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65 Cards in this Set
- Front
- Back
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What is the function and chemical composition of peptidoglycan?
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- function: gives rigid support, protects against osmotic pressure
- composition: sugar backbone with cross-linked peptide side chains |
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What is the function and chemical composition of the cell wall/cell membrane?
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- function: major surface antigen
- composition: peptidoglycan for support - Teichoic acid induces TNF and IL-1 - found in gram positive bacteria |
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What is the function and chemical composition of the outer membrane?
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- function: site of endotoxin (lipopolysaccharide); major surface antigen
- composition:Lipid A induces TNF and IL-1; polysaccharide is the antigen - found in gram negative bacteria |
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What is the function and chemical composition of the plasma membrane?
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- function: site of oxidative and transport enzzymes
- composition: lipoprotein bilayer |
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What is the function and chemical composition of the ribosome?
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- function: protein synthesis
- composition: 50S and 30S subunits |
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What is the function and composition of the periplasm?
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- function: space between the cytoplasmic membrane and peptidoglycan wall in gram-negative bacteria
- composition: contains many hydroplytic enzymes, including B-lactamases |
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What is the function and composition of the capsule?
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- function: protects against phagocytosis
- composition: polysaccharide (except B. antracis, which contains D-glutamate |
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What is the function and composition of pilus/fimbria?
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- function: mediate adherence of bacteria to cell sruface; sex pilus forms attachment between 2 bacteria during conjugation
- composition: glycoprotein |
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What is the function and composition of flagellum?
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- function: motility
- composition: protein |
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What is the function and composition of spores?
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- function: provides resistance to dehydration, heat, and chemicals
- composition: keratin-like coat; dipicolinic acid |
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What is the function and composition of plasmid?
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- function: contains a variety of genes for Ab rxn, enzymes, and toxins
- composition: DNA |
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What is the function and composition of glycocalyx?
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- function: mediates adherence to surfaces, especially foreign surfaces (i.e indwelling catheters)
- composition: polysaccharide |
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What type of cell membranes/walls do mycoplasma bacteria have?
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- contain sterols and have no cell wall
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What type of cell membranes/walls do mycobacteria have?
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- contain mycolic acid
- high lipid content |
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Which bacteria do not gram stain well and why?
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1. Treponema (too thin to be visualized)
2. Rickettsia (intracellular parasite) 3. Mycobacteria (high-lipid-content cell wall requires acid-fast stain) 4. Mycoplasma (no cell wall) 5. Legioonella pneumophila (primarily intracellular) 6. Chlamydia (intracellular parasite; lacks muramic acid in cell wall) |
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The giemsa stain is used to stain which bacteria?
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- Borrelia
- Paslmodium - trypanosomes - Chlamydia |
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The PAS (periodice acid-Schiff) stain is used to stain which structures?
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"PASs the sugar"
- stains glycogen, mucopolysaccharids - used to diagnose Whipple's disease (Tropheryma whippeli) |
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The Ziehl-Neelsen stain is used to stain which type of organisms?
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- acid-fast organisms
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The India ink stain is used to stain what?
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- Cryptococcus neoformans (mucicarmine can also be used to stain thick polysaccharide capsule red)
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The silver stain can be used to stain which microrganisms?
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- fungi (i.e. Pnuemocystis)
- Legionella |
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What type of media is used for the isolation of H. influenzae?
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- chocolate agar with factors v (NAD+) and X (hematin)
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What type of media is used for the isolation of N. gonorrhoeae?
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- Thayer-Martin (or VPN) media -- vancomycin (inhibits gram-positive organisms), Polymyxin (inhibits gram-negative organisms), and Nystatin (inhibits fungi)
**"to connection to Neisseria, please use your VPN client"** |
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What type of media is used for the isolation of B. pertussis?
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- Bordet-Gengou (potato) agar
*Bordet for Bordetella* |
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What type of media is used for the isolation of C. diptheriae?
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- Tellurite plate
- Loffler's media |
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What type of media is used for the isolation of M. tuberculosis
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Lowenstein-Jensen agar
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Which type of media is used for the isolation of M. pneumoniae?
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eaton's agar
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Which type of media is used for the isolation of lactose-fermenting enterics?
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- pink colonies on MacConkey's agar (fermentation produces acid, turning plate pink)
- E. coli is also grown on eosin-methylene blue (EMB) agar as blue-black colonies with metallic sheen |
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Which type of media is used for the isolation of Legionella?
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Charcoal yeast extract agar buffered with cysteine
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Which type of media is used for the isolation of fungi?
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Sabouranud's agar
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What are obligate aerobes?
Give examples |
- use an oxygen-dependent system to generate ATP
- examples incluse Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, and Bacillus, H. influenzae |
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What are oligate anaerobes?
Give examples |
- lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage
- generally foul smelling (short-chain fatty acids) - difficult to culture, and produce gas in tissue (CO2 and H2) - usually fermentation only - examples: clostridium, Bacteroides, and Actinomyces |
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Which bacteria are intracellular? Are they able to make ATP?
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- Rickettsia, Chlamydia
- can't make their own ATP "stay inside (cells) when it is Really Cold" |
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Which bacteria are facultative intracellular?
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- Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella
"Some Nasty Bugs May Live FacultativLy" |
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What are the characteristics of encapsulated bacteria? Give some examples
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- positive quellung (capsular) reaction
- if encapsulated bug is present, capsule swells when specific anticapsular antisera are added - examples: S. pneumoniae, K. pneumoniae, H. infleunzae type B, N. meningitidis, Salmonella, group B strep --> "Some Killers Have Nice Shiny Bodies" |
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What is the purpose of bacterial capsule?
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- capsules serve as an antiphagocytic virulence factor
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Which bugs are urease-positive bugs?
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- Proteus, Klebsiella, H. pylori, Ureaplasma
"Particular Kinds Have Urease" |
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Which bacteria are pigment-producing bacteria? What type of pigment do they produce?
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- Actinomyces israelii - yellow "sulfur" granules, which are composed of a mass of filaments and formed in pus
- S. aureus - yellow pigment - P. aeruginosa - Blue-green pigment - Serratia marcescens - red pigment |
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What is the function of Protein A (in S. aureus)?
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- binds Fc region of Ig
- prevents opsonization and phagocytosis |
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What is the function of IgA protease/ Which pathogens secrete it?
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- enzyme that cleaves IgA
- Secreted by S. pneumoniae, HiB and Neisseria in order to colonize respiratory mucosa |
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What is the function of the M protein (found in Group A strep)?
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helps prevent phagocytosis
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What are the characteristics of an EXOtoxins?
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- source from certain species of some gram+ and gram negative bacteria
- secreted from cell - polypeptid - located on plasmid or bacteriophage - high toxicity - induces high-titer Abs called antitoxins - toxoids used as vaccines - destroyed rapidly at 60C (except staphylococcal enterotoxin) |
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Which pathogens typically have exotoxins?
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tetanus, botulism, diphtheria
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What are the characteristics of an ENDotoxin?
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- source comes from outer cell membrane of most gram-negative bacteria
- NOT secreted from cell - lipopolysaccharide (structural part of bacteria; released when lysed) - genes located on bacterial chromosome - low toxicity - usually causes fever, shock - modes of action includes TNF and IL-1 - poorly antigenic - no toxoids formed and no vaccine available - stable at 100C for 1 hour |
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What pathogens typically have endotoxins?
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meningococcemia, sepsis by gram-negative rods
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What are superantigens and what is their function?
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bind directly to MHC II and T-cell receptor simultaneously, activating large numbers of T cells to stimulate release of IFN-y and IL-2
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Which bugs have superantigens?
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- S. aureus
- S. pyogenes |
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Describe the superantigen of S. aureus
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- TSST-1 superantigen causes toxic shock syndrome (fever, rash, shock)
- other S. aureus toxins include enterotoxins that cause food poisoning as well as exfoliatin, which causes staphylococcal scalded skin syndrome |
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Describe the superantigen of S. pyogenes.
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scarlet fever-erythrogenic toxin causes toxic shock-like syndrome
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Which pathogens have ADP ribosylating AB-toxins?
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1. C. diphtheria
2. V. cholerae 3. E. coli 4. B. pertussis |
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How do ADP ribosylating AB toxins work?
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- interfere with host cell function
- B (binding) component binds to a receptor on surface of host cell, enabling endocytosis - A (active) component ten attaches an ADP-ribosyl to a host cell protein (ADP ribosylation), altering protein function |
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How does the diphtheriae toxin work?
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- inactivates elongation factor (EF-2) [similar to Pseudomonas exotoxin A)
- causes pharyngitis and "pseudomembrane" in throat |
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How does the cholera toxin work?
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- ADP ribosylation of G protein stimulates adenylyl cyclase
- increases pumping of Cl- into gut and decreases sodium absorption - water moves into gut lumen --> voluminous rice-water diarrhea |
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How does the E.coli toxin work?
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- heat-labile toxin stimulates adenylate cyclase
- heat-stable toxin stimulates Guanylate cyclase - both causes water diarrhea - "labile-like the Air, stable like the ground" |
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How does the pertussis toxin work?
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- increases cAMP by inhibiting Gai
- causes whooping cough - inhibits chemokine receptor --> lymphocytosis |
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How does the C. perfringens toxin work?
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- alpha toxin: lecithinase that acts as a phospolipase to cleave cell membrane and causes gas gangrene
- get double zone of hemolysis on blood agar |
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How does the tetanus toxin work?
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- blocks the release of inhibitory neurotransmitter GABA and glycine
- causes lockjaw |
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How does the botulinum toxin work?
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- blocks release of ACh
- causes anticholinergic symptoms, CNS paralysis, especially cranial nerves - spores found in canned food, honey (causes floppy baby) |
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How does the anthrax toxin work?
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- edema factor, part of the toxin complex, is an adenylate cyclae
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How does the shigella toxin work?
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- Shiga toxin (also produced by E.coli 0157:H7) cleaves host cell rRNA (inactivates 60S ribosome)
- also enhances cytokine release causing HUS |
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How does the S. pyogenes toxin work?
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- streptolysin 0 is a hemolysin
- antigen for ASO Ab, which is used in the diagnosis of rheumatic fever |
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Which pathogens as cAMP inducers?
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1. V. cholerae
2. Pertussis 3. E. coli (ETEC) 4. B. anthracis |
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In relation to a bacterial growth curve what does the term "lag" mean?
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metabolic activity without division
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In relation to a bacterial growth curve what does the term "log" mean?
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rapid cell division
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In relation to a bacterial growth curve what does the term "stationary" mean?
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- nutrient depletion slows growth
- spore formation in some bacteria |
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In relation to a bacterial growth curve what does the term "death" mean?
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- prolonged nutrient depletion and buildup of waste products leads to death
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