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Portals of Entry Mucous membranes – – – – Conjunctiva Respiratory Gastrointestinal tract Urogenital Skin – Abrasions or bite Parenteral – Puncture or injection Mucous Membranes: Conjunctiva Conjunctiva: Mucous membranes that cover the eyeball and lines the eyelid Trachoma: Chlamydia trachomatis Mucous Membranes: Respiratory Inhaled into mouth or nose in droplets of moisture or dust particles Easiest and most frequent • Common cold • Flu • Tuberculosis • Whooping cough • Pneumonia • Measles • Strep Throat • Diphtheria Mucous membranes: Gastrointestinal Tract Salmonellosis Salmonella sp. Shigellosis Shigella sp. Cholera Vibrio cholorea Ulcers Helicobacter pylori Botulism Clostridium botulinum Fecal - Oral Diseases : • These pathogens enter the G.I. Tract at one end and exit at the other end. • Spread by contaminated hands & fingers or contaminated food & water • Poor personal hygiene. Mucous Membranes: Genitourinary System - STD’s Gonorrhea Neisseria gonorrhoeae Syphilis Treponema pallidum Chlamydia Chlamydia trachomatis HIV Herpes Simplex II Skin Skin: Largest organ of the body. When unbroken: Effective barrier for most microorganisms. Some microbes can gain entrance through openings in the skin: Hair follicles and sweat glands Parenteral Microorganisms are deposited into the tissues below the skin or mucous membranes: • • • • • • Punctures injections bites scratches surgery splitting of skin due to swelling or dryness Preferred Portal of Entry Small pox: Variolation Streptococcus pneumoniae • Inhalation: Pneumonia • Gastrointestinal Tract: No disease Salmonella typhi • Gastrointestinal Tract: Typhoid Fever • On skin: No disease To Cause a Disease 1. Adherence To host surfaces 2. Avoid phagocytosis Prevent host defenses from destroying 3. Penetrate Get into host and spread 4. Enzymes Spread, prevent host defenses and cause damage at site of infection 5. Toxins Cause damage to tissues Adherence Adhesions: Bind to receptors on host cells By: • Glycocalyx Streptococcus mutans Dextran (plaque) • Waxes Mycobacteria • Fimbriae Escherichia coli • M protein Streptococcus pyogenes • Tapered end w/ hooks Treponema pallidum Capsules Adherence & Prevent phagocytosis • • • • • • Streptococcus pneumoniae Klebsiella pneumoniae Haemophilus influenzae Bacillus anthracis Streptococcus mutans Yersinia pestis Enzymes Increase virulence & Avoid phagocytosis Coagulase Coagulate blood Kinases Digest fibrin clot: Spreading (Streptokinase and staphylokinase) Hyaluronidase Collagenase IgA proteases Hemolysins Hydrolyzes hyaluronic acid Hydrolyzes collagen Destroy IgA antibodies lyse RBC’s (Connective tissue) Hemolysins Alpha hemolysin • Incomplete lyses of RBC’s Beta hemolysin • Complete lyses of RBC’s Leukocidins Enzymes that attack certain types of WBC’s: 1. Kills WBC’s which prevents phagocytosis 2. Releases & ruptures lysosomes * Lysosomes: Contain powerful hydrolytic enzymes: Cause more tissue damage Toxins Spread and damage to the host Endotoxins: Exotoxins: • Toxemia: • Toxoid: • Antitoxin: Inside the cell (Released upon cell lyses) Secreted out of the cell Presence of toxin in host's blood Inactivated toxin used in a vaccine Antibodies against toxin Enzymes: Necrotizing Factor “Flesh Eating Bacteria” (Death (necrosis) to tissue cells) Exotoxins Exotoxins Mostly Gram +ve bacteria Most genes are located on plasmids or phages Exotoxin Source Mostly Gram +ve Metabolic product Chemistry By-products of growing cell Protein Water soluble No Yes Small - Very potent 1 mg of Clostridium botulinum toxin Fever? Neutralized by antitoxin LD50 can kill 1 million guinea pigs Exotoxins: Three types 1. Cytotoxins: kill cells 2. Neurotoxins Interfere with normal nerve impulses 3. Enterotoxins Effect cells lining the G.I. Tract * Many toxins have A & B subunit: A: Active: Causes change in host B: Binding Exotoxins Bacteria Exotoxin Corynebacterium diphtheriae A-B toxin: Inhibits protein synthesis Streptococcus pyogenes Membrane-disrupting Clostridium botulinum A-B toxin. Neurotoxin - Flaccid paralysis C. tetani A-B toxin. Neurotoxin: Prevents CNS inhibition - spastic paralysis Vibrio cholerae A-B toxin. Enterotoxin Stimulates cAMP to cause severe diarrhea Staphylococcus aureus Enterotoxin Endotoxin Endotoxins Source Gram –ve Metabolic product Present in LPS of outer membrane Chemistry Lipid Fever? Yes Neutralized by antitoxin No LD50 Relatively large Endotoxins: Part of the Gram -ve Bacterial cell wall LPS (Lipopolysaccharides) • O Antigen • Lipid A Heat Stable (Exotoxins are typically heat liable) Lipid A – Toxin: Portion of the LPS • Fever: in many Gram –ve bacterial infections • Gram –ve cells: When “digested”: Endotoxins are released: Fever E. coli (0157:H7) Enterotoxin causes a hemolytic inflammation of the intestines Results in bloody diarrhea Endotoxins