Lecture 8. Microbes and Disease

Question 1

What parts of the respiratory tract are usually sterile?

Answer 1

Trachea, bronchus and alveoli

Question 2

How many bacteria are there in the stomach?

Answer 2

10³ - 10⁵/g

Question 3

How many bacteria are there in the duodenum?

Answer 3

10⁵ - 10⁸/g

Question 4

How many bacteria are there in the ileum?

Answer 4

10⁸ - 10¹⁰/g

Question 5

How many bacteria are there in the colon?

Answer 5

> 10¹⁰/g

Question 6

What is the mircobiome?

Answer 6

The ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space

Question 7

What are the suggested health benefits of the human microbiome?

Answer 7

Shield body tissues against invasion of ‘bad bugs’
Production of vitamins by bacteria (e.g. vitamin K in gut)

Question 8

What conditions is the microbiome implicated in (not proven)?

Answer 8

Obesity
Type 1 Diabetes
Crohn’s disease
Irritable bowel syndrome
Colon cancer

Question 9

What determines virulence?

Answer 9

Factors that aid in adhesion to and entry into cells,
antiphagocytic activity, immune system evasion and production of toxins

Question 10

What are examples of conventional virulence factors?

Answer 10

Bacterial toxins, adhesins, cell surface carbohydrates and capsules, secreted hydrolytic enzymes, LPS

Question 11

What can virulence factors be?

Answer 11

Plasmid or phage encoded

Question 12

What does the α-toxin of S. aureus do?

Answer 12

Creates pores

Question 13

What are ‘new’ bacterial pathogens?

Answer 13

Pathogens not previously been known as pathogens
Includes bacteria with a wide environmental distribution, that can cause infections in the immuno-compromised
Such opportunistic pathogens are increasingly important in causing outbreaks in hospitals

Question 14

What is an example of a ‘new’ pathogen species?

Answer 14

Burkholderia cepacia, highly versatile bacteria mainly associated with plants and soil

Question 15

What was the first modern antibiotic?

Answer 15

Arsphenamine (Salvarasan) in 1909 which was an arsenic-based treatment for syphilis

Question 16

What was the first antibiotic derived from a natural source?

Answer 16

Penicillin 1928

Question 17

What are the five major types of antibiotic?

Answer 17

β-lactams
Macrolides
Fluoroquinolones
Tetracyclines
Aminoglycosides

Question 18

What mechanisms cause resistance in penicillins?

Answer 18

Reduced permeability and inactivation

Question 19

What mechanism causes resistance in aminoglycosides?

Answer 19

Inactivation

Question 20

What mechanism causes resistance in macrolides?

Answer 20

Target alteration

Question 21

What mechanism causes resistance in sulfonamides?

Answer 21

New resistance pathway

Question 22

What mechanism causes resistance in tetracyclines and erythromycin?

Answer 22

Efflux

Question 23

What are the solutions to antibiotic and antimicrobial resistance?

Answer 23

New drugs derived from old drugs
New targets (the cell wall, new target proteins)
Drug combinations and augmentative compounds

Question 24

When was the first vaccination?

Answer 24

1796 Edward Jenner vaccine against smallpox

Question 25

What was the first proof that attenuated (weakened) vaccination worked?

Answer 25

1879 Louis Pasteur with Pasteurella multocida (chicken cholera)

Question 26

What does Clostridium tetani neurotoxin cause?

Answer 26

Tetanus

Question 27

What are the symptoms of tetanus?

Answer 27

Over-activity of motor neurons causing muscle spasms ‘lockjaw’

Question 28

How is tetanus prevented?

Answer 28

Because even a lethal dose of toxin is too small to raise immunity, formalin (an inactivated toxin) is used
3-4 doses provide ~100% protection that lasts ~10 years

Question 29

What is meningitis?

Answer 29

Inflammation of the protective membranes that cover the brain and spinal cord

Question 30

What causes 75% of acute bacterial meningitis cases?

Answer 30

Haemophilus influenzae
Streptococcus pneumoniae (pneumococcus)
Neisseria meningitidis (meningococcus)

Question 31

What is Haemophilus influenzae?

Answer 31

Gram-negative coccobacillus
Non-encapsulated strains carried asymptomatically in urinary tract

Question 32

How many serotypes of Heamophilus influenzae are there?

Answer 32

Six serotypes (a-f)

Question 33

What serotype is responsible for 90% of invasive infections of Haemophilus influenzae?

Answer 33

Serotype b (Hib)

Question 34

How is Hib treated?

Answer 34

There are three conjugated Hib vaccines, all exhibit >90% efficacy