Term
Phenotypic Bacterial Classification |
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Definition
- Hemolysis: Gamma (none), alpha (partial), and beta (full)
- Gram staining: G+ (purple) and G- (pink/red)
- Cell shape: Coccus (sphere), bacillus (rods), coccobacillus, spirochete (spiral), and vibrio (kidney bean)
- Arrangement: Chains, clusters, and pairs (diplococci) |
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Term
Bacterial Species not seen through Gram Staining |
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Definition
- Mycobacteria: Too much lipid in cell wall --> Acid-fast stain
- Treponema pallidum: Too thin to see --> Dark-field microscopy or immunofluorescence
- Mycoplasm pneumoniae: No cell wall/very small --> No stain
- Legionella pneumoniae: Intracellular --> Silver stain/immunofluorescence
- Chlamydiae: Intracellular --> Giemsa stain or inclusions
- Rickettsiae: Intracellular --> Giemsa or immunofluoresence |
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Term
Oxidative-Fermentation Test |
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Definition
- Determines if the strain is a obligate aerobe, facultative anaerobe, aerotolerant anaerobe, and obligate anaerobe
- Yellow discoloration in tubes means culture growth |
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Term
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Definition
- Coagulase: Stimulates coagulation
- S. aureus: +
- S. epidermidis: -
- Easy way to test for the difference between the two |
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Term
Antibiotic Resistance and Susceptibility Testing |
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Definition
- Kirby-Bauer and E-strip Tests
- Particularly important now because so many organisms are antibiotic resistant |
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Term
Common Causes of Meningitis |
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Definition
- Depends on age group
- S. pneumoniae, N. meningitidis, enterovirus, and herpes simplex virus for 6-60 year olds
- N. meningitidis --> G- diplococci
- S. pneumoniae --> G+ diplococci |
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Term
Eukaryotes vs. Prokaryotes |
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Definition
- Eukaryotes: Nuclear membrane, 23 pairs of chromosomes, divides via mitosis, 80S ribosomes, presence of organelles, no cell wall, and cell membrane with sterols
- Prokaryotes: No nucleus, 1 chromosome, divides via binary fission, no organelles, 70S ribosomes, cell wall and cell membrane but no sterols |
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Term
Cell Wall of Gram-negative vs. Gram-positive Bacteria |
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Definition
- Gram-positive: Thick peptidoglycan layer, teichoic acid, no LPS, no periplasmic space, and no outer membrane
- Gram-negative: Thinner peptidoglycan layer within periplasm, no teichoic acid, and LPS and lipid A in outer membrane |
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Term
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Definition
- Repeating units of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) units
- Cross-linked by tetrapeptide
- Cross-linking is the site for B-lactams such as penicillin G
- Lysozyme cleaves NAM and NAG bonds --> Weakens cell wall so cell might burst when put in hypotonic medium
- Found both in gram-negative and gram-positive |
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Term
Lipopolysaccharide (LPS) Structure |
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Definition
- Outer portion: repeating O-antigen subunits
- Middle portion: Core polysaccharide --> Hydrophilic
- Inner portion: Lipid A --> Embeds structure into the outer membrane
- Potent endotoxin due to lipid A --> Important in sepsis responses
- Found only in gram-negative bacteria |
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Term
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Definition
- Found only in some gram-positive bacteria
- Polymers of ribitol or glycerol connected by phosphates
- Found in peptidoglycan layer
- Endotoxin but less potent than LPS
- Can mediate cell attachments and may contain antigenic determinants for vaccines, identification, and antibody formation |
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Term
Gram-Negative Bacterial Cell Wall |
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Definition
- Inner membrane
- Periplasm containing thin peptidoglycan layer
- LPS, mebrane proteins, and porins within outer layer
- Porins determine what moves in and out of the cell wall and membranes
- No sterols in either the inner or outer membranes |
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Term
Bacterial Cytoplasmic Membrane |
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Definition
- Does not contain sterols
- Site of active transport of molecules, electron transport chain, synthesis of cell wall precursors, and signal transduction |
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Term
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Definition
- Contains nucleoid, 70S ribosomes, granules, plasmids, and transposons |
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Term
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Definition
- Polysaccharide layer surrounding outer membrane
- Found in some gram-postive and gram-negative strains
- Increases virulence
- Makes surface sticky --> Non-specific binding to surrounding
- Seen on staining through the Quellung reaction
- Inhibits phagocytosis
- Surface of capsule can be used to create vaccines that will opsonize the bacteria |
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Term
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Definition
- Collections of bacteria
- Bacteria stick together via capsules
- Develop on the surface of teeth, contact lenses, mechanical valves, and artificial joints
- Produce polysaccharides which form mushroom-like shapes that help surround and protect bacterial colonies from phagocytosis and opsonization
- Overwhelm immune response simply by being too large for one macrophage or phagocytic cell to engulf on it's own |
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Term
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Definition
- Found on some gram-positive and gram-negative bacteria
- Good target for antibodies
- Allows bacterium to move
- Structure is anchored into the inner plasma membrane and functions as a protein motor
- Movement can increase virulence
- E. coli have flagella --> Cause UTIs by traveling up the urethra |
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Term
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Definition
- Pili/fimbriae
- Shorter than flagella
- Allow specific adhesion and binding of bacterium to surfaces or specific host cells
- Can be used as targets for vaccines, etc |
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Term
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Definition
- Long pillus extended from one bacterium to another
- Pulls two cells close enough to eachother to transfer genetic material
- Conjugation: Process for genetic exchange |
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Term
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Definition
- Primarily present in G- bacteria
- Proteinaceous syringes that extend from the bacterium to the host cell
- Injects substances into host cell --> Genetic material, proteins, etc
- Makes the host cell do what the bacterium wants it to |
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Term
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Definition
- Only present in Clostridium and Bacillus (G+ rods)
- Mechanism for survival in response to adverse environmental stimuli
- Have a keratin-like coat --> Extremely resistant to heat and disinfectants
- Metabolically inactive so can survive for many years
- Can germinate when conditions are right --> One bacterial cell
- Dipicolinic acid in the coat is also a Ca++ chelator
- Interior contains basically just the nucleoid and no other cytoplasm |
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Term
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Definition
- Occurs through binary fission
- Can be alot faster than in eukaryotes
- Only need to replicate one chromosome
- Replication time will determine how fast species can be cultured --> S. pneumoniae needs 2 weeks
- Transcription and translation are coupled so DNA replication and protein synthesis can be very fast |
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Term
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Definition
- Can occur on solid media, broth culture, blood agar, or on biofilms
- Lag phase: Bacteria are acclamating to their new environment --> No growth
- Exponential phase: Exponential growth
- Stationary phase: Growth stops
- Decline: Cells begin to die
- Four phases represented on a standard growth curve
- Phases and cell number can be seen by performing a direct cell count
- Turbidity of broth culture is also proportional to cell mass |
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Term
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Definition
1. Cell wall extends to size of about 2 cells
2. Chromosome replicates
3. Septum forms and DNA binds at the mesosome
4. Cell splits into two separate daughter cells |
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Term
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Definition
- Primarily through catabolism to form ATP
- Cellular components are then synthesized through anabolism
- Minimal growth requirements: Carbon, nitrogen, and iron |
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Term
Differences in Catabolism |
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Definition
- Anaerobes: Glucose --> Pyruvate via glycolysis --> Fermentation to get ATP + NADH (2 ATP)
- Aerobes: Glucose --> Pyruvate --> Kreb's --> Electron Transport Cahin (38 ATP) |
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Term
Metabolism and Classification |
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Definition
- Specific can be classified by:
1. Carbon source
2. Obligate vs. facultative intracellular grwoth
3. Aerobes vs. anaerobes
4. Ability to ferment certain sugars |
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Term
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Definition
- Obligate aerobe --> +SOD/+catalase
- Facultative anaerobe --> +SOD/+catalase
- Aerotolerant anaerobe --> +SOD/-catalase
- Strict anaerobe --> -SOD/-catalase
- Microaerophile --> +SOD/(-/+catalase)
- SOD and catalase used to degrade free radicals such as superoxide and hydrogen peroxide that are normally produced through ETC |
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Term
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Definition
- Identification test
- Determines Staphylococcus from Streptococcus bacteria
- Staphylococcus + --> Facultative anaerobe
- Streptococcus - --> Strict anaerobe |
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Term
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Definition
- Determines the ability to ferment lactate
- If bacteria grows then bacteria is able to ferment, if not then no |
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Term
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Definition
- Many antibiotics target the assembly of cell wall proteins/structures
- Peptidoglycan units must be transported into periplasm to be assembled
- Bacitracin: Inhibits recycling of bactoprenol (NAM transporter)
- B-lactams: Inhibit tetrapeptide cross-linking
- Fosfomycin: Inhibits NAG-NAM binding |
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Term
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Definition
- Encodes a protein that is required for virulence
- Might allow for adhesion and allow the bacteria to establish infection
- Examples: Pili/adhesin or biofilm protein |
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Term
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Definition
1. Low free iron availability: Stimulates diptheria toxin production
2. 37C vs. 20C: Stimulates pilin protein production by E. coli that allows bacteria to adhere to bladder wall
3. Eukaryotic cell binding: Initiates type III secretion system formation --> Inserts genes that inhibit macrophage phagocytosis, cytokine secretion, and initiate apoptosis (Yersinia)
4. High cell density/Quorum sensing: Used by P. aeuruginosa in CF patientsĀ |
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Term
Negative Regulatory Protein |
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Definition
- Binds gene promoter and inhibits transcription
- Ex. Diptheria toxin promoter region bound when Fe concentrations are high |
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Term
Positive Regulatory Proteins |
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Definition
- Activator proteins bind DNA at promoter to activate transcription
- Also directly interact with RNA polymerase
- Two component system: Signal sensor in membrane and transducer that actually binds DNA + RNA polymerase
- Ex. Salmonella: Type III secretion system injects proteins to induce gut epithelial cells to engulf bacteria --> Sensor in bacterial membrane now realize that it's in phagosome --> Stimulates proteins that allow bacteria to live in that environment |
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Term
Methods for Evading Host Immune System |
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Definition
- Anti-phagocytic capsule (H. influenzae, N. meningiditis, and S. pneumoniae)
- Intracellular growth
- Antigenic variation (N. gonorrhoeae): DNA rearrangement occurs within pilin protein genes |
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Term
Mechanism of Antigenic Variation |
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Definition
- N. gonorrhoeae: Has 18 pilin genes --> Only PilE gene can be transcribed because it has promoter, others are PilS genes
- Variation due to recombination of PilS genes into the PilE gene to create a new pilin gene formation |
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Term
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Definition
- Bacteria pickes up naked DNA from the environment
- DNA then inserts itself into the chromosome via homologous recombination
- Common in N. gonorrhoeae and S. pneumoniae
- Transformation can occur to change pilin protein and account for antigenic variation as well |
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Term
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Definition
- Process of mutations causing a gene to now encode a protein with different function --> Generally presents as a difference in phenotype
- Genotype: Linear DNA sequence
- Phenotype: Growth/appearance of bacterial cell
- Can result from a missense, nonsense or frame-shift mutation
- Most mutations are silent or very detrimental
- Slow and inefficent process but it does happen |
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Term
Development of Antibiotic Resistance |
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Definition
- Due to the prevalence of prophylactic treatment with antibiotics
- Antibiotics are put into cattle feed --> Environmental tolerance
- Resistance found in chromosomal DNA that has entered via recombination
- Changes the structure of antibiotic targets such as ribosomes, membrane transporters, and RNA polymerase
- Renders the antibiotic ineffective at active site
- DNA can also now encode sequences for efflux pumps for antibiotics
- Ex. DNA might now encode for a methylase which methylates active site |
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Term
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Definition
- Small circular replicons --> Contain origin of replication (ori) site
- Carry non-essential genes for cell growth/replication
- Some carry transfer (Tra) genes --> Allows for transfer or conjugation between cells
- Other plasmids not containing Tra genes can be transferred but they must be recombined into a plasmid containing the Tra gene first (mobilization)
- Can transfer between bacteria and even yeast |
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Term
Fertility Plasmid Conjugation |
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Definition
1. One bacterial cell with a plasmid containing the F+ gene will extend sex pilus to another cell
2. Sex pilus then contracts to pull cells close together
3. Plasmid undergoes special type of DNA replication --> One parent strand goes to one cell while the other remains --> Complementary strands replicated during transfer
4. Plasmids can then recombine with other plasmids or incorporate into chromosome |
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Term
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Definition
1. Transposons: Carry genes needed for transposition (transposase) and generally carry the antibiotic resistance genes --> Must be taken up from environment by bacterial cellsĀ
2. Conjugative Transposons: Also have tra genes --> Able to move between two bacterial cells
- Transposons can then insert themselves into plasmids within the cytoplasm |
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Term
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Definition
- Viruses that infect bacterial cells
- Consist of DNA/RNA molecule and surrounding proteins
- Most have a capsid and phage tail --> Attachment
- Need to infect a cell to replicate |
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Term
Lytic Phase of Bacteriophage |
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Definition
- Converts the infected bacteria into a phage-producing factory
- Virulent phage: Phage that only grows lytically
- Can produce 100-10,000 new phage
- Proteins and DNA synthesized --> Phage particles assembled
- Bacterial cell wall degraded by enzymes --> Phages released |
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Term
Lysogenic Phase for Bacteriophage |
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Definition
- Phage DNA becomes incorporated into bacterial chromosome at attachment (att) site
- Some phage have tRNA-like genes that simply integrate via homologous recombination with tRNA genes
- Repressor protein is transcribed --> Represses the lytic gene
- Prophage: Phage integrated into host DNA
- Lysogenic/Temperate Phage: Capable of both the lytic and lysogenic phases
- Enters into lytic phase once repressor protein is no longer produced and lytic gene is turned on --> Random event |
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Term
Generalized Transduction by Bacteriophage |
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Definition
- Phage carried bacterial chromosomal DNA within its capsule
- This DNA was acquired during lytic phase when bacterial DNA was packaged into phage instead of phage DNA
- These phage cannot duplicate because they do not contain phage DNA
- This DNA must be integrated into the host in order to replicate again |
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Term
Specialized Transducing by Bacteriophage |
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Definition
- Phage DNA contains extra genes that appeared due to imprecise excision from host DNA, integration of a transposon or another random recombination event
- These phages are always lysogenic
- DNA is then incorporated into new host DNA
- Lysogenic conversion occurs in the host
- Ex. Diptheria and cholera toxins |
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Term
Therapeutic Uses of Bacteriophage |
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Definition
- Since bacteriophages infect bacteria, could potentially be used to treat infections
- Highly specific to bacterial species
- Non-toxic to animals and plants
- Side effects and allergic reactions have rarely been seen |
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Term
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Definition
- Contiguous blocks of virulence genes found in bacterial DNA --> Usually on plasmids
- Found in diverse bacterial species
- Genes generally code for proteins with the same functions and amino acid sequences
- Implies that these genes came from one common ancestor
- Acquired by genetic transfer between species --> Different GC content from rest of DNA
- Bacterial strains without island of DNA show little or no virulence --> Specific DNA sequences confer virulence |
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Term
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Definition
- Ratio determined by the LD50/ID50
- Can change depending on particular host --> Age, disease state, medications, etc
- Decreased LD50 --> Increased virulence
- Shigella: Extremely virulent (ID50~10-100)
- Salmonella: ID50= 10^6 normally, but much lower in patients on antacids
- Factors: Pili, capsules, LPS, peptidoglycan, and teichoic acid structure, flagella, outer membranes, and surface proteins |
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Term
Susceptibility in Immunodeficiencies |
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Definition
- B-cells: Bacterial infections (antibodies crucial)
- T-cells: Viral and fungal infections (Killer T-cells crucial)
- B+T-cells: Bacterial, viral, fungal, and protozoal infections
- Phagocytic deficiencies
- Complement deficiences: Recurrent Neisseria infections
- Factors for immunodeficiencies: AIDS, immunosuppressive drugs, diabetes, genetic disorders, old age, stress, poor nutrition, pregnancy, splenectomy, tobacco, drugs, alcohol, and medications |
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Term
Acute vs. Chronic Infections |
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Definition
- Most infections are acute and assymptomic
- Symptoms short lived if present at all
- Chronic infections --> May begin as asymptomatic (carrier) but can transmit to others
- MRSA, gonorrhea, and chlamydia are common chronic infection bacteria |
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Term
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Definition
1. Incubation period: Time from acquisition to first specific symptom (days to months)
2. Prodrome: Period with general illness symptoms (fever, malaise, muscle cramps, etc)
3. Clinical Illness: Time from the first specific symptom to the resolution
4. Recovery: Time till you're back to normal |
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Term
Transmission and Entry of Pathogen |
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Definition
- Relates back to the structure of the bacteria itself
- G- are tough --> Can live in water/environment
- G+ are more delicate --> Transmitted by close contact (Neisseria)
- Points of entry: Nose, mouth, eyes, respiratory tract, genitourinary tract, and skin (cuts and sores) |
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Term
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Definition
- Must overcome normal flora for space, food, etc
- Normal flora also produce natural antibiotics
- IgA protease --> Break down mucosal IgA antibodies
- Factor A: Binds Fc region on IgG to inhibit complement activation
- Leukocidins: Destroy leukocytes and macrophages
- Coagulase: Helps surround pathogen with fibrin clot
- Capsules inhibit phagocytosis
- Biofilm formation also inhibits phagocytosis and opsonization
- Ability to escape phagosome after phagocytosis
- Ability to inhibit lysosome binding with phagosome after phagocytosis |
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Term
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Definition
- Pili, capsules, and teichoic acid structure |
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Term
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Definition
- Localized --> S. aureus abcess
- Minimal spread --> Erysipelas due to Strep.
- Disemination systemically --> N. gonorrhoeae
- Intracellular growth: Invade using special surface proteins or type III secretion systems
- Can also grow in biofilmsĀ |
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Term
Invasion, Inflammation and Intracellular Survival |
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Definition
- One way to cause disease
- Produce enzymes to help spread and break down barriers --> hyaluronidase, collagenase, phospholipase, and streptokinase
- Anti-phagocytic factors --> Factor A and capsule
- Pyogenic inflammation --> Pus-producing --> Neutrophils (acute)
- Granulomatous inflammation --> Chronic with macrophages and T-cells |
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Term
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Definition
- Secreted by pathogens
- Encoded by genes on phages or plasmids
- Very toxic in small doses
- Good antigens --> Can produce toxoids
- Some have A-B subunit --> A is active (toxic) and B is the binding portion for cell receptors
- Superantigens: Simultaneously bind T-cell receptor and MHC class II molecule on APC --> Cytokine storm!!! |
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Term
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Definition
- Integral part of cell wall of G- rods and cocci --> Primarily LPS
- Also possible with peptidoglycan, teichoic acid on G+ bacteria (S. aureus) --> Not as potent
- Encoded by genes in bacterial chromosome
- Less toxic than exotoxins
- Not good antigens --> No toxoids
- Released upon lysis or blebbing of bacteria
- Most common cause of sepsis and disseminated intravascular coagulation (DIC)
- Induce high concentrations of IL-1, TNF, NO, and complement |
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Term
Other Causes of Bacterial Pathogenesis |
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Definition
- By-products: Acids and gas production leading to tissue damage
- Immunopathogenesis: Molecular mimicry --> Cross-reactivity between pathogen and host tissue
- Ex. Rheumatic heart disease
- Neoplasia: Can be caused by persistent infections |
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Term
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Definition
1. Stain with crystal violet
2. Stain with Grams iodine
3. Wash with alcohol
4. Stain with safranin |
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