infections 2

Question 1

Antibiotic MoA: Penicillins

Answer 1

Agents that interfere with cell wall synthesis
Interfere with the synthesis of the bacterial cell wall peptidoglycan, bactericidal

Side effects:
not many, mostly allergic reactions: rash, fever and if serious: anaphylactic shock
gastrointestinal disturbances
Safe in pregnancy

Question 2

Narrow
Benzylpenicillin
Phenoxymethylpenicillin (Pen. V): r

Penicillinase-resistant
Flucloxacillin:

Broad Spectrum
Amoxicillin:

Anti-pseudomonal
Ticarcillin (with clavulanic acid) or piperacillin (with tazobactam):

Mecillinams
Pivmecillinam (converted to active mecillinam)

Answer 2

Narrow
Benzylpenicillin sodium (Pen. G): range of streptococcal, meningococcal and other infections, IV; benzathine benzylpenicillin for syphilis, IM
Phenoxymethylpenicillin (Pen. V): respiratory tract infection children, strep throat

Penicillinase-resistant
Flucloxacillin: Staphylococcal infections, e.g. bone, joint, skin soft tissue infections

Broad Spectrum
Amoxicillin: Range infections – UTI, CAP, otitis media, H. pylori (with other Abx)

Anti-pseudomonal
Ticarcillin (with clavulanic acid) or piperacillin (with tazobactam): active against wide range G+, G- and anaerobic organisms, for serious/complicated infections (e.g. HAP, septicemia)

Mecillinams
Pivmecillinam (converted to active mecillinam), useful for many Gram negative bacteria including e. coli, thus useful for UTIs (lecture 6)

Question 3

Antibiotic MoA: Cephalosporins

Answer 3

agents that inhibit cell wall synthesis

Mechanism of action
Interference bacterial peptidoglycan synthesis after binding to the β-lactam-binding proteins

side effects:
- anaphylactic shock
gastrointestinal issues
-diarrheas

Question 4

what are the 5 generations of cephalosporin

Answer 4

Cefalexin, cefadroxil, cefradrine (1st generation) and cefaclor (2nd generation) similar spectrum and by mouth: use e.g. skin & soft tissue, respiratory and urinary tract infections (susceptible G+/G-)

Cefuroxime (2nd generation): less susceptible beta-lactamases, range G+/- infections (less +, improved -)

Cefixime (3rd generation): Only acute infections (given orally)

Cefotaxime, ceftazidimine, ceftriaxone (3rd generation, all IV/IM): better G-negative activity, ceftazidime - Pseudomonas
Septicaemia (e.g. cefuroxime, cefotaxime)
Meningitis (e.g. ceftriaxone, cefotaxime)

Cefepime (4th generation, IV/IM): broad spectrum incl. Pseudomonas
Ceftaroline fosamil (5th generation, IV): extended activity compared to e.g. cefotaxime, for gram positive. Use e.g. CAP and complicated skin & soft tissue infections (including MRSA) [Ceftobiprole – HAP/CAP]

Question 5

Antibiotic moa: Carbapenems

Answer 5

-inhibit cell wall synthesis

Question 6

Antibiotic moa: glycopeptides

Answer 6

-cell wall synthesis inhibitor 
Vancomycin – bactericidal
IV for complicated G-positive (e.g. staphylococcal) infections: CAP, HAP, skin, bone, skin & soft tissue (also teicoplanin)
Orally C. difficile
But: ototoxicity and nephrotoxicity

Question 7

Antibiotic moa: Tetracyclines

Tetracycline, Doxycycline, Demeclocycline, Minocycline, (tigecycline)

Answer 7

Agents affecting bacterial protein synthesis

Mechanism of action
Inhibits protein synthesis, bacteriostatic

Side effects
gastrointestinal disturbances, staining growing teeth
and bone deformities, hepatotoxicity, phototoxicity

Key clinical uses (broad-spectrum)
Sinusitis (doxycycline), CAP (doxycycline), some STIs (e.g. chlamydia doxycycline)
rickettsial and chlamydial infections, brucellosis, anthrax and Lyme disease
useful 2nd choice (e.g. patients allergies) for several infections

Question 8

Antibiotic moa:

Aminoglycosides & Chloramphenicol

Answer 8

Agents affecting bacterial protein synthesis

Chloramphenicol
Key clinical uses
Topically in bacterial conjunctivitis (drops/ointment) or otitis externa
Systemic use reserved for infections where benefit of drug outweighs haematological toxicity:
e.g. life-threatening infections caused by Haemophilus influenzae

Aminoglycosides
bactericidal against many aerobic G-ve, some G+ve
mostly G-ve enteric organisms
IM/IV route (neomycin topical only, too toxic)
Serious infections such as sepsis, need monitor levels
Unwanted effects: ototoxicity (common), nephrotoxicity

gentamicin, streptomycin, amikacin, tobramycin, neomycin sulfate, spectinomycin