Microscopy in Clinical Laboratory

Flashcards covering key concepts, principles, techniques, and stains related to microscopy in diagnostic evaluation from lecture notes.

Microscopy

The direct detection of microorganisms in clinical specimens and the characterization of organisms growing in culture.

Etiologic Agents

Microorganisms, including bacteria, fungi, viruses, and parasites, whose identification is a key role of microscopy.

Magnification (Light Microscopy)

The principle where visible light passes through a specimen and a lens, resulting in the apparent enlargement of an organism.

Resolution (Light Microscopy)

The detail of the magnified object maintained, defined as the closest distance between two objects that permits the definition of each.

Immersion Oil

A substance used in microscopy specifically to increase the resolution of the image.

Contrast (Light Microscopy)

The principle that allows objects to stand out clearly from the background in microscopy.

Bright Field Microscopy

A technique where visible light passes directly through the specimen and a lens, resulting in the magnification of the organism, governed by magnification, resolution, and contrast.

Kohler Illumination

A method that provides maximum illumination and resolution by properly positioning the condenser to ensure that light is focused through the specimen.

Direct Smears

Prepared from primary clinical samples to identify types of cells present (microorganisms, white blood cells, epithelial cells) and provide preliminary information for patient care.

Indirect Smears

Prepared from cultivated microorganisms to identify a single morphotype of cells from an isolated colony, used to correlate with initial direct smear findings.

Gram Stain

The principal differential staining technique used for the examination of bacteria, classifying them as either Gram-positive or Gram-negative based on their cell wall properties.

Gram-Positive Organisms

Bacteria that retain the primary stain (Crystal violet) and appear deep purple after undergoing the Gram stain procedure.

Gram-Negative Organisms

Bacteria that lose the primary stain after decolorization and take up the counterstain (Safranin), appearing pink to red.

Acid-Fast Stains

Differential stains used to detect bacteria whose cell walls contain mycolic acids, such as Mycobacterium.

Ziehl-Neelsen Stain

An acid-fast staining method where the primary stain enters the bacterial cell wall, typically aided by heating.

Kinyoun’s Stain

An acid-fast 'cold method' where the primary stain contains phenol, allowing it to penetrate the bacterial cell wall without the need for heating.

Phase-Contrast Microscopy

A technique where beams of light pass through a specimen to create different light intensities and greater contrast, permitting the observation of living organisms and their movement (e.g., in wet-mounts) without staining.

Fluorescent Microscopy

A technique where fluorochromes are excited to higher energy levels and then release excess energy as visible light upon returning to a normal state, making objects appear brightly lit against a dark background.

Acridine Orange Stain

A nonspecific cationic fluorescent dye that stains nucleic acid, primarily used to confirm the presence of bacteria in indeterminate blood cultures.

Calcofluor White Stain

A fluorescent dye that binds strongly to cellulose and chitin, significantly enhancing the visibility of fungi in tissue and other specimens.

Auramine-Rhodamine Stain

A basic fluorescent dye that binds to mycolic acid, causing cells to appear bright yellow or orange against a green background.

Dark-Field Microscopy

A technique that achieves contrast by directing light at an oblique angle, so that only light which hits the object is visualized against a dark background.

Digital or Virtual Microscopy

Involves automation and digital imaging to adapt microscopes for multiple uses, including slide scanning and coordinate tracking, and facilitates real-time consultation and transmission of images and results.