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CLINICAL MEDICINE QUESTIONS AND ANSWERS WITH SOLUTIONS 2024
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CLINICAL MEDICINE QUESTIONS ANDANSWERS WITH SOLUTIONS 2024
What type of antibiotic is good for bloodstream infections - bacteriostatic or bacteriocidal? - ANSWER
Bacteriocidal
T/F? Penicillin is a broad spectrum antibiotic? - ANSWER False, it is narrow spectrum
What broad classes of bacteria does penicillin cover? - ANSWER - Gram +
- Anaerobes
What are the 2 classes of cell wall synthesis inhibitors? - ANSWER 1. Beta-Lactams: these bind to and
blocks transpeptidase (a penicillin binding protein) and prevent formation of the cross-links in
peptidoglycan
2. Glycopeptides: bind to the terminal amino acid of tetrapeptide and blocks transpeptidase from acting
What does penicillin-binding protein do? - ANSWER It forms the 1,4 cross links between NAMS and UMP
on the exterior of the bacterial cell for completion of peptidoglycan synthesis
- inhibited by penicillin
What does transpeptidase (a penicillin binding protein) do? - ANSWER - Forms peptide cross links
between glycan chains to make peptidoglycan layers
T/F? Beta-lactams and glycopeptides are bacteriostatic? - ANSWER False, they are all bactericidal
Name the 4 classes of beta-lactams. - ANSWER 1. Penicillin
2. Cephalosporins
3. Carbapenems
4. Monobactams
Describe penicillins. - ANSWER - Original was only used in gram + bacteria (modifications now used
against both gram + and gram -)
,- Penicillins are sensitive to beta-lactamase that is secreted by the bacteria and cause it to be ineffective
Name the modifications of penicillins. - ANSWER 1. Ampicillin
2. Amoxicillin
3. Methicillin
What are cephalosporins? - ANSWER - Structure: Beta-Lactam ring attached to a 6-member ring
- Beta-Lactamase resistant
- Classified according to each generation: each generation corresponds to a modification that improves
absorption and increases spectrum (classes 1-5)
What generations of Cephalosporins are resistant against both gram - and gram + bacteria? - ANSWER 4
and 5
Describe carbapenems. - ANSWER - Newly made in the 1990s
- Broadest spectrum
- Resistant to beta lactamase
- Can only be given thru IV in a hospital
- Useful against gram - bacteria that are resistant to many other drugs
Which beta-lactams are resistant to beta-lactamase? - ANSWER - Methicillin (only 1 derivative of
penicillin)
- Cephalosporins
- Carbapenems
- Monobactams
What are the two types of glycopeptide antibiotics available? - ANSWER - Vancomycin
- Teichoplanin
Describe Vancomycin and Teichoplanin. - ANSWER - Bind to the terminal amino acid, alanine, of the
tetrapeptide chain and prevent transpeptidase from making cross-links between the peptidoglycans
,- Lipophilic
- Only used against gram + bacteria
- Administered via IV
- Drug of choice for hospital acquired MRSA
(Pneumonic - In the hospital watch a lot of TV which is positive - so the Teichoplanin and Vancomycins
are given for hospital acquired MRSA and useful against gram + only)
What are the 6 types of protein synthesis inhibitors? - ANSWER 1. Aminoglycosides (A)
2. Tetracyclines (T)
3. Erythromycin (E)
4. Chloramphenicol (C)
5. Clindamycin
6. Oxazolidonones
7. Macrolides
ATECCOM
Which, if any, of the protein synthesis inhibitor antibiotics are bactericidal? - ANSWER Aminoglycosides
What antibacterial agents are useful against hospital acquired and regular MRSA (separately)? - ANSWER
- Hospital acquired: Vancomycin and Teichoplanin
- Regular MRSA: Oxazolidones
What are the 4 categories of drugs that inhibit nucleic acid synthesis? - ANSWER 1. Quinolones
2. Folate synthesis
3. Methonidazole
4. Rifampin
Describe the quinolones. - ANSWER - Bacteriocidal
- Inhibit DNA gyrase (a topoisomerase 1)
- Broad spectrum, effective against intracellular microbes (viruses)
, - Administered orally
- Well tolerated/mild on host
- The examples Ciprofloxacin and Levoquin have a fluorine derivative added for improved absorption
that can cause tendon rupture and peripheral neuropathy
Describe Rifampin. - ANSWER - Bacteriocidal
- Binds to the beta subunit of RNA polymerase and makes it non functional; so inhibits transcription and
translation
- Use is restricted to treatment of mycobacterium tuberculosis (an opportunistic infection associated
with HIV) or prophylactic for meningities
How do mycobacterium tuberculosis become resistant to Rifampin? - ANSWER - When using,
mycobacterium replicates VERY slowly, slower than eukaryotic cells, so these drugs must be given for
long time periods (6 months to a year).
- Over time the virus develops resistance, via changing their RNA polymerase. So Rifampin is used in
combination with another drug
Decribe folate inhibitors. - ANSWER - Bacteriostatic
- Bacteria make folate to make the deoxyribonucleotides for DNA synthesis (humans get folate from
diet, while bacteria make it)
- Folate synthesis pathway is an absolute selective pathway
- Resistance to the sulfonamids became common because it was used so much
Describe sulfonamides. - ANSWER - Earliest folate synthesis inhibitor
- Is a structural analog of paramino benzoic acid (PABA), so it blocks folate synthesis by binding to the
dihydropteroic acid
- Resistance to the sulfonamides (e.g., Sulfamethoxazole) became so common place that now the drugs
have to be given in combination with Trimethoprim which will block the dihydrofolate reducatase so that
tetrahydrofolate is not made
How are bacteria resistant to sulfonilamides? - ANSWER - By altering their dihydrofolate reducatses
- By altering their dihydropteroate synthase
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