Transcript Mucous membranes

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