Differentiate between the structure, pathogenic properties and mechanisms by which bacteria, viruses and fungi cause disease. Organism StructurePathogenic PropertiesBacteriaBacteriaUnicellular-Prokaryotic(no nucleus).-Rigid outer wall,(made of peptidoglycan). This is action site of someabx. ONLY produced by bacteria.CocciRound sphericalStrep-chain Staph-clusterBacilliRod shaped-e-coli.SpirochetesHelical (spiral)-syphilisPolymorphicNo specific shape and no rigid cell wall-mycoplasmpna.DiplococcipairsGram negative.-Don’t retain gram stain-Cause fever, dic, septic shock.-Outer membrane is made oflipopolysaccharide, which activates almost every aspectof inflammation (cytokines, TNF, IL).-Have extra membrane making them more resistant to abx than gram +.-Ex- Neisseria (gonorrhea, meningitis), salmonella, shigella, & klebsiella.Gram positive.Retain gram stain-purpleLack extra cell to release cytotoxins.Some secrete teichotic acid=protects from lysis.Ex- Strep, staph, bacillus(anthrax), clostridium(tetanus)Acid Fast Bacilli (AFB)-Thick walls made of lipids which allows them to take up stain fast.
-Grow very slow. (thickness)-Abx=months – years.-Cultures=8weeks.-Ex- M. Tuberculosis, M. Laprae(leprosy), M. Avium.VirusConsist of nuclei acid protected by protein shell (capsid)Some have protective envelope surrounding capsid.Envelope-plasma membrane from previously infected cell.Most common in humansSpread from person to person or from animal, also from vector (mosquitos).Life cycle=intracellular-attachment to target cell-penetration-uncoating-rlease of viral nucleic acid from capsid-replication-synthesis of viral proteins and MRNA-Assembly- formation of new virons.-release- lysis or budding.Rapidly proliferate(multiply)and produce more virons than immune system can handle.Hide with in cells and away from immune and inflammatory responses.Frequent antigen shifts/driftsSuppress immune sys.Coat with self-proteins similar to normal cells.Self-limiting.FungiEukaryotic (nucleus)Thick rigid wallsDx by microscopic obs.Treated with potassium hydroxide to visualize
Antifungals treat deep or systemic infx. And are toxic to host cell. Fungal cell is similar to human cell. Candid albicans= most common cause of fungal infx. -opportunistic yeasts. -skin, gi, mouth, vagina. -overgrowth. -neutropenic or immunosuppressed may have disseminated infix. (spread) -Candida=most common infx in people with cancer and hiv. d. Identify the clinical manifestations associated with infectious diseases.
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