What is the treatment for bacterial infections?

Treatment of Bacterial Infections

For most bacterial infections, targeted antibiotic therapy based on culture and susceptibility testing is the gold standard, but empirical broad-spectrum coverage must be initiated immediately in critically ill patients or those with suspected resistant organisms. 1, 2

General Principles of Bacterial Infection Management

Diagnostic Approach

• Obtain cultures before initiating antibiotics from blood, urine, sputum, or fecal sources depending on the infection site to identify the causative organism and guide targeted therapy 1
• Use imaging (CT or PET-CT scans) when further confirmation is needed, particularly for pneumonia, abdominal abscesses, or deep tissue infections 1
• Microbiologic cultures with susceptibility testing are critical because antimicrobial resistance patterns vary significantly by geographic location and healthcare setting 1

Initial Empirical Therapy Selection

The choice of empirical antibiotics depends on three key factors: infection severity, patient immune status, and likelihood of resistant pathogens. 1

For Community-Acquired Infections (Mild-to-Moderate Severity)

• Use narrow-spectrum agents: ampicillin/sulbactam, cefazolin or cefuroxime plus metronidazole, or ticarcillin/clavulanate 1
• Avoid fluoroquinolones as first-line therapy due to increasing resistance and adverse effect risks 3, 4
• For uncomplicated urinary tract infections, use nitrofurantoin, fosfomycin, or trimethoprim-sulfamethoxazole (only if local E. coli resistance <20%) 3, 5

For Severe Infections or Immunocompromised Patients

• Initiate broad-spectrum coverage immediately with agents active against resistant gram-positive bacteria (MRSA) and gram-negative organisms including Pseudomonas 1
• Recommended regimens include: meropenem, imipenem/cilastatin, piperacillin/tazobactam, or fourth-generation cephalosporins (cefepime) plus metronidazole 1
• For suspected MRSA, add vancomycin, linezolid, or daptomycin 1

For Gram-Negative Bacteremia in Critically Ill Patients

• Use combination therapy with two different antimicrobial classes if recent colonization or infection with multidrug-resistant organisms is suspected 2
• Options include: carbapenem plus aminoglycoside, or antipseudomonal cephalosporin plus fluoroquinolone 2
• De-escalate to single-agent therapy once culture results confirm susceptibility 2

Site-Specific Treatment Algorithms

Complicated Skin and Soft Tissue Infections

• Prompt surgical intervention plus appropriate antibiotics targeting likely pathogens including MRSA and anaerobes 1
• Adjust therapy after culture results become available 1
• Higher-risk patients (APACHE II score >15, advanced age, nosocomial infection) require potent broad-spectrum therapy 1

Intra-Abdominal Infections

• Community-acquired: Use ertapenem, ticarcillin/clavulanate, or cefuroxime plus metronidazole 1
• Healthcare-associated (postoperative): Complex multidrug regimens are required due to more resistant flora including Pseudomonas, Enterobacter, and MRSA 1
• Local nosocomial resistance patterns should dictate empirical treatment 1

Pyelonephritis

• Oral ciprofloxacin 500mg twice daily for 7 days if local resistance <10% 3
• Trimethoprim-sulfamethoxazole 160/800mg twice daily for 14 days only if susceptibility confirmed 3
• If using oral β-lactams, start with initial IV ceftriaxone 1g or aminoglycoside 3

Bloodstream Infections

• Treatment duration should be 7-14 days for uncomplicated bacteremia, with longer courses for complicated infections 2
• Remove intravascular devices if persistent bacteremia occurs despite appropriate therapy 2

Special Populations

Neutropenic Patients

• Broad-spectrum antibiotics with reliable gram-negative coverage are essential 2, 4
• For febrile neutropenia, use anti-pseudomonal beta-lactam (piperacillin/tazobactam) as first-line therapy 4
• Prophylaxis with levofloxacin is recommended for prolonged neutropenia 1

Patients with Recurrent Infections

• Do not use the same antibiotic class if recent exposure occurred within 3-6 months due to increased resistance risk 3
• Prophylactic strategies may be considered, but treating asymptomatic bacteriuria is not recommended as it fosters resistance 3

Critical Management Principles

De-escalation Strategy

• Once culture and susceptibility results are available, narrow antibiotic spectrum to the most appropriate single agent 1, 2
• This approach reduces toxicity, cost, and selective pressure for resistance 1

Duration of Therapy

• Do not subject patients to prolonged antimicrobial therapy or arbitrary changes if persistent signs of infection occur; instead, investigate the underlying cause 1
• Treatment should continue until symptoms resolve 1

Resistance Considerations

• Current resistance trends frequently require multiple agents due to polymicrobial nature of infections 1
• MRSA, ESBL-producing Enterobacteriaceae, and resistant anaerobes (B. fragilis group) are increasingly common 1
• Review local antibiograms before selecting empirical therapy 1

Common Pitfalls to Avoid

• Never delay appropriate broad-spectrum therapy in critically ill patients with suspected bacterial infection, as this increases mortality 2
• Avoid using antibiotics with known high local resistance rates (>20%) for empirical therapy 3
• Do not fail to obtain pre-treatment cultures in patients with serious infections or recurrent disease 3
• Inadequate treatment duration (particularly for pyelonephritis requiring 7-14 days) leads to treatment failure 3
• Do not continue empirical broad-spectrum coverage once susceptibility results allow for targeted therapy 1, 2
• Underestimating infection severity in neutropenic patients can lead to delayed treatment and increased mortality 4