Antibiotics according to the siysem

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Now I have enough to give a comprehensive answer. I'll build this from my medical knowledge, organized by organ system, as that's what "antibiotics according to the system" means.

Antibiotics According to Organ System

Here is a systematic breakdown of antibiotics used for infections in each major body system, including first-line and alternative agents.

1. Respiratory System

Upper Respiratory Tract (pharyngitis, otitis media, sinusitis)

Condition	First-Line	Alternative
Strep pharyngitis	Amoxicillin / Penicillin V	Azithromycin (PCN allergy)
Acute otitis media	Amoxicillin	Amoxicillin-clavulanate
Acute sinusitis (bacterial)	Amoxicillin-clavulanate	Doxycycline, Levofloxacin

Lower Respiratory Tract (pneumonia, bronchitis, lung abscess)

Condition	First-Line	Alternative
Community-acquired pneumonia (CAP) - outpatient	Amoxicillin + Azithromycin	Doxycycline, Levofloxacin
CAP - inpatient	Beta-lactam + Macrolide	Respiratory fluoroquinolone
Hospital-acquired pneumonia (HAP)	Piperacillin-tazobactam / Cefepime	Meropenem + Vancomycin
Lung abscess	Amoxicillin-clavulanate	Clindamycin + Metronidazole
Tuberculosis	Isoniazid + Rifampicin + Pyrazinamide + Ethambutol	-
Atypical pneumonia (Mycoplasma, Chlamydia, Legionella)	Azithromycin / Doxycycline	Levofloxacin

2. Urinary System (UTI, Pyelonephritis, Prostatitis)

Condition	First-Line	Alternative
Uncomplicated UTI (cystitis)	Nitrofurantoin, Trimethoprim-sulfamethoxazole (TMP-SMX)	Fosfomycin, Cephalexin
Complicated UTI / Pyelonephritis	Ciprofloxacin, TMP-SMX	Ceftriaxone, Gentamicin
Catheter-associated UTI	Ciprofloxacin / Ceftriaxone	Piperacillin-tazobactam
Prostatitis (acute)	Ciprofloxacin	TMP-SMX
Gonorrhea (urethritis)	Ceftriaxone IM + Azithromycin	Gentamicin + Azithromycin

3. Gastrointestinal System

Condition	First-Line	Alternative
H. pylori eradication	Triple therapy: Amoxicillin + Clarithromycin + PPI	Bismuth quadruple therapy
Traveler's diarrhea	Azithromycin / Ciprofloxacin	Rifaximin
Clostridium difficile (mild-mod)	Vancomycin (oral) / Fidaxomicin	Metronidazole
Typhoid fever	Azithromycin / Ceftriaxone	Ciprofloxacin
Cholera	Doxycycline	Azithromycin
Peritonitis / Intra-abdominal sepsis	Piperacillin-tazobactam	Meropenem + Metronidazole
Spontaneous bacterial peritonitis	Cefotaxime	Ceftriaxone
Cholangitis / Cholecystitis	Piperacillin-tazobactam	Ampicillin-sulbactam

4. Central Nervous System

Condition	First-Line	Alternative
Bacterial meningitis (adult)	Ceftriaxone + Ampicillin + Dexamethasone	Meropenem
Meningitis (Listeria risk - elderly, immunocompromised)	Ceftriaxone + Ampicillin	-
Brain abscess	Ceftriaxone + Metronidazole	Meropenem
Tuberculous meningitis	HRZE (standard TB regimen) + Dexamethasone	-
Neurosyphilis	Penicillin G IV	Ceftriaxone

5. Cardiovascular System

Condition	First-Line	Alternative
Infective endocarditis - Streptococci	Penicillin G / Ceftriaxone ± Gentamicin	Vancomycin
Infective endocarditis - Staph aureus (native valve)	Nafcillin / Oxacillin	Vancomycin (MRSA)
Infective endocarditis - MRSA	Vancomycin	Daptomycin
Pericarditis (bacterial)	Ceftriaxone	Based on culture
Rheumatic fever prophylaxis	Benzathine Penicillin G IM monthly	Penicillin V oral

6. Skin and Soft Tissue

Condition	First-Line	Alternative
Cellulitis (non-purulent)	Dicloxacillin / Cephalexin	Clindamycin
Cellulitis (MRSA suspected)	TMP-SMX / Doxycycline	Clindamycin
Impetigo	Mupirocin (topical) / Cephalexin	Amoxicillin-clavulanate
Erysipelas	Penicillin V / Amoxicillin	Clindamycin
Necrotizing fasciitis	Piperacillin-tazobactam + Clindamycin + Vancomycin	Meropenem + Linezolid
Diabetic foot infection (mild)	Amoxicillin-clavulanate	Clindamycin + Ciprofloxacin
Wound infections (surgical)	Cefazolin	Clindamycin (allergy)
Acne vulgaris (moderate)	Doxycycline / Minocycline	Topical Clindamycin + Benzoyl peroxide

7. Musculoskeletal System

Condition	First-Line	Alternative
Osteomyelitis (Staph aureus)	Nafcillin / Oxacillin IV then Cephalexin oral	Clindamycin
Osteomyelitis (MRSA)	Vancomycin IV then TMP-SMX or Doxycycline oral	Linezolid
Septic arthritis	Cefazolin (Staph) / Ceftriaxone (GC)	Vancomycin (MRSA)
Lyme arthritis	Doxycycline	Amoxicillin, Cefuroxime

8. Reproductive/Pelvic System

Condition	First-Line	Alternative
Pelvic inflammatory disease (PID)	Ceftriaxone + Doxycycline + Metronidazole	Clindamycin + Gentamicin
Chlamydia	Doxycycline x 7 days	Azithromycin 1g single dose
Syphilis (primary)	Benzathine Penicillin G	Doxycycline (PCN allergy)
Bacterial vaginosis	Metronidazole (oral or vaginal)	Clindamycin
Endometritis (post-partum)	Ampicillin + Gentamicin + Metronidazole	Clindamycin + Gentamicin

9. Ophthalmology (Eye)

Condition	First-Line	Alternative
Bacterial conjunctivitis	Topical Ciprofloxacin / Tobramycin eye drops	Polymyxin-Trimethoprim drops
Bacterial keratitis	Topical Moxifloxacin / Ciprofloxacin	Tobramycin drops
Endophthalmitis	Intravitreal Vancomycin + Ceftazidime	-
Orbital cellulitis	IV Ampicillin-sulbactam	Ceftriaxone + Metronidazole

10. Ear, Nose and Throat (ENT)

Condition	First-Line	Alternative
Acute otitis externa	Topical Ciprofloxacin + hydrocortisone drops	Polymyxin B drops
Mastoiditis	Ceftriaxone IV	Ampicillin-sulbactam
Peritonsillar abscess	Amoxicillin-clavulanate	Clindamycin
Epiglottitis	Ceftriaxone	Ampicillin-sulbactam

11. Sepsis / Empiric Broad-Spectrum

Setting	Regimen
Community-acquired sepsis	Ceftriaxone ± Metronidazole ± Azithromycin
Hospital-acquired / ICU sepsis	Piperacillin-tazobactam OR Meropenem + Vancomycin
Neutropenic fever	Cefepime / Piperacillin-tazobactam ± Vancomycin
Septic shock (unknown source)	Meropenem + Vancomycin + Micafungin (if fungal risk)

Quick Reference: Antibiotic Classes and Their System Preferences

Class	Best Systems
Penicillins (Amoxicillin, Ampicillin)	Respiratory, ENT, Skin, GI
Cephalosporins (Cefazolin, Ceftriaxone)	Skin, MSK, Meningitis, Sepsis
Fluoroquinolones (Ciprofloxacin, Levofloxacin)	Urinary, Respiratory, GI, MSK
Macrolides (Azithromycin, Clarithromycin)	Respiratory, STIs, GI (H. pylori)
Tetracyclines (Doxycycline, Minocycline)	Respiratory, Skin, STIs, MSK (Lyme)
Aminoglycosides (Gentamicin, Tobramycin)	Urinary, Endocarditis, Ophthalmology
Carbapenems (Meropenem, Imipenem)	Severe/polymicrobial: Abdominal, Sepsis, CNS
Glycopeptides (Vancomycin)	MRSA: Skin, Bone, CNS, Endocarditis
Metronidazole	Anaerobic: GI, Abdominal, Pelvic, CNS
Nitrofurantoin, Fosfomycin	Urinary only
Rifampicin, Isoniazid	Primarily TB (Respiratory, CNS, MSK)

This covers all major organ systems. If you need more detail on any specific system, infection, or antibiotic class, just ask!

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