Normal flora

Question 1

Normal flora of the skin

Answer 1

Microbes found in most superficial layers are G+ cocci

• S. epidermitis,
• Cornyebacteria
• S.aureus may be the in the normal flora
• Varies with the anatomical location

Question 2

Normal flora of the conjuctiva

Answer 2

Sparse, but s.epidermidis and certain cornyebacteria are dominant

• Hemophilis & Nisseria are occasionall found
• The conjuctiva is kept moist and clean by the secretion of the lacrimal gland

Question 3

Normal flora of the oral cavity:

Answer 3

• Oral bacteria include: streptococci, staphylococci, lactobacilli and cornyebacteria + anaerobes
• Age has a great influence

At birth: no teeth, oral cavity is sterile unti first feed
- Sterp. salivarius is predominant until apperance of teeth

• Tooth eruption leads to colonization by S.mutans and S.sanguis

Question 4

Normal flora of the respiratory tract

Answer 4

• nostril alsways heavily colonized
• S. epidermidis and cornyebacteria, and in some cases with staph. aureus
• Helathy sinuses are sterile
• The pharynx is colonized by streptococci and various G- cocci
• The lower respiratory tract is free of microorganisms because they have a cleansing system

Question 5

Normal flora of the urogenital tract

Answer 5

• Urine is normally sterile since the urinary tract is flushed with urine every 5h
• After birth the vagina becomes colonized by cornyebacteria, staphylococci, streptococci, E.coli and lactobacillus
• In puberty the vaginal flora will contain glycogen that lactobacillus acedophilus is able to convert to lactic acid inihibiting colonized by all other bacterie

Question 6

Beneficial effects of normal flora

Answer 6

1. synthesizes and excretes vitamins
   - Enteric bacteria: Vit K/B12
   - Lactic acid bacteria: certain Vit.B
2. Prevents colonization by pathogens: compete for the attachement site and nutrients
3. Production of enzymes: urease, desaminase and esterase
4. Production of naturl Ab´s:
   - Induce immunological response
   - Natural Ab cross-react with certain related pathogens–> prevent infection
5. stimulate development of certain tissues
   - E.g. certain lymphoid tissues like Peyers patches