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125 Cards in this Set
- Front
- Back
What is the function of Peptidoglycan? Chemical composition? |
- Gives rigid support and protects against osmotic pressure
- Sugar backbone with peptide side chains cross-linked by transpeptidase |
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What is the function of Cell Wall / Cell Membrane (which kind of bacteria have this)? Chemical composition?
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Gram Positives
- Major surface antigen - Made of peptidoglycan for support - Lipoteichoic acid induces TNF and IL-1 |
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What is the function of Outer Membrane (which kind of bacteria have this)? Chemical composition?
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- Gram Negatives
- Site of endotoxin (LPS) - major surface antigen - Lipid A induces TNF and IL-1 - O-polysaccharide is the antigen |
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What is the function of the Plasma Membrane in bacteria? Chemical composition?
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- Site of oxidative and transport enzymes
- Phospholipid bilayer |
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What is the function of ribosomes? Chemical composition?
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- Protein synthesis
- 50S and 30S subunits |
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What is the function of the Periplasm? Chemical composition?
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- Space between the cytoplasmic membrane and outer membrane in gram-negative bacteria
- Contains many hydrolytic enzymes, including β-lactamases |
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What is the function of the bacterial capsule? Chemical composition?
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- Protects against phagocytosis
- Polysaccharide (except Bacillus anthracis, which contains D-glutamate) |
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What is the function of the pilus/fimbria? Chemical composition?
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- Mediates adherence of bacteria to cell surface
- Sex pilus forms attachment between 2 bacteria during conjugation - Made of glycoprotein |
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What is the function of flagella? Chemical composition?
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- Motility
- Made of proteins |
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What is the function of Spores? Chemical composition?
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- Resistant to dehydration, heat, and chemicals
- Keratin-like coat; dipicolinic acid; peptidoglycan |
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What is the function of Plasmids? Chemical composition?
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- Contains a variety of genes for antibiotic resistance, enzymes, and toxins
- Made of DNA |
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What is the function of Glycocalyx? Chemical composition?
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- Mediates adherence to surfaces, especially foreign surfaces (eg, indwelling catheters)
- Made of polysaccharide |
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What are the different morphologies of bacteria?
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- Circular (coccus)
- Rod (bacillus) - Branching filamentous - Pleomorphic - Spiral - No cell wall |
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What are some G+ cocci? G-?
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G+
- Staphylococcus - Streptococcus G- - Neisseria |
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What are some G+ rods / bacilli?
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- Clostridium
- Corynebacterium - Bacillus - Listeria - Mycobacterium (acid fast) - Gardnerella (gram variable) |
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What are the types of G- rods / bacilli?
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- Enterics
- Respiratory - Zoonotic |
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What are the Enteric G- rods / bacilli?
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- E. coli
- Shigella - Salmonella - Yersinia - Klebsiella - Proteus - Enterobacter - Serratia - Vibrio - Campylobacter - Helicobacter - Pseudomonas - Bacteroides |
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What are the Respiratory G- rods / bacilli?
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- Haemophilus (pleomorphic)
- Legionella (silver) - Bordetella |
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What are the Zoonotic G- rods / bacilli?
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- Francisella
- Brucella - Pasteurella - Bartonella |
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What are the branching filamentous G+?
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- Actinomyces
- Nocardia (weakly acid fast) |
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What are the Pleomorphic G-?
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- Rickettsiae (Giemsa)
- Chlamydiae (Giemsa) |
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What are the Spiral G-?
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Spirochetes:
- Borrelia (Giemsa) - Leptospira - Treponema |
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What are the bacteria with no cell wall (do not gram stain)?
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Mycoplasma
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What is unusual about the cell membranes / walls of Mycoplasma?
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Contain sterols and have no cell wall
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What is unusual about the cell membranes / walls of Mycobacteria?
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Contain mycolic acid; high lipid content
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Which bugs do not gram stain well?
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These Microbes May Lack Real Color:
- Treponema (too thin to be visualized) - Mycobacteria - Mycoplasma (no cell wall) - Legionella pneumophila (primarily intracellular) - Rickettsia (intracellular parasite) - Chlamydia (intracellular parasite, lacks muramic acid in cell wall) |
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How can you visualize Treponema bacteria (causes syphilis)?
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- Use dark-field microscopy and fluorescent antibody staining
- It is too thin to be visualized with Gram stain |
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How can you visualize Mycobacteria (causes TB)?
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- Carbolfuchsin in acid-fast stain detects the high lipid content in cell wall
- Does not Gram stain well |
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How can you visualize Legionella?
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- Silver stain
- Does not Gram stain well |
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Which bacteria can be stained with the Giemsa stain?
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Certain Bugs Really Try my Patience:
- Chlamydia - Borrelia - Rickettsiae - TRYpanosomes - Plasmodium |
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What does the PAS (periodic acid-Schiff) stain, stain? Use?
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PASs the SUGAR:
- Stains glycogen, mucopolysaccharides - Used to diagnose Whipple disease (Tropheryma whipplei) |
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Which bacteria can be stained with the Ziehl-Neelsen (Carbol Fuchsin) stain?
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Acid fast organisms
- Nocardia - Mycobacterium |
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Which microbe can be stained with the India Ink stain?
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Cryptococcus neoformans (mucicarmine can also be used to stain thick polysaccharide capsule red)
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Which microbes can be stained with the Silver stain?
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- Fungi (eg, Pneumocystis)
- Legionella - Helicobacter pylori |
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What are the special culture requirements of H. influenzae?
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Chocolate agar w/ factors V (NAD+) and X (Hematin)
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What are the special culture requirements of N. gonorrhoeae and N. meningitidis?
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Thayer-Martin (or VPN) media
- Vancomycin (inhibits G+ organisms) - Polymyxin (inhibits G- organisms except Neisseria) - Nystatin (inhibits fungi) "To connect to Neisseria, please use your VPN client" |
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What are the special culture requirements of B. pertussis?
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Bordet-Gengou (potato) agar
(Bordet for Bordetella) |
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What are the special culture requirements of C. diphtheriae?
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- Tellurite agar
- Löffler medium |
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What are the special culture requirements of M. tuberculosis?
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Löwenstein-Jensen agar
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What are the special culture requirements of M. pneumoniae?
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- Eaton agar
- Requires cholesterol |
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What are the special culture requirements of Lactose-Fermenting enterics?
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- MacConkey agar (fermentation produces acid, turning the colony PINK)
- E. coli is also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen |
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What are the special culture requirements of Legionella?
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Charcoal yeast extract agar buffered with cysteine and iron
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What are the special culture requirements of Fungi?
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SABouraud agar = "SAB's a fun guy"
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What are the requirements of Obligate Aerobes?
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Use an O2-dependent system to generate ATP
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Which kind of bacteria use an O2-dependent system to generate ATP?
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Obligate Aerobes: Nagging Pests Must Breathe
- Nocardia - Pseudomonas - MycoBacterium tuberculosis |
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What is the relationship of Pseudomonas to O2? Where does it infect?
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P. aeruginosa in an obligate aerobe seen in burn wounds, complications of diabetes, nosocomial pneumonia, and pneumonias in cystic fibrosis patients
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What is the relationship of Mycobacterium tuberculosis to O2? Where does it infect?
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Obligate Aerobe
- Reactivation has a predilection for the apices of the lung (which have the highest PO2) - Reactivation may occur after immune compromise or TNF-α inhibitor use |
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What are the requirements of Obligate Anaerobes?
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Anaerobes Can't Breathe Air
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Which kind of bacteria can not be exposed to oxygen? Where are they found?
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Obligate Anaerobes: Can't Breathe Air
- Clostridium - Bacteroides - Actinomyces Anaerobes are normal flora in the GI tract, pathogenic elsewhere |
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What are the characteristics of Clostridium, Bacteroides, and Actinomyces?
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Obligate Anaerobes
- Lack catalase and/or superoxide dismutase and thus are susceptible to oxidative damage - Generally foul smelling (short-chain FAs) - Difficult to culture - Produce gas in tissue (CO2 and H2) - Normally found in GI tract, pathogenic elsewhere |
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Which antibiotics are ineffective against Obligate Anaerobes? Why?
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AminO2glycosides:
- Ineffective against anaerobes because these antibiotics require O2 to enter into bacterial cell - Obligate Anaerobes only are grow in areas without O2 |
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What are the obligate intracellular bugs?
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Stay inside (cells) when it is Really Cold:
- Rickettsia - Chlamydia |
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What are the facultative intracellular bugs?
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Some Nasty Bugs May Live FacultativeLY
- Salmonella - Neisseria - Brucella - Mycobacterium - Listeria - Francisella - Legionalla - Yersinia pestis |
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What are the encapsulated bacteria?
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SHiNE SKiS
- Streptococcus pneumoniae - Haemophilis Influenzae type B - Neisseria meningitidis - Escherichia coli - Salmonella - Klebsiella pneumoniae - Strep group B |
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What is the function of the capsule on:
SHiNE SKiS - Streptococcus pneumoniae - Haemophilis Influenzae type B - Neisseria meningitidis - Escherichia coli - Salmonella - Klebsiella pneumoniae - Strep group B |
- Capsules act as an anti-phagocytic virulence factor
- Capsule + protein conjugate serves as an antigen in vaccines |
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How do hosts clear encapsulated bacteria?
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- Opsonize bacteria and then cleared by spleen
- Asplenics have decreased opsonizing ability and are at risk for severe infections (give S. pneumoniae, H. influenzae, and N. meningitidis vaccines) |
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What vaccines should asplenics get in particular? Why?
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- Asplenics have decreased opsonizing ability and are at risk for severe infections (give S. pneumoniae, H. influenzae, and N. meningitidis vaccines = encapsulated bacteria)
- Opsonization and clearance by spleen is the method of hosts to remove encapsulated bacteria |
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What are the Catalase-Positive organisms?
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You need PLACESS for your CATs
- Pseudomonas - Listeria - Aspergillus - Candida - E. coli - S. aureus - Serratia |
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What is the action of catalase?
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Degrades H2O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase (protective mechanism)
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What is wrong with patients with chronic granulomatous disease?
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They have a deficiency of NADPH oxidase
- This enzyme generates superoxide for neutrophils to fight infection These patients are at increased susceptibility to recurrent infections with Catalase (+) organisms because this enzyme degrades H2O2 (another ROS) |
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What vaccines are available for encapsulated bacteria?
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Pneumococcal vaccines:
- PCV: Pneumococcal Conjugate Vaccine - PPSV: Pneumococcal Polysaccharide Vaccine with no conjugated protein H. Influenzae type B (conjugate vaccine) Meningococcal vaccine (conjugate vaccine) |
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What are the characteristics of vaccines made for encapsulated bacteria (Pneumococcal, H. influenzae type B, Meningococcal)?
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Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching
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What are the urease positive bugs?
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CHuck norris hates PUNKSS
- Cryptococcus - H. pylori - Proteus - Ureaplasma - Nocardia - Klebsiella - S. epidermidis - S. saprophyticus |
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What are the pigment producing bacteria?
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- Actinomyces israelii = yellow granules
- S. aureus = yellow pigment - Pseudomonas aeruginosa = blue-green pigment - Serratia marcescens = red pigment |
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Which bacteria makes yellow "sulfur" granules, composed of filaments of bacteria?
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Actinomyces israelii
(Israel has yellow sand) |
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Which bacteria makes yellow pigment?
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S. aureus
(aureus = gold in Latin) |
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Which bacteria makes blue-green pigment?
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Pseudomonas aeruginosa
(Aerugula is green) |
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Which bacteria makes a red pigment?
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Serratia marcescens
(think red maraschino cherries) |
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What is the function of bacterial virulence factors? Examples?
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Promotes evasion of host immune response
- Protein A - IgA Protease - M Protein |
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What is the function of "Protein A"? Which bacteria express(es) this?
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Bacterial virulence factor
- Binds Fc region of IgG - Prevents opsonization and phagocytosis - Expressed by S. aureus |
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What is the function of "IgA Protease"? Which bacteria expresses this?
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Bacterial virulence factor
- Enzyme that cleaves IgA - Secreted by S. pneumoniae, H. influenzae type B, and Nesseria (SHiN) in order to colonize the respiratory mucosa |
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What is the function of "M Protein"? Which bacteria expresses this?
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Bacterial virulence factor
- Helps prevent phagocytosis - Expressed by group A streptococci |
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Which bacterial virulence factor helps prevent phagocytosis of group A streptococci?
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M protein
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Which bacterial virulence factor helps prevent opsonization and phagocytosis of S. aureus by binding the Fc region of IgG?
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Protein A
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Which bacterial virulence factor cleaves IgA? Which bacteria have this virulence factor?
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IgA Protease
- Secreted by S. pneumoniae, H. influenzae type B, and Nesseria (SHiN) in order to colonize the respiratory mucosa |
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What is the source of Exotoxins vs. Endotoxins?
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- Exotoxin: certain species of G+ and G- bacteria
- Endotoxin: outer cell membrane of most G- bacteria |
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Are Exotoxins and/or Endotoxins secreted from cells?
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- Exotoxin: secreted from cells
- Endotoxin: not secreted |
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What is the structure/chemistry of Exotoxins vs. Endotoxins?
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- Exotoxin: polypeptide
- Endotoxin: lipopolysaccharide (structural part of bacteria; released when lysed) |
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What is the location of genes of Exotoxins vs. Endotoxins?
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- Exotoxin: plasmid or bacteriophage
- Endotoxin: bacterial chromosome |
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What is the relative toxicity of Exotoxins vs. Endotoxins?
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- Exotoxin: high (fatal dose on the order of 1 µg)
- Endotoxin: low (fatal dose on the order of hundreds of µgs) |
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What are the clinical effects of Exotoxins vs. Endotoxins?
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- Exotoxin: various effects
- Endotoxin: fever, shock (hypotension), DIC |
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What is the mode of action of Exotoxins vs. Endotoxins?
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- Exotoxin: various modes
- Endotoxin: induces TNF, IL-1, and IL-6 |
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What is the antigenicity of Exotoxins vs. Endotoxins?
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- Exotoxin: induces high-titer antibodies called antitoxins
- Endotoxin: poorly antigenic |
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Are there vaccines for Exotoxins vs. Endotoxins?
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- Exotoxin: toxoids used as vaccines
- Endotoxin: no toxoids formed and no vaccine available |
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What is the relative heat stability of Exotoxins vs. Endotoxins?
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- Exotoxin: destroyed rapidly at 60 degrees C (except staphylococcal enterotoxin)
- Endotoxin: stable at 100 degrees C for 1 hr |
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What are the typical diseases associated with Exotoxins vs. Endotoxins?
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- Exotoxin: tetanus, botulism, diphtheria
- Endotoxin: meningococcemia, sepsis by G- rods |
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Exotoxins
1) Source? 2) Secreted? 3) Chemistry? 4) Location of genes? 5) Toxicity? 6) Clinical effects? 7) Mode of action? 8) Antigenicity? 9) Vaccines? 10) Heat stability? 11) Typical diseases? |
1) Source: certain species of G+ and G- bacteria
2) Secreted: yes 3) Chemistry: polypeptide 4) Location of genes: plasmid or bacteriophage 5) Toxicity: high (fatal dose on order of 1 µg) 6) Clinical effects: varies 7) Mode of action: varies 8) Antigenicity: induces high-titer antibodies called antitoxins 9) Vaccines: toxoids used as vaccines 10) Heat stability: destroyed rapidly at 60 degrees C (except staphylococcal entertoxin) 11) Typical diseases: tetanus, botulism, diphtheria |
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Endotoxins
1) Source? 2) Secreted? 3) Chemistry? 4) Location of genes? 5) Toxicity? 6) Clinical effects? 7) Mode of action? 8) Antigenicity? 9) Vaccines? 10) Heat stability? 11) Typical diseases? |
1) Source: outer cell membrane of most G- bacteria
2) Secreted: no 3) Chemistry: lipopolysaccharide (structural part of bacteria; released when lysed) 4) Location of genes: bacterial chromosome 5) Toxicity: low (fatal dose on order of hundreds of µgs) 6) Clinical effects: fever, shock (hypotension), DIC 7) Mode of action: induces TNF, IL-1, IL-6 8) Antigenicity: poorly antigenic 9) Vaccines: no toxoids formed and no vaccine available 10) Heat stability: stable at 100 degrees C for 1 hrs 11) Typical diseases: meningococcemia, sepsis by G- rods |
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What are some possible mechanisms of exotoxins?
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- Inhibit protein synthesis
- Increase fluid secretion - Inhibit phagocytic ability - Inhibit release of NT - Lyse cell membranes - Superantigens causing shock |
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What are the characteristics of an ADP ribosylating A-B toxin?
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- B (binding) component binds to host cell surface receptor
- A (active) component attaches ADP-ribosyl to disrupt host cell proteins |
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Which bacteria release exotoxins that inhibit protein synthesis?
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- Corynebacterium diphtheriae
- Pseudomonas aeruginosa - Shigella spp. - Enterohemorrhagic E. coli (EHEC), including O157:H7 strain |
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Corynebacterium diphtheriae exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Diphtheria toxin (ADP ribosylating A-B toxin)
2) Mechanism: inactivates elongation factor (EF-2) which inhibits protein synthesis 3) Manifestation: pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck) |
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Pseudomonas aeruginosa exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Exotoxin A (ADP ribosylating A-B toxin)
2) Mechanism: inactivates elongation factor (EF-2) which inhibits protein synthesis 3) Manifestation: host cell death |
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Shigella spp. exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Shiga Toxin (ST) - (ADP ribosylating A-B toxin)
2) Mechanism: inactivates 60S ribosome by removing adenine from rRNA, which inhibits protein synthesis 3) Manifestation: GI mucosa damage → dysentery; also enhances cytokine release, causing Hemolytic Uremic Syndrome (HUS) |
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Enterohemorrhagic E. coli (EHEC) exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Shiga-LIKE toxin (SLT) - (ADP ribosylating A-B toxin)
2) Mechanism:inactivates 60S ribosome by removing adenine from rRNA, which inhibits protein synthesis (same as Shiga Toxin) 3) Manifestation: enhances cytokine release, causing Hemolytic Uremic Syndrome (HUS); but does not invade host cells |
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Which bacteria release exotoxins that increase fluid secretion?
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- Enterotoxigenic E. coli (ETEC)
- Bacillus anthracis - Vibrio cholerae |
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Enterotoxigenic E. coli (ETEC) exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Heat-LABILE toxin (LT) - (ADP ribosylating A-B toxin)
2) Mechanism: overactivates AC → ↑cAMP → ↑Cl- secretion in gut and H2O efflux (same as cholera toxin) 1) Toxin: Heat-STABLE toxin (ST) 2) Mechanism: overactivates GC → ↑cGMP → ↓ resorption of NaCl and H2O in gut 3) Manifestation: watery diarrhea - labile in the Air (AC) but stable on the Ground (GC) |
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Bacillus anthracis exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: edema factor
2) Mechanism: mimics AC enzyme → ↑cAMP 3) Manifestation: likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax |
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Vibrio cholerae exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: cholera toxin - (ADP ribosylating A-B toxin)
2) Mechanism: overactivates Gs → ↑AC → ↑cAMP → ↑Cl- secretion in gut and H2O efflux (same as heat labile toxin of ETEC) 3) Manifestation: voluminous "rice-water" diarrhea |
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Which bacteria release exotoxins that inhibit phagocytic ability?
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Bordetella pertussis
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Bordetella pertussis exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Pertussis toxin - (ADP ribosylating A-B toxin)
2) Mechanism: disables Gi → overactivates AC → ↑cAMP → impairs phagocytosis to permit survival of microbe 3) Manifestation: Whooping Cough (child coughs on expiration and "whoops" on inspiration - toxin may not actually be a cause of cough but can cause the 100 day cough in adults) |
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Which bacteria release exotoxins that inhibit release of NT?
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- Clostridium tetani
- Clostridium botulinum |
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Clostridium tetani exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Tetanospasmin
2) Mechanism: protease that cleaves SNARE proteins → prevents release of inhibitory (GABA and glycine) NTs from Renshaw cells in spinal cord 3) Manifestation: spasticity, risus sardonicus, and "lockjaw" |
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Clostridium botulinum exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Botulinum toxin
2) Mechanism: protease that cleaves SNARE proteins → prevents release of stimulatory (ACh) signals at neuromuscular junctions 3) Manifestation: flaccid paralysis, floppy baby |
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Which bacteria release exotoxins that lyse cell membranes?
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- Clostridium perfringens
- Streptococcus pyogenes |
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Clostridium perfringens exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: alpha toxin
2) Mechanism: phospholipase (lecithinase) that degrades tissue and cell membranes 3) Manifestation: degrades phospholipids → myonecrosis ("gas gangrene") and hemolysis ("double zone" of hemolysis on blood agar) |
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Streptococcus pyogenes exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Streptolysin O
2) Mechanism: protein that degrades cell membrane 3) Manifestation: lyses RBCs, contributes to β-hemolysis; host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse w/ immune complexes of poststreptococcal glomerulonephritis) 1) Toxin: Exotoxin A 2) Mechanism: bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-γ and IL-2 → shock 3) Manifestation: toxic shock syndrome - fever, rash, shock |
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Which bacteria release exotoxins that are superantigens causing shock?
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- Staphylococcus aureus
- Streptococcus pyogenes |
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Staphylococcus aureus exotoxin:
1) Toxin 2) Mechanism 3) Manifestation |
1) Toxin: Toxic Shock Syndrome Toxin (TSST-1)
2) Mechanism: bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IFN-γ and IL-2 → shock 3) Manifestation: toxic shock syndrome - fever, rash, shock, other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin) |
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Which bacteria have endotoxins? Structure?
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LPS found in outer membrane of G- bacteria (both cocci and rods)
|
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What is the mnemonic to remember traits of Endotoxin?
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ENDOTOXIN:
- Edema - Nitric oxide - DIC / Death - Outer membrane - TNF-α - O-antigen - eXtremely heat stable - IL-1 - Neutrophil chemotaxis |
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What are the actions of Endotoxin (especially Lipid A)?
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- Activates macrophages
- Activates complement - Activates tissue factor |
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What are the effects of activated macrophages following endotoxin synthesis (especially Lipid A)?
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- IL-1 → Fever
- TNF → Fever and hypotension - Nitric Oxide → hypotension |
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What are the effects of activated complement following endotoxin synthesis (especially Lipid A)?
|
- C3a → hypotension and edema
- C5a → neutrophil chemotaxis |
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What are the effects of activated tissue factor following endotoxin synthesis (especially Lipid A)?
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Coagulation cascade → DIC
|
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What are the mechanisms of exchanging genetic material between bacteria?
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- Transformation
- Conjugation - Transposition - Transduction |
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What is Transformation?
|
Ability to take up naked DNA (ie, from cell lysis) from environment (aka "competenence")
|
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What is the term for the ability to take up naked DNA (ie, from cell lysis) from environment (aka "competenence")? Which bacteria is this a feature of?
|
Transformation
- S. pneumoniae, H. influenzae type B, and Nesseria (SHiN) - Any DNA can be used - Adding deoxyribonuclease to environment will degrade naked DNA in medium → no transformation seen |
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What is Conjugation?
|
Two types:
F+ x F- - F+ plasmid contains genes required for sex pilus and conjugation - Bacteria without plasmid are termed F- - Plasmid (dsDNA) is replicated and transferred through pilus from F+ cell - No transfer of chromosomal genes Hfr x F- - F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell - Replication of incorporated plasmid DNA may include some flanking chromosomal DNA - Transfer of plasmid and chromosomal genes |
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What is F+ x F- conjugation?
|
- F+ plasmid contains genes required for sex pilus and conjugation
- Bacteria without plasmid are termed F- - Plasmid (dsDNA) is replicated and transferred through pilus from F+ cell - No transfer of chromosomal genes |
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What is Hfr x F- conjugation?
|
- F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination (Hfr) cell
- Replication of incorporated plasmid DNA may include some flanking chromosomal DNA - Transfer of plasmid and chromosomal genes |
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What is Transposition?
|
- Segment of DNA (eg, transposon) that can "jump" (excision and reintegration) from one location to another
- Can transfer genes from plasmid to chromosome and vice versa - When excision occurs, may include some flanking chromosomal DNA which can be incorporated into a plasmid and transferred to another bacterium - Eg: antibiotic resistance on R plasmid |
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What happens in Generalized Transduction?
|
- PACKAGING event
- Lytic phage infects bacterium - Leads to cleavage of bacterial DNA - Parts of bacterial chromosomal DNA may become packed in viral capsid - Phage infects another bacterium, transferring these genes |
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What happens in Specialized Transduction?
|
- EXCISION event
- Lysogenic phage infects bacterium - Viral DNA incorporates into bacterial chromosome - When phage DNA is excised, flanking bacterial genes may be excised with it - DNA is packaged into phage viral capsid and can infect another bacterium |
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Which toxins are encoded in a lysogenic phage (specialized transduction)?
|
ABCDE:
- shigA-like toxin - Botulinum toxin (certain strains) - Cholera toxin - Diphtheria toxin - Erythrogenic toxin of Streptococcus pyogenes |