What makes a Pathogen?

Question 1

Define a pathogen

Answer 1

An organism that can cause disease in animals and plants

Question 2

Define virulence

Answer 2

Relative ability to cause disease

Degree of pathogenicity

Question 3

Virulence Factors

Answer 3

Determinants that cause damage to the cell or are required for the survival of the pathogen in the host

Question 4

Define enteric pathogen

Answer 4

A pathogen that resides in the GIT

Question 5

Define an obligate intracellular pathogen

Answer 5

A pathogen that lives exclusively within the hot and depends on the host for survival

Question 6

Define a fastidious intracellular pathogen

Answer 6

A pathogen that lives within the host and has stringent growth requirements

Question 7

Properties that cause disease

Answer 7

• VF
• pathogenicity islands
• toxins

Question 8

Possible infection outcomes

Answer 8

• clearance
• homeostatic interaction
• disease

Question 9

Assumptions about TB

Answer 9

• ineffective immune response underlies disease progression
• lesion are homogenous
• inactive and active lesions have very different bacterial burdens

Question 10

Define genetics

Answer 10

• the study of individual genes, their functions, and roles

Question 11

Define genome

Answer 11

The complete genetic repository of an organism

Question 12

Define genomics

Answer 12

• The study and use of complete genome sequences

Question 13

Emerging themes in microbiology

Answer 13

• genome organisation, composition and diversity
• horizontal gene transfer
• genome decay among obligate intracell. pathogens
• phase and antigenic variation among mucosal pathogens

Question 14

Things that affect genome organization, composition and diversity

Answer 14

• wide variation of genome organization
• high percentage of predicted gene encode proteins of unknown function
• variability in GC content between organisms

Question 15

Define HGT

Answer 15

The transfer of DNA, frequently cassettes of genes, between organsims

Question 16

Mechanisms of HGT

Answer 16

• transformation (plasmids)
• conjugation (transposons)
• transduction (phages)
• genomic recombination

Question 17

Describe reductive, convergent evolution

Answer 17

Prolonged intracellular lifestyle leads to loss of genes not needed for life in the host

Question 18

Examples of organisms that exhibit genome decay and host adaptation

Answer 18

• Rickettsia prowazekii
• Chamydia trachomatis
• Treponema pallidum

Question 19

What is phase variation?

Answer 19

Reversible high-frequency gain and loss of a phenotype resulting from changes of expression of single and multiple genes
- Salmonella flagellin

Question 20

What is antigenic variation?

Answer 20

• variation of surface structure by pathogens

mutation, recombination, switching

Question 21

Why do organisms use phase and anitgenic variation?

Answer 21

to avoid detection or outpace a host’s immune system

Question 22

Mechanisms of phase variation in N meningitidis

Answer 22

Tandem repeats in promoter sequences affect:

• transcription
• translation
• replication

Question 23

Define core genome

Answer 23

• all the genes that each member of a species possesses

Question 24

Define distributed genes

Answer 24

All the genes that are not shared by all the strains of a species

Question 25

Define a supragenome

Answer 25

Core genome plus all of the distributed genes of a species

Question 26

Define a symbiome

Answer 26

The organismal ecosystem complete with the eukaryotic host and all of its assicated microbiomes

Question 27

Define hologenome

Answer 27

The symbiome’s genome

Question 28

Basic tenets of the damage-response framework

Answer 28

• pathogenesis is an outcome of an interaction between a host and a microorganism
• the host-relevant outcome of this host-microorganism interaction is determined by the amount of damage to the host
• host damage can result from microbial factors and/or host repsonse

Question 29

Describe levels of graph of damage-response framework

Answer 29

• death
• disease
• latency
• colonization
• commensalism