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50 Cards in this Set
- Front
- Back
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Which of the following can grow in the presence of oxygen: strict, obligate, or facultative anaerobes?
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facultative anaerobes
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What is the final electron acceptor in respiration?
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molecular oxygen
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The total count of bacteria includes what?
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both living/viable and dead bacteria
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What determines the number of living/viable bacteria?
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colony count (# colonies x dilution factor)
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What site does RNA polymerase bind to initiate the synthesis of mRNA?
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promoter
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At what site is transcription terminated?
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attenuator
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Does the presence of leucine increase or terminate transcription?
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terminates
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To what sequence does the repressor bind?
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operator
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Does the presence of allolactose induce or terminate synthesis of beta-galactosidase?
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induce
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How does PAB (p-aminobenzoic acid; a component of folic acid) overcome sulfa addition?
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competitively
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How does folic acid overcome sulfa addition?
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noncompetitively
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How does folic acid overcome sulfa addition?
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noncompetitively
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When the body's defenses are low (bacterial endocarditis, bacterial meningitis, agranulocytopenia--low neutrophil count), what type of drugs are preferred (-cidal or -static)?
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bactericidal
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Which type of drugs can be faster acting, -cidal or -static)?
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bacteriostatic
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Does trimethoprim block the function or synthesis of folic acid?
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function
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What is the bacterial resistance mechanism for vancomycin?
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target (cell wall) modification (change in binding site in the peptidoglycan target)
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What is the bacterial resistance mechanism for quinolones (nalidixic acid, cipro)?
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mutations in genes encoding DNA gyrase and topoisomerase IV & by efflux pumps
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What is the bacterial resistance mechanism for aminoglycosides?
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enzymatic modification of drug by R plasmid encoded enzyme; drug has reduced affinity for ribosome, and transport into cell is reduced.
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What is the bacterial resistance mechanism for tetracyclines?
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efflux pump pushes drug out of cell
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What is the bacterial resistance mechanism for macrolides?
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resistance by target (ribosome) modification; methylation of 23S ribosomal RNA (methylase)
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What newer macrolide has been modified to bind to two separate sites on the 23S rRNA to combat bacterial resistance?
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telithromycin
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What is the bacterial resistance mechanism for oxazolidinones (linezolid)?
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mutations in 23S rRNA
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On what is the gene coding for beta-lactamase carried?
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transposon
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What does MRSA stand for?
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methicillin-resistant Staphylococcus aureus
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What is the action of oxazolidinones (linezolid)?
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Bind to the 50S subunit of bacterial ribosomes to prevent assemply of translational complex and initiation of protein synthesis
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What is the antibiotic action of polyene (amphotericin B)?
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binds to sterols in eukaryotic cell membranes, leading to membrane leakiness and, at high levels, lysis; bind more avidly to ergosterol in fungi membranes than cholesterol in higher eukaryotes
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What bacterial adhesin do gram negative bacteria have that gram positive don't?
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pili (fimbriae)
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What two types of bacterial adhesins do both gram positive and gram negative bacteria have?
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surface proteins and capsules
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Give an example of a gram negative surface protein (bacterial adhesin)
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invasin
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What normal cellular receptors do invasins recognize?
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integrins
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Name a receptor for certain gram positive bacteria?
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fibronectin
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How do meningococci and pneumococci prevent complement activation?
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secreting polysaccharide capsule masks that cover surface components that can activate complement via the alternative path
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What bacteria avoid complement activation by coating in circulating IgA antibodies?
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meningococci
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How does herpes simplex virus defend against complement?
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it has an envelope glycoprotein that binds complement component C3b
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How do Salmonella and E. coli defend against complement?
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They hinder complement access to its target (bacterial outer membrane) rather than preventing formation of complement membrane attack complexes.
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What type of strains (smooth or rough) inhibit access of the membrane attack complex to bacterial otuer membrane?
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smooth
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What is the difference between smooth and rough strains?
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smooth have a long O-antigen polysaccharide chain while rough have little or no O antigen.
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How does Group A Streptococci avoid phagocytosis?
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Diversion--it activates complement C5a peptidase that inactivates this chemotactic product of the complement cascade
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How do highly invasive bacteria (like pseudonomads, staphylococci, group A stretococci, and gas gangrene) avoid phagocytosis?
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produce exotoxins called leukocidins which kill neutrophils and macrophages
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What do staph and strep produce that binds to IgG molecules at the wrong end (Fc portion)?
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protein A
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Intraphgosomal microbes like tuberculosis, psittacosis, and legionnaires disease survive inside phagocytes via what mechanism?
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inhibition of lysosome fusion with phagosomes
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How do microbes like shigellae, Listeria monocytogenes, rickettsiae, and influenza viruses survive inside phagocytes?
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escape into the cytoplasm by destroying the phagosomal membrane
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What does Listeria monocytogenes secrete to escape from the phagosome?
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listeriolysin (pore-forming toxin)
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How does Leishmania survive inside phagocytes?
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innate resistance to lysosomal enzymes
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Name a microbe that inhibits oxidative killing of phagosomes by inhibiting respiratory burst.
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Legionella
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What microbe produces a catalase that breaks down the H2O2 used for oxidative killing by phagocytes?
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Staphylococcus aureus
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How do herpes simplex virus, varicella zoster virus, and respiratory syncytial virus spread?
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by causing infected cells to fuse with uninfected, neighboring cells.
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What are these types of viruses notable for forming?
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syncytia and multinucleated giant cells
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How do Shigella and Listeria monocytogenes spread to other cells?
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directly by inducing polymerization of actin
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How do superantigens (toxins made by certain streptococci) divert lymphocytes?
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they stimulate a nonspecific T-cell response
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