ANTIBIOTICS

• Sepsis (broad)-> (Vanc + Cefepime) , Abdominal concern (+ Flagyl), ESBL risk: (Meropenem + Vanc)

• Nec Fasc -> Vancomycin + Meropenem + Clindamycin (Meropenem = Cefepime + Metronidazole)

• CAP-> Ceftriaxone + Azithro (5) ((MRSA/Pseudomonas risk: Cefepime + Vanc ± Azithro (7)))

  • PO: Augmentin + Doxy/Azithro OR Levo, (MRSA: Linezolid)

• HAP -> Cefepime + Vanc ((septic: Meropenem + Vanc)) (7)

  • PO: Levo/Cipro (psedo) if susceptible + MRSA PO: Linezolid

• Aspiration Pneumonia- > Ceftriaxone ± Flagyl (7)((Severe: Cefepime + Flagyl)), Abscess/necrosis: 2–6 weeks

  • PO: Augmentin ((Severe Levo + Flagyl))

• UTI / Pyelonephritis -> Ceftriaxone ((septic: Cefepime)), ESBL: Meropenem , Pyelo: 7–10 days, Complicated/septic: 10–14 days

  • PO -> - TMP-SMX or Levo or Cipro

• Urosepsis -> Cefepime +VANC ((Shock/ESBL risk: Meropenem)) 7–14 days

  • PO -> - TMP-SMX or Levo or Cipro and (MRSA: Linezolid)

• Cholangitis / Cholecystitis -> Stable: Ceftriaxone + Flagyl ((Sicker/pseudomonas risk: Cefepime + Flagyl)), Septic shock/ESBL: Meropenem 4–7 days

  • PO-> Augmentin ((Severe Levo + Flagyl))

• Diverticulitis / Intraabdominal Infection-> Stable: Ceftriaxone + Flagyl 4–7 days((Severe: Cefepime + Flagyl)), ESBL/shock: Meropenem complicated 7–14 days

  • PO-> PO-> Augmentin ((Severe Levo + Flagyl))

• SBP (Spontaneous Bacterial Peritonitis) -> Ceftriaxone ((septic Cefepime)), ESBL risk: Meropenem (5 day)

  • PO-> TMP-SMX ((Severe Cipro))

• Cellulitis -> IV: Ceftriaxone

  • PO-> Cephalexin (Penicillin allergy: Clinda) 5–7 days

• Purulent / Abscess -> Vanc

  • PO Step-down TMP-SMX , or doxy or Linezolid 5–10 days

• Diabetic Foot Infection -> Mild PO: Cephalexin ± Doxy, sever-> IV: Vanc + Cefepime + Flagyl ((ESBL risk: Meropenem + Vanc)),

  • PO-> Augmentin or Levo + Flagyl

• Osteomyelitis -> CTX + Vanc ((Polymicrobial: Vanc + Cefepime + Flagyl))

  • PO Linezolid or TMP-SMX or levo or clinda 4–6 weeks

• Septic Arthritis -> Vanc + Ceftriaxone ((IVDU/pseudomonas risk: Vanc + Cefepime))

  • PO-. TMP-SMX 2–4 weeks

• Meningitis -> Vanc + Ceftriaxone ((Age >50/immunocompromised: add Ampicillin)) , Healthcare-associated: Vanc + Cefepime

  • Typically prolonged IV therapy (ID consult) - Pneumococcal: 10–14 days Meningococcal: ~7 days

• Bacteremia / Sepsis Unknown Source-> Vanc + Cefepime ((Abdominal concern: add Flagyl)), ESBL risk: Meropenem + Vanc

  • PO MRSA bacteremia: -> prolonged IV , Sometimes Linezolid

  • Gram-negative bacteremia:- > Levo or Cioro, or tmp-smx 7–14 days

• Infective Endocarditis -> Vanc + Ceftriaxone ((Prosthetic valve: Vanc + Cefepime))

  • Mostly prolonged IV therapy Usually 4–6 weeks IV

• Necrotizing Fasciitis / Fournier Gangrene -> Vanc + Meropenem + Clinda OR Vanc + Cefepime + Flagyl + Clinda

  • PO Rare early PO , later Augmentin or TMP-SMX or Linezolid (ID) 2–3+ weeks

• C. diff Colitis -> PO vanc or Fidaxomicin ((Fulminant :PO Vanc + IV Flagyl))

  • Usually 10 days

• Neutropenic Fever - > Cefepime+ vanc (ESBL/shock: Meropenem)

  • PO-> Depends ANC recovery/cultures , Levo

• PID (Pelvic Inflammatory Disease) -> Ceftriaxone + Doxy + Flagyl

  • PO -> Doxy + Flagyl 14 days total

• Bite Wounds (Human/Animal) -> IV severe: Unasyn

  • Po-> Augmentin or Clinda 5–7 days

• Dental / Odontogenic Infection -> - Unasyn OR Ceftriaxone + Flagyl

  • Po-> Augmentin or Clinda 5–7 days

• ESBL risk → prior ESBL, heavy FQ exposure, LTCF/recurrent hospitalization → use Meropenem

• MRSA risk → prior MRSA, HD, IVDU, purulence, healthcare exposure, severe sepsis → add Vancomycin (or Linezolid/Daptomycin)

• Pseudomonas risk → structural lung disease, prior Pseudomonas, prolonged/recent antibiotics, ICU/healthcare exposure → use Cefepime, Zosyn, or Meropenem ± double coverage if critically ill

INDIVIDUAL ABX

Ceftriaxone / Rocephin

• good gram-negative + some gram-positive coverage.

• Covers: E. coli, Klebsiella, Proteus, Strep pneumo.

• Good for: CAP, pyelo, UTI, cholangitis, diverticulitis, SBP.

• Does not cover: pseudomonas, anaerobes, MRSA.

• Common combos

  • Azithro for CAP

  • Metronidazole for abdominal/biliary infection.

• PO step-down

  • Augmentin (diverticulitis, cholangitis)

  • Cephalexin/Keflex (UTI, sometimes skin/soft tissue if susceptible).

  • TMP-SMX (UTI, pyelo if susceptible)

  • Levofloxacin or ciprofloxacin (UTI/pyelo if susceptible).
    Cefepime

• Think ceftriaxone + pseudomonas.

• Good for: HAP, ICU infections, neutropenic fever, septic shock, healthcare-associated infection

• Does not cover: anaerobes, MRSA.

• Common combos

  • Metronidazole / Flagyl for abdominal source.

  • Vancomycin / Vanc for MRSA concern.

  • Vancomycin / Vanc + metronidazole / Flagyl for septic unclear source.
    PO step-down:

  • Levofloxacin / Levaquin.

  • Ciprofloxacin / Cipro.

Vancomycin — MRSA drug.

• Covers: MRSA, resistant gram positives, some Enterococcus.

• Good for: MRSA pneumonia, purulent cellulitis, bacteremia, line infection, severe sepsis.

• Does not cover: gram negatives, anaerobes.
  PO step-down:

• Linezolid / Zyvox (MRSA pneumonia, bacteremia).

• TMP-SMX / Bactrim (skin infection, UTI).

• Doxycycline / Vibramycin (skin/soft tissue, CAP).

Flagyl / Metronidazole — anaerobe coverage.

• Covers: Bacteroides, GI anaerobes.

• Good for: diverticulitis, cholangitis, intraabdominal infection, abscess, aspiration with necrosis.

• Usually paired with: ceftriaxone / Rocephin, cefepime / Maxipime.
  PO step-down:

• Metronidazole / Flagyl (diverticulitis, intraabdominal infection).

Meropenem — "Very broad rescue antibiotic"

• Covers: ESBL organisms, Pseudomonas, anaerobes, resistant GNRs

• Good for: Septic shock, prior ESBL, failed broad therapy, severe abdominal infection

• Combine with: Vanc (if MRSA concern)

• PO step-down (culture-guided): Levo/Cipro, TMP-SMX

Azithromycin — _"Atypical coverage"

• Covers: Legionella · Mycoplasma · Chlamydi

• Good for: CAP combination therap

• Combo: Ceftriaxone + Azithr

• PO step-down: PO Azithro (same drug)

Doxycycline — "MRSA skin + atypicals"

• Covers: CA-MRSA · Atypicals · Tickborne (Rickettsia, Anaplasma, Ehrlichia)

• Good for: Mild MRSA SSTI · CAP alternative (if no severe illness)

• Weakness: Poor strep coverage — never monotherapy if strep suspected

TMP-SMX (Bactrim) — "MRSA + UTI drug"

• Covers: CA-MRSA · Urinary GNRs · Pneumocystis (PCP)

• Good for: Cystitis · Pyelonephritis (if susceptible) · MRSA abscess/SSTI · PCP prophylaxis/treatment

• Watch: AKI (blocks creatinine secretion — rises without true GFR drop) · Hyperkalemia (blocks distal K+ excretion) · Bone marrow suppression · Sulfa allergy

• Avoid: ESBL organisms · Pseudomonas · Strep coverage unreliable

• Rule of thumb: Always check local resistance E. coli resistance to TMP-SMX >20% in many regions, culture-guide whenever possible

Cephalexin — "MSSA/strep cellulitis"

• Covers: MSSA · Streptococcus (Group A, B, C)

• Good for: Non-purulent cellulitis · mild SSTI · step-down from IV oxacillin/nafcillin

• Does NOT cover: MRSA · GNRs · Anaerobes

• Rule of thumb: Purulent SSTI (abscess, furuncle) → think MRSA → use TMP-SMX or doxy instead. Non-purulent cellulitis (no pus, no abscess) → strep is the driver → cephalexin is ideal.

Augmentin (Amoxicillin-Clavulanate) — "Oral anaerobe + polymicrobial coverage"

• Covers: Strep · MSSA · Oral anaerobes · Some GNRs (E. coli, Klebsiella, H. influenzae)

• Good for: Aspiration pneumonia step-down · Bite wounds (human & animal) · Mild abdominal step-down · Sinusitis · Diabetic foot (mild)

• Does NOT cover: Pseudomonas · MRSA · ESBL organisms

• Watch: GI intolerance (take with food) · Hepatotoxicity with prolonged use (clavulanate-driven)

• Rule of thumb: Best oral option when you need anaerobe + gram positive + some gram negative in one pill. If MRSA concern add TMP-SMX/doxy on top.

Ciprofloxacin — "Urinary pseudomonas drug"

• Covers: GNRs · Pseudomonas · Atypicals · Anthrax

• Good for: Pyelonephritis · Resistant UTI · Abdominal step-down (+ Flagyl for anaerobes) · Pseudomonas SSTI/bone

• Does NOT cover: MRSA · Strep (unreliable) · Anaerobes

• Watch: Tendinopathy/rupture · QTc prolongation · C. diff risk · Lowers seizure threshold · Resistance rising fast — check local antibiogram

• Rule of thumb: Great urinary drug but check susceptibilities first — E. coli resistance >20% in many centers. Never rely on cipro alone for strep or anaerobic coverage. If abdominal infection always pair with Flagyl.

Levofloxacin — "Respiratory fluoroquinolone"

• Covers: CAP organisms (Strep pneumo, atypicals) · GNRs · Pseudomonas (partial — don't rely on for serious Pseudo infections)

• Good for: CAP (monotherapy if outpatient, low-severity) · Pyelonephritis · Sinusitis · Step-down for susceptible GNR infections

• Does NOT cover: MRSA · Anaerobes (unreliable) · True Pseudomonas infections

• Watch: QTc prolongation · Tendinopathy/rupture · Delirium/neurotoxicity (especially elderly) · C. diff risk · Resistance selection — avoid overuse

• Levo vs Cipro: Levo = better gram positive + atypical coverage (respiratory) Cipro = better Pseudomonas + urinary penetration

• Rule of thumb: Fluoroquinolones should be reserved — rising resistance and collateral damage make them a 2nd line choice in most cases. Use when beta-lactam not an option or confirmed susceptibility.

Clindamycin — "Toxin suppression + anaerobes"

• Covers: Strep · CA-MRSA (check D-zone test) · Oral & abdominal anaerobes

• Good for: Necrotizing fasciitis adjunct (toxin suppression) · Dental/oral infections · Aspiration (alternative) · CA-MRSA SSTI

• Does NOT cover: GNRs · Enterococcus · Hospital MRSA (unreliable)

• Watch: Highest C. diff risk of all oral antibiotics · Check inducible clindamycin resistance (D-zone) before using for MRSA

Linezolid — "Oral MRSA powerhouse"

• Covers: MRSA · VRE · Strep · Atypicals

• Good for: MRSA pneumonia (DOC over vanc by some guidelines) · Oral step-down for MRSA · VRE infections · When vancomycin contraindicated

• Does NOT cover: GNRs · Pseudomonas · Anaerobes

• Watch: Thrombocytopenia (check CBC weekly) · Serotonin syndrome (avoid with SSRIs/SNRIs/MAOIs) · Peripheral & optic neuropathy with prolonged use (>2 weeks)

• -Rule of thumb: Linezolid is one of very few oral antibiotics with true MRSA efficacy — use it strategically for step-down. Clindamycin for MRSA only if D-zone negative and non-severe.