Bacteria Flashcards
Gram Negative
Thin layer of peptidoglycans between outer membrane and cytoplasmic membrane.
O Antigen
Surface antigen on gram negative bacteria that is species specific
Core Polysaccharide
Contributes to membrane integrity, anchors O antigen
Lipid A
An Endotoxin anchoring the core polysaccharide
Monocyte/Macrophage interaction with LPS
Production of cytokines IL-1, IL-6, IL-8, and TNFα. Activates C3a and C5a complements, causing histamine release. Activates coagulation cascade.
Gram Positive cell wall
Thick outer peptidoglycan layer with teichoic and lipoteichoic acids. Lipoteichoic acids share LPS properties.
Acid fast cell walls
Peptidoglycan w/ lipid based polymers woven throughout. Mycolic acid is present as a cord factor.
Cell-wall less bacteria
No peptidoglycan. Sterols within bilayer maintain fluidity. Has adhesions on “neck.” Cannon be stained using gram stains or treated with wall inhibiting antibiotics.
Pilus & Fimbria
External structures composed of fimbrins, adhesins, and pilins. Responsible for adhesion to host cell surface, communication, virulence factor, and recombination
Endospore
Dormant survival form, not metabolically active. Formed as a response to adverse conditions. High amount of calcium Blount to dipiclonic acid.
Exoenzyme
Bacterial products that can be degradative or hydrolytic
Exotoxins
Proteins secreted by many bacteria. Gram negative can transport via type 3 transportation.
A-B toxin
Most common type of toxin. Two units. B-unit binds to host cell receptor. A-unit mediates enzymatic activity (is toxic) and translocates after B-unit binds.
Membrane disrupting toxins
Hydrolytic. Pore former, destruction of phospholipid bilayer. Kills host cell.
Super Antigens.
Form bridges between MHC II of macrophages and T cell receptors. Causes cytokine storm of IFNγ, IL-1, IL-6, and TNFα.
Endotoxins
Structural component of bacteria, released when lysed.
Blood Agar (BAP)
Differential medium. Does not hydrolyze RBCs = γ, partially hydrolyzes = α and a green coloration, completely hydrolyzes = β and clearing of agar.
Chocolate agar (CHOC)
Enriched medium
Thayer Martin/New York Agar
Modified chocolate agar containing antibiotics to prevent growth of genital flora, allowing Neisseria species to grow. Enrichment and selective
Mannitol Salt Agar (MSA)
Selective and differential. Staphylococcus will grow. S. aureus will change color from red to yellow.
MacConkey (MAC)
Selective and differential. Only some gram-negative will grow. Those that ferment lactose will change the color to red/purple.
Sorbitol MacConkey (SMAC)
Modified MAC. Selective and differential. Some gram negative can grow. Those that can ferment sorbitol change the color to red/purple.
Hektoen agar
Selective and differential. Salmonella will show as green colonies with black centers. Shigella will show yellow-green colonies. Lactose fermenters will turn it salmon colored.
Eosin methylene blue
Selective and differential for Coliforms. Gram-positive can not grow.
ENT/BEA
Selective and differential. Inhibits staphylococci and all gram-negative bacteria. Colonies that metabolize esculin form a black precipitate.
MYC/SAB
Used for fungi
Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS)
selective and differential. All enterobacteria and enterococci are inhibited, as well as all gram-positive bacteria. Vibrio cholera turns the media yellow. Other vibrios are blue. Some non cholera vibrios may produce H2S and have black centers in their blue colonies.
Buffered Charcoal Yeast Extract (BCYE)
Enrichment. Grows Gram-negative Legionella pneumophila. Colonies will be white-grey/blue-grey
Regan-Lowe/Bordet Gengou
Enrichment medium. Cultures Bordetella Pertussis.
Lowenstein Jensen
Selective and enrichment medium used to culture mycobacterium. Penicillins are added to kill gram positive and gram negative bacteria.
Catalase test.
Determines if catalase is present. Distinguishes staph from strep. Add H2O2, +/- bubbles.
Oxidase test
Determine if Oxidase is present. Add chemical, +,- dark purple color.
Coagulase test
Important in identification of S. Aureus and Y. Pestis. +/- agglutination results after antibodies against coagulase are added.
Lancefield test
Differentiate between groups of streptococcus. +/- agglutination results
Nitrite
Determines if organism can reduce nitrate to nitrite. Red is positive. Can use dipstick
Urease
Broth contains urea and a pH indicator. If urease is present, solution turns pink
Índole test
If Índole is present, bacteria can split tryptophan. This will turn the test bright red
Sugar fermentations
Multiple tubes with different sugars have the same organism added to each, allowing us to determine which sugars can be metabolized by said organism.
Susceptibility testing
Discs with various chemicals are added to cultured bacteria. Zones of clarity indicate dying bacteria and show sensitivity to that chemical.
CAMP Test
Used to identify S. Agalactiae and Listeria. S. Aureus (known positive) is streaked in a line, and your test is streaked perpendicular to S. Aureus streak without touching. Positive shows an “arrowhead” hemolysis between junction of S. Aureus and CAMP producer.
Transformation
Naked DNA uptake
Transduction
bacterial DNA transfer via viruses
Conjugation
DNA transfer via cell/cell contact.
