What antibiotics are used to treat infections like pneumonia and gastrointestinal infections?

Antibiotics for Pneumonia and Gastrointestinal Infections

For optimal patient outcomes, pneumonia and gastrointestinal infections should be treated with specific antibiotics based on infection type, severity, and patient risk factors for resistant organisms. 1

Pneumonia Treatment

Community-Acquired Pneumonia (CAP)

Treatment options depend on severity and risk factors:

Outpatient/Non-severe CAP:

• First-line options:
  • Aminopenicillin (e.g., amoxicillin) ± macrolide
  • Aminopenicillin/β-lactamase inhibitor (e.g., amoxicillin-clavulanate) ± macrolide
  • Non-antipseudomonal cephalosporin (e.g., cefotaxime, ceftriaxone) ± macrolide
  • Respiratory fluoroquinolones (levofloxacin, moxifloxacin) 1

Hospitalized Patients (non-ICU):

• First-line options:
  • Non-antipseudomonal cephalosporin III (ceftriaxone, cefotaxime) + macrolide
  • Respiratory fluoroquinolone (levofloxacin, moxifloxacin)
  • Penicillin G ± macrolide 1

Severe CAP (ICU):

• Without Pseudomonas risk:

  • Non-antipseudomonal cephalosporin III + macrolide OR
  • Moxifloxacin/levofloxacin ± non-antipseudomonal cephalosporin III

• With Pseudomonas risk:

  • Antipseudomonal cephalosporin (ceftazidime) OR
  • Acylureidopenicillin/β-lactamase inhibitor (piperacillin-tazobactam) OR
  • Carbapenem (meropenem preferred)
  • PLUS ciprofloxacin OR macrolide + aminoglycoside 1, 2

Hospital-Acquired Pneumonia (HAP)

Based on mortality risk and MRSA risk factors:

Not at high risk of mortality, no MRSA risk:

• Piperacillin-tazobactam (4.5g IV q6h) OR
• Cefepime (2g IV q8h) OR
• Levofloxacin (750mg IV daily) OR
• Imipenem (500mg IV q6h) OR
• Meropenem (1g IV q8h) 1

Not at high risk of mortality, with MRSA risk:

• Same antibiotics as above PLUS
• Vancomycin OR Linezolid 1

High mortality risk or recent IV antibiotics:

• Two of the following (avoid using two β-lactams):
  • Piperacillin-tazobactam OR
  • Cefepime/ceftazidime OR
  • Levofloxacin/ciprofloxacin OR
  • Imipenem/meropenem OR
  • Amikacin/gentamicin/tobramycin OR
  • Aztreonam
• PLUS MRSA coverage:
  • Vancomycin OR Linezolid 1

Special Pathogens in Pneumonia

• Legionella spp.: Levofloxacin, moxifloxacin, or macrolide (azithromycin preferred) ± rifampicin
• Chlamydophila pneumoniae: Doxycycline, macrolide, levofloxacin, or moxifloxacin
• Acinetobacter baumannii: Third-generation cephalosporin + aminoglycoside or ampicillin-sulbactam 1

Intra-Abdominal Infections (IAI)

Community-Acquired IAI:

• First-line options:
  • Aminopenicillin/β-lactamase inhibitor
  • Cephalosporins + metronidazole
  • Fluoroquinolones + metronidazole 1

Hospital-Acquired IAI:

• Without MDR risk:

  • Piperacillin-tazobactam
  • Cefepime or ceftazidime + metronidazole
  • Carbapenems (ertapenem for non-Pseudomonas coverage) 1

• With MDR risk:

  • Piperacillin-tazobactam
  • Carbapenems (meropenem, imipenem)
  • Ceftazidime/avibactam or ceftolozane/tazobactam (for ESBL-producing organisms)
  • Consider adding vancomycin for enterococcal coverage 1

Duration of Treatment

• Pneumonia: Generally 7-8 days for responding patients; extended treatment (14-21 days) for specific pathogens like Legionella 1, 3
• Intra-abdominal infections: Typically 4-7 days after adequate source control 1

Important Considerations

1. Antibiotic Resistance:

   • Monitor local resistance patterns
   • Limit carbapenem use to preserve effectiveness 1
   • Consider risk factors for MDR organisms (prior hospitalization, recent antibiotics)

2. Adverse Events:

   • Fluoroquinolones: Risk of tendinopathy, CNS effects
   • Ceftriaxone: Higher risk of Clostridium difficile infection compared to other antibiotics 4
   • High-dose amoxicillin: Higher incidence of gastritis and diarrhea 5

3. Switching from IV to Oral:

   • Consider when clinical improvement has occurred
   • Temperature normal for 24 hours
   • No contraindications to oral route 3

4. Biomarkers:

   • Procalcitonin can guide shorter treatment duration in responding patients 3

5. Cultures:

   • Always obtain cultures in hospital-acquired infections and critically ill patients before starting antibiotics
   • Adjust therapy based on culture results 1

Remember that early, appropriate antimicrobial therapy significantly reduces mortality in both pneumonia and intra-abdominal infections, especially in cases with septic shock 1.