 Mucous membranes –Conjunctiva –Respiratory –Gastrointestinal tract –Urogenital  Skin –Abrasions or bite  Parenteral –Puncture or injection Portals of Entry

Mucous Membranes: Conjunctiva  Conjunctiva: Mucous membranes that cover the eyeball and lines the eyelid 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 Common cold Flu Flu Tuberculosis Tuberculosis Whooping cough Whooping cough Pneumonia Pneumonia Measles Measles Strep Throat Strep Throat Diphtheria 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. 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 Spread by contaminated hands & fingers or contaminated food & water Poor personal hygiene. Poor personal hygiene.

Mucous Membranes: Genitourinary System - STD’s  Gonorrhea Neisseria gonorrhoeae Neisseria gonorrhoeae  Syphilis Treponema pallidum Treponema pallidum  Chlamydia Chlamydia trachomatis 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 Punctures injections injections bites bites scratches scratches surgery surgery splitting of skin due to swelling or dryness splitting of skin due to swelling or dryness

Preferred Portal of Entry  Small pox: Variolation  Streptococcus pneumoniae Inhalation: Pneumonia Inhalation: Pneumonia Gastrointestinal Tract: No disease Gastrointestinal Tract: No disease  Salmonella typhi Gastrointestinal Tract: Typhoid Fever Gastrointestinal Tract: Typhoid Fever On skin: No disease 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

 Adhesions: Bind to receptors on host cells  By: GlycocalyxStreptococcus mutans Dextran (plaque) GlycocalyxStreptococcus mutans Dextran (plaque) WaxesMycobacteria WaxesMycobacteria FimbriaeEscherichia coli FimbriaeEscherichia coli M proteinStreptococcus pyogenes M proteinStreptococcus pyogenes Tapered end w/ hooks Treponema pallidum Tapered end w/ hooks Treponema pallidum Adherence

Capsules Adherence & Prevent phagocytosis Streptococcus pneumoniae Streptococcus pneumoniae Klebsiella pneumoniae Klebsiella pneumoniae Haemophilus influenzae Haemophilus influenzae Bacillus anthracis Bacillus anthracis Streptococcus mutans Streptococcus mutans Yersinia pestis Yersinia pestis

Increase virulence & Avoid phagocytosis  CoagulaseCoagulate blood  Kinases Digest fibrin clot: Spreading (Streptokinase and staphylokinase)  HyaluronidaseHydrolyzes hyaluronic acid (Connective tissue)  CollagenaseHydrolyzes collagen  IgA proteasesDestroy IgA antibodies  Hemolysinslyse RBC’s Enzymes

Hemolysins  Alpha hemolysin Incomplete lyses of RBC’s Incomplete lyses of RBC’s  Beta hemolysin Complete lyses of RBC’s 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: Inside the cell (Released upon cell lyses)  Exotoxins: Secreted out of the cell Toxemia:Presence of toxin in host's blood Toxemia:Presence of toxin in host's blood Toxoid:Inactivated toxin used in a vaccine Toxoid:Inactivated toxin used in a vaccine Antitoxin:Antibodies against toxin Antitoxin: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 SourceMostly Gram +ve Metabolic product By-products of growing cell ChemistryProtein Water soluble Fever?No Neutralized by antitoxin Yes LD 50 Small - Very potent 1 mg of Clostridium botulinum toxin can kill 1 million guinea pigs

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: Three types

Exotoxins BacteriaExotoxin Corynebacterium diphtheriae Corynebacterium diphtheriae A-B toxin: Inhibits protein synthesis Streptococcus pyogenes Streptococcus pyogenesMembrane-disrupting Clostridium botulinum Clostridium botulinum A-B toxin. Neurotoxin - Flaccid paralysis C. tetani C. tetani A-B toxin. Neurotoxin: Prevents CNS inhibition - spastic paralysis Vibrio cholerae Vibrio cholerae A-B toxin. Enterotoxin Stimulates cAMP to cause severe diarrhea Staphylococcus aureus Staphylococcus aureusEnterotoxin

Endotoxin

Endotoxins SourceGram –ve Metabolic product Present in LPS of outer membrane ChemistryLipid Fever?Yes Neutralized by antitoxin No LD 50 Relatively large

Endotoxins: Part of the Gram -ve Bacterial cell wall  LPS (Lipopolysaccharides) O Antigen O Antigen Lipid A Lipid A  Heat Stable (Exotoxins are typically heat liable)  Lipid A – Toxin: Portion of the LPS Fever: in many Gram –ve bacterial infections Fever: in many Gram –ve bacterial infections Gram –ve cells: When “digested”: Endotoxins are released: Fever 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