Antibiotics (cell wall inhibitors)

Question 1

Penicillin-G (natural)

Answer 1

Works on Gram+ Strept, anaerobes
B-lactamase sensitive
1st tier

Question 2

What specific bacteria is penicillin G effective against?

Answer 2

Pasteurella, Arcanobacterium, Listeria monocytogenes
Spirochetes: leptospira and borrelia

Question 3

Ampicillin, amoxicilin (semi-synthetic aminopenicillines)

Answer 3

Gram +, anaerobes and Gram - (E. coli, Klebs, proteus)
B-lactamase sensitive
1st tier

Question 4

Clavamox

Answer 4

Amoxicillin used to treat infections in all tissues except (CNS)

Question 5

Anti staphyloccal penicillins

Answer 5

Meth-, naf-, oxa-, cloxa-, dicloxacillin
Active against penicillinase-producing staph spp.
MRSA (S. aureus), MRSP (S. pseudointerdeius)

Question 6

Extended-spectrum penicillins

Answer 6

3rd and 4th tier
Addition of virulent Gram -
Pseudomonas, serratia, enterobacter

Question 7

Examples of extended spectrum penicillins

Answer 7

Carbapenems: Meropenem
Carben-, ticar-, mezlo-, piperacillin

Question 8

Which extended spectrum penicillin is a public health concer?

Answer 8

Carbapenem- resistant enterobacteriaceae (CRE)

Question 9

PK of penicillins

Answer 9

Poor lipid solubility (weak acid)
Poor penetration of BBB, inside cells, in eye, mammary gland and prostate
Cross placental barrier (found in milk)

Question 10

Penicillin delivery

Answer 10

Per Os (not for strong infections)
IM and IV with sodium and potassium salts
IM only for less solubles forms

Question 11

Penicillins are considered _________ dependent drugs

Answer 11

Time
T > MIC 50%
Q4-6h dosing

Question 12

Renal excretion

Answer 12

Active tubular excretion, concentrated in urine
Probenecid used in combo with penicillins to delay renal excretion

Question 13

Na+, K+ salt soluble IV formulations

Answer 13

Short duration of action (4hrs)

Question 14

Procaine penicillin

Answer 14

P-G added with procaine salt
Only IM (or SC) 24 hrs duration of action

Question 15

Benzathine Penicillin

Answer 15

Benzathine salt with P-G
Only IM (or SC) long acting (3 days)

Question 16

Adverse effects of ampicillin

Answer 16

Ampicillin associated enterocolitis (oral prep)

Question 17

K+, Na+ formulation adverse effects

Answer 17

Cause problem if poor renal and cardiac function

Question 18

Procaine salt IM adverse effects

Answer 18

Induce CNS stimulation in horses
Toxic for GPs, chinchillas, birds, turtles and snakes

Question 19

What happens when penicillin makes contact with the brain?

Answer 19

Causes seizures

Question 20

What is the major adverse effect of penicillins

Answer 20

Hypersensitivity/ allergy: most treated patients have Abs against
Local allergy after parenteral use to anaphylaxis
Worse if expired or poorly prepared drugs
Cross-hypersensitivity

Question 21

Regulatory compliance food animal considerations

Answer 21

Withdrawal issues → 10% humans allergic, milk residues, ELDU of cephalosporins prohibited
Absorption with intrauterine infusion

Question 22

Inherited resistance

Answer 22

Spectrum (no cells walls): Mycoplasma and chlamydia

Question 23

Acquired resistance (↑MIC)

Answer 23

Degraded enzyme synthesis
Failed delivery to target- PBP (↓ porins, efflux pumps)
Mutation (@ PBP for binding)