Antibiotics expanded

Question 1

What is the mechanism of action of penicillins?

Answer 1

Penicillins bind to penicillin-binding proteins (PBPs), inhibit the transpeptidation reaction with peptidoglycan in the cell wall, weakening the wall and stopping synthesis.

Question 2

What are the clinical uses of Penicillin G?

Answer 2

Penicillin G is used for oropharyngeal, meningitis, STI, endocarditis, and is the drug of choice for syphilis.

Question 3

What side effects are associated with the use of Penicillins?

Answer 3

Common side effects include hypersensitivity reactions, seizures (only for oral dosing), nausea, vomiting, diarrhea, and opportunistic fungal infections.

Question 4

Describe the spectrum and dosing considerations for Amoxicillin.

Answer 4

Amoxicillin covers Gram-positive cocci and some Enteric Gram-negative bacilli. It is used for HEENT infections like otitis media, sinusitis, and pharyngitis. Pediatric dosing for otitis media is 80-90mg/kg divided BID-TID.

Question 5

How does resistance to penicillins occur?

Answer 5

Resistance to penicillins often occurs through the production of penicillinase, an enzyme that inactivates the antibiotic.

Question 6

What is the role of Cephalosporins in bacterial infections?

Answer 6

Cephalosporins bind to penicillin-binding proteins on the cytoplasmic membrane, inhibit transpeptidation reactions that cross-link peptidoglycan chains in the cell wall, thus breaking them and inhibiting cell wall synthesis.

Question 7

List some key side effects of Cephalosporins.

Answer 7

Key side effects of cephalosporins include hypersensitivity reactions, gastrointestinal issues, seizures, and a potential for cross-reactivity with penicillin in cases of penicillin allergy.

Question 8

What are the indications for using Vancomycin and its side effects?

Answer 8

Vancomycin is indicated for MRSA/MRSE infections, meningitis, and is also used as a backup drug for GI infections like Clostridioides difficile. Side effects include ‘red man syndrome’, ototoxicity, nephrotoxicity, and potential toxicity requiring monitoring of lab values.

Question 9

Explain the action of Aminoglycosides and their usage.

Answer 9

Aminoglycosides bind to the 30S ribosomal subunit, causing a change at the genetic level which interrupts protein synthesis. They are used primarily for Gram-negative bacterial infections and certain mycobacterial diseases like tuberculosis.

Question 10

What are the clinical implications of antibiotic resistance in Fluoroquinolones?

Answer 10

Resistance in fluoroquinolones usually involves gene mutations that alter the target enzymes (DNA gyrase and topoisomerase IV), diminishing the drug’s effectiveness in treating infections.

Question 11

What are the common dosing and side effects of Azithromycin?

Answer 11

Azithromycin dosing typically involves 500mg on day 1 followed by 250mg for days 2-5 for respiratory infections. Common side effects include gastrointestinal upset, decreased risk of prolonged QT interval, and interactions with hepatic enzymes.

Question 12

What enzyme do Penicillins target in bacteria?

Answer 12

Penicillins target penicillin-binding proteins (PBPs).

Question 13

Why must Penicillin G be administered via injection?

Answer 13

Penicillin G has to be injected because it is not stable in the acidic environment of the stomach.

Question 14

What is the spectrum of activity for Penicillin V?

Answer 14

Penicillin V targets gram-positive cocci and has a narrow spectrum.

Question 15

How do Cephalosporins differ from Penicillins in their action?

Answer 15

Cephalosporins and Penicillins both bind to PBPs but cephalosporins are less susceptible to penicillinases, making them effective against some penicillin-resistant bacteria.

Question 16

What are the primary uses of first-generation Cephalosporins?

Answer 16

First-generation Cephalosporins are used primarily for gram-positive bacterial infections and prophylaxis in surgical settings.

Question 17

What is the mechanism of action for Macrolides?

Answer 17

Macrolides bind to the 50S ribosomal subunit, inhibiting protein synthesis in bacteria.

Question 18

List some clinical uses of Erythromycin.

Answer 18

Erythromycin is used for treating respiratory tract infections, skin infections, and is also effective against atypical pathogens.

Question 19

Why are Aminoglycosides not absorbed orally?

Answer 19

Aminoglycosides are not absorbed orally due to their polar nature which prevents their passage through the lipid-rich cell membranes of the gastrointestinal lining.

Question 20

What are the serious side effects of Gentamicin?

Answer 20

Gentamicin can cause nephrotoxicity, ototoxicity, and in rare cases, neurotoxicity.

Question 21

What is unique about the absorption of Tetracyclines?

Answer 21

The absorption of Tetracyclines can be significantly impaired by the presence of calcium, iron, or magnesium due to chelation forming non-absorbable complexes.

Question 22

What infections are Doxycycline commonly used to treat?

Answer 22

Doxycycline is used to treat infections such as Lyme disease, Rocky Mountain spotted fever, and respiratory tract infections caused by Mycoplasma.

Question 23

What is the primary action of Fluoroquinolones on bacterial cells?

Answer 23

Fluoroquinolones inhibit DNA gyrase and topoisomerase IV, enzymes critical for bacterial DNA replication and transcription.

Question 24

What is the concern with Fluoroquinolone use and tendons?

Answer 24

Fluoroquinolones can cause tendon damage, including tendonitis and tendon rupture, particularly in older adults.

Question 25

How do Sulfonamides inhibit bacterial growth?

Answer 25

Sulfonamides inhibit dihydropteroate synthase, an enzyme involved in folate synthesis in bacteria.

Question 26

What combination therapy enhances the effectiveness of Trimethoprim?

Answer 26

Trimethoprim is often combined with Sulfamethoxazole to enhance bacterial killing by blocking two consecutive steps in folate synthesis.

Question 27

Describe the antibiotic action of Metronidazole.

Answer 27

Metronidazole is a prodrug that, when reduced in anaerobic bacteria and protozoa, disrupts DNA synthesis and causes cell death.

Question 28

What are the clinical indications for using Vancomycin?

Answer 28

Vancomycin is used for severe infections like MRSA, its use is critical in treating resistant strains of gram-positive bacteria.

Question 29

What are common resistance mechanisms against Macrolides?

Answer 29

Resistance to Macrolides can occur through methylation of their ribosomal binding site, efflux pump expression, or hydrolysis by esterases.

Question 30

Which antibiotic is preferred for pseudomembranous colitis due to Clostridioides difficile?

Answer 30

Vancomycin or Fidaxomicin are preferred for treatment of pseudomembranous colitis due to Clostridioides difficile.