• Penicillin G (IV)
    • Used in Strep pneumo, GAS, N meningitidis, Syphilis, Pasteurella multocida, Listeria monocytogenis, Actinomyces Israeli
  • Pencillin V (oral)
    • Strep throat from GAS
  • Amino penicillins (Ampi, Amox)
    • Broader gram -neg, covers enterococci
  • Penicillinase-resistant penicillins IV (Methicillin, Naficillin, Oxacillin)
    • Skin infections (not MRSA)
  • Pencillinase-resistant penicillins Oral (Cloxacillin, Dicloxacillin)
    • Skin infections (not MRSA)
  • Antipseudomonal penicillins (Carbenicillin, Ticarcillin, Piperacillin)
    • Anaerobic and pseudomonas coverage
  • Combination with beta-lactamase inhibitors (Amoxi/Clav, Ticarcillin/Clav, Ampi/sulfabactam, Pip/Tazo)
    • Broad coverage, including anaerobes, Timentin and Pip/Tazo cover pseudomonas
    • Used for hospital-acquired pneumonias


Each generation has increasing spectrum against gram negatives but less against gram positives (except fourth)

Note: MRSA and enterococci resistant to cephalopsporins

First gen (eg. cephalexin, cefazolin, cefadroxil)

  • Excellent gram-positive coverage
    • Used as alternative to penicillin for staph/strep infection when penicillin allergy
    • Used before surgery as prophylaxis

Second gen (eg. cefuroxime, cefoxitin, cefotetan)

  • Cefuroxime good coverage against strep pneumoniae and H influenza
    • Used for CAP, sinusitis, otitis media
  • Cefotetan, cefoxitin, cefmetazole have good anaerobic coverage (bacteroides fragilis)
    • Used for intraabdominal infection, aspiration pneumonias, colorectal surgery prophylaxis

Third gen (eg. ceftriaxone, ceftazidime, cefotaxime, cefixime)

  • Ceftriaxone and cefotaxime excellent CSF penetration for meninigits
    • Cefotaxime in neonates/children (ceftriaxone can interfere with bilirubin metabolism in neonates)
    • Ceftriaxone for N gonorrhea (many resistant to penicillin and tetracycline)
  • Ceftazidime, cefoperazone antipseudomonal

Fourth gen (Cefepime)

  • Added benefit against gram positives (and covers gram negatives like 3rd gen) and pseudomonas
  • Pseudomonas (Pseudomonas coverage with Ceftazidime, Cefepime)

Fifth gen (Ceftaroline)

  • Only cephalosporin with activity against MRSA

Carbapanems (Meropenem, Imipenem, Ertapenem)

  • Broad coverage (except MRSA)
  • Ertapenem IV once a daily
    • Drug of choice for severe diabetic foot infections (usually polymicobic)
    • Ertapenem is only carbapenem that does NOT cover pseudomonas

Monobactam (Aztreonam)

  • Magic bullet for gram negative aerobic bacteria, including pseudomonas
  • Used with gram positive antibiotics like Vancomycin and Clindamycin for broad-coverage



  • Broad coverage, including anaerobic
    • Side effects include aplastic anemia, Gray Baby Syndrome
  • Used for meningitis when severe allergy to penicillins including cephalosporins
  • Young children and pregnant women who have Rocky Mountain spotted fever (cannot be treated with tetracycline)

Lincosamides (Clindamycin)

  • Anaerobic, gram positive and MRSA coverage
    • Not useful against gram-negative
    • Side effects pseudomembranous colitis (C-diff)
  • Used with aminoglycoside (cover gram-neg) in wound infections of the abdomen
  • Female genital tract infections
    • Septic abortions
    • Alternative to metronidazole for bacterial vaginosis
  • Used with beta-lactam (penicillin) or vancomycin for toxic shock syndrome with GAS or staph aureus
  • Aspiration pneumonia

Oxalidinones (Linezolid)

  • Gram-positive, MRSA, VRE
    • Expensive
    • Side effects Serotonin Syndrome (avoid if on antidepressants)
  • Used with beta-lactam to cover hospital acquired pneumonia


Erythromycin, Azithromycin, Clarithromycin, Telithromycin (Ketolide)

  • Gram-positive, some gram-negative, atypicals (Legionella, Chlamydia pneumoniae, Mycoplasma)
  • Use for outpatient community-acquired pneumonia
    • Telithromycin efficacy against macrolide resistant Strep pneumo
      • Black box warning for respiratory failure in myasthenia gravis

Tetracyclines (Doxycycline)

  • Chlamydia trachomatis
  • Mycoplasma pneumoniae (Walking pneumonia)
  • Animal/Tick-borne Bruciella and Rickettsia
  • Acne
    • Side effects: Phototoxic dermatitis


Gentamicin, Tobramycin, Amikacin (good against resistant), Neomycin (topical, as toxic)

  • Break down cell walls, used with beta-lactams
  • Aerobic gram-neg, Pseudomonas
    • Side effects: CN8 toxicity (Hearing loss irreversible), renal toxicity, neuromuscular blockade



  • Ciprofloxacin
    • Gram-negatives, best for Pseudomonas
    • Enterobacteriacae except anaerobes (E coli, salmonella, shigella, Campylobacter)
    • Complicated UTI, prostatitis, epididymitis
    • Gram-neg intracellular (Legionella, Burcella, Salmonella, Mycobacterium)
  • Levofloxacin
    • Expanded gram-positive
    • Community acquired pneumonia, skin infections
  • Moxifloxacin
    • Strep pneumo and anaerobic (intraabdominal infections)
    • Poor urinary concentration

Lipoglycopeptides (Vancomycin)

  • All Gram-posiitve (MRSA, enterococcus, indwelling IV catheter resistant staph epidermidis)
    • Endocarditis (Strep/staph) in penicillin-allergic
    • Red man syndrome (rapid infusion, treat with slow infusion and antihistamine)
  • Daptomycin similar to vancomycin with some side effects:
    • Monitor CPK levels (myopathy risk)
    • Eosinophilic pneumonia (stop dapto and give steroids)

Sulfonamides (TMP SMX)

  • Gram positive, gram negative, some protozoans (Pneumocystis carinii, Toxoplasma gondii, Isospora belli)
    • Increases INR
  • T (Resp Tree): Otitis media, sinusitis, bronchitis, pneumonia
  • M (Mouth): Shigella, Salmonella, E coli
  • P (Pee): UTI, prostatitis, urethritis
  • S (AIDS): PCP prophylaxis

Bug Coverage

Pseudomonas Aeruginosa

  • Penicillins (Ticarcillin, Ticarcillin/Clav, Piperacillin, Pip/Tazo)
  • Third gen cephalosporins (Ceftazidime)
  • Fourth gen cephalosporins (Cefepime)
  • Carbapenems (Imipenem, Meropenem, Doripenem)
  • Aztreonam
  • Ciprofloxacin
  • Aminoglycosides (Amikacin, Gentamicin, Tobramycin)
  • Polymixins

Anaerobes (Bacteroides Fragilis)

  • Penicillins with beta-lactamase inhibitor (Amoxi/Clav, Ticarcillin/Clav, Ampi/subactam, Pip/Tazo)
  • Second gen cephalosporins (Cefoxitin, Cefotetan, Cefmetazole)
  • Carbapenems (Imipenem, Meropenem, Doripenem, Ertapenem)
  • Chloramphenicol
  • Clindamycin
  • Metronidazole
  • Moxifloxacine
  • Tigecycline

Atypical (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella)

  • Fluoroquinolone (levofloxacin, moxifloxacin)
  • Macrolide (erythromycin, azithromycin)
  • Doxycycline


  • Vancomycin
  • Linezolin
  • Daptomycin
  • Quinupristin/dalfopristin
  • Tigecycline
  • Ceftaroline
  • Clindamycin
  • Tetracycline (Doxycycline/Minocycline)


  • Linezolid
  • Daptomycin
  • Tigecycline


  • Oral vancomycin (or metronidazole)

"No Tazo"

  • SPACE (Serratia, Pseudomonas, Acinetobacter, Citrobacter, and Enterobacter) infections (inducible β-lactamase AmpC)
    • Avoid Tazo as 30% treatment failure
    • Use Cipro/Carbapenem

Penicillin Allergy

  • 85% of "penicillin-allergic" will tolerate penicillin
    • High-risk: Resp distress, angioedema within one hour
    • Low-risk : >10 years ago (most lose IgE), do not remember
      • Skin-test, then if negative penicillin challenge, then allergy ruled out
  • Aztreonam is only monobactam with no reactivity with penicillin
    • Consider in Type I immediate hypersensitivity
    • Consider desensitization
  • Otherwise, if no Type I allergy, avoid specific implicated drug (may consider skin-test + graded challenge)
    • Cephalosporin (2% cross-reactivity with penicillin skin test-positive)
      • If allergy to cephalosporin, avoid same R group side chain cephalosporins
    • Carbapenem (<1% will not tolerate despite skin-test positiive)

Fluoroquinolone Allergy

  • If history of anaphylaxis reaction to one fluoroquinolone, avoid entire class
  • For delayed on-set maculopapular nonpruritic rash, may consider graded challenge of another fluoroquinolone

Vancomycin Allergy

  • Avoid if bullous reaction or thrombocytopenia
  • If Red Man Syndrome (flushing, pruritus, urticaria), premedicate with antihistamine (diphenhydramine) and acetaminophen, hold opiates if possible, and infuse slower (eg. half rate, or 1g over >100 mins)