IDSA Treatment Guidelines for Bacterial and Viral Infections
Core Principle: Antibiotics Target Bacteria, Not Viruses
Antibiotics are indicated exclusively for bacterial infections and have no direct antiviral activity against most viral pathogens, though they may be necessary to treat bacterial co-infections or secondary bacterial infections that complicate viral illnesses. 1, 2
Bacterial Infection Treatment Guidelines
Skin and Soft Tissue Infections
For mild community-acquired skin infections, amoxicillin-clavulanate, dicloxacillin, cefuroxime, or cefalexin provide appropriate Gram-positive coverage. 1
- For MRSA infections, vancomycin dosed at 15-20 mg/kg/dose every 8-12 hours (targeting trough levels of 15-20 mcg/mL) is the standard of care, with linezolid or daptomycin as alternatives. 1
- For impetigo, topical mupirocin is slightly more effective than oral erythromycin, with no significant differences between topical and oral antibiotics overall 1
- Necrotizing infections require immediate surgical debridement plus broad-spectrum antibiotics covering Gram-positives, Gram-negatives, and anaerobes. 1
Intra-Abdominal Infections
Community-acquired complicated intra-abdominal infections require coverage of facultative Gram-negative organisms and anaerobes, with agent selection based on infection severity. 1
- Microbiologic workup should focus on identification and susceptibility testing of facultative and aerobic Gram-negative bacilli 1
- Avoid empiric use of clindamycin, cefotetan, cefoxitin, or quinolones alone in contexts where Bacteroides fragilis is likely, due to substantial resistance patterns. 1
Catheter-Related Bloodstream Infections
For catheter-related bloodstream infections, obtain follow-up blood cultures 2-4 days after initial positive cultures to document clearance of bacteremia. 1
- Catheter removal is mandatory for infections caused by S. aureus, P. aeruginosa, Bacillus species, fungi, or mycobacteria. 1
- For coagulase-negative staphylococci in long-term catheters without these high-risk pathogens, treatment may be attempted with systemic plus antibiotic lock therapy without catheter removal 1
Community-Acquired Pneumonia
For outpatient CAP in healthy adults without comorbidities, amoxicillin 1 g three times daily is the preferred first-line therapy. 3
- For adults with comorbidities, use combination therapy with β-lactam (amoxicillin-clavulanate, cefpodoxime, or cefuroxime) plus macrolide (azithromycin or clarithromycin) or doxycycline. 3
- For hospitalized non-ICU patients, use β-lactam (ampicillin-sulbactam, cefotaxime, ceftriaxone, or ceftaroline) plus macrolide, or respiratory fluoroquinolone monotherapy. 3
- For ICU patients, use β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or respiratory fluoroquinolone. 3
- Avoid macrolide monotherapy in areas where pneumococcal resistance exceeds 25%. 3
- Standard duration is 5-7 days for uncomplicated CAP 3
Bacterial Enteric Infections
HIV-infected persons with Salmonella septicemia require long-term fluoroquinolone therapy (primarily ciprofloxacin) to prevent recurrence. 1
- For travelers, antimicrobial prophylaxis is generally not recommended, but ciprofloxacin 500 mg daily may be considered for immunosuppressed patients traveling to high-risk areas 1
- Empiric therapy with ciprofloxacin 500 mg twice daily for 3-7 days should be provided for traveler's diarrhea 1
Bacterial Respiratory Infections in HIV
Antibiotic chemoprophylaxis may be considered for HIV-infected patients with frequent recurrent serious bacterial respiratory infections, but use cautiously due to risk of drug-resistant organisms. 1
- TMP-SMZ (given for PCP prophylaxis) and clarithromycin or azithromycin (given for MAC prophylaxis) are appropriate for drug-sensitive organisms 1
- In HIV-infected children with recurrent serious bacterial infections, IVIG should be considered, particularly in those with documented antibody deficiency. 1
Viral Infection Management
Primary Principle
Antibiotics have no direct therapeutic effect on viral infections and should not be used for viral illness alone. 4, 5
When Antibiotics Are Indicated During Viral Infections
Antibiotics are appropriate during viral infections only when bacterial co-infection or secondary bacterial infection is documented or highly suspected based on clinical deterioration, persistent fever beyond expected viral course, or specific risk factors. 6, 2
- Approximately half of bacterial sepsis cases occur following acute respiratory viral infections, with viral infections predisposing to bacterial superinfection through enhanced bacterial infiltration and altered immune responses. 6
- In COVID-19 patients, bacterial co-infections occur and may contribute to mortality, but routine empiric antibiotics are not recommended without evidence of bacterial infection. 2
Specific Viral Infections Requiring Antiviral (Not Antibiotic) Therapy
For suspected or confirmed cutaneous or disseminated HSV or VZV infections in immunocompromised patients, intravenous acyclovir should be added to the antimicrobial regimen. 1
COVID-19 Specific Guidance
For hospitalized patients with severe COVID-19 pneumonia, tofacitinib (a JAK inhibitor) plus standard of care reduces the composite outcome of death or respiratory failure, but patients must receive at least prophylactic anticoagulation due to thrombotic risk. 1
- Tofacitinib carries black box warnings for serious infections (including tuberculosis and opportunistic infections), mortality, thrombosis, and malignancy 1
- Patients receiving JAK inhibitors should not receive tocilizumab or other immunomodulators concurrently. 1
Critical Pitfalls to Avoid
Do not use antibiotics prophylactically for viral infections without specific indications, as this promotes antibiotic resistance without clinical benefit. 1, 2
Do not assume all respiratory infections in immunocompromised patients are bacterial—obtain cultures and consider fungal and viral etiologies. 1
Do not delay surgical source control (abscess drainage, catheter removal, debridement) when treating bacterial infections, as antibiotics alone are insufficient. 1
Do not continue antibiotics beyond 5-7 days for uncomplicated bacterial pneumonia in responding patients, as prolonged therapy increases resistance risk without added benefit. 3
Do not use vancomycin for MSSA infections—β-lactam antibiotics are superior and should be used in the absence of allergy. 1