Microbiology 3-4

Question 1

What is bacteriostatic?

Answer 1

Antibacterial that prevents bacterial growth.

Question 2

What is most widely prescribed family of antibiotics and give two examples.

Answer 2

Beta-lactams

Penicillin and methicillin

Question 3

How do beta-lactams work?

Answer 3

Interfere with peptidoglycan synthesis in the cell walls of bacteria.

Question 4

What is an antibiotic?

Answer 4

An agent that kills or inhibits the growth of a microorganism.

Question 5

What is an antimicrobial?

Answer 5

Chemical that selectively inhibits microbes.

Question 6

What is the minimal inhibitory concentration?

Answer 6

The lowest concentration of an antibiotic that is needed for the growth of an infection.

Question 7

What are the three sources of antibiotic resistance?

Answer 7

Plasmids, transposons and naked DNA.

Question 8

How do transposons work?

Answer 8

Integrate into chromosomal DNA.

Question 9

What are the four mechanisms by which ABR works?

Answer 9

1) Change the metabolic profile of the bacterium
2) Change the binding or target site
3) Inactivate the antibiotic
4) Decrease drug accumulation so concentration to inhibit growth is not reached

Question 10

What are aminoglycosides?

Answer 10

A group of antibiotics that target protein synthesis on the 30S ribosomal subunit in prokaryotes.

Question 11

What is a downside of ahminoglycosides?

Answer 11

High toxicity so use is limited.

Question 12

How does Rifampicin work?

Answer 12

Targets transcription of genes and blocks RNA polymerase. Turns tears and urine red so compliance is affected.

Question 13

How does Vancomycin work?

Answer 13

Targets the integrity of the cell wall and biosynthesis.

Question 14

How does Linezolid work?

Answer 14

Inhibits initiation of protein synthesis by binding to the 50S subunit.

Question 15

How does Daptomycin work?

Answer 15

Targets the cell membrane.

Question 16

What are quinolones?

Answer 16

The first synthetic antibiotics to be synthesised, targeting gyrase in gram-negative bacteria and topoisomerase in gram-positive bacteria.

Question 17

How can ABR be reduced?

Answer 17

• Stricter control on antibiotic prescription
• Reduced use of broad spectrum antibiotics that suppress gut biota
• Combination therapy
• Knowledge of local strains
• Quicker identification

Question 18

What increased risk of ABR?

Answer 18

• Crowded wards
• Immunosuppression
• Transmission by staff
• Broken skin (IV and catheters)

Question 19

What are non-enveloped viruses surrounded by?

Answer 19

Protein capsule

Question 20

What are enveloped viruses surrounded by?

Answer 20

Lipid capsule derived from previous host

Question 21

What is the Baltimore classification system?

Answer 21

Virus classification system based on type of genome and type of replication. Grouped in families.

Question 22

Why do RNA viruses and retroviruses have a high mutation rate?

Answer 22

Use their own polymerase to replicate so lose the ability to proof-read.

Question 23

Why are RNA genomes limited in size?

Answer 23

Instability of genome in comparison to DNA genomes.

Question 24

Which is the largest type of virus?

Answer 24

Coronavirus

Question 25

How do viruses gain access to host cells?

Answer 25

Attach to the ‘viral receptors’ on the cell surface. These receptors were initially used for cell signalling and transportation but viruses have managed to take advantage of them for cell entry.

Question 26

What is the cytopathic effect?

Answer 26

Structural changes to the host cell caused by a virus. As we cannot see viruses we rely on their effects on host cells to diagnose and differentiate between them.

Question 27

What are syncytia?

Answer 27

Viruses with surface proteins that are able to fuse at neutral pH.

Question 28

How is a virus diagnosed? (5)

Answer 28

• Viral genome detected by PCR
• Antigen detected by IFA or ELISA
• Virus particles detected by electron microscopy
• Detect cytopathic effect
• Detect antibodies