Medical Pharmacology Chapter 35  Antibacterial Drugs

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Antibacterial Therapy

Current Antibacterial Therapy




  • Community-acquired bacterial pneumonia: Streptococcus pneumoniae, (Pneumococcus) Gram stain, sputum

    • Most frequent cause: Streptococcus pneumoniae (pneumococci)

      • Chest X-RAY

      • > 30% of recent S. pneumoniae isolates:

        • relatively or highly resistant to penicillin and sometimes cephalosporins.

    •  Other pathogens:

      •  Haemophilus influenzae

      •  Staphylococcus aureus

      •  Klebsiella pneumoniae

      •  occasionally: other gram-negative bacilli and anaerobic mouth organisms

      • "Atypical" pathogens:

        • Legionella

        • Mycoplasma pneumoniae

        • Chlamydia pneumoniae

        • respiratory viruses

        • tuberculosis

        • Pneumocystis carinii

  • Diagnosis

  • Treatment: In Hospitalized Patients--

    • Pending culture results and susceptibility testing:

      •  Reasonable first-choice: cefotaxime or ceftriaxone

        •  Cefotaxime (Claforan), ceftriaxone (Rocephin), high-doses of penicillin (IV) effective in treating pneumococcal pneumonia (intermediate resistance)

      •   Vancomycin (Vancocin): high resistance

      •  Vancomycin (Vancocin) and cephalosporin: severe illness-- not responding to a beta-lactam.

      • A macrolide (erythromycin, azithromycin (Zythromax), or clarithromycin (Biaxin)) added to a fluoroquinone (good activity against S. pneumoniae --  levofloxacin (Levaquin), grepafloxacin and trovafloxacin) can be used to cover Legionella, Mycoplasma, chlamydia.

        • If aspiration pneumonia is a concern: clindamycin (Cleocin) or metronidazole (Flagyl) may be added.


  • Treatment for Ambulatory Patients

    • Treatment Recommended for otherwise healthy patients with pneumonia due to Mycoplasma or Chlamydia:

      • Oral macrolide ( erythromycin,  azithromycin (Zythromax), or  clarithromycin (Biaxin)),  doxycycline (Vibramycin, Doryx), or fluoroquinones with good anti-pneumococcal activity (levofloxacin (Levaquin), grepafloxacin, trovafloxacin)

      •  Penicillin-resistant pneumococci: may be resistant to a macrolide or doxycycline

      • Older patients or patients with underlying disease: recommendation --

        •  levofloxacin (Levaquin)

        •  grepafloxacin

        •  trovafloxacin

  • Treatment for hospital-acquired bacterial pneumonia

    • Most often cause by gram-negative bacilli:

      • Klebsiella

      • Enterobacter

      • Serratia

      • Acinetobacter AND

    • Pseudomonas aeruginosa

    • Staphylococcus aureus

    • The initial treatment: third-generation cephalosporin --

      •  cefotaxime (Claforan)

      •  ceftizoxime (Cefizox)

      •  ceftriaxone (Rocephin)

      •  ceftazidime (Fortax, Taxidime, Tazicef)

    • Or:

      •  cefepime (Maxipime)

      •  ticarcillin (Ticar)/ clavulanic acid

      •  piperacillin (Pipracil)/tazobactam

      •  meropenem (Merrem IV)

      •  imipenem

    • with or without the aminoglycoside {tobramycin (Nebcin), gentamicin (Garamycin), or amikacin (Amikin)}

    •  Considering third-generation cephalosporins:

      • Cefotaxime (Claforan), ceftizoxime (Cefizox), and ceftriaxone (Rocephin)} limited activity against Pseudomonas

      • Ceftazidime (Fortax, Taxidime, Tazicef)} more activity against staphylococci and other gram-positive cocci

    • In the intensive care unit, nosocomial pneumonia due to highly resistant gram-negative bacteria and Pseudomonas aeruginosa

      • Good first choices

        • imipenem

        • meropenem (Merrem IV)

        • plus aminoglycoside

        • add vancomycin (Vancocin) in hospitals where methicillin (Staphcillin)-resistant staphylococci are common.

The Choice of Antibacterial Drugs (Abramowicz, M, ed) The Medical Letter of Drugs and Therapeutics, vol. 40 (Issue 1023), March 27, 1998



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