RESUMO
BACKGROUND: Onychomycosis is a common problem noticed in clinical practice. Currently available standard laboratory methods show inconsistent sensitivity; hence there is a need for newer methods of detection. AIMS: This study involves comparison of standard laboratory tests in the diagnosis of onychomycosis, namely, potassium hydroxide mount (KOH mount) and mycological culture, with histopathologic examination using periodic acid-Schiff (PAS) staining of the nail clippings. METHODS: A total of 101 patients with clinically suspected onychomycosis were selected. Nail scrapings and clippings were subjected to KOH mount for direct microscopic examination, culture using Sabouraud's dextrose agar (with and without antibiotics) and histopathologic examination with PAS staining (HP/PAS). Statistical analysis was done by McNemar's test. RESULTS: Direct microscopy with KOH mount, mycological culture, and HP/PAS showed positive results in 54 (53%), 35 (35%), and 76 (75%) patients respectively. Laboratory evidence of fungal infection was obtained in 84 samples by at least one of these three methods. Using this as the denominator, HP/PAS had a sensitivity of 90%, which was significantly higher compared to that of KOH mount (64%) or mycological culture (42%). CONCLUSIONS: Histopathologic diagnosis with PAS staining of nail clippings was the most sensitive among the tests. It was easy to perform, rapid, and gave significantly higher rates of detection of onychomycosis compared to the standard methods, namely KOH mount and mycological culture.
Assuntos
Arthrodermataceae/isolamento & purificação , Fungos Mitospóricos/isolamento & purificação , Unhas/microbiologia , Onicomicose/diagnóstico , Compostos de Potássio , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Meios de Cultura , Feminino , Humanos , Hidróxidos , Masculino , Pessoa de Meia-Idade , Micologia/métodos , Unhas/patologia , Onicomicose/microbiologia , Reação do Ácido Periódico de Schiff , Sensibilidade e EspecificidadeAssuntos
Histocitoquímica , Mycobacterium leprae/análise , Mycobacterium tuberculosis/análise , Mycobacterium/análise , Micobactérias não Tuberculosas/análise , Reação do Ácido Periódico de Schiff , Humanos , Hanseníase/diagnóstico , Infecções por Mycobacterium não Tuberculosas/diagnóstico , Tuberculose/diagnósticoRESUMO
Microdensitometry showed that the membrane profiles of normal cultivable mycobacteria were very asymmetric (outer layer denser and thicker than the inner layer), while the profiles of normal-looking M. leprae in lepromatous patients, in experimentally infected armadillos and in nude mice were approximately symmetric; moreover, the membrane of M. leprae was thicker than that of cultivable species. Using two cytochemical methods for the ultrastructural detection of periodic acid-Schiff (PAS)-positive molecules (the Thiéry procedure, and staining with phosphotungstic acid at low pH) we found that the membrane of cultivable mycobacteria, growing in vitro or in vivo, had PAS-positive components exclusively in the outer layer, while the normal-looking M. leprae in patients and in armadillos had membranes with PAS-positive components in both layers. The membranes of damaged cultivable mycobacteria, in vivo or in vitro, and of damaged M. leprae, in patients or armadillos, were PAS-negative.