Antibacterials

Question 1

Define the term ‘Bacteria’

Answer 1

Bacteria are prokaryotes that have no cell NUCLEUS

Question 2

What is peptidoglycan?

Answer 2

Peptidoglycan is a large polysaccharide rigid envelope surrounding bacterial cytoplasmic membrane. Protects bacterial cells from environmental stress and helps cell morphology

Question 3

Define the gram stain experiment and explain how different types of bacteria behave (Gram-positive/negative and atypical)

Answer 3

The Gram stain is an experiment that uses crystal violet/iodine complex molecules to stain bacterial cell walls containing peptidoglycan. Gram-positive bacteria have a thick layer of the polysaccharide peptidoglycan hence it will retain the stain as a purple colour. Gram-negative bacteria have a thin peptidoglycan layer and thus will not be able to maintain the stain (usually it stains red). Atypical bacteria will not retain the stain and will remain colourless

Question 4

What are the 3 types of bacteria?

Answer 4

a) Cocci - spherical
b) Bacilli - rod-shaped
c) Atypical

Question 5

What are atypical bacteria? Give 3 examples

Answer 5

Atypical bacteria are a type of bacteria that do not have a cell wall and are hard to detect. Examples include Chlamydia, Legionella, Mycoplasma

Question 6

What is the difference between bacteriostatic and bactericidal agents?

Answer 6

Bactericidal antimicrobials have the power to kill the organism whereas Bacteriostatic antimicrobials can only stop the bacteria from growing and dividing

Question 7

What are the 3 classes of antimicrobials? Define each

Answer 7

1) Cell wall active
Bactericidal in nature - weaken bacterial cell wall and causes death when bacteria try to divide

2) Protein synthesis inhibitors
Bactericidal and Bacteriostatic in nature - Prevents bacterial growth

3) Nucleic acid synthesis inhibitors
Bactericidal and Bacteriostatic in nature - Prevents bacterial division

Question 8

Give examples of drug classes that act as cell wall active antibacterials (HINT:6)

Answer 8

penicillin
cephalosporins
glycopeptides
daptomycin
carbapenems
aztreonam

Question 9

Give examples of drug classes that act as protein synthesis inhibitors (HINT:8)

Answer 9

tetracyclines
tigecycline
aminoglycosides
macrolides
fusidic acid
linezolid
chloramphenicol
dalfopristin/quinipristin

Question 10

Give examples of drug classes that act as nucleic acid inhibitors (HINT:3)

Answer 10

nitroimidazoles
quinolones
sulphonamides

Question 11

Can an agent become BACTERICIDAL?

Answer 11

YES. If 2 agents that are bacteriostatic are used together, the effect is bactericidal

Question 12

What does MIC stand for and what does it mean

Answer 12

Minimum inhibitory concentration. The lowest concentration of an antimicrobial that will INHIBIT visible bacterial growth to be exceeded for an antimicrobial to be effective

Question 13

Define MBC

Answer 13

Minimum bactericidal concentration. Minimum concentration of an antimicrobial agent needed to kill 99.9% of the original inoculum

Question 14

What are concentration dependant antimicrobials? Give examples

Answer 14

Have a long post-antibiotic effect where the antibacterial still suppresses bacterial growth even if concentration < MIC.
Examples include aminoglycosides like gentamicin and quinolones like ciprofloxacin

Question 15

How do bactericidal agents and MIC/MBC correlate?

Answer 15

Bactericidal agents have MIC = MBC equal or a few dilutions apart

Question 16

How do bacteriostatic agents and MIC/MBC correlate?

Answer 16

Bacteriostatic agents have the MBC > MIC different