Microbiologic confirmation of an infectious diseses may be obtained by direct demonstration of the organism, by growing the organism in culture or by serologic method.
Direct demonstration of an infective agent may be:
By direct microscopy: India ink preparation(cryptococi), dark ground illumination(vibrio spirochestes), KOH preparation(dermatophytes) and wet wount(stool parasites).
By staining:Gram stain(malaria),Giemsa stain(chlamydia), Ziehl-Nielsen stain(acid-fast bacilli), silver stains(pneumocystis).
By antigen detection using latex agglutination teste. (meningococcus, pneumcococcus) and enzyme immunoassay.
Culture method: Proper collection technique(for clinical specimen), suitable transport and culture media and optimal growth conditions may be requuired for fastidious organisms(such as anaerobes), phenotyphic characterization may be done and antibiotic sensitivity determined after culture of the organism.
Serologic method: This method may be the only method for diagnosing viral, rickettisal, chalamydial and mycoplasma infections. Serology also provides supportive evidnce for certain bacterial infections( also for streptococci, widal for typhoid).
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