MICROBIO - BLOCK 3 REVIEW

Module 3 Review

Bacterial Refresher

• Ability to define and use definitions in sentences with examples is important.
• Compare and contrast bacteria with eukaryotic host cells.
• Learn and define features of bacteria structure with morphology.
• Compare gram-positive and gram-negative bacteria.
• Learn how Acid-Fast bacteria differ from Gram +/-.
• Name bacteria based on visual presentation.
• Recognize growth requirements of bacteria.
• Identify bacterial growth phases, including identification from a graph, and what occurs during each phase.
• Outline binary fission and how it differs from horizontal transfer.
• Compare the three types of horizontal DNA transfer: conjugation, transduction, and transformation.
• Review the establishment of infectious diseases and provide examples of "damage".

Review of Last Class

• E. coli has over 700 different strains or serotypes.
• Only bacteria have cell walls.
• Only bacteria have pili/fimbriae, flagella (*sperm human exception), and capsules.
• Human cells don't produce spores but bacteria do.
• Instead of an enclosed nucleus, bacteria have a nucleoid, which contains the suspended genetic material.
• Unlike eukaryotic genetic material, the genophore, or prokaryotic DNA, is double-stranded and circular.
• Bacteria cells can live independently as part of an organism, while human cells are part of tissues, organs, and function as a whole organism.

Bacteria Structure and Morphology

• Cell wall- made up of NAG, NAM, and cross-linked peptides; it protects against osmotic pressure and helps determine the shape.
• Plasma membrane- phospholipid membrane under the cell wall (Gram+), or inside and outside of a thin layer of cell wall (Gram-).
• Cytoplasm- jelly-like fluid inside bacterial cells.
• Ribosomes- synthesize proteins.
• Nucleoid- "nucleus-like container" that contains the suspended genetic material.
• Pili/fimbriae- finger-like projections that help with the attachment of cells to other surfaces.
• Flagella- long, helical filaments for motility.
• Capsule- slimy outer coating to prevent phagocytosis.

Comparing Gram+ and Gram- Bacteria

• Gram+ have a cell membrane and thick outer cell wall.
• Gram- have inner and outer cell membranes, and a thin cell wall.
• A key component of Gram- bacteria is lipopolysaccharide (LPS).
• Both Gram+ and Gram- contain a periplasmic space.
• Gram+ bacteria have teichoic and lipoteichoic acid.

Acid-Fast Bacteria

• Acid-Fast cell walls contain waxes.
• A special acid-fast stain is needed.

Bacteria Growth

• Important growth requirements include carbon, nitrogen, energy sources, water, and ions.
• Some bacteria secrete siderophores to "steal" iron from the host.
• Obligate anaerobes cannot grow in the presence of oxygen.
• Obligate aerobes can only grow in the presence of oxygen.
• Facultative anaerobes can grow with or without oxygen.
• Obligate intracellular pathogens can only grow within living cells because they rely on ATP derived from the host.
• Bacteria often need sugar or other food/nutrient sources and contain permeases to facilitate entry of most metabolites.
• Facilitated diffusion involves substances that are carried across the membrane down a concentration gradient; uptake is driven by intracellular use.
• Active transport involves moving molecules across a cell membrane into a region of higher concentration, assisted by enzymes, and requires energy.
• Group translocation involves energy dependent transports of certain sugars, which are chemically altered in the process.

Identifying Bacteria Growth

• During the lag phase, bacterial cells engage in metabolic activity without cell division to acclimate to growth conditions.
• During the logarithmic (exponential) phase rapid cell division occurs.
• Beta-lactam antibiotics such as penicillin are effective during this period, because they interfere with cell wall production.
• During the stationary phase, the curve plateaus because proliferation and cell death are in balance; it is reached when nutrients are running low and/or toxin levels are elevated.
• During the death phase, the number of bacteria declines.

Binary Fission

• Asexual reproduction that separates a bacterial cell body into two new parts.
• Duplicates genetic material, and divides into two parts (cytokinesis).
• Asexual & semiconservative because each new chromosome comprises one strand of DNA from the parental chromosome and one complementary daughter strand.

Horizontal Gene Transfer

• Occurs when an organism transfers genetic material to another organism that is not its offspring; types include: conjugation, transduction, and transformation.
• Enables bacteria to respond and adapt to their environment more rapidly by acquiring large DNA sequences from another bacterium in a single transfer.

Stages of Infectious Disease & "Damage":

1. Encounter: The agent meets the host.
2. Entry: The agent enters the host.
3. Spread: The agent spreads from the site of entry.
4. Multiplication: The agent multiplies in the host.
5. Damage: The agent, the host response, or both cause tissue damage.
6. Outcome: The agent or the host wins out, or they learn to coexist.

• Toxins line endotoxins (LPS), exotoxins like proteases and superantigens, lead to pro-inflammatory cytokine release, which leads to inflammation.

Antibiotics

• Key aspects to describe for the 6 classes of antibiotics covered:
  • The mechanism of action
  • Major adverse effects
  • Common clinical uses
• It is important to recognize and describe the mechanisms of resistance for each class of antibiotics covered.
• Recognize and appreciate the importance of antibiotic stewardship and conservative treatment.

Penicillins

• A beta-lactam antibiotic
• Binds penicillin-binding proteins (transpeptidase) via the beta-lactam ring
• Blocks cross-linking of peptidoglycan in cell wall -> osmotic imbalance -> death (bactericidal)
• Hypersensitivity is a key adverse effect
• Treatment use involves Gram-positive aerobes like S. pyogenes or S. pneumoniae.

Cephalosporins

• A beta-lactam antibiotic
• Inhibits cell wall synthesis the same way as penicillins
• Bactericidal
• Hypersensitivity is a major adverse effect
• Clinical Use depends on the class

Aminoglycosides

• Key action involves binding the 30s subunit of the bacterial ribosome and inhibiting protein synthesis
• Bactericidal
• Requires O² for uptake, making it ineffective against anaerobes.
• Nephrotoxic, ototoxic, and teratogenic adverse effects.
• Used to treat severe Gram-negative rod infections
• Use is limited due to adverse effects and resistance.

Tetracyclines

• Binds the 30S subunit -> inhibits protein synthesis
• Bacteriostatic
• Cannot take with divalent cations (ex: milk and Ca²⁺) -> inhibits drug absorption in the gut
• Discoloration of teeth, inhibition of bone growth in children, photosensitivity, and teratogenic adverse effects.
• Used to treat Borrelia burgdorferi, Mycoplasma pneumoniae, Rickettsia, Chlamydia, etc.

Macrolides

• Binds the 50S subunit -> inhibits protein synthesis
• Bacteriostatic Arrhythmia - prolonged QT interval and GI upset can occur
• Versatile antibiotic
• Treats atypical pneumonia (ex: Mycoplasma), STIs (Chlamydia), Gram-positive cocci (alternative to penicillin).

Fluoroquinolones

• Inhibits prokaryotic Topoisomerase II (DNA gyrase) and IV -> impairs DNA synthesis
• Bactericidal
• Tendonitis or tendon rupture, arrhythmia - prolonged QT interval can occur
• Used to treat Gram-negative rods of urinary and GI tracts and Otitis externa

Mechanisms of Resistance

• Penicillins and Cephalosporins
  • β-lactamases cleaves β-lactam rings
  • Mutations in penicillin-binding-proteins
  • Countering the counter: β-lactamase inhibitors – ex: Clavulanic acid (Augmentin)
• Aminoglycosides
  • Bacterial transferase enzymes inactivate the drug
• Macrolides
  • Alteration of 50S subunit binding site prevents drug binding
• Fluroquinolones
  • Mutations in Topoisomerase genes alter drug-protein interaction
  • Efflux pumps
• Tetracyclines
  • Transport pumps decrease uptake and/or increase efflux out of cells

Remember These Classes

• Gene resistance encoding plasmids
• Conjugation, transformation, etc.

Gram Positive Cocci

• Be able to describe, compare, and contrast the Gram+ cocci
• Using diagnostic/laboratory tests, discriminate which culture is which bacteria (e.g. coagulase test)
• Know which strains of bacteria fall in each grouping (e.g. Aerobic, Catalase-, Beta-hemolytic, Gram+ cocci, that are susceptible to bacitracin= S. pyogenes)
  • Using patient's history, signs/symptoms (aka clinical presentation), diagnostic tests, unique virulence factors, etc.
    • Including contraindications for treatment (i.e. what antibiotic you wouldn't prescribe to someone with a penicillin allergy? Penicillin)
• Staphylococcus: Gram+ cocci, aerobic, catalase+*
• Staphylococcus aureus: coagulase+
• Staphylococcus epidermidis: coagulase-, novobiocin sensitive
• Staphylococcus saprophyticus: coagulase-, novobiocin resistant
• Staphylococcus lugdenensis, Staphylococcus haemolyticus: coagulase-
• Streptococcus: Gram+ cocci, aerobic, catalase-*
• Viridans strep (E. mutans, E. mitis): alpha hemolysis, optochin resistant
• Streptococcus pneumoniae: alpha hemolysis, optochin sensitive
• Streptococcus agalactiae (Group B strep): beta hemolysis, bacitracin resistant
• Streptococcus pyogenes (Group A strep): beta hemolysis, bacitracin sensitive
• Enterococci (Group D; E. faecium, im, E. faecalis): gamma hemolysis, growth in 6.5% NaCl

Gram Negative Cocci

• Key features*
• Be able to describe, compare, and contrast the Gram+ cocci with Gram- cocci
• Gram+ cocci
  • Staphylococcus (cluster)
  • Streptococcus (chain)
• Gram- cocci
  • Neisseria spp. (diplococci)
• Using diagnostic/laboratory tests, discriminate which culture is which bacteria*
• Diplococci, aerobic
  • N. gonorrhoeae, Maltose negative
  • N. meningitidis, Maltose positive

Virulence Factors

• Staphylococcus (general)*
• Biofilm- firmly adheres bacterial colonies, reinforces adhesion to host & protects from immune cells & antibiotics
• Capsule- inhibits phagocytosis
• Cell Wall & Cell Surface Components:
  • Lipoteichoic acid & peptidoglycan- endotoxin-like effects. Trigger macrophages to release pro-inflammatory cytokines. Can help with adhesion by binding fibronectin
• Cytotoxins (alpha, beta, delta, gamma, and Panton-Valentine leukocidin)- lyse red & white blood cells
• Enzymes- Coagulase, Fibrinolysin (Staphylokinase), Hyaluronidase, Lipase, Nuclease
• Superantigens- Type of antigen that results in excessive activation of immune system that causes significant damage to host
• Exfoliative toxins (A & B)- proteases that destroy the granular layer of the epidermis
• Enterotoxins- stimulate T-cell & macrophage release of cytokines & trigger Mast cell degranulation -> peristalsis & vomiting
• Toxic shock syndrome toxin I (TSST)- stimulates T cell proliferation & release of cytokines which cause blood vessel leakage
• Streptococci (general)*
• Capsule- inhibits phagocytosis
• Cell Wall & Cell Surface Components:
  • Lipoteichoic acid & peptidoglycan- endotoxin-like effects
  • F proteins
  • M-protein, can also facilitate epithelial cell invasion
  • Surface C5a peptidase
• Superantigens
• Streptococcal pyrogenic exotoxins
• Streptolysins S & O- lyse blood cells
• Streptokinases A & B- enzymes that break up blood clots to promote bacterial spread
• DNAses- decrease pus viscosity, aids in evasion of Neutrophil Extracellular Traps (NETs)
• Streptococcus pneumoniae*
• IgA protease, degrades IgA to allow bacteria to reach mucous membranes of respiratory & genital tract
• Pneumolysin
• Produces hydrogen peroxide
• Phosphorylcholine
• Streptococcus pyogenes*
• Streptococcal pyrogenic exotoxins
• Enterococcus: causes Toxic Schock Syndrome and uses Biofim*

Diseases

• Staph*
• Staphylococcus aureus- Skin infections, Non-skin infections, SSSS/Ritter's food poisoning, toxic shock syndrome TSST
• Staphylococcus epidermidis- Normal skin flora... usually skin conditions like boils, impetigo, cellulitis, scalded skin syndrome
• Staphylococcus saprophyticus- UTI in sexually active young women.
• Staphylococcus lugdunensis- native valve endocarditis
• Staphylococcus haemolyticus- catheter-associated UTI
• Staph Treatment*
• Penicillin B-lactam antibiotic
• Methicillin-- no-longer available, MRSA
• Cephalosporins B-lactam antibiotic
• Carbapenem B-lactam, MDR
• Vancomycin
• Linezolid inhibit initiation of bactericidal protein synthesis (70s subunit like the macrolides)
• Reserved for patients with proven MDR infections & to life-threatening complicated infections with MDR to first line treatments Clindamycin slows or stops the growth of bacteria bacteriosatic
• Topical form for skin infections
• Strep*
• pneumoniae- otitis media & sinusitis, pneumococcal meningitis
• Treatment: Penicillin or Ceftriaxone Viridans Strep
• Deep tissue abscesses, Bacteremia in cancer patients tooth decay (aka dental caries S. mutans Treatment: vulnerable to antibiotics with exception of S. mitis S.pyogenes: Step pharyngitis Treatment: Penicillin. Patients should be given antibiotics within first 7-10 days of infection to prevent rheumatic fever ;scarlot fever, rheumatic fever, Skin diseases impetigo, cellulitis, necrotizing fascitin, heart disease
• Other Strep* Agalactiae
• Early onset- bacteremia - pnemonia menintitis ; other infections bacteremia leading to pnemonia & infections of bones skin & soft tissues; Urinary tract infections; wound ifection
• Treatment
• Enterococcus:* resistant to most Abx

Gram-Negative Bacilli

• Key features:

  • Able to describe their common virulence factors & what they do (e.g how do they help the pathogen subvert the immune system, or make the host sick, or increase spread, etc.)
  • Using diagnostic/laboratory tests, discriminate which culture is which bacteria (e.g. coagulase test)

• Diplococci*

• Gram + (chain/cluster) vs. Gram -.

• Gram -. Neisseria spp. Able to describe their common virulence factors & what they do

• Both Gonorrhoeae & Meningitidis = Lipooligosaccharide, endotoxin = Pili, motility, host cells, IgA protease, outer membrane protein

• meningitidis: Capsule, which inhibits complement pathways = diagnose & treat and prevent contraindications

• Using diagnostic/laboratory and in each group know which strains of bacteria fall in each group*: Aerobic Maltese

• No: N. gonorhoeae, Moraxilla

• Yes: N.meningitides Gram - cocci

• Virulence factors gram - vs gram+:*

• Both Meningitidis & Gonorroehae = Lipooligosaccharide, endotoxin = Pili motility help host cell = IgA protease = other membrane protein

• meningitidis: Capsule inhibit pathway able Diagnose

• prevent vaccine Cefriaxone gonorrhoeae IM Ceftiaxoin

• Able to what and factors do which to the help help immune make and increase yersinia

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• they in disarmo phagocitos and can in site

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Review of Last Class: I

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Review of Last Class Part2

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In Summary

• Practice good antibiotic stewardship.
• Not every infection requires an antibiotic.
• Choose the right antibiotic for the right infection.