Chapter 23

Question 1

commensal organisms

Answer 1

-Bacteria normally found at various nonsterile body sites

Question 2

human microbiota or microbiome

Answer 2

• consortium of colonizing microbes
• change constantly:
• Vary with type of tissue and conditions
• Temperature, humidity, food consumed, hygienic practices
• Some can cause disease if reach abnormal location or host is compromised

Question 3

Skin

Answer 3

-difficult to colonize
-Dry, salty, acidic, protective oils
-Epidermal secretions contain enzymes such as lysozyme that degrade bacterial peptidoglycan
-Mostly Gram-positive bacteria
-More resistant to salt and dryness
Staphylococcus epidermidis

Question 4

Oral and Nasal Cavities

Answer 4

• human infant’s mouth- Streptococcus, Lactobacillus (Gram-positive rods)
• As teeth emerge, other bacteria start growing-Streptococcus mutans: grows in biofilm on tooth enamel
• may cause disease if they enter bloodstream (septicemia)

Question 5

Respiratory Tract

Answer 5

• lungs and trachea are usually “sterile”
• ciliated mucous lining of the trachea, bronchi, and bronchioles makes up the mucociliary escalator.
• Sweeps foreign particles up and out of the lung

Question 6

Stomach

Answer 6

• very high acidity (low pH)
• Few microbes survive
• Decreased stomach acidity = Hypochlorydia
• Vibrio cholerae survives stomach passage
• Establishes infection in intestine

Question 7

Intestine

Answer 7

• Escherichia coli

- Facultative anaerobe

Question 8

Probiotics

Answer 8

• living microbes that are ingested to restore the natural microbial balance.
• The most commonly used genera are Lactobacillus.

Question 9

Genitourinary Tract

Answer 9

• kidneys and urinary bladder are normally “sterile”

- urethra contains Staphylococcus epidermidis -May cause urinary tract infections

Question 10

Commensal microbes

Answer 10

• benefit the human host.
• Make vitamins and digest food in the gut
• Prevent colonization by pathogens by occupying their niche
• Make immunomodulin proteins
• Have potential use as vaccine delivery vehicles

Question 11

Opportunistic pathogens

Answer 11

• cause disease when immune system barriers are breached.

- Because the host is immunocompromised

Question 12

immune system

Answer 12

• an integrated system of organs, tissues, cells, and cell products.
• It differentiates self from nonself
• neutralizes potentially pathogenic organisms or substances.
• capable of responding to nearly any foreign molecular structure.

Question 13

two broad types of immunity

Answer 13

1. Nonadaptive (innate) immunity

2. Adaptive immunity

Question 14

Nonadaptive (innate) immunity

Answer 14

• Barriers to infection
• Nonspecific responses to destroy invading cells
• Present at birth

Question 15

Adaptive immunity

Answer 15

-Reaction to specific antigens
small regions of foreign proteins, sugars, chemicals
-Retains “memory” of those antigens
-Faster response if exposed a second time

Question 16

a successful attack that causes a disease must

Answer 16

1. breach the host’s physical and chemical barriers to gain entrance to the body.
2. survive the innate defense mechanisms and begin to multiply.
3. surmount the last line of defense, adaptive immunity.