter cats. This study data shows that Trichophyton species and M gypseum infections do occur but are uncommon. Based upon the rapid response to conventional treatment, these infections do not represent a treatment challenge, as most cats reached mycological cure within 3 weeks.

Treatment of shelter cats with oral terbinafine and concurrent lime sulphur rinses

Dermatophytosis is an important contagious and infectious skin disease in an animal shelter. Itraconazole is the commonly used systemic antifungal drug, but it is expensive in some countries and, at times, difficult to obtain. Terbinafine is a fungicidal allylamine with documented in vitro and in vivo efficacy against Microsporum canis in pet cats and in cats with experimental infections. To describe the use of oral terbinafine for the treatment of M. canis dermatophytosis in shelter cats. The response to treatment of 85 shelter cats with naturally occurring M. canis dermatophytosis was monitored by examination, weekly toothbrush fungal cultures and the number of colony-forming units on fungal culture plates. Cats were treated with either 14 (n = 21) or 21 days (n = 64) of terbinafine per os (p.o.) along with concurrent twice weekly lime sulphur rinses and daily environmental disinfection. Cats treated with 14 days of terbinafine p.o. showed an initial response to therapy but by week 6 had relapsed and required rescue therapy with a course of itraconazole (10 mg/kg p.o.) to obtain a cure. Cats treated with 21 days of terbinafine p.o. showed a response to treatment similar to published reports using itraconazole p.o. for 21 days. The mean and median number of days to mycological cure was 22.70 (range 13-39). Terbinafine was well tolerated. None of the cats developed oral lesions postgrooming of lime sulphur rinses. Where itraconazole is not available, substitution with terbinafine in established protocols may allow shelters to treat cats that otherwise would go untreated.

Use of lime sulphur and itraconazole to treat shelter cats naturally infected withMicrosporum canisin an annex facility: an open field trial

Dermatophytosis is the most common contagious and infectious skin disease of cats. It is of particular importance in animal shelters because it is a known zoonosis, highly contagious, and easily transmitted. In this open clinical trial, 58 cats with confirmed Microsporum canis dermatophytosis and 32 uninfected bonded pairs or littermates were treated with a combination of 21 days of oral itraconazole (10 mg kg(-1)) and twice weekly lime sulphur rinses until cured. Cats were not clipped in this treatment programme. Fungal cultures were obtained once weekly on all cats, and cats were considered cured when they had two consecutive negative weekly fungal cultures. Cats were held in the facility and received continued topical treatment until the fungal cultures were finalized. None of the cats developed oral ulcerations as a result of grooming the lime sulphur rinses. Oral ulcerations only developed in cats with clinical signs associated with upper respiratory disease. None of the uninfected cats living in contact with infected cats became culture positive or developed skin lesions. When data were examined retrospectively and the number of days to finalize the cultures was subtracted (21 days) from the total number of days the cats were housed in the annex, the mean number of days of treatment required for cure was 18.4 +/- 9.5 SEM (range 10-49 days). Cats with more severe infections required longer therapy. In this shelter, the combination of oral itraconazole and topical lime sulphur rinses for the treatment of dermatophytosis was effective and safe.

Reconstructed interfollicular feline epidermis as a model for Microsporum canis dermatophytosis

Microsporum canis is a pathogenic fungus that causes a superficial cutaneous infection called dermatophytosis. The complexity of mechanisms involved in dermatophytic infections makes relevant in vivo studies particularly difficult to perform. The aim of this study was to develop a new in vitro model of M. canis dermatophytosis using feline fetal keratinocytes in reconstructed interfollicular epidermis, and to investigate its relevance in studying the host-pathogen relationship. Histological analysis of reconstructed interfollicular feline epidermis (RFE) revealed a fully differentiated epidermis. A proliferation assay showed replicating cells only in the basal layer, indicating that RFE is a well-stratified living tissue, leading to the formation of a horny layer. Histopathological analysis of RFE infected by M. canis arthroconidia revealed that the fungus invades the stratum corneum and produces SUB3, a keratinase implicated in the infectious process. In view of these results, an M. canis dermatophytosis model on RFE seems to be a useful tool to investigate mechanisms involved in natural M. canis feline infections.

In vivo expression analysis of Microsporum canis secreted subtilisin‐like serine proteases in feline dermatophytosis

The cellular and molecular pathophysiology of dermatophytosis is largely unknown in both humans and animals. During the past 5 years, we developed a broad research programme to better understand the host‐fungus relationship in Microsporum canis ringworm. This allowed us to isolate and characterize several putative fungal virulence factors, especially keratinolytic proteases, belonging to two gene families encoding three subtilisin‐like serine proteases (SUBs) and three metalloproteases (MEPs). We demonstrated that all the SUBs and two MEPs were produced in hair of experimentally‐infected guinea pigs. Using the same model, we also demonstrated the immunogenicity of at least two proteases, SUB3 and MEP3. However, we recently showed that SUB3 and MEP3 produced as recombinant proteases and used as subunit vaccines failed to protect against a M. canis experimental infection in guinea pigs. As a prelude to investigation of the role of SUBs in M. canis infection in natural hosts and to their potential use as vaccines in cats, this study was designed to establish their presence in in vivo clinical conditions in the cat and human. RT‐nested PCRs using specific primers of internal fragments of SUB1, SUB2 and SUB3 were performed on total RNA extracted from infected hair or scales from naturally infected cats (n = 4) and humans (n = 2). Two specific primer pairs were also designed for the amplification of an internal fragment of M. canis actin mRNA, which was used as a positive control for M. canis RNA extraction and RT‐nested PCR. Fungal strains from which one or more SUB mRNA(s) could not be detected from infected samples were checked by PCR for the presence of the correspondent SUB gene(s) in their genomes. Results indicated that M. canis actin mRNA was detected in all samples, indicating that both M. canis RNA extraction and RT‐nested PCR conditions were successful. The three SUBs were transcribed in two cats while mRNAs encoding two of them were detected in the other two cats. The SUB1 gene was found to be transcribed in humans. All SUB genes where in vivo transcription was not detected were demonstrated to be present in the genomes of the corresponding strains. These results suggest that M. canis SUBs are strongly involved in the cat‐fungus relationship, whereas SUB1 could play a significant role in M. canis dermatophytosis in humans. Indeed, although being a very difficult technique to perform in filamentous fungi, the RT‐nested PCR used in this study demonstrated that all SUB genes could be transcribed in vivo in the cat. It suggests strongly that the corresponding encoded proteases are expressed by the fungus during invasion of feline keratinized structures. Although these data were obtained from a rather small number of samples, they are the first ones dealing with the molecular pathogenesis of dermatophytosis during natural infections. Moreover, they must be included in the frame of our previous and present studies focusing on different aspects of the host‐fungus relationship, including both the characterization of M. canis virulence factors and the host response to infection. Funding: Fonds de la Recherche Scientifique Médicale.

Evaluation of immunogenicity and protective efficacy of a Microsporum canis metalloprotease subunit vaccine in guinea pigs

In order to identify protective immunogens against Microsporum canis infection, a purified recombinant keratinolytic metalloprotease (r-MEP3) was tested as a subunit vaccine in experimentally infected guinea pigs. Both humoral and cellular specific immune responses developing towards r-MEP3 were evaluated, by enzyme-linked immunosorbent assay and by in vitro lymphocyte transformation tests respectively. Vaccination induced a strong antibody response, and a significant but transient lymphoproliferative response against the protein. However, the protocol failed to prevent fungal invasion or development of dermatophytic lesions. These results show that under the present experimental conditions, r-MEP3 specific antibodies are not protective against a challenge exposure. They also suggest that in the same model, the induction of cell-mediated immunity towards r-MEP3 is not sufficient, indicating the need for further research in the field of specific immune mechanisms involved in M. canis dermatophytosis.

Humoral and cellular immune response to a Microsporum canis recombinant keratinolytic metalloprotease (r-MEP3) in experimentally infected guinea pigs.

In order to better understand the host-fungus relationship in Microsporum canis dermatophytosis and to identify major fungal antigens, the immune response to a crude exoantigen preparation and to a purified recombinant keratinolytic metalloprotease (r-MEP3) was evaluated in guinea pigs experimentally infected with M. canis. Humoral and cellular immune responses were assessed from day 0 to day 57 post-infection (PI), the former by enzyme-linked immunosorbent assay (ELISA) and the latter via a lymphocyte proliferation assay. Infected guinea pigs developed humoral and cellular responses to both M. canis exoantigen and r-MEP3, while no specific immune response to these antigens was observed in control animals. This is the first report on the development of both humoral and cell-mediated immune responses to a purified keratinase in M. canis dermatophytosis.

Purification and characterization of a 43.5 kDa keratinolytic metalloprotease from Microsporum canis.

A keratinolytic protease secreted by a feline clinical isolate of Microsporum canis cultivated in a broth containing feline keratin as the sole nitrogen source was purified from the culture filtrate by affinity chromatography on bacitracin-agarose and by hydrophobic chromatography on octyl-agarose. The enzyme had an apparent molecular mass of 43.5 kDa and the pI was 7.7. It had a significant activity against keratin azure, elastin-Congo red and denatured type I collagen (azocoll). Using the latter substrate, the optimum pH was around 8 and the apparent optimum temperature around 50 degrees C. The protease was strongly inhibited by 1,10-phenanthroline, phosphoramidon and EDTA. The first 13 N-terminal amino acid sequence showed a 61% homology with that of the extracellular metalloprotease of Aspergillus fumigatus and with the neutral protease I of A. oryzae, confirming that this 43.5 kDa keratinase is a metalloprotease. This keratinolytic metalloprotease could be a virulence-related factor involved in pathophysiological mechanisms of M. canis dermatophytosis.