chapter 27-4

Question 1

Normal microbial flora of other regions

Answer 1

Restricted group of organisms colonizes upper respiratory tract.
–staph, gram - cocci…
Lower respiratory tract lacks microflora in healthy individuals.

Question 2

Normal microbial flora of other regions: Urogenital tract

Answer 2

Urogenital tract
-Bladder typically sterile in both males and females.
Urethra not so much.
Lactobacillus creates acidic environment in vagina.
Altered conditions can cause potential pathogens in urethra to multiply and become pathogenic (E. coli).

Question 3

Brief intMicrobes that make us sick

Answer 3

Pathogens use various strategies to establish virulence.

Virulence: relative ability of a pathogen to cause disease.

Question 4

Measuring virulence

Answer 4

Virulence estimated from experimental studies of LD50.

Highly virulent pathogens show little difference in cells required to kill 100% vs. 50% of the population.

Question 5

Toxicity

Answer 5

Organism causes disease by means of a toxin that inhibits host cell function or kills host cells.
–Toxins can travel to sites within host not inhabited by pathogen.

Question 6

Steps of infection

Answer 6

Exposure
Adherence
-specific adherence: bacteria like viruses that cause infection often adhere to specific epithelial cells.
Invasion

Question 7

Adherence

Answer 7

Adherence can be facilitated by:

• extracellular macromolecules not covalently attached to bacterial cell surface.
• fimbriae and pili.

Question 8

Invasion

Answer 8

Starts at site of adherence
-via small breaks in epithelium
-via intact skin in immunocompromised people
May spread throughout host via circulatory or lymphatic systems.

Question 9

Colonization and growth

Answer 9

Availability of nutrients most important in affecting pathogen growth.
Colonization defined as multiplication of pathogen after it has access to host tissues.
Damage by a pathogen caused when present in large numbers.
Initial inoculum may be too small to cause disease.