Advantages of bacteria replication
- Allows selection and adaptation to environmental changes
- Difficult for host to control bacterial growth rely upon vaccines and antibiotics
Most species of bacteria utilize ______ for growth
Carbohydrates (glucose)
Some bacteria use _______ or _________ for growth so they don’t have to compete with other bacteria for glucose
Amino acids (clostridia) Fatty acids (leptospira)
Most bacteria range in size from ___ to ___ µm
Filter sterilization is ≤ ___ µm
- 4 - 2.0µm
0. 45µm
Cell wall defines shape; What is the nomenclature for different bacteria with spherical structure?
Single cells Pairs - Diplococci Chains - Streptococci Tetrads - Micrococci Grapelike structures - Stapylcocci
What nomenclature is used to describe rod and spiral bacterial structure
Rods = bacilli; coccobacilli = long rods
Spirals (comma shaped) = Vibrio; 4-20 coils = Spirochetes
What does penicillin do?
Inhibits cell wall synthesis
What does gram-negative bacteria have that gram-positive bacteria does not have (5)
1) Thin peptidoglycan layer
2) Outer membrane
3) Pili
4) Porin proteins
5) Periplasmic space
What are the four steps for classification of bacteria (positive vs. negative gram stain)
Step 1: Crystal violet
Step 2: Gram’s iodine
Step 3: Decolorizer (alcohol or acetone) - extracts crystal violet from gram negative only
Step 4: Safranin Red - stains gram negative
Cell Envelope
- Cellular material located external to the cell membrane (unique to bacteria and target of many antibiotics)
Difference between Peptidoglycan for Gram positive and Gram negative bacteria
Gram Positive: Thick peptidoglycan - permeable barrier
Gram Negative: Thin peptidoglycan - Crosslinked to the outer membrane (Outer membrane = permeable barrier)
Basic subunit of the peptidoglycan includes:
Disaccharide linked to a D/L pentapeptide
- NH2 group for cross linking
- D-Alanine to D-Alanine bond which is broken and used for cross linking
Cross-linking differences between gram negative and gram positive bacteria
Gram Negative: Little crosslinking
Gram positive: Highly crosslinking between polysaccharides - rigid structure
Teichoic Acid (Gram positive - Cell envelope)
Polysaccharide that is crosslinked to cytoplasmic membrane and peptidoglycan (membrane stability) TLR signaling (Innate immunity)
Gram Negative (Cell Envelope)
- Outer Membrane
- Periplasmic Space
- Inner membrane
Outer membrane: Permeability barrier
- Lipopolysaccharide
- Porins (Molecular sieve 600 Dalton cutoff)
Periplasmic Space: Peptidoglycan - thin; not an effective barrier
Inner Membrane: Proteins embedded in phospholipid membrane
Function of outer membrane
Cell growth stimulates innate immunity
Important things to know about lipopolysaccharide (LPS)
Unique to Gram-negative bacteria
- O-antigen is variable
- Lipid A - fever inducing - also known as endotoxin
- PAMP recognized by TLRs
Which cells of innate immunity recognize PAMPs
Macrophages and Neutrophils
PAMP for gram negative bacteria vs Gram positive bacteria
Gram neg. - LPS
Gram pos. - Lipoteichoic Acid
Pili and Fimbriae
Pili and Fimbriae: polymers of proteins
Function: Adherence to eukaryotic cells and between bacteria
Fimbriae are components of some vaccines
Flagella (And there appearance in Pseudomonads and Enteric bacteria)
Flagella: polymers of proteins
Function: Motility (non-motile bacteria are often nonvirulent)
Pseudomonads - have a single polar flagellum
Enteric bacteria - have flagella distributed over the entire cell surface
What is the basis of the evolution of virulence factors
Evolved by gene duplication of flagellum
Flagellum retains motility function, while the duplicated genes evolve new functions
Virulence Factors
Type II:
Type III:
Type IV:
Type II: Secrete protein across the inner membrane
Type III: Deliver toxins directly into host cells
Type IV: Deliver DNA into host cells
Capsule
Capsule: Polymer of polysaccharide or protein
Function: Prevent host cell phagocytosis
- Many capsules are developed to produce vaccines
Haemophilus
Reservoir and Characteristics?
Humans are the only known reservoir; effective immunization controls diseases
- Unique growth properties
- Haemophilus influenzae type B
- Capsule and neutralizing antibodies
- Conjugate vaccines
Hib (Haemophilus influenza type B) pathogenisis
Hib is transmitted among humans via the respiratory tract from clinically active case, convalescent patients, or carriers
Explain Hib primary infections
Colonization of nasopharynx
Occasional invasion of sinuses, middle ear, bronchi
- Life threatening infections due to invasion of blood stream/meninges
Hib virulence is associated with the expression of:
Type b polysaccharide capsule
The _____ and the _____ can become inflamed during bacterial meningitis
Pia mater; arachnoid
6 types of Hib and associated sugars
A - Glucose B - Ribose and ribitol** C - Galactose D - Hexose E - Hexosamine F - Galactosamine
Hib meningitis is most prevalent in what population?
The very young (< 1 yr)
Describe immunity to Hib
- Good relationship between age and susceptibility
- In children less than 3 mo, maternal Ab is protective
- Most invasive disease occurs between 3 mo and 3 yrs
- Children < 3 yrs show humoral immunodeficiency to Hib
- Children > 3 yrs develop Ig to Hib
1st generation Hib vaccine
Effectiveness and problems
Purified capsular polysaccharide of Hib 90% effective in children > 24 mo; ineffective < 18 mo Problems: - Poor immunogens - Stimulate T-independent Ab - Poor immunologic memory
2nd generation Hib vaccine
Vaccine:
Protein carrier:
PRP (Polysaccharide) protein conjugates
Vaccine: PRP-D
Protein Carrier: Diptheria toxoid
