Antimicrobials

Question 1

What antibiotics inhibit cell wall synthesis? How do they work?

Answer 1

Penicillin
Cephalosporin
Vancomycin

PREVENT CELL VALL

Inhibit crosslinking of peptidoglycan strands in ell wall

Question 2

What are penicllins effective against?

Answer 2

Gram positive bacilli and streptococci

Question 3

What is staph aureus resistant to pencillin

Answer 3

Beta- lactamase - dsetroy beta lactam ring

Question 4

What is significance of flocloxacillin?

Answer 4

Side chain stops it being susceptible to beta-lactamases

Question 5

What are beta-lactamase inhibitors?

Answer 5

Carbapenem
Clavulanic acid

Question 6

Action and organisms of cephalosporins?

Answer 6

Cell wall inhibtion
Ca act against beta lactamase producing organisms

Staphylococci
Gram negative bacilli
Pseudomonas
Baceroids

Broad spectrum

Question 7

What is the activity of vancomycin?

Answer 7

glycopeptide
PRevents petidoglycan assemble in cell wall

Active against gram postiive organisms

Question 8

Which abx interrupt the cell membrane

Answer 8

Polymyxins
Amphotericin and nystatin
Imidazoles

Question 9

What is the activity of polymyxins

Answer 9

Broad spectrum
Active agains gram negative including pseudomonas

Question 10

How do amphotericin and nystatin work?

Answer 10

Bind to ergosterol in fungal cell membrane - change ionic transport and affect permatbility

Question 11

What is activity of amphotericin?

Answer 11

Candida
Aspergillus
Cyptococcus
Histoplasma
Caccidiodes
Blastomyces

Question 12

How to imidazoles work

Answer 12

Inhibit ergosterol prodcution by acting on CYP450

Question 13

What imidazole is effective against aspergillus?

Answer 13

Itraconazole

Question 14

What are side effects of azoles?

Answer 14

LFT derangement
Hepatotoxicity

Question 15

Which antibiotics inhibit protein synthesis?

Answer 15

Tetracyclines
Gentamicin
Neomycin
Macrolides
Chloramphenicol

Question 16

Which antibiotics inhibit nucleic acid synthesis?

Answer 16

Fluoroquinolones - Ofloxacin, Ciprofloxacin
Sulphonamides
Metronidzaole

Question 17

Action of tetracyclines

Answer 17

Interrupt the cycle of attachment of aino acids to the first binding site during protein synthesis by inhibition of aminoacyltransferase RNA and the mRNA ribosome complex

Question 18

Sensitvity of tetracyclines?

Answer 18

Gram positive,
Gram negative
Chlamydia

Question 19

SE of tetracyclines

Answer 19

Teratogenic
GI disturbance

Question 20

What is the action of gentamycin/neomycin

Answer 20

PRevent binding of mRNA to ribosome and can also cause mRNA to be misread - incorporation of wrong amino acid into protein

Question 21

Senstivity to gentamicin

Answer 21

Staphylococci
Aerobic gram negative
(ineffective against anaeobes and streptococci as require aerobic transport)

Question 22

SE of gentamicin

Answer 22

Ototoxicity
Nephrotoxicity

corneal epithelial toxicity

Intravitreal - retinal toxicity

Question 23

How does erythromycin work?

Answer 23

Binds to ribosomal subunit and interferes with translocation

Question 24

MOA of chloramphenicol

Answer 24

Inhibits protein synthesis

INhibits peptidyltransferase - prevents the transfer of the peptide chain to other aminio acids

Question 25

Sensitvity of chloramphenicol

Answer 25

Broad spectrum Active against Gram positive and negative

Question 26

Side effects of chloramphenicol

Answer 26

Aplastic anaemia Grey baby syndrome in neonates CI in pregnancy and breastfeeding

Question 27

Fluoroquinolones MOA

Answer 27

INhibit DNA synethsis Inhibit DNA gyrase - for folding/unfolding DNA

Question 28

Sensitvity of fluoroquinolone

Answer 28

Pseudomonas Chlamydia Enterobacteria Mycoplasma Less effective against gram positive and anaerobes

Question 29

Side effects of fluoroquinolones

Answer 29

photosensitive rash GI upset

Question 30

MOA of sulphonamides

Answer 30

INhibit metabolism of para-aminobenzoic acid to folate Inhibit DNA synthesis

Question 31

What is the MOA of metronidazole

Answer 31

Disrupts DNA synthesis

Question 32

What is metronidazole used for?

Answer 32

Orbital cellulitis with cefuroxime Effective against anaerobic bacteria and protozoan parasites such as Giardia, trichomonas, entamoeba

Question 33

SE of metronidazole

Answer 33

LFT abnormality Low PLTs

Question 34

How does 5-fluocytosine work?

Answer 34

Converted in fungal cells to 5-FU which is incorporated instead of uracil into fungal RNA Inhibition of DNA synethsis Against candida and cryptococcus

Question 35

What is aciclovir derived from

Answer 35

Acyclic analogue of Guanosine

Question 36

What is the MOA of aciclovir

Answer 36

INhibtion of viral DNA polymerase following phosphorylation by viral thymidine kinase - only effective in infected cells

Question 37

What is aciclovir effective against?

Answer 37

Heptes Not CMV

Question 38

What are SE of aciclovir

Answer 38

Renal insufficeincy GI disturbance Headache

Question 39

What is ganciclovir active against?

Answer 39

CMV

Question 40

Treatment for CMV retinitis

Answer 40

GAnciclovirW

Question 41

hat are SE of ganciclovir

Answer 41

NEtropenia Thrombocytopenia Renal impariment

Question 42

What is foscarnet

Answer 42

Paraphosphate analogue of phosphonoacetic acid

Question 43

MOA of foscarnet

Answer 43

Inhibts viral specific DNA polymerase and reverse transcriptases

Question 44

How can resistance develop?

Answer 44

Altering antibioic target Destruction of drug Prevention of transport of drug into microbe Alternative enzymic pathways resistance to drug