Introduction

Question 1

what are the characteristics of a pathogenic bacteria

Answer 1

1. when a bacteria has the ability to evade host defese mechanisms such that mechanisms pathogenicity out ways comensalism
2. bacteria posses pathogenicity genes and expresses pathogenicity factors at the right time.
3. genetic variation which contribute to fittness.
4. ability to colonise and invade host barriers
5. Antibiotic resistance

Question 2

decribe the typical process of an infection

Answer 2

1. For an infecious agent to cause disease it much have inoculated by a favourable infectious dose.
2. then they use surfce porteins called adhesins to attach themselves to host cells.
3. after, they produce toxins which are able to destroy tissues and barriers to have access to host.
4. after entry into cells or tissues, they produce other virulence mechanisms that help them survive host enviroment and defences to be able to multiply.
5. leasd to immune response, inflamation and further tissue damage.

for the infection to be sustained, infection processes inflicted ty the organism must be stronger then host defense mechanisms.

Question 3

what are mobile genetic elements and which processes are they involved in?

Answer 3

they are genetic materials that can move around in genome or can be transfered from species to species.
examples are: transposons, plasmids, pathogencity islands, integrons and IS elements.

thes are able to transfer the following amongst different species.

a. new pathogenicity factors (virulence)
b. resistance genes (antibiotic resistance)
c. high genome flexibility and increase fittness.

Question 4

what is the mode of action of cholera toxin?

Answer 4

it is an AB5 multimeric protein complex toxin produced by vibrio cholera.
it is a hexamer with one A subunit and 5 B subunits.
Firt the B subunit binds to GM1 gangliosides on intestinal epithelia.
Once bound the toxin is endocytosed the A1 subunit separates itself to catalyse the ribosylation of ADP on the G alpha subunit. This ribosylation results in permanent activation of G alpha leading to increased adenylate cyclase activity

irrreversible increase in adenylate cyclase activity which increases cAMP levels causes the opening of chloride channels which induces loss of water and elctrolytes from the body in the form of diarrhoea.

Question 5

How are novel pathogens developed and how do they affect humans?

Answer 5

Novel pathogens are prodced when pathogens acquire new virulence genes from mobile elements from other species or when less pathogenic or non-pathogenic species develop mutations which help them adapt better to human host.
Some also develop resistance mechanisms that withstand antibiotics.

Question 6

What was the hypotheis is louis Pasteurs experiment with the swan-necked flask and what was the outcome of the experiment.

Answer 6

Hypothesis:
if cells can be generated spontaneously from non-living things, it should be appear in sterile broth.

Outcome:
theory of spontaneous generation was disproved and it was established that the open flask was cloudy due to particles in the air which fell into the glass.

Question 7

What are the kochs postulates of the germ theory.

Answer 7

1. the organism must be found in abundunce in all organisms suffering the diesease and must not be found in healthy orgainsms.
2. the organism must be isolated from sick individuals and grown in culture.
3. when microorgainsm is intoduces into healthy induviduals, it should cause disease
4. Microorganism isolated from both newly inoculated individuals should be identical to that of the first diseased individual.

Question 8

Why is the determination of a whole genome sequence of a pathogen important? What can be learned from genome sequence?

Answer 8

1. Determination of antibiotic sensitvity and resistance for personalized treatment.
2. For tracing epidemics (bacterial evolution)
3. For diagnosis
4. For learning about molecular basis of bacterial charateristics like pathogenicity.
5. studing microbes even when they are not culturable.

Question 9

Which factors favor the appearance and spread of infectious diseases

Answer 9

1. climate change
2. misuse and misrescription of antibiotics
3. Urbanization and globalization
4. Natural disasters (flood)
5. War
6. poor sanitation and lack of education on infectious diseases amoung general public

Question 10

Name 5 organs or systems and one pathogen affecting them.

Answer 10

Gastrointestinal tract- Vibrio cholera and helicobacter pylori
urinary tract- Uropathogenic Escherichia coli
respiratotory system- mycobacterium Tuberclosis
genital tract- neisseria gonorrheae
Skin- staphylococus arues, tinea species (capitis, corporis)
CNS- Neisseria meningidits, streptococcus pneumonia