What is the first-line treatment for common bacterial infections?

First-Line Treatment for Common Bacterial Infections

The first-line treatment for common bacterial infections should be selected from the WHO Access group antibiotics, which include narrow-spectrum agents with favorable risk-benefit profiles and lower resistance potential. 1

General Principles for Antibiotic Selection

• The WHO AWaRe framework categorizes antibiotics into three groups: Access, Watch, and Reserve, to guide appropriate prescribing practices 1
• First-line antibiotics should typically come from the Access group, which includes widely available, affordable antibiotics with good clinical activity against commonly susceptible bacteria 1
• Second-line options typically come from the Watch group and should be used when resistance to first-line agents is suspected or confirmed 1

First-Line Treatments by Infection Type

Respiratory Tract Infections

• For community-acquired pneumonia (CAP) of mild to moderate severity:

  • Amoxicillin is recommended as first-line treatment based on its effectiveness against common respiratory pathogens 2
  • Phenoxymethylpenicillin (penicillin V) is an alternative first-line option for mild to moderate CAP 2
  • For patients with comorbidities, amoxicillin-clavulanic acid or doxycycline are appropriate second-line options 2

• For severe CAP requiring intensive care:

  • Combination therapy with a β-lactam (ceftriaxone or cefotaxime) plus a macrolide is recommended 2
  • For suspected Pseudomonas aeruginosa, piperacillin-tazobactam or a carbapenem with ciprofloxacin may be necessary 2

• For acute bronchitis:

  • Antibiotics generally show no benefit over placebo and should be avoided unless bacterial infection is strongly suspected 2

Skin and Soft Tissue Infections

• For mild impetigo and other superficial skin infections:

  • Dicloxacillin, cefalexin, or clindamycin are recommended first-line options 2

• For non-purulent skin and soft tissue infections:

  • Benzylpenicillin, phenoxymethylpenicillin, clindamycin, nafcillin, cefazolin, or cefalexin are recommended 2

• For purulent skin infections (likely Staphylococcus aureus):

  • Dicloxacillin, cefazolin, clindamycin, cefalexin, doxycycline, or sulfamethoxazole-trimethoprim are appropriate 2

• For MRSA infections or when MRSA is highly suspected:

  • Vancomycin, linezolid, clindamycin, daptomycin, ceftaroline, doxycycline, or sulfamethoxazole-trimethoprim should be used 2

Gastrointestinal Infections

• For invasive bacterial diarrhea:
  • Ciprofloxacin is recommended as first-line treatment 2
  • For confirmed Shigella infections, ceftriaxone (Watch category) may be used 2
  • For cholera, azithromycin is the first-choice treatment, with doxycycline as an alternative 2

Sepsis

• For sepsis in adults and children:
  • Combination therapy with an aminoglycoside (gentamicin) plus a β-lactam (amoxicillin, ampicillin, or benzylpenicillin) is recommended as first-line treatment 2, 1
  • Second-line options include amikacin plus cloxacillin, or cefotaxime or ceftriaxone 2

Special Considerations

• Local resistance patterns should guide antibiotic selection, especially in areas with high resistance to specific antibiotics 2, 1
• Previous antibiotic exposure should be considered when selecting empiric therapy, as this increases the risk of resistant organisms 3
• Duration of therapy should generally be 7-14 days for most infections, though shorter courses (5-7 days) may be appropriate for certain conditions like CAP when using higher doses 4, 5

Common Pitfalls to Avoid

• Using broad-spectrum antibiotics (Watch or Reserve groups) when narrow-spectrum options would be effective, which contributes to antimicrobial resistance 1
• Continuing empiric therapy without adjustment after culture and susceptibility results become available 3
• Prescribing fluoroquinolones as first-line therapy for conditions where they should be reserved as second-line options, due to their adverse effect profile (neuropsychiatric disorders, tendon problems, cardiac issues) and increasing resistance rates 3
• Using third-generation cephalosporins for non-serious infections, as resistance rates are rapidly increasing (from 1% in 2005 to 10% in 2012 for E. coli in some regions) 3

By following these evidence-based recommendations for first-line antibiotic therapy, clinicians can effectively treat common bacterial infections while practicing good antimicrobial stewardship.