What is the best course of treatment for a suspected infection?

Treatment of Suspected Infection

Initiate intravenous antimicrobials within 1 hour of recognizing infection, using broad-spectrum agents with activity against all likely pathogens based on the suspected source and local resistance patterns. 1

Immediate Assessment and Stabilization

Hemodynamic Support

• Aggressively infuse crystalloids or colloids for tissue hypoperfusion, targeting systolic blood pressure ≥90 mmHg in adults, with more than 4L potentially required in the first 24 hours 1
• Add dopamine or epinephrine if hypoperfusion persists despite liberal fluid resuscitation 1
• Monitor for clinical indicators of adequate perfusion: normal capillary refill time (<2-3 seconds in adults <65 years), absence of skin mottling, warm extremities, well-felt peripheral pulses, return to baseline mental status, and urine output >0.5 mL/kg/hour in adults 1

Oxygenation

• Apply oxygen to achieve saturation >90%; if no pulse oximeter available, administer oxygen empirically in severe cases 1
• Position patients semi-recumbent (head of bed 30-45°) to prevent aspiration 1

Diagnostic Workup (Without Delaying Antimicrobials)

Obtain at least 2 sets of blood cultures (aerobic and anaerobic) before starting antimicrobials, provided this causes no substantial delay (>45 minutes) 1

• Sample fluid or tissue from the suspected infection site whenever possible without harming the patient 1
• Perform Gram stain, culture, and antibiogram on sampled material 1
• Obtain imaging (chest CT, ultrasound, or other modality) to identify the infection source and assess for complications like abscess formation 1

Empiric Antimicrobial Selection

General Principles

Select broad-spectrum IV antimicrobials at adequate dosages with high likelihood of activity against suspected pathogens based on:

• The identified or suspected infection source 1
• Patient risk factors (immunosuppression, recent healthcare exposure, prior antibiotic use) 1
• Local antimicrobial resistance patterns 1

Source-Specific Considerations

Respiratory tract infections:

• Extend coverage to include atypical organisms (Legionella, Mycoplasma) by adding a macrolide to a β-lactam 1
• For patients with risk factors (corticosteroids, immunosuppressants, purine analogues), consider Pneumocystis coverage with high-dose co-trimoxazole 1

Intra-abdominal or pelvic sepsis:

• Add metronidazole for anaerobic coverage 1

Central line-associated infections:

• Add vancomycin when line infection is suspected, administered through the catheter when possible 1
• Remove the line for tunnel infections, persistent bacteremia despite treatment, atypical mycobacterial infection, or candidemia 1

Skin and soft tissue infections:

• Add vancomycin for suspected MRSA coverage in cellulitis 1
• For fungating malignant wounds unresponsive to vancomycin plus cefepime after 4-7 days, initiate empiric antifungal therapy with amphotericin B (0.3-1 mg/kg/day) or fluconazole (400-600 mg daily) 2

Febrile neutropenia:

• Use monotherapy with an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, or carbapenem) for high-risk patients 1
• Consider oral quinolone plus amoxicillin-clavulanate for low-risk patients without organ failure, pneumonia, or indwelling catheters 1

Suspected fungal infection:

• Initiate antifungal therapy after 3-7 days of persistent fever despite appropriate antibacterials 1
• Use liposomal amphotericin B or an echinocandin (caspofungin) if prior azole exposure or non-albicans Candida colonization 1
• Fluconazole is acceptable if low aspergillosis risk, low local azole resistance rates, and no prior azole prophylaxis 1

Source Control

Drain or debride the infection source whenever possible 1

• Remove any foreign body or device potentially causing infection 1
• For intra-abdominal infections with adequate source control achieved, limit antimicrobial therapy to 4-7 days 1

Reassessment at 48-72 Hours

If Clinically Improving and Afebrile

• Narrow antimicrobial therapy once pathogen identification and sensitivities are established 1
• Consider transition to oral antibiotics in low-risk patients 1
• Discontinue aminoglycosides in high-risk patients on dual therapy if no pathogen identified 1

If Persistent Fever or Clinical Deterioration

• Continue initial therapy if clinically stable 1
• If clinically unstable, seek expert infectious disease consultation immediately 1
• Broaden or rotate antibacterial coverage based on clinical developments 1
• Perform additional imaging (high-resolution chest CT for suspected aspergillosis, abdominal CT for intra-abdominal source) 1
• Consider bronchoalveolar lavage if pulmonary infiltrates present 1
• Initiate antifungal therapy if fever persists beyond 4-7 days despite appropriate antibacterials 1

Duration of Therapy

Continue antimicrobials for a minimum of 48-72 hours beyond clinical improvement or evidence of bacterial eradication 3

• For complicated skin and soft tissue infections: 7-14 days based on clinical response 2
• For intra-abdominal infections with adequate source control: 4-7 days 1
• For demonstrated fungal infections: minimum 14 days or until neutropenia resolves 1
• For Streptococcus pyogenes infections: minimum 10 days to prevent acute rheumatic fever 3

Critical Pitfalls to Avoid

• Never initiate empirical antimicrobials for undefined febrile illness without obtaining blood cultures first, as this is a major cause of culture-negative infections and obscures diagnosis 1
• Do not use the 875 mg amoxicillin dose in patients with GFR <30 mL/min 3
• Avoid oral quinolone therapy in patients who received quinolone prophylaxis 1
• Do not routinely obtain blood cultures after completing therapy in asymptomatic patients 1