Microbiology of Humans

Question 1

When are humans clonized by microorganisms?

Answer 1

At birth

Question 2

Human microbiomes

Answer 2

• Skin
• Oral cavity
• GI tract
• Respiratory tract
• Genitourinary tract

Question 3

Skin: Composition

Answer 3

Composed of an inner layer of living cells and an outer layer of dead cells

Question 4

Normal microbiome of the skin

Answer 4

• Mycobacterium,
• Staphylococcus
• Streptococcus

Question 5

Adaptations of the skin

Answer 5

• Dead cell layer forms a tough barrier that prevents microorganisms from penetrating deeper tissues
• Generally a dry, acid environment that does not support the growth of most microorganisms
• The normal microbiome secretes bacteriocin that kills incoming competitors
• Glandular secretions are slightly acidic and have some antimicrobial effects and only colonized by only a few well-adapted species (Gram+)
• The skin may also harbor anaerobes

Question 6

Normal microbiome of the oral cavity

Answer 6

• Staphylococci
• Streptococci
• Corynebacteria

Question 7

What environments are found in the oral cavity

Answer 7

Both aerobic & anaerobic niches

Question 8

Dental plaque formation

Answer 8

• Bacteria colonize tooth surfaces
• Extensive growth of oral microorganisms results in dental plaque
• Anaerobic bacterial species begin to grow
• Fermentation demineralizes the tooth enamel

Question 9

Normal microbiome of the GI tract

Answer 9

• Microbial populations differ in different areas
• Influenced by diet and physical conditions
• The acidity of stomach and duodenum prevent many organisms from colonizing the GI tract

Question 10

Normal microbiome found in the colon

Answer 10

Mostly strict anaerobes or facultative aerobes
* Digest complex carbohydrates and produce VFAs
* Ferment VFAs and produce gas
* Methanogens convert CO2 and H2 to CH4
* Sulfate reducers produce H2S

Question 11

Benefits of microorganisms in the colon

Answer 11

• Carry out a variety of essential metabolic reactions that produce various nutrients that benefit the host
• Contribute to the ‘maturing’ of the gastrointestinal tract

Question 12

Normal microbiome of the Respiratory tract

Answer 12

• Microbiome of the nose and nasopharynx is very similar to that of the mouth
• The lower respiratory tract is considered free of microorganisms in healthy individuals

Question 13

Genitourinary tract (men)/Urinary tract (women)

Answer 13

• Generally free due to flushing action of urine
• Altered conditions can cause potential pathogens in the urethra to multiply and cause disease

Question 14

Sterile zones

Answer 14

• Blood
• Spinal fluid
• Internal portion of urinary tract (bladder, kidney)
• Peritoneal cavity (gut cavity)
• Pleural cavity (lung cavity)
• Sinuses
• Interior region of other body tissues (bone, muscle)