Antimicrobials [17-18] Flashcards by Scarlett Clegg

What is selective toxicity

Using antibiotics to exploit difference in processes & structures of pro/eukaryotes to reduce host cell toxicity
E.g cell wall

How well did you know this?

Not at all

Perfectly

2 types of antibiotic

Bacteriostatic (inhibit multiplication)
Bactericidal

How well did you know this?

Not at all

Perfectly

What do antibiotics target in bacteria

Cell wall synthesis
Membrane synthesis
Protein synthesis
Metabolic pathways
Nucleic acid synthesis

How well did you know this?

Not at all

Perfectly

Is cell wall thicker in gram positive or gram negative

Gram positive

How well did you know this?

Not at all

Perfectly

Explain crosslinking

Transpeptidase links L-lys D-ala D-ala residues from different cell walls

How well did you know this?

Not at all

Perfectly

Penicillin MOA

Binds to transpeptidase so it can inhibit cross linking

How well did you know this?

Not at all

Perfectly

Example of 4 b-lactams

Penicillin
Cephalosporin
Monobactam
Carbapenem

How well did you know this?

Not at all

Perfectly

What is flucloxacillin

Beta lactamase resistant penicillin
Acts of gram positive
Gram positive are more reliant on cross linking because they have a larger cell wall

How well did you know this?

Not at all

Perfectly

What is a good all rounded penicillin

Amoxicillin - broad spectrum pencilling
For gram positive and negative

How well did you know this?

Not at all

Perfectly

Describe cephalosporins

Beta lactam ring
Bind to penicillin binding protein
Prevents cross linking
Treats pneumonia and meningitis
Can cause diarrhoea

How well did you know this?

Not at all

Perfectly

What is given in the case of a penicillin allergy

Monobactams
B lactam ring is peripheral
Beta lactamase resistant
Against gram neg

How well did you know this?

Not at all

Perfectly

Mechanisms of penicillin resistance

Porin downregulation
Inactivation of antibiotic via enzymes
Production of efflux pumps to pump antibiotics out of cell
Target site modification
Production of beta lactamase
Modification of penicillin-binding proteins

How well did you know this?

Not at all

Perfectly

Explain penicillin allergy

Antigens are degradation products of penicillin
Rash
Itching
Could cause anaphylactic shock
Lack of consciousness

How well did you know this?

Not at all

Perfectly

4 antibiotics that inhibit protein synthesis

Streptomycin
Chloramphenicol
Erythromycin
Tetracyclines

How well did you know this?

Not at all

Perfectly

Streptomycin MOA

Changes shape of 30s portion of ribosome
mRNA code read incorrectly

How well did you know this?

Not at all

Perfectly

Chloramphenicol MOA

Binds 50s portion of ribosome
Inhibits peptide bond formation

How well did you know this?

Not at all

Perfectly

Erythromycin MOA

Binds to 50s portion of ribosome
Prevents translocation of ribosome along mRNA

Tetracyclines MOA

Interfere with attachment of tRNA to mRNA-ribosome complex
Competitively binds A site
- Chlamydia
Resistance a growing problem

What drug class is is streptomycin

Aminoglycoside

Which antibiotics activity is enhanced by penicillins

Aminoglycosides

What drug class is erythromycin

Macrolide

Macrolides pharmacokinetics & adverse effects

Oral - enteric coated
Most effective against gram positive
Metabolised by CYP3A4
Resistance - efflux or methylation of ribosomal targets
Heart arrhythmias
GI disturbance

Chloramphenicol pharmacokinetics & adverse effects

Oral / IV
Resistance - enzymatic inactivation by acetyltransferase, efflux, ribosomal mutations
Grey baby syndrome

What is folate

Made from PABA - component in DNA synthesis

What inhibits conversion of PABA to folate

Sulfonamides

What inhibits folate utilisation

Trimethoprim

Sulphonamide PK

Crosses BBB N-acetylated in liver

Trimethoprim most common use

UTI and respiratory tract infection

What do fluoroquinolones do

Inhibit DNA gyrase Blocks DNA supercoiling

Fluroquinolones PK

Oral Crosses BBB gram +ve and -ve Inhibits CYP1A2 Affects GI

Examples of mycobacteria and

Mycobacterium tuberculosis Mycobacterium leprae

Mycobacteria traits

Thick waxy lipid-rich hydrophobic cell walls Contain mycolic acids in cell wall Can survive in macrophages Becoming a major problem in immunocompromised patients

2 mycobacterium treatments

Rifampicin Daptomycin

Rifampicin traits

Derivative of Rifamycin Inhibits prokaryotic DNA dependent RNA polymerase Good against +ve -ve and mycobacteria Potent inducer of CYP3A4

4 forms of antibiotic resistance

Modified permeability - porin substitution Drug inactivation - beta lactamases Interaction prevention - modified penicillin binding proteins Drug conc regulation - efflux

3 methods of acquiring resistance

Transformation Transduction Conjugation

What is transformation

Transfer of free DNA (containing antibiotic resistant gene) to competent recipient cell (can take up DNA)

What is transduction

Transfer of bacteria DNA containing antibiotic resistance gene via bacteriophage

What is conjugation

Plasmids transferred by conjugation Direct contact between cells Doesn’t require bacteria to be the same species

How can we tackle antibiotic resistance

Improve public awareness Reduced inappropriate antibiotic use Invest in drug R&D Reduce use of broad spectrum antibiotics in livestock