5.5 Pathogen Portal of entry

Question 1

The skin

Answer 1

• > largest body surface
• > provides excellent barrier to infection
• > skin is generally dry and acidic, but also a salty environment that does not support the growth of most microorganisms, apart from normal skin flora
• > waterproof impermeable barrier
• > infections frequently begin at other sites such as the host’s mucous membranes (not the skin - unless breach of barrier)

Question 2

Pathogen Portal of entry

Answer 2

1. Respiratory tract
   - > nose
   - > mouth
   - > lungs
2. Gastrointestinal tract
   - > throat
   - > stomach
   - > intestines
3. mucous membranes
   - > nose
   - > eyes
   - > urogenital tract
4. Parenteral (Skin penetration)
   - > Bites
   - > Cuts
   - > Injections

Question 3

1. Respiratory Tract

Answer 3

mainly airborne transmission -> Droplet / Particle

• > Tuberculosis (Mycobacterium tuberculosis)
• > Whooping cough (Bordetella pertussis)
• > Pneumonia (Streptococcus pneumoniae)
• > Strep throat (Group A Streptococcus)
• > Diptheria (Corynebacterium diptheriae)
• > Legionnaires disease (Legionella pneumophilia)

Question 4

2. Gastrointestinal Tract

Answer 4

Entry is given via contaminated food and water or contaminated hands and fingers

A. food - borne disease
B. water - borne disease
C. fecal-oral transmission

microorganisms are usually destroyed by stomach acid + enzymes and bile + enzymes in small intestine

gastrointestinal pathogens adapted to survive “hostile” environments

• > Salmonellosis (diarrhea + vomiting) - Salmonella sp.
• > Shigellosis (dysentery) - Shigella sp.
• > Cholera (diarrhea + vomiting) - vibrio cholerae
• > Stomach ulcers - Helicobacter pylori
• > Botulism - Clostridium botulinum

Question 5

3. Mucous membranes

Answer 5

Protective layer/barrier on top of endothelial cells (part of skin)

mucous membrane covers large parts of urogenital tract

sexual transmitted diseases (STDs)

• > Gonorrhea (Neisseria gonorrhoeae)
• > Syphilis (Treponema pallidum)
• > Chlamydia (Chlamydia trachomatis)

mucous membranes also covering gastrointestinal tract and respiratory tract

Conjunctiva: mucus membrane covering eyeball and lining of eyelid
-> Trachoma (blindness) - chlamydia trachomatis

Question 6

4. Parentarel (Skin penetration)

Answer 6

Pathogens gain entry through “breach” of skin barrier

• > natural skin openings (hair follicles and sweat glands)
• > splitting of skin due to swelling or dryness
• > punctures / injections (deposited into the tissues below the skin / mucous membranes)
• > bites / scratches
• > surgery
• > injection