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79 Cards in this Set

  • Front
  • Back
Bacterial Growth Curve
Growth Requirements
1. Oxygen requirements 2. Nutrient requirements 3. Temperature requirements
Growth Requirements: Oxygen
1. Obligate aerobes 2. Anaerobes 3. Facultative anaerobes
Obligate Aerobes
Require oxygen
Anaerobes
Do not require oxygen: 1. Obligate anaerobes: damaged by oxygen 2. Aerotolerant anaerobes (microaerophilic): tolerate small amounts of oxygen 3. Facultative anaerobes: grow under aerobic/anaerobic conditions
Growth Requirements: Nutrient Requirements
1. Undemanding: simple media 2. Demanding (fastidious): complex media
Growth Requirements: Nutrient Requirements-Common Undemanding Species
E. coli, Salmonella, and other gram-negative enteric bacteria
Growth Requirements: Nutrient Requirements-Common Demanding (Fastidious) Species
Haemophilus and Neisseria spp.
Temperature Requirements
Most pathogenic spp. near normal body temperatures (35ºC to 37ºC)
Cell Division
Binary fission; simpler process than mitosis 1. Chromosome duplication 2. New cell envelope synthesis
Chromosomal Duplication: Initiation
1. At specific sequence (replication origin) in DNA 2. Once it starts, it won't stop (even under unsuitable conditions, e.g. starvation)
Chromosomal Duplication: Nutrients Available
1. Synthesis of new chromosome begins before previous chromosome synthesis is complete (born pregnant)
Cell Envelope Synthesis
New membrane and cell wall in center of cell, forming a septum that eventually divides cytoplasm into two daughter cells
Spore Formation (Sporogenesis)
1. Variant of cell division 2. Induced by depletion of essential nutrients 3. Often produces and releases antibiotics and toxins 4. Gram-positive only (some spp.)
Spore Germination
1. Produce vegetative (normal) cells 2. Initiated by damage to spore coat, due to: A) Trauma B) Water C) Aging 3. Requires specific nutrients 3.
Spore Resistance
1. Resistant to heat, drying, chemicals (e.g. disinfectants) 2. Can survive for long periods of time
Spore Vulnerability
1. Once germination has begun and coat is disrupted, spore is vulnerable to same agents as vegetative cells 2. Autoclaving for 15 minutes 3. Aldehyde disinfectants
Most Important Spore Formers
1. Bacillus spp. 2. Clostridium spp.
Bacterial Genetic Elements
1. Chromosome 2. Plasmids 3. Bacteriophages 4. Transposons
Bacterial Genetic Elements: Chromosome
1. Single, double-stranded, circular DNA molecule 2. ~5 million base pairs
Bacterial Genetic Elements: Gene Structure
1. Cistron 2. Operator 3. Operon 4. Promoter 5. Replicon
Bacterial Genetic Elements: Gene Structure-Cistron
Region of DNA that codes for a single protein; a complementation unit
Bacterial Genetic Elements: Gene Structure-Operator
Nucleotide sequence, located between promoter and first structural gene of an operon, that binds a repressor protein
Bacterial Genetic Elements: Gene Structure-Operon
Bacterial transcription unit comprising a promoter, operator, and one or more structural genes
Bacterial Genetic Elements: Gene Structure-Promoter
Nucleotide sequence in an operon that is recognized by RNA polymerase
Bacterial Genetic Elements: Gene Structure-Replicon
Replication unit, consisting of a replication origin, a replication terminus, and the intervening coding sequence
Lac Operon
Bacterial Genetic Elements: Bacteriophages
Viruses that infect bacteria
Bacterial Genetic Elements: Bacteriophages-Types
1. Lytic phage 2. Lysogenic phage
Lytic Phage
Replicates independently of host chromosome and kills bacterial host cell
Lysogenic Phage
1. Can integrate genome into host bacteria without killing it 2. Toxin genes are carried by some 3. May become lytic under unsuitable living conditions
Common Lysogenic Phages
1. E. coli lambda phage 2. Corynephage Beta; carries diptheria toxin
Bacterial Genetic Elements: Transposons
1. Move from one position in chromosome or between different molecules of DNA 2. Lack replication origin
Bacterial Genetic Elements: Transposons-Types
1. Simple transposons 2. Complex transposons
Bacterial Genetic Elements: Transposons-Simple
Encode only the proteins needed to move (insertion sequences)
Bacterial Genetic Elements: Transposons-Complex
Carry other genes: 1 Antibiotic resistance 2. Pathogenicity Island
Pathogenicity Islands
1. Large, complex transposons that contain all the genes needed for a pathogenic mechanism 2. May contain several operons
Pathogenicity Islands Control
Coordinately controlled by environmental (temperature), metabolic, and other triggers
Mechanisms of Genetic Transfer
Recombination: Types
1. Homologous 2. Nonhomologous
Recombination: Types-Homologous
Between closely related DNA sequences 2. Generally results in substitution of one sequence for another 3. Basis for periodic shifts in Salmonella flagella and Neisseria gonorrhoeae pilus antigens
Recombination: Types-Nonhomologous
1. Occurs between dissimilar DNA sequences 2. Generally results in insertions or deletions 3. Basis for integration of phages into host chromosome and movement of transposons
Mechanisms of Bacterial Virulence
1. Adherence 2. Invasion 3. Tissue Damage 4. Bacteremia 5. PAMPs 6. Toxins 7. Antibiotic Resistance 8. Evasion of host immune system
Mechanisms of Bacterial Virulence: Adherence
1. Prevents bacteria from being washed away and allows colonization 2. Accomplished via adhesin molecules
Mechanisms of Bacterial Virulence: Adherence-Adhesin Molecules
1. Interact with host cell receptors to attach bacteria to host 2. Most commonly associated with fimbriae (common pili) of enteric bacteria and N. gonorrhoeae, but present elsewhere as well
Mechanisms of Bacterial Virulence: Invasion
Breaking through tissue barriers into sterile sites and colonizing tissue
Sterile Sites
1. Blood 2. CSF 3. Brain 4. Organ parenchyma 5. Lower lung airways 6. Joint spaces 7. Bone
Mechanisms of Bacterial Virulence: Tissue Damage
1. Damaging metabolites 2. Degradative enzymes 3. Exotoxins 4. Intracellular growth 5. Ectopic bacterial growth
Mechanisms of Bacterial Virulence: Tissue Damage-Metabolites
Acids, gases, and other byproducts formed during bacterial growth
Mechanisms of Bacterial Virulence: Bacteremia
Primary mechanism for spreading bacteria throughout body
Mechanisms of Bacterial Virulence: PAMPs
Repetitive microbial structures that bind TLRs, activate macrophages and promote cytokine release
Examples of PAMPs
1. Peptiodoglycan 2. LPS 3. Lipotechoic acid 4. Techoic acid 5. Flagellin 6. CpG oligodeoxynucleotides
Mechanisms of Bacterial Virulence: Toxins
1. Endotoxin 2. Exotoxin
Mechanisms of Bacterial Virulence: Toxins-Endotoxin
1. Lipid A component of LPS 2. Outer membrane of gram-negatives 3. Released during early stages of infection 4. Initiates complement and clotting pathways
1. Lipid A component of LPS 2. Outer membrane of gram-negatives 3. Released during early stages of infection 4. Initiates complement and clotting pathways
Mechanisms of Bacterial Virulence: Toxins-Exotoxins (Types)
1. Cytolytic 2. A-B 3. Superantigen
Mechanisms of Bacterial Virulence: Toxins-Exotoxins (Cytolytic)
Tissue-degrading enzymes
Mechanisms of Bacterial Virulence: Toxins-Exotoxins (A-B)
Composed of one or more B subunits, which bind to cell surface, and an A subunit, which enters the cell and acts on it
Mechanisms of Bacterial Virulence: Toxins-Exotoxins (Superantigens)
1. Activate T cells in the absence of antigen by cross-linking the T cell receptor and class II major histocompatibility complex on antigen-presenting cells 2. Cause inappropriate release of cytokins, with possible life-threatening autoimmune response and T cell death 3. e.g. TSST
Mechanisms of Bacterial Virulence: Evasion of Host Immune System
1. Encapsulation 2. Biofilms 3. Intracellular growth 4. Reduction of phagocytic cell function 5. Inactivation of antibody 6. Inhibition of complement action 7. Antigenic variation
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Encapsulation
1. Polysaccharide (slime) layer 2. Poorly antigenic 3. Deter phagocytosis because they are slippery and tear way 4. Protect against degradation in phagolysosomes
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Biofilms
1. Sticky webs of polysaccharide that protect against host defenses and antimicrobials 2. Require quorum sensing
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Intracellular Growth
1. Escape host immune detection 2. Can be obligate or facultative 3. Chronic stimulation of immune response may result in granuloma formation (e.g. facultatives)
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Intracellular Growth (Obligate Intracellular Species)
1. Rickettsia spp. 2. Chlamydia spp. 3. Coxiella spp.
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Intracellular Growth (Facultative Intracellular Species)
1. Mycobacterium spp. 2. Salmonella spp. 3. Listeria spp. 4. Brucella spp. 5. Francisella spp. 6. Yersinia spp. 7. Legionella spp.
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Intracellular Growth (Mechanisms)
1. Inhibition of phagolysosome fusion (M. tuberculosis) 2. Protective outer layers (M. tuberculosis) 3. Lysosomal enzyme resistance
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Reduction of Phagocytic Cell Function
1. Inhibition of phagocytosis: A) Capsule B) Certain cell surface proteins (e.g. M protein) 2. Reduction of phagolysosomal killing: A) Inhibition of phagolysosome fusion B) Capsule C) Catalase detoxification 3. Killing phagocytes via exotoxins
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Reduction of Phagocytic Cell Function (Killing of Phagocytes)
1. Streptolysins of S. pyogenes 2. Lethal toxin of anthrax 3. Alpha toxin of C. perfringens
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Inactivation of Antibody
1. Immunoglobulin A (IgA)-degrading proteases 2. IgG-binding surface proteins
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Inactivation of Antibody (IgA-degrading Proteases)
1. Permit mucosal surface colonization 2. e.g. A) N. gonorrhoeae B) N. meningitidis C) S. pneumoniae D) H. influenzae
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Inactivation of Antibody (IgG-Binding Surface Proteins)
1. Protect bacterial cells from antibody action 2. e.g. Protein A of S. aureus
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Inhibition of Complement Action
Antigen in LPS may protect cells from complement-mediated lysis by preventing access to membrane
Mechanisms of Bacterial Virulence: Evasion of Host Immune System-Antigenic Variation
DNA rearrangement involving homologous recombination
Antibacterial Immunopathogenesis
1. Inflammation 2. Tissue-damageing immune responses 3. Cross-reacting antibacterial antibodies 4. Deposition of immune complexes 5. Sepsis 6. Superantigens
Antibacterial Immunopathogenesis: Inflammation
1. Complement, neutrophils, macrophages, and other responses to bacteria lead to inflammation 2. Cell-mediated immune responses induced by intracellular infections may lead to granulomas
Antibacterial Immunopathogenesis: Tissue Damaging Immune Responses
1. More common in viruses 2. Bacterial examples: A) Chlamydia spp. (LGV) B) Treponem spp. (syphilis) C) Borrelia spp. (Lyme disease)
Antibacterial Immunopathogenesis: Cross-Reacting Antibacterial Antibodies
Rheumatic fever, a sequela to streptococcal infections, is caused by antibodies to M protein that cross-react with and initiate damage to heart
Antibacterial Immunopathogenesis: Deposition of Immune Complexes
Poststreptococcal glomerulonephritis results from accumulation of antigen-antibody complexes in glomeruli of kidneys
Antibacterial Immunopathogenesis: Sepsis
Bacterial cell wall components activate TLRs and induce systemic release of tumor necrosis factor-alpha, IL-1, and IL-6, which activate phase responses
Antibacterial Immunopathogenesis: Superantigens
Activate T cells to release large amounts of cytokines (cytokine storm) to cause sepsis-like pathogenesis