What antibiotics are used to treat different types of infections?

Antibiotics for Different Types of Infections

The most appropriate antibiotic treatment varies by infection type, with first-line options including amoxicillin-clavulanic acid for mild to moderate intra-abdominal infections, cephalosporins with metronidazole for severe intra-abdominal infections, and targeted therapy based on the specific pathogen and site of infection for skin/soft tissue infections. 1

Respiratory Tract Infections

• For upper respiratory tract infections (URTI), antibiotics are generally not indicated as most cases are viral in origin 1
• For lower respiratory tract infections (LRTI) in children under 3 years with pneumonia, amoxicillin (80-100 mg/kg/day) is the first-line treatment due to Streptococcus pneumoniae being the most common bacterial pathogen 1
• For children over 3 years with pneumonia, treatment should be guided by clinical presentation - amoxicillin for suspected pneumococcal infection or macrolides if Mycoplasma pneumoniae or Chlamydia pneumoniae are suspected 1
• For community-acquired pneumonia in adults, a 5-day course of antibiotics covering common pathogens is recommended, with options including amoxicillin, doxycycline, or a macrolide 2

Intra-abdominal Infections

• For mild to moderate intra-abdominal infections, first-choice antibiotics include:

  • Amoxicillin-clavulanic acid 1
  • Ampicillin plus gentamicin plus metronidazole (particularly in children) 1

• For severe intra-abdominal infections, first-choice antibiotics include:

  • Cefotaxime or ceftriaxone plus metronidazole 1
  • Piperacillin-tazobactam 1
  • Meropenem (as a second choice) 1

• For surgery involving the intestinal or genitourinary tract, recommended options include:

  • Single-drug regimens: piperacillin-tazobactam, ticarcillin-clavulanate, carbapenems (imipenem, meropenem, ertapenem) 1
  • Combination regimens: ceftriaxone plus metronidazole, or fluoroquinolones (ciprofloxacin, levofloxacin) plus metronidazole 1

Skin and Soft Tissue Infections

• For nonpurulent cellulitis, a 5-6 day course of antibiotics active against streptococci is recommended 1
• For surgery of trunk or extremity away from axilla or perineum, options include:
  • Oxacillin/nafcillin, cefazolin (IV) or cephalexin (oral), sulfamethoxazole-trimethoprim, or vancomycin 1
• For surgery of axilla or perineum, metronidazole plus either ciprofloxacin, levofloxacin, or ceftriaxone is recommended 1
• For necrotizing infections, broad-spectrum coverage is necessary:
  • Vancomycin or linezolid plus piperacillin-tazobactam or a carbapenem; or plus ceftriaxone and metronidazole 1
  • For documented group A streptococcal necrotizing fasciitis, penicillin plus clindamycin is recommended 1

Urinary Tract Infections

• For lower urinary tract infections, first-choice antibiotics include:

  • Amoxicillin-clavulanic acid 1
  • Sulfamethoxazole-trimethoprim 1
  • Nitrofurantoin (as a second choice) 1

• For mild to moderate pyelonephritis and prostatitis:

  • Ciprofloxacin (first choice) 1
  • Ceftriaxone or cefotaxime (second choice) 1

• For severe pyelonephritis and prostatitis:

  • Ceftriaxone or cefotaxime (first choice) 1
  • Amikacin (second choice) 1

Special Populations: Neutropenic Patients

• For initial infections in neutropenic patients (first 7 days):

  • Broad-spectrum monotherapy with carbapenems, antipseudomonal cephalosporins, or piperacillin-tazobactam 1
  • Combination therapy using an aminoglycoside plus an antipseudomonal penicillin or extended-spectrum cephalosporin 1

• For subsequent infections in neutropenic patients (after 7 days):

  • Pathogen-specific therapy based on culture results 1
  • Consider adding coverage for resistant gram-positive organisms (vancomycin, linezolid, or daptomycin) if clinically indicated 1

Important Clinical Considerations

• Local resistance patterns should significantly influence antibiotic selection for empiric therapy 2
• Shorter courses (5-7 days) are now recommended for many common infections, with extension based on clinical response rather than defaulting to longer courses 1
• For many infections, narrow-spectrum antibiotics should be preferred when the causative pathogen is known to reduce the development of antimicrobial resistance 3
• Amoxicillin-clavulanic acid is particularly useful for treating infections caused by beta-lactamase-producing organisms, including respiratory tract infections, skin infections, and urinary tract infections 4, 5

Common Pitfalls and Caveats

• Inappropriate initial empirical antibiotic therapy is associated with increased mortality, particularly in nosocomial infections 1
• Prior antibiotic exposure is a significant risk factor for receiving inadequate antimicrobial therapy 1
• Vancomycin should not be used empirically for all infections but reserved for situations where MRSA is suspected or confirmed 1
• When using doxycycline or other antibiotics, they should only be used to treat infections proven or strongly suspected to be caused by susceptible bacteria to reduce the development of drug-resistant bacteria 3
• The emergence of resistant S. pneumoniae strains with elevated penicillin MICs in certain geographical areas may necessitate higher doses of amoxicillin-clavulanic acid 6