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Microsporum nanum: First Recorded Isolation from Animals in the United States
Abstract
The first cases in the United States of swine infections caused by the fungus Microsporum nanum are reported. The infections
occurred in a herd of Yorkshire swine in Pennsylvania. The dermatophyte, which readily produced experimental infections, was
identified by isolation and studies in pure cultures.
... N. nana is considered to prefer pigs as their major host and infection in pigs has been reported in Europe [31], North America [32], and New Zealand [33]. It has also been attributed to the outbreaks of ringworm in Iberian pigs in Spain [34]. ...
Keratinophilic fungi are mostly soil-inhabiting organisms with occasional infections in humans and animals. Even though most dermatophytes are host-adapted, cross-species infections are common by zoophilic and geophilic dermatophytes. N. nana is considered an etiological agent of ringworm in pigs but has also been isolated from other animals, including humans. However, it also possesses many characteristics of geophilic dermatophytes including the ability to grow in soil. N. nana produces characteristic pear-shaped macroconidia and usually exhibits an ectothrix pattern of hair infection. It has been isolated from dermatitis lesions as well as from soil. N. nana infections in pigs are not of much concern as far as economy or health is concerned. But it has been associated with onychomycosis and gonathritis in humans, which are significant in human medicine. The shift in the predominance of dermatophytes in humans and the ability to evolve into a potential tinea pathogen necessitates more understanding of the physiology and genetics of N. nana. In this review, we have attempted a detailed analysis of the studies about N. nana, emphasizing growth and cultural characters, physiology, isolation, infection in humans and animals, molecular characterization and antifungal susceptibility.
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É comunicado o segundo caso de infecção humana por Microsporum nanum no Brasil. A investigação epidemiológica visando determinar a fonte de infecção não obteve sucesso. O padrão dermatológico das lesões foi o de Tinea corporis clássica.
Microsporum nanum is a dermatophyte that can cause disease in both man and animals and is most frequently associated with ringworm infection in pigs. Human infections are rare in the literature. Three new cases of human M. nanum infection are reported here. Two patients had inflammatory tinea faciei and one had tinea cruris. The patients were successfully treated with clotrimazole or miconazole cream, sometimes combined with griseofulvin. All three patients were hog farmers and lived in the same small rural area. Occupational exposure is suggested as the cause of infection.
The first human infection by M. nanum in Romania is here reported. The agent was isolated from a solitary lesion on the glabrous skin in a girl, aged 8 years. The causative fungus was identified by the presence of numerous, rarely biseptate, “light-bulb” macro-conidia found in the culture. The strain was inoculated with positive results into guinea-pig and man. Its antigenic capacity proved to be similar with that of M. gypseum complex.RésuméOn rapporte le premier cas roumain ?infection mycosique par M. nanum. L'agent a été isolé ?une lésion solitaire cutanée apparue sur le dos ?une petite fille de 8 ans. ľidentification du parasite a été possible grâce à. la présence dans les cultures de nombreux petits fuseaux caractéristiques. La souche isolée a été inoculée avec succès au cobaye et à ľhomme. Les propriétés antigéniques du M. nanum se sont montrées similaires avec celles du M. gypseum.ResumenSe relata la primera infección humana por M. nanum en Rumania. El agente causal fue aislado de una lesión solitaria de piel lampiña de una nina de 8 años de edad. El hongo fue identificado por la presencia de numerosas macroconidias, rara vez biseptadas, piriformes halladas en los cultivos. La cepa fue inoculada con resultados positivos en cobayo y en seres humanos. La capacidad antigénica resultó ser similar a la del complejo M. gypseum.ZusammenfassungErster Bericht über eine M. nanum-Infektion beim Menschen in Rumänien. Der Erreger wurde aus einem Einzelherd vom oberen Teil des Rückens eines 8 jährigen Mädchens isoliert. Die Ränder des Krankheitsherdes waren etwas erhaben und mit Bläschen besetzt, eine zentrale Abheilung war jedoch nicht festzustellen. Im Nativpräparat von den Bläschen und Schuppen fanden sich zahlreiche Pilzfäden. Auf Sabouraud-Glucose-Agar mit Chloramphenicol-Zusatz wuchsen weißcremige flaumige Kolonien, die nach 7–10 Tagen puderig und leicht gelblichbraun wurden. Die Identifizierung erfolgte aufgrund der typischen, sehr zahlreichen, zwiebelförmigen, ein- bis zweizelligen, selten dreizelligen Makrokonidien.Die experimentelle Übertragung des Stammes auf Meerschweinchen gelang in 2 von 3 Fällen; auch bei 2 von 3 freiwilligen Versuchspersonen konnten deutliche Krankheits-erscheinungen erzeugt werden. Die antigenen Eigenschaften des Stammes erwiesen sich als ähnlich wie die des M. gypseum-Komplexes.
Microsporum nanum was first described in 1954 by Fuentes, Aboulafia, and Vidal,1 who isolated a "dwarf form" of Microsporum gypseum from a case of tinea capitis (kerion) in an 8-year-old white boy. They classified this organism as M. gypseum var. nanum. Seven months later these same investigators1 isolated a similar strain from a glabrous skin infection in an adult. In 1956 Fuentes2 reported that the 2 isolates previously described had proved to be stable in their gross and microscopic characteristics over a period of 3 years. He then proposed that this organism be considered a new species: Microsporum nanum. Ajello3 now classifies M. nanum as a separate species of Microsporum.
The initial case reported by Fuentes et al.1 presented the following findings: 1. The lesion was a kerion. 2. The fungus invaded hair as an endothrix. 3. Infected hairs exposed to Wood's light fluoresced with
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.