Antibacterials

Question 1

Are these bacteriostatic or bacteriocidal:
Sulphanomides, trimethoprines, tetracyclines, chloramphenicol

Answer 1

Bacteriostatic

Question 2

Are these bacteriostatic or bactericidal? Penicillins, cephalsporins, fluroquinolones, aminoglycosids,

Answer 2

Bactericidal

Question 3

What do beta lactams do?

Answer 3

Prevent cross linking peptides binding to TPS chain, target PBPs, stops peptidoglycan wall forming
Target gram (-) bacteria

Question 4

What are beta lactamases?

Answer 4

Enzymes produced by bacteria that targets and breaks beta lactam ring in antibiotics

Question 6

What are staphylococcal beta lactamase?

Answer 6

The beta lactamases that targets penicillin -> called penicillinase

Question 7

What is clavulanic acid?

Answer 7

Inhibits beta lactamase ring (contains beta lactam ring itself that binds instead of the beta lactam)

Question 8

Penicillin

Answer 8

Oral bioavailability, widely distributed but doesn’t cross the BBB, eliminated by kidney

Question 9

Cephalosporin

Answer 9

Orally available, wide distribution and does cross BBB, eliminated by kidney

Question 10

What are adverse reactions of beta lactam antibiotics?

Answer 10

Wide therapeutic ration, hypersensitivity reactions, GI superinfection

Question 11

Aminoglycosides

Answer 11

Interrupts translation of mRNA into proteins - alters shape and function
Binds to A site
Effects gram negative
Energy dependent process so usually effects aerobic bacteria
Conc. dependent bacteriocidal
Poor gut absorbtion -> given IV
SEs: nephrotoxcity, ototoxicity

Question 12

Macrolides

Answer 12

Binds to P site preventing translocation -> premature release of ribosome complex
Gram (+), bacteriostatic but bacteriocidal at high dose
Oral admin and wide distribution
Adverse GI effects

Question 13

Tetracyclines

Answer 13

Binds to site A - prevents RNA binding and effects proteinsynthesis agains an/aerobic + pos/neg bacteria
Oral bioavailability varies
Wide distribution in body
Bacteriostatic
Enters cell via diffusion/carrier protein
SEs: GI (Don’t give to ruminants), oral (oesophageal ulceration)

Question 14

Chloramphenicol

Answer 14

Inhibits peptide bond formation, induce spectrum of activity
Well absorbed after oral doseing
Bacteriostatic
SEs: anaemia via BM suppression

Question 15

Sulphonamides

Answer 15

Competitive inhibitor of DHPS -> stops folate synthesis
1st class
Wide spectrum - pos/neg
Well absorbed from gut, widely distributed, renal excretion
Bacteriostatic
SEs: hypersensitivity, IM, reactions, keratoconjunctivitis

Question 16

Trimethopium

Answer 16

Inhibits DHFR - stops folate synthesis
Administer with sulphonamide
Combination is bacteriocidal

Question 17

Fluroquinolones

Answer 17

Stops DNA gyrase coiling DNA
Wide spectrum of activity. High neg, some pos
Well absorbed from gut, good distribution, renal and hepatic excretion
SEs: rare, inhibits cartilage growth in young animals, renal degredation
Bacteriocidal
Popular due to efficacy and lack of toxicity but not be used as first line of TM

Question 18

Metronidazole

Answer 18

DNA fragmentation
Obligate anaerobes
Well absorbed from gut, good distribution to all tissues
Renal and hepatic excretion
SEs: rare
Also effects protazoa infections

Question 19

Resistant strains?

Answer 19

MRSA - Methicillin resistant S. Aerues, can only be treated by vancomysin but VRSA also exists now
1/2 Aba produced used in agriculture