List out the antibiotics which are commonly used
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Excellent! I now have a detailed table from the Textbook of Family Medicine (9e). Here is a well-organized, thorough answer:
Commonly Used Antibiotics by Class
Based on Textbook of Family Medicine, 9th Edition (Table 15-2) and Harrison's Principles of Internal Medicine, 22E.
1. Beta-Lactams
Mechanism: Inhibit bacterial cell wall synthesis by blocking peptidoglycan cross-linking.
| Sub-class | Key Agents |
|---|---|
| Penicillins | Penicillin V/G, amoxicillin, ampicillin, dicloxacillin, nafcillin, oxacillin |
| Extended-spectrum penicillins | Piperacillin, ticarcillin |
| Beta-lactam/inhibitor combos | Amoxicillin-clavulanate, piperacillin-tazobactam, ampicillin-sulbactam |
| 1st gen cephalosporins | Cefazolin, cephalexin |
| 2nd gen cephalosporins | Cefuroxime, cefoxitin |
| 3rd gen cephalosporins | Ceftriaxone, cefixime, ceftazidime |
| 4th gen cephalosporins | Cefepime |
| 5th gen cephalosporins | Ceftaroline (MRSA activity) |
| Carbapenems | Meropenem, imipenem, ertapenem, doripenem |
| Monobactams | Aztreonam (gram-negative only) |
2. Macrolides
Mechanism: Inhibit bacterial protein synthesis by binding the 50S ribosomal subunit.
- Azithromycin
- Clarithromycin
- Erythromycin
Used for respiratory tract infections, atypical pneumonia (Mycoplasma, Chlamydia, Legionella), skin infections, STIs.
3. Fluoroquinolones
Mechanism: Inhibit DNA gyrase (topoisomerase II) and topoisomerase IV, blocking DNA replication.
- Ciprofloxacin (broad gram-negative coverage)
- Levofloxacin (respiratory fluoroquinolone)
- Moxifloxacin (anaerobic coverage too)
- Norfloxacin (urinary tract)
Used for UTIs, pneumonia, skin/soft tissue infections, GI infections, anthrax.
4. Tetracyclines
Mechanism: Inhibit protein synthesis at the 30S ribosomal subunit.
- Doxycycline (most commonly used; broad-spectrum)
- Minocycline
- Tetracycline
Used for Chlamydia, Lyme disease, acne, atypical pneumonia, rickettsial infections, malaria prophylaxis.
5. Aminoglycosides
Mechanism: Bind 30S ribosomal subunit; bactericidal; concentration-dependent killing.
- Gentamicin
- Tobramycin
- Amikacin
- Streptomycin
- Neomycin (topical/GI use)
Used for serious gram-negative infections, often in combination. Require monitoring for nephrotoxicity and ototoxicity.
6. Glycopeptides
Mechanism: Inhibit cell wall synthesis by binding D-Ala-D-Ala terminus of peptidoglycan precursors.
- Vancomycin (drug of choice for MRSA)
- Teicoplanin
Used for MRSA, Clostridioides difficile (oral vancomycin), serious gram-positive infections.
7. Lincosamides
Mechanism: Bind 50S ribosomal subunit; inhibit protein synthesis.
- Clindamycin
Used for anaerobic infections, dental infections, skin/soft tissue infections, community-acquired MRSA.
8. Sulfonamides / Folate Inhibitors
Mechanism: Inhibit folate synthesis (sulfonamides) and dihydrofolate reductase (trimethoprim).
- Trimethoprim-sulfamethoxazole (TMP-SMX / Co-trimoxazole)
Used for UTIs, Pneumocystis jiroveci pneumonia (PCP), toxoplasmosis, MRSA skin infections.
9. Nitroimidazoles
Mechanism: Produce reactive intermediates that damage bacterial/protozoal DNA.
- Metronidazole
- Tinidazole
Used for anaerobic bacterial infections (C. difficile, intra-abdominal infections), Trichomonas, Giardia, H. pylori regimens.
10. Oxazolidinones
Mechanism: Inhibit initiation of protein synthesis at the 50S subunit.
- Linezolid
Reserved for drug-resistant gram-positive organisms (MRSA, VRE).
11. Rifamycins
Mechanism: Inhibit bacterial RNA polymerase.
- Rifampin (rifampicin)
Used for TB, leprosy, MRSA (in combination), meningococcal prophylaxis.
12. Nitrofurans
Mechanism: Reactive intermediates damage multiple bacterial targets.
- Nitrofurantoin
First-line for uncomplicated lower UTI; active against E. coli and gram-positive urinary pathogens.
13. Polymyxins
Mechanism: Disrupt outer membrane of gram-negative bacteria.
- Colistin (polymyxin E)
- Polymyxin B
Last-resort agents for extensively drug-resistant (XDR) gram-negatives (Acinetobacter, Pseudomonas, Klebsiella).
Quick Clinical Reference Summary
| Class | Gram+ | Gram- | Anaerobes | Common Uses |
|---|---|---|---|---|
| Penicillins | ✓✓ | ± | ± | Strep, dental |
| Cephalosporins | ✓✓ | ✓✓ | - | Skin, UTI, pneumonia |
| Carbapenems | ✓✓ | ✓✓ | ✓✓ | Severe/resistant infections |
| Macrolides | ✓ | ± | - | Atypical pneumonia, STIs |
| Fluoroquinolones | ± | ✓✓ | ± | UTI, pneumonia, GI |
| Aminoglycosides | - | ✓✓ | - | Serious gram-neg infections |
| Vancomycin | ✓✓ | - | - | MRSA, C. diff |
| Metronidazole | - | - | ✓✓ | Anaerobes, C. diff, parasites |
| TMP-SMX | ✓ | ✓ | - | UTI, PCP, MRSA skin |
| Tetracyclines | ✓ | ✓ | - | Atypicals, Lyme, acne |
Source: Textbook of Family Medicine 9e, Table 15-2; Harrison's Principles of Internal Medicine 22E
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