Lecture | Bacterial Identification Flashcards
Microscopy, staining techniques, biochemical test, imumunodiagnosis, molecular diagnosis is for
Bacterial identification
Used for the detection of microorganisms directly in the clinical specimen and for characterization of organisms grown in culture
Microscopy
Defined as the use of microscope to manify objects
Microscopy
visible light is passed through the specimen and then through a series of lenses that bend the lights
Bright-field microscopy or Light microscopy
Microscopic technique for visual inspection at a time of smear (fixed smear), culture preparation, microscopic examination of gram stain preparation
Bright-field microscopy or light microscopy
Does not use fixed smear and allows to view organism in wet preparation or mark
Phase-contrast microscopy
Uses beam of light passing through the specimen
Phase-contrast microscopy
Deflected light is called
Refractive index
Greater refractive index means
Decrease light intensity
Staining is not part of phase-contrast, this allow identification of viable microorganisms such as
Fungal identification
Fluorescent microscopy uses a dye known as
Fluorochrome
Darkfield microscopy is usually employed for the diagnosis of
Spirochetes
Phase-contrast and dark-field has a similarity of not using any stain or dye to achieve contrast, instead they
Alter the microscopic technique
2 types of Electron microscopy
SEM & TEM
Creates image by detecting reflected or “knock-off” electrons
Scanning Electron Microscopy
Creates 3D information of sample surface and its composition
SEM
Uses transmitted electron
Transmitted electron Microscopy
Detects the transmitted electron to create an image, offering valuable information in the INNER structure of the sample and morphology inside
TEM
Fixation makes sure that—
Material would cling to the surface of the microscope slide
2 process of fixation
- Heat
- 95% methanol
Preparation : Specimen or Organism Type
(For Gross Examination)
WET PREPARATION : ?
Parasites and material >1 mm in size
Preparation : Specimen or Organism Type
(For Microscopic Examination)
WET PREPARATION (direct/sedimented) : ?
Fluids or semi fluid
Preparation : Specimen or Organism Type
(For Microscopic Examination)
CYTOCENTRIFUGED (direct/presedimented) : ?
Clear or slightly turbid fluid
Preparation : Specimen or Organism Type
(For Microscopic Examination)
Smear : ?
Clear or slightly turbid fluid
Preparation : Specimen or Organism Type
(For Microscopic Examination)
? : pus/fluid, tissue homogenate, swab rinse
Drop
Preparation : Specimen or Organism Type
(For Microscopic Examination)
Pellet : ?
Blood culture and dilute specimen
Preparation : Specimen or Organism Type
(For Microscopic Examination)
? : swabbed material
Rolled
Preparation : Specimen or Organism Type
(For Microscopic Examination)
Imprint (touch preparation) : ?
Tissue
Directed toward coloring the forms and shapes present. Ex: methylene blue
Simple stain
Directed toward coloring specific components of the elements present. Ex: Gram’s Stain; Acid-Fast Stain
Differential Stain
Performed to visualize selected tissue element, entities, and microorganisms
Special stains
Special stain for flagella
Leifson Stain
Special stain for endospore
Schaeffer-Fulton Stain
Special stain that uses Malachite green
Schaeffer-Fulton Stain
A type of stain wherein it’s the background that is stained
Negative stain
Examples of negative stains
India ink ; Nigrosin
Use to visualize/examine the presence of Cryptococcus neoformans on Cerebrospinal specimen
India ink
Principal stain for microscopic examination of bacteria
Gram stain
Gram stain principle is based on the —?— of the group of microorganisms
Cell wall composition
Primary stain of Gram Stain
Crystal violet
Mordant of Gram stain
Gram’s iodine
Decolorizer of Gram stain
Alcohol/acetone
Counterstain of gram stain
Safranin
Gram+ that has an acid that contributes to the ability of gram+ organism to resist alcohol decolorization
Teichoic acid
Gram+ contains highly cross-linked layer that retains primary dye
Peptidoglycan
Where peptidoglycan is loosely distributed
Gram-
Stain utilized for the detection of mycobacterium
Acid-fast stain
A component of the cell that gives the cell wall the ability to resist decolorization
Mycolic acid
Acid-fast stain methods
- Ziehl Neelsen (Hot method)
- Kinyoun (Cold Method)
Primary stain of acid-fast
Carbolfuchsin
Decolorizer of acid-fast stain
- Acid Alcohol (3% HCL + 95% Ethanol)
Counter stain of acid-fast
Methylene blue
Mordant of acid-fast
Phenol ( increased concentration in Kinyoun method)
A mixture of phenol and the dye basic fuchsin
Carbolfuchsin
Alternative for acid alcohol
20% Sulfuric Acid
2 types of fluorochrome
- Acridine orange
- Auramine Rhodamine
A fluorochrome that confirms the presence of bacteria in blood cultures
Acridine orange
Determination: bacteria will give off bright orange fluorescence
Acridine orange
Stain that is also used for detection of cell wall-deficient bacteria that are incapable of retaining the dyes used in gram stain
Acridine orange
Used for the detection of our mycobacteria
Auramine Rhodamine
Has a very high affinity with the waxing mycolic acid found in the cell wall of mycobacteria
Auramine Rhodamine
Determination: it would nonspcifically bind to nearly all microbacteria, giving off a bright yellow appearance or orange against a greenish background
Auramine Rhodamine
Acridine orange detects presence of cell wall deficient bacteria such as
Mycoplasma and ureaplasma
Enhance detection of micro-bacteria directly from patient specimen. Has higher specificity and sensitivity
Auramine rhodamine
Colonial morphology is observable after how many hours
18-24 hours of incubation
Inoculation of the clinical specimen onto laboratory media
Primary plating
Initial mid culture media we use to plate
Primary media
Term us to introduce specimen unto the laboratory media
Inoculate
Interpretation of primary culture
Plate reading
Comparative examination of the colony morphology
Plate reading
Media that contain specific nutrients required
Enrichment media