Culturing Methods
Medical microbiology Lab
By: M. Shenagari
Enrichment mediumsThe most frequently used enrichment mediumis
the blood agar plate containing 5% whole blood.Selective mediums
allow only certain bacteria to grow and suppress the reproduction
of others.Indicator mediums are used to register metabolic
processes.
Identification of BacteriaMorphological characteristicsForm
(sphere, rod, spiral)Size; pseudogroupings (clusters, chains,
diplococci)Staining (Gram-positive, Gram-negative); flagella
(presence, arrangement);capsule (yes, no); spores (form, within
cell formation)
Physiological characteristicsRespiratory chain enzymes
(oxidases, catalases)Enzymes that break down carbohydrates,
alcohols, glycosides(e.g., betagalactosidase)Protein metabolism
enzymes (e.g., gelatinase, collagenase)Amino acid metabolism
enzymes (e.g., decarboxylases, deaminases, urease)Other enzymes:
hemolysins, lipases, lecithinases, DNases, etc.End products of
metabolism (e.g., organic acids detected by gas
chromatography)Resistance/sensitivity to chemical
noxaeCharacteristics of anabolic metabolism (e.g., citrate as sole
source of C)
Chemical characteristicsDNA structure (base sequences)Structure
of cell wall mureinAntigen structure: fine structures detectable
with antibodies(e.g., flagellar protein or polysaccharides of the
cell wall or capsule)Fatty acids in membranes and cell wall;
analysis using different chromatographicmethods
