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Function and chemical composition of bacterial structure: Peptidoglycan
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Function:
1. Rigid support
2. Protects against osmotic pressure
Chemical composition:
Sugar backbone with cross-linked peptide side chains
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Function and chemical composition of bacterial structure: Cell wall/cell membrane
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Gram positives only
Function: Major surface antigen
Chemical composition: Teichoic acid, which induces TNF and IL-1
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Function and chemical composition of bacterial structure: Outer membrane
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Gram negatives only
Function: Site of endotoxin (lipopolysaccharide) and major surface antigen
Chemical composition: Lipid A induces TNF and IL-1, and polysaccharide is the antigen
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Function and chemical composition of bacterial structure: Plasma membrane
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Function: Site of oxidative and transport enzymes
Chemical composition: Lipoprotein bilayer
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Function and chemical composition of bacterial structure: Ribosome
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Function: Protein synthesis
Chemical composition: 50S and 30S subunits
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Function and chemical composition of bacterial structure: Periplasm
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Function: Space between the cytoplasmic membrane and outer membrane in gram-negative bacteria
Chemical composition: Contains many hydrolytic enzymes, including beta-lactamases
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Function and chemical composition of bacterial structure: Capsule
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Function: Protects against phagocytosis
Chemical composition: Polysaccharide (except Bacillus anthracis which contains D-glutamate)
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Function and chemical composition of bacterial structure: Pilus/fimbria
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Function: Mediates adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation
Chemical composition: Glycoprotein
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Function and chemical composition of bacterial structure: Flagellum
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Function: Motility
Chemical composition: Protein
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Function and chemical composition of bacterial structure: Spore
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Function: Provides resistance to dehydration, heat, and chemicals
Chemical composition: Keratin-like coat and dipicolinic acid
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Function and chemical composition of bacterial structure: Plasmid
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Function: Contains a variety of genes for antibiotic resistance, enzymes, and toxins
Chemical composition: DNA
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Function and chemical composition of bacterial structure: Glycocalyx
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Function: Mediates adherence to surfaces, especially foreign surfaces (eg indwelling catheters)
Chemical composition: Polysaccharide
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Function of this structure: IgA proteases
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Function: Allow some organisms to colonize mucosal surfaces
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Which bacteria have IgA proteases?
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1. Streptococcus pneumoniae
2. Neisseria meningitidis
3. Neisseria gonorrheae
4. Hemophilus influenzae
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Which bacterial substances induce cytokines, and which are they?
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Cytokines induced:
1. IL-1
2. TNF
Gram positive inducer: Teichoic acid
Gram negative inducer: Lipopolysaccharide (Endoxtoxin)
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What does the capsule of Bacillus anthracis consist of?
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D-glutamate
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What bacterial structure contains D-glutamate?
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Capsule of Bacillus anthracis
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What are the main differences between gram negative and gram positive organisms?
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Peptidoglycan cell wall: Gram positive has thick. Gram negative has thin.
Flagellar basal body rings: Gram positive has two. Gram negative has four.
Outer antigen: Gram positive: Teichoic acid. Gram negative: Lipidpolysaccharide
Periplasmic space: Gram positive does not have. Gram negative has.
Porin channel: Gram positive does not have. Gram negative has.
Lysozyme and penicillin attack: Gram positive are sensitive. Gram negative are resistant.
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What bacteria do not gram stain well?
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Mnemonic: These Rascals May Microscopically Lack Color
1. Treponema
2. Rickettsia
3. Mycobacteria
4. Mycoplasma
5. Legionella pneumophila
6. Chlamydia
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Why does the following bug not gram stain well?: Treponema
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Too thin to be visualized
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Why does the following bug not gram stain well?: Rickettsia
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Intracellular parasite
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Why does the following bug not gram stain well?: Mycobacteria
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high-lipid-content cell wall
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Why does the following bug not gram stain well?: Mycoplasma
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No cell wall
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Why does the following bug not gram stain well?: Legionella pneumophila
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Primarily intracellular
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Why does the following bug not gram stain well?: Chlamydia
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Intracellular parasite which lacks muramic acid in cell wall
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How is the following bug visualized?: Treponema
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1. Darkfield microscopy
2. Fluorescent antibody staining
3. silver stain
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Why does the following bug not gram stain well?: Mycobacteria
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Acid fast for high lipid content cell wall
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What are the stages of bacterial growth and what are their relative lengths?
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1. Lag phase: x
2. Log phase: 1.5x
3. Stationary phase: 2.5x
4. Death phase: 4x
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What happens in the following phase of bacterial growth, and where does it fall in the order?: Lag
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1st phase: Metabolic activity without division
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What happens in the following phase of bacterial growth, and where does it fall in the order?: Log
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2nd phase: Rapid cell division
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What happens in the following phase of bacterial growth, and where does it fall in the order?: Stationary
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3rd phase: Nutrient depletion slows growth
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What happens in the following phase of bacterial growth, and where does it fall in the order?: Death
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4th phase: Prolonged nutrient depletion and buildup of waste products leads to death
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Bacterial endotoxins and exotoxins: Source?
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Exotoxin: Certain species of gram positive and gram negative bacteria
Endotoxin: Cell wall of most gram-negative bacteria
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Bacterial endotoxins and exotoxins: Secreted from cell?
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Exotoxin: Yes
Endotoxin: No
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Bacterial endotoxins and exotoxins: Chemistry
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Exotoxin: Polypeptide
Endotoxin: Lipopolysaccharide
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Bacterial endotoxins and exotoxins: Location of genes
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Exotoxin: Plasmid or bacteriophage
Endotoxin: Bacterial chromosome
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Bacterial endotoxins and exotoxins: Toxicity (fatal dosage)
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Exotoxin: High (fatal dose on the order of 1 microgram)
Endotoxin: Low (fatal dose on the order of hundreds of micrograms)
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Bacterial endotoxins and exotoxins: Clinical effects
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Exotoxin: Toxin specific
Endotoxin: Fever and shock
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Bacterial endotoxins and exotoxins: Mode of action
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Exotoxin: Toxin specific
Endotoxin: Includes TNF and IL-1
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Bacterial endotoxins and exotoxins: Antigenicity
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Exotoxin: Induces high-titer antibodies called antitoxins
Endotoxin: Poorly antigenic
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Bacterial endotoxins and exotoxins: Vaccines
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Exotoxin: Toxoids used as vaccines
Endotoxin: No toxoids formed and no vaccine available
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Bacterial endotoxins and exotoxins: Heat stability
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Exotoxin: Destroyed rapidly at 60 degrees celsius (except Staphylococcal enterotoxin)
Endotoxin: Stable at 100 degrees celsius for 1 hour
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Bacterial endotoxins and exotoxins: Typical diseases
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Exotoxin: Tetanus, botulism, diphtheria
Endotoxin: Meningococcemia, sepsis by gram negative rods
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Mechanism of superantigens
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1. Bind directly to MHC II and T cell receptor
2. Large numbers of T cells are activated.
3. Stimulates release of IFN-gamma and IL-2
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Mechanism of ADP ribosylating A-B toxins
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Interfere with host cell function
1. B (binding) component binds to a receptor on surface of host cell.
2. The toxin is endocytosed.
3. A (active) component attaches an ADP-ribosyl to a host cell protein.
4. That protein's function is altered.
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List of bugs that release superantigens
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1. Staphylococcus aureus
2. Streptococcus pyogenes
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List of bugs that release ADP ribosylating A-B toxins
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1. Corynebacterium diphtheriae
2. Vibrio cholerae
3. E. coli
4. Bordetella pertussis
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What to know about exotoxins released by Staphylococcus aureus
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Superantigens
1. TSST-1 causes toxic shock syndrome (fever, rash, shock).
2. Enterotoxins cause food poisoning.
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What to know about exotoxins released by Streptococcus pyogenes
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Scarlet fever (superantigen)
1. Erythrogenic
2. Causes toxic shock-like syndrome
Streptolysin O (hemolysin). The antigen for ASO antibody is found in rheumatic fever
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What to know about exotoxins released by Corynebacterium diphtheriae
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ADP ribosylating A-B toxin (similar to Pseudomonas exotoxin A)
Encoded by beta-prophage
Disease: Pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy
Mechanism:
Inactivates elongation
factor 2 (EF-2)
Mnemonic: ABCDEFG
ADP ribosylation
Beta-prophage
Corynebacterium
Diphtheriae
Elongation Factor 2
Granules (metachromatic)
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