Introduction to the Microbial World
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True pathogen- virulence factors
Organisms of the microbiome- mechanical failures of innate barrier- often mixed
Microbes of immunodeficiency disease- single microbes- specific to a particular immune defect
Prion - infectious proteins- Acellular
Virus- Acellular- electron microscope- DNA or RNA-obligate intracellular( can't live or procreate without having a cell to live in)- Rx- Anti fusion, anti nucleic acid, anti release
Prokaryote (bacteria)- light microscope- Cells with no internal membrane bound organelles (no nucleus, no mitochondria, no ER)- replicate cont. by binary fission, asexual- mono and polycistronic mRNA- no introns- 70s ribosomes - cell membranes without sterols- cell wall- peptidoglycan- Rx- Anti cell wall penicillin, cephalosporins, vancomycin- Anti 70s ribosomes- tetracycline, macrolides, lincosomides
#Mycoplasma - unusual prok. - has sterols in membrane and doesn't have a cell wall.
Bacteria have DNA and RNA
Eukaryote- light microscope to naked eye- DNA and RNA
fungus- ergosterol- complex carbohydrate cell wall
Anti- ergosterol- nystatin, imidazoles, terbinafine
- Anti chitin- Nikkomycin
Parasite- cholesterol- most anti parasitic drugs have some toxicity for human cells- more difficult to treat
Epidemiology of infectious diseases
Normal flora- Assist digestion and producs Vitamin K for clotting blood.
Skin- Staphylococcus epidermidis
Nose- Staph. Aureus, S. epi.
Oropharynx- Viridans streptococci, other strep., non pathogenic Niesseria and haemophilus
Colon- E. coli
Vagina (during menarche)- Lactobacillus, streptococcus. Pre menarch and post menopausal females may have Staph. aureus
In vagina- Thayer martin agar
THE MOST COMMON Q- Mechanism of pathogenesis of an organism
Viruses- attach to cells by specific cell membrane receptors- ' tropism'
Hemogglutinin-most RNA viruses
CD4 and chemokine receptors - HIV (via gp120)
CD21- Epstein Barr virus
Acetylcholine receptor- rabies
Gram positives - Lipoteichoic acids binds to fibronectin
Strep pyogenes M protein binds to fibrinogen
Mycoplasma protein P1 binds to sialic acid
Gram negatives and positives - Pili (fimbriae) and bind to sugar receptors
Bodetella pertussis- hemagglutinin binfd to integrin
staph A and Staph epi (catheters)
Plasmodium falciparum binds to ICAM -1 and glycophorins on erythrocytes
Plasmodium vivax binds to duffy antigen
Evasion of innate immune responses
Strep pyogenes- degrades IL-8
Psedomonas - C3a, C5a anaphylatoxins
Capsules (slim layer, glycocalyx)
Some Killers Have Pretty Nice Slimy Capsules
Haemophilus influenza type B
Inhibition of opsonization-
Strep pyo.-M protein - destroys C3 convertase
Staph A- Protein A binds the Fc of igG
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