LPS Structure
O antigen is polysacharide and is highly variable
Core sugar is hexose or manose and is variable
Lipid A is the antigenic portion and is highly conserved
LPS is recognized by TLR4
Induces release of TNF, IL-1, 6
Gram Negative Cell Wall
LPS and 2 plasma membranes with a single small peptidoglycan layer. Two periplasmic spaces where beta lactamases and other resistance mechanisms lie
Mycobacterial cell wall
outer lipid, mycolic acid, carbohydrate chains, peptidoglycan, PM, …
Peptidoglycan synthesis
starts with glucosamine turned into Murnac with use of UTP. Attached to GLCNAC. Cross linking of terminal D-D alamine residues by transpeptidases. PBP, site of action of beta lactams.
Beta Lactam mechanism
Structurally similiar to D-alanyl alanine structure, binds to PBP and irreveribly acetalates PBP, inactivating it. Bacteriocidal.
Encapsulated bacteria
Streptococcus Haemophilus Nisseria Klebsiella Bacillus anthracus (peptide capsule)
Gram Positive Strucutre
Thick peptidoglycan that is linked by pentaglycines.
Has teichoic acid
Can undergo sporulation.
More lysozyme sensitive.
Bacterial Conjugation
- Transfer of genetic material via a sex pilus (F)
- Donor must be F+ and receptor F negative
- If F factor is incorporated into the genome the bacterial becomes HFR because the genes on the F plasmid will be transcribed and translated at a higher rate.
- Genes can be excised along with the F factor onto a plasmid which will result in an F’ plasmid. Some of these genes can be resistance genes.
Bacterial Transformation
Uptake of free DNA.
There must be significant homology of DNA sequences for proper integration
-Gram positives more commonly use transformation
Bacterial Transduction
- Bacteriophages will infect bacteria and insert their genome into the bacterial genome.
- When a bacterial genome contains viral DNA the bacteria is said to be lysogenized (capable of being lysed)
- With lysis the phage will remove it’s DNA and some neighboring segments and be ready to reinfect a nearby cell thus transferring genes.
Spores
- Allow for a hardy, metabolically silent stage.
- Clostridium, bacillus
IgA Proteases
-Strep Pneumo, Niesseria, H Flu
Intracellular Bacteria
ricketsia, chlamydia, salmonella, shigella, yersinia, mycobacteria, listeria, legionella, Brucella, fransciella
alpha hemolysis
- partial hemolysis, greenish discoloration of agar
- strep viridans, Strep Pneumo
Beta Hemolysis
- Complete clearing of agar
- staph, strep, listeria
- GAS - Strep pyogenes - bacitracin sensitive
- GBS - Strep agalactias - bacitracin resistant
gamma hemolysis
- no hemolysis
- enterococcus
Catalase
- Peroxide to water and oxygen
- Strep and enterococcus are catalase negative
Coagulase
- Converts fibrinogen to fibrin
- Staph aureus is coag positive
Diptheria and Pseudomonas exotoxin
- ADP ribosylation, inactivate E2-f
Shiga Toxins
-N-glycosidases of 28S RNA. Halt protein sythesis
Heat Labale Enterotoxins
- Choler and E Coli
- ADP ribosylate G alpha S that causes increase in cAMP
Pertussis Toxins
- B component binds to receptor and A is enymatically active
- ADP ribosylate g alpha i which prevents the inhibition of AC, leading to elevated intracellular cAMP
Heat Stable Enterotoxin
- E Coli
- Activates gyunulate cylase incresing cGMP causing diahrea.
Anthrax edema factor
-Increase intracellular cAMP which leads to elevated intracellular calcium and activation of calmodulin.
