MicroBiology Flashcards
Colonization
presence of bacteria on a host without or inducing disease. Ex: Staph aureus colonization in the nose
Infection
An organism abnormally present and multiplying in host tissues usually leading to an immune response
Disease
Impairment of physiologic function with associated signs and symptoms.
Infectivity
Impairment of physiologic function with associated signs and symptoms.
Pathogenicity
Ability of microbe to cause disease
Virulence
Degree of pathogenicity within a specified group which depends on both bacterial and host factors
Gram-positive cell wall
Purple stained; Outside to inside: Thick peptidoglycan cell wall (with teichoic acid), membrane
Gram-negative cell wall
Pink stain; Outside to inside: Lipopolysachharide (endotoxin), membrane, small petidoglycan wall, membrane
Acid-fast stain
Acid-fast organisms like Mycobacterium contain large amounts of fatty acids, waxes, and complex lipids within their cell walls called mycolic acids (resist staining by ordinary methods such as a gram stain).
Coagulase test
Used to differentiate Staphylococcus aureus (positive) from coagulase negative Staphylococcus.
Coagulase is an enzyme produced by S. Aureus that converts (soluable) fibrinogen in plasma to (insoluble) fibrin.
Hemolysis on blood agar
Alpha: partially breaks down the RBCs and leaves greenish color behind, due biliverdin
Beta: breaks down the red blood cells and hemoglobin completely, leaving a clear zone around the bacterial growth
Gamma: if the organism does not produce hemolysis and does not break down the blood cells, no clearing will occur
Indole test
Used to determine the ability of the organism to convert tryptophan into indole
Kirby-Bauer
A test of the antibiotic sensitivity of bacteria; uses antibiotic disks to test whether particular bacteria are susceptible to specific antibiotics.
Bacterial virulence factors
1)Adherence, 2) surface modifications, 3) invasion, 4) modify the host
Endotoxins
Within the bacteria; LPS in gram neg bacteria