Laboratory diagnosis

In diagnosis: Laboratory tests
Laboratory tests can be valuable aids in making a diagnosis, but, as screening tools for detecting hidden disease in asymptomatic individuals, their usefulness is limited. The value of a test as a diagnostic aid depends on its sensitivity and specificity.

1. LABORATORY DIAGNOSIS OF FUNGI BY : ANJALI SHARMA (M.Sc.) DEPARTMENT OF MICROBIOLOGY

2. CONTENTS : DIRECT MICROSCOPY CULTURE MEDIA DNA PROBES SEROLOGICAL TESTS

3. 1) DIRECT MICROSCOPY Collection of samples – from skin scrapping, nails scrabs ,sputum etc .) Morphology : conidia , filamentousspores , ( asexual , sexual ) hyphae etc . In light microscope . Includes different dyes : 10%KOH SOLUTION: To dissolve tissue material. Alkali resistance fungi intact or stained with special dye. E.g: indian ink – for identification of cryptococcus .

4. 2. CALCOFLOUR WHITE : Bind to cell wall of fungi. 3. METHAMINE SILVER : Diagnosis of fungi in tissue.

5. CULTURE MEDIA : SABOURAUD’S DEXTROSE AGAR: Facilitates slow growing fungi appearance. Bacteria can’t grow on this agar , beacuse of the low pH. And presence of antibiotics.

6. DNA PROBES : Visual identify of colony growing in culture at earlier stage of growth. Diagnosis made rapid . DNA PROBE TEST : cryptococcus, blastomyces .

7. SEROLOGICAL TESTS: PRESENCE OF ANTIBODIES : P resence of antibodies in patients’ serum or spinal fluid used for – systemic mycoses . It is not uselful for other kind of mycoses . 2. COMPLIMENT FIXATION: E.g.: histoplamosis , blastomycosis ,coccidiomycoses . 3. AGGLUTINATION TESTS : E.g. : Cryptomycoses . Polysaccharide capsular antigens detected in C. Neoforms .