How do you effectively treat bacterial infections?

Effective Treatment of Bacterial Infections

The most effective approach to treating bacterial infections is to use targeted antimicrobial therapy based on the suspected or confirmed pathogen, with empiric broad-spectrum antibiotics reserved for severe infections or when the causative organism is unknown. 1

Initial Assessment and Empiric Therapy Selection

• Empiric broad-spectrum antimicrobial therapy should be initiated promptly for patients presenting with sepsis or septic shock to cover all likely pathogens, including bacterial and potentially fungal or viral coverage 1
• For community-acquired infections of mild-to-moderate severity, agents with narrower spectrum of activity should be used (e.g., ampicillin/sulbactam, cefazolin or cefuroxime plus metronidazole, ticarcillin/clavulanate, ertapenem) 1
• For healthcare-associated infections, broader coverage is needed due to more resistant flora, which may include Pseudomonas aeruginosa, Enterobacter species, Proteus species, MRSA, enterococci, and Candida species 1
• Local antimicrobial resistance patterns should guide empiric therapy selection 1

Antimicrobial Selection Based on Infection Site

Respiratory Infections

• For community-acquired pneumonia, high-dose amoxicillin (1.5-4 g/day), amoxicillin/clavulanate, respiratory fluoroquinolones (levofloxacin, moxifloxacin), or cephalosporins are recommended 1
• For hospital-acquired or ventilator-associated pneumonia, antipseudomonal coverage is often required with agents such as cefepime, ceftazidime, carbapenems, or piperacillin-tazobactam 1

Intra-abdominal Infections

• For mild-to-moderate community-acquired intra-abdominal infections, narrower spectrum agents like ampicillin/sulbactam or cefazolin plus metronidazole are appropriate 1
• For severe infections, broader coverage with carbapenems, third/fourth-generation cephalosporins plus metronidazole, or piperacillin/tazobactam is recommended 1

Skin and Soft Tissue Infections

• For uncomplicated skin infections, antibiotics targeting Staphylococcus aureus and Streptococcus species are appropriate, such as dicloxacillin or cloxacillin 2
• For complicated infections or those with risk for MRSA, consider vancomycin, linezolid, or daptomycin 1

Urinary Tract Infections

• For uncomplicated UTIs, trimethoprim-sulfamethoxazole, fluoroquinolones, or nitrofurantoin are appropriate first-line options 1
• For complicated UTIs, broader coverage may be needed with fluoroquinolones, third-generation cephalosporins, or carbapenems 1

Principles of Antimicrobial Therapy

• Empiric antimicrobial therapy should be narrowed once pathogen identification and sensitivities are established and/or adequate clinical improvement is noted 1
• For optimal efficacy, beta-lactam antibiotics should maintain free plasma concentrations between four and eight times the MIC of the causative bacteria 3
• Patients should be counseled that antibacterial drugs should only be used to treat bacterial infections and not viral infections (e.g., the common cold) 4
• The full course of therapy should be completed to prevent treatment failure and development of resistance 4

Special Considerations

Immunocompromised Patients

• Immunocompromised patients who are very ill typically require very broad-spectrum empirical agents that include specific coverage for resistant gram-positive bacteria, such as MRSA 1
• Coverage for gram-negative bacteria may include monotherapy with an antipseudomonal cephalosporin, carbapenems, or a combination of either a fluoroquinolone or an aminoglycoside plus an extended-spectrum penicillin or cephalosporin 1
• Immunocompromised patients should not be given oral beta-lactams without careful consideration 3

Combination Therapy

• Combination antimicrobial therapy is indicated for: empirical treatment of life-threatening infections, treatment of polymicrobial infections, prevention of bacterial resistance emergence, and for synergistic effects 5
• For severe gram-negative infections caused by Enterobacter cloacae, Pseudomonas aeruginosa, and Serratia marcescens, combination therapy should be considered 5
• A two-drug combination of bactericidal broad-spectrum antibiotics is recommended for immunocompromised patients, generally combining an aminoglycoside and a beta-lactam antibiotic 6

Antimicrobial Resistance Considerations

• Recent antibiotic use is a major risk factor associated with infection caused by resistant pathogens 1
• Common mechanisms of bacterial resistance include enzymatic inhibition, membrane impermeability, alteration of target enzymes, active efflux of antibiotics, and alteration of ribosomal targets 7
• The WHO has identified ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) as critical priority pathogens due to their resistance patterns 8

Common Pitfalls to Avoid

• Delaying antimicrobial therapy in patients with severe sepsis, which is associated with greater mortality 1
• Using inappropriate initial antibiotic therapy, which increases the risk of hospital mortality 1
• Failing to adjust antimicrobial therapy based on culture results 1
• Using antibiotics for viral infections, which contributes to antimicrobial resistance 4
• Discontinuing therapy prematurely when symptoms improve, which may lead to treatment failure and resistance development 4
• Not considering local resistance patterns when selecting empiric therapy 1