Antibacterial chemotherapy

Antibacterial chemotherapy

Quiz on antibiotics: penicillins, cephalosporins, aminoglycosides, tetracyclines, macrolides, and antimetabolites. The issue of resistance will also be covered.

published on May 26, 201351 responses 0

Chloramphenicols have serious side effects that may preclude their clinical use. What are they?

Hepatotoxicity
Nephrotoxicity
Ototoxicity
Irreversible aplastic anaemia.

Which of these statements is NOT correct regarding bacterial resistance to classical bacteriocidals (penicillin and cephalosporins)?

Bacterial resistance can arise due to inhibition of penicillin binding
proteins.
Bacterial resistance can arise due to mutations in transpeptidases
Bacterial resistance can arise due to increased beta-lactamase activity
Bacterial resistance can arise due to the transfer of resistance genes
via conjugative plasmids.

What is the mechanism of action of trimethoprim?

Inhibits dihydropteroate reductase and pyrimidine synthesis.
Prevents synthesis of dihydrofolic acid
Competes with para-amino benzoic acid for dihydrofolate reductase
Prevents synthesis of tetrahydrofolic acid

Which statement best describes the administration of penicillin?

They have long plasma half lives.
Benzyl-penicillin is easily hydrolysed in the stomach so it is not clinically
useful.
Penicillins distribute well through body fluids and through the blood
brain barrier.
Clavulanic acid is often administered together with penicillins as a
suicide substrate for beta lactamases.

Regarding cephalosporins, which statement is NOT correct?

Cephalosporins are generally administered orally.
Some of them eg. cefoperazone, cefotaxime, cefuroxime, latamoxef
can cross the blood brain barrier and so can treat meningitis.
They are first choice drugs for treating gram negative rods of
Enterobacteriaceae eg. E. Coli, enterobbacter and Klebsiella
They have the same mechanism of action as penicillins.

Regarding benzyl-penicillin, which statement is incorrect?

Benzylpenicillin is active against most gram positive cocci and some
gram negative bacteria.
Phenoxylmethyl penicillin (POMP) is more potent than benzyl penicillin
because it is more acid stable and orally active.
Benzylpenicillin is susceptible to beta lactamases.
Benzylpenicillin cannot be used to treat certain gram negative rods
such as B. fragilis, Treponema, leptospira and actinomyces.

What is the mechanism of action of tetracyclines?

They inhibit the formation of the cell wall mediated by transpeptidases
of peptidoglycan.
They bind to mRNA and the ribosomal 30S subunit preventing binding
of aminoacyl tRNA.
They prevent mRNA translocating from the nucleus into the cytosol.
They inhibit ribosomal 50S subunit preventing elongation of the peptide
chain and moevement of the ribosome.

Which of the following categories correctly pair the drug class with examples of the drug?

Tetracyclines: erythromycin
Macrolides: streptomycin
Aminoglycosides: clarithromycin
DNA Gyrase inhibitor: ciprofloxacin

What is an advantage of extended spectrum penicillins, such as carbenicillin, ticarbenicillin, azlocillin and pipercillin?

They are resistant to beta-lactamase activity.
They can act against pseudomonads.
They are well absorbed orally.
They are very effective against gram negative bacteria.

What are the differences between amoxycillin and ampicillin?

Amoxycillin is resistant to beta lactamases produced by S. Aureus and
many gram negative organisms.
Amoxycillin can be delivered in pro-drug form, whereas ampicillin can
not.
Amoxycillin gives lower blood levels compared to ampicillin and causes
more GI tract disturbances.
Ampicillin is more prone to cause diarrhoea and GI tract disturbances.

What are some side effects of penicillins?

Select the three correct answers
Joint effusions
Spleen and lymph gland enlargement
Liver damage
Urticarial skin eruptions

Which pair correctly describes the absorption of beta-lactamase resistant penicillins?

Cloxacillin - well absorbed
Flucloxacillin - variable absorption
Methicillin - well absorbed
Nafcillin - poorly absorbed