Microbial Pathogenicity

Question 1

What are the important microbial pathogens?

Answer 1

Viruses, fungi, prions, protozoa, helminths and bacteria

Question 2

What can viruses cause?

Answer 2

H1N1 influenza virus (single stranded RNA, enveloped)

Question 3

How is H1N1 influenza virus described?

Answer 3

Easily spreads and is rarely fatal

Question 4

What can fungi cause?

Answer 4

Tricophyton spp. (ringworm)

Question 5

What is trichophyton spp.?

Answer 5

A colony of fungi growing on the skin which produces legions

Question 6

What can prions cause?

Answer 6

Kuru

Question 7

What is kuru?

Answer 7

A degenerative brain disease caused by a misfiled protein (prion)

Question 8

How do prions reproduce?

Answer 8

When pathogenic prions interact with a normal prion, it mutates the normal one. chain reaction

Question 9

What can protozoa cause?

Answer 9

Plasmodium spp. (malaria parasites)

Question 10

What can helminths cause?

Answer 10

Ancylostoma duodenale (hook worm)

Question 11

What can bacteria cause?

Answer 11

Bacillus Anthracis

Question 12

What is bacillus anthracis?

Answer 12

A gram positive, endospore forming rod shaped bacterium

Question 13

What is the forms of bacillus anthracis?

Answer 13

Cutaneous anthrax and inhalation anthrax

Question 14

What is cutaneous anthrax?

Answer 14

Infects the skin (papule>ulcer>eschar)

Question 15

What is inhalation anthrax?

Answer 15

If spores enter lungs (mediastinal lymphadenopathy)

Question 16

What do gram positive bacteria have?

Answer 16

Thick cell walls that consist primarily of peptidoglycan

Question 17

What does gram positive bacteria do in the stain?

Answer 17

Traps and retains crystal violet stain

Question 18

What do gram negative bacteria have?

Answer 18

Cell walls with two layers (a thin peptidoglycan layer and a thick outer membrane that contains polysaccharides bonded to lipids)

Question 19

What do gram negative bacteria do in the stain?

Answer 19

Do not retain the stain, crystal violet is easily rinsed away

Question 20

What is koch’s postulates?

Answer 20

Guidelines used to demonstrate that a specific pathogen causes specific disease symptoms

Question 21

Where must the pathogen be present (koch’s postulates)?

Answer 21

In every individual with the disease

Question 22

What can a sample of the microorganism taken from the diseased host do (Koch’s postulates)?

Answer 22

be grown in pure culture

Question 23

What can a sample of the pure culture do (koch’s postulates)?

Answer 23

Cause the same disease when injected into a health host

Question 24

What can the microorganism do (koch’s postulates)?

Answer 24

Be recovered from the experimentally infected host

Question 25

What are the exceptions to koch's postulates?

Answer 25

Microbes that can't be cultured (treponema pallidum) and pathogens that can also be found in healthy subjects and don't produce the same symptoms (vibrio cholera)

Question 26

What happens before the key stages of microbial pathogenesis?

Answer 26

Exposure to the pathogen

Question 27

What is the first stage of microbial pathogenesis?

Answer 27

Adherence to host cells (skin or mucous)

Question 28

What happens after adherence to host cells?

Answer 28

Invasion of host tissues (through epithelium)

Question 29

What happens after invasion of host tissues?

Answer 29

Replication within the host tissue (fast so immune system can't act on it)

Question 30

What happens after replication within the host tissue?

Answer 30

Disease causing damage to host tissues (pathology)

Question 31

What can disease causing damage to host tissues be caused by?

Answer 31

Toxicity and invasiveness

Question 32

How can toxicity cause damage to host tissues?

Answer 32

Toxin effects are local or systematic

Question 33

How can invasiveness cause damage to host tissues?

Answer 33

Further growth at original sites and distant sites

Question 34

What are the bacterial virulence factors for adherence to host cells?

Answer 34

Adhesions such as fimbria (bind to cells) e.g. neisseria gonorrhoeae

Question 35

What are the bacterial virulence factors for invasion of host tissues?

Answer 35

Motility (move through mucus) (flagella) and internal-related proteins (InIB)

Question 36

What are the bacterial virulence factors for replication within host tissues?

Answer 36

Siderophores (bind iron) the siderophore yersinia actin solubilises metal bound to host proteins and transports it back to the bacteria. Capsules (resist phagocytosis)

Question 37

What are the bacterial virulence factors for disease causing damage to host tissue?

Answer 37

Endotoxins which cause inflammation and exotoxins which an be fatal

Question 38

What are endotoxins and exotoxins?

Answer 38

Toxic virulence factors

Question 39

What are endotoxins?

Answer 39

Lipopolysaccharide (LPS) components found in the outer membrane of gram negative bacteria (released after bacteria is destroyed/dies) and elicit a strong immune response. e.g. neisseria gonorrhoeae (causes inflammation)

Question 40

What are the possible effects of endotoxin Lipid A?

Answer 40

Fever, blood clotting, inflammation and shock

Question 41

What are exotoxins?

Answer 41

Produced within the living bacteria and then released into the surrounding medium

Question 42

What are the three types of exotoxins?

Answer 42

Cytotoxins (destroy red blood cells), neurotoxins (effect the nervous system) and enterotoxins (effect the gut)