Bugs in the system

Question 0

Define infection

Answer 0

The establishment of an organism on/in a host associated with multiplication and destruction/dysfunction of the host

Question 1

What is the bacterial reproduction mechanism in broth?

Answer 1

-Binary fission

Question 2

What can cause infection?

Answer 2

Bacteria, archea, protozoa, fungi, prions, viruses

Question 3

What are the possible mechanisms of infection transmission

Answer 3

• Air borne droplets (coughing/sneezing)
• Direct contact (exchange of bodily fluids)
• Animal transmission
• Contaminated products
• Maternal->foetal

Question 4

Describe the concept of gram staining

Answer 4

• Stain cells with crystal violet
• Add iodine which forms complexes with crystal violet
• Add acetone to decolourise cells by removing complexes. Those cells which thick peptidoglycan wall (i.e. gram positive bacteria) will retain crystal violet-iodine complexes as they will be too large to pass through
• Counterstain with safranin
• View under microscope to see staining colour

Question 5

Why are acid fast stains useful and what type of bacteria do they stain?

Answer 5

• Stain bacteria which do not have thick peptidoglycan wall content and also have an extra cell membrane
• Mycobacterium Tb and Leprosy

Question 6

Define pathogen

Answer 6

-Any micro/organism which parasitises a host and causes disease

Question 7

Why are bacterial cell walls of interest and significance?

Answer 7

• Used in detection and diagnosis
• Can be a target for antibiotics
• Gram -ve have LPS with endotoxin effects

Question 8

Name the most common gram +ve cocci

Answer 8

• Streptococcus

- Staphlococcus

Question 9

Name the most common gram -ve cocci

Answer 9

-Neisseria

Question 10

Name the most common gram +ve bacilli

Answer 10

-Clostridium

Question 11

Name the mose common gram -ve bacilli

Answer 11

• Escherchia Coli
• Pseudomonas
• Helicobacter
• Salmonella

Question 12

Which microorganisms are prokaryotic and which are eukaryotic?

Answer 12

• Bacteria and Archea are prokaryotic

- Protozoa and Fungi are Eukaryotic

Question 13

List the main differences between prokaryotes and eukaryotes

Answer 13

Prokaryotes

• No membrane bound organelles
• 1 Chromosome
• Coupled biochemical reactions
• V.labile mRNA
• 30s and 50s ribosomal subunits

Eukaryotes

• Membrane bound organelles
• Many chromosomes
• Compartmentalised reactions
• mRNA stable
• 40s and 60s ribosomal subunits

Question 14

Name the main mechanisms by which bacteria aquire antibiotic resistance

Answer 14

• Antibiotic inactivation by hydrolysis, group transfer or redox
• Target modification
• Efflux pumps
• Target Bypass
• Mutations
• Horizontal transfer of plasmids