Wk 8

Question 1

What are the two ways of microscopic counting?

Answer 1

Direct smear and counting chamber

Question 2

What is direct smear?

Answer 2

Counts carried out on a fixed and stained smear from a define volume of fluid

Question 3

What is counting chamber?

Answer 3

Counts carried out on a fixed volume of bacterial suspension using a calibrated slide

Question 4

What is a disease?

Answer 4

A disorder of structure or function in the host that adversely impacts the host and is not simply a direct result of physical injury

Question 5

Define infectious disease

Answer 5

Disease caused by pathogens and transmittals to other hosts

Question 6

Define pathogenesis

Answer 6

Biological mechanisms that lead to a disease

Question 7

Define pathogenicity

Answer 7

Ability of microorganism to damage a host

Question 8

Define infection

Answer 8

The invasion and multiplication of pathogens in an individual or population

Question 9

What is virulence?

Answer 9

Relative capacity of a pathogen to damage a host (pathogens express wide range of virulence)

Question 10

To act as a pathogen, what at the four things one must do?

Answer 10

1. Find an appropriate niche within a host
2. Compete with normal micro iota to adhere to host tissues
3. Evade or overcome normal host defenses
4. Express genes that encode the factors causing disease

Question 11

What is inflammation?

Answer 11

Biological host tissue response to harmful stimuli such as pathogens and/or their metabolites

Question 12

How can inflammation manifest?

Answer 12

Local tissue damage, toxemia, acute systemic disease, chronic disease

Question 13

What is virulence factor? Is it intracellular or extracellular, and in what ways?

Answer 13

Def: bacterial traits that confer pathogenicity & enable pathogenic bacteria to colonize extracellular or intracellular niches in hosts
Majority of pathogenic bacteria are extracellular pathogens
Obligate intracellular pathogens need host to replicate while facultative intracellular pathogens can multiply in phagocytes or non-phagocytes

Question 14

Define superantigen. What does it result in/cause?

Answer 14

Def: exotoxin causing dysfunction of immune system. It subverts the adaptive immune response by cross linking two of the most important antigen-recognition receptors
Results in: massive T-cell proliferation and cytokine release & no immune protection

Question 15

Define biofilm.

Answer 15

Bacterial populations adherent to each other and/or surfaces and enclosed in a bipolymer matrix (can be planktonic (free) or sessile (attached))

Question 16

How is a biofilm formed?

Answer 16

1. Attachment of bacteria to surface and formation of mono layer of cells
2. Clustering of cells and formation of micro colonies
3. Maturation with production of extracellular polymers and hydrated eco polymer matrix

Question 17

How can a biofilm manifest?

Answer 17

Dental plaques, biofilms in catheters, UTI’s

Question 18

Define quorum sensing.

Answer 18

Bacteria produces small signal molecules to communicate with others. When the population reaches a define density, the signal attains a critical threshold concentration at which they coordinate expression of bacterial genes to act as a community rather than alone.

Question 19

Similarity and difference between plasmid and bacteriophages.

Answer 19

Both may carry genes for antibiotic resistance, toxin, and other virulence factors between bacteria.
Plasmid: small, circular DNA present in bacteria
Bacteriophage: virus that infected and replicates within bacteria

Question 20

Define conjugation

Answer 20

Transfer of genetic material through direct contact between donor and recipient

Question 21

Define transformation

Answer 21

Alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material

Question 22

Define transduction

Answer 22

Foreign DNA is introduced into another cell via a viral vector