What are the guidelines for antibiotic (AB) use in an internal medicine ward for patients with various infections, including pneumonia and urinary tract infections, considering factors such as suspected pathogens, local resistance patterns, allergy history, and impaired renal function?

Antibiotic Use Guidelines for Internal Medicine Ward

Core Principles of Antibiotic Stewardship

Appropriate antibiotic use means prescribing the right antibiotic at the right dose for the right duration for a specific condition, with shorter courses preferred when clinically safe and evidence-supported. 1

Key Stewardship Concepts

• Avoid defaulting to 10-day courses regardless of condition, as this is a common error that increases resistance and adverse events without improving outcomes 1
• Prolonged antibiotic use beyond symptom resolution does not reduce resistance—it actually increases it through selection pressure 1
• Shorter antibiotic courses show similar clinical outcomes with fewer drug-related adverse events compared to longer courses 1
• At least 30% of antibiotic courses in the United States are unnecessary, particularly for bronchitis and sinusitis 1
• Antimicrobial overuse causes adverse events in up to 20% of patients, ranging from allergic reactions to Clostridioides difficile infections 1

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Community-Acquired Pneumonia (CAP)

Outpatient Treatment - Healthy Adults Without Comorbidities

Use amoxicillin 1 gram orally three times daily for 5-7 days as first-line therapy. 2, 3

• Alternative: Doxycycline 100 mg orally twice daily for 5-7 days 2, 3
• Macrolides (azithromycin, clarithromycin) should ONLY be used when local pneumococcal macrolide resistance is documented <25% 2, 3
• Never use macrolide monotherapy in areas with ≥25% resistance—this leads to treatment failure and breakthrough bacteremia 2, 3

Outpatient Treatment - Adults With Comorbidities

Use combination therapy: amoxicillin-clavulanate 875/125 mg twice daily PLUS azithromycin 500 mg day 1, then 250 mg daily for 5-7 days total. 2, 3

• Comorbidities requiring combination therapy include: COPD, diabetes, chronic heart/lung/liver/renal disease, alcoholism, malignancy, asplenia, immunosuppression 2, 3
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily OR moxifloxacin 400 mg daily) for 5 days 2, 3
• Critical: If patient used antibiotics within past 90 days, select agent from different antibiotic class to reduce resistance risk 2, 3

Inpatient Treatment - Non-ICU

Use ceftriaxone 1-2 grams IV daily PLUS azithromycin 500 mg daily (IV or oral). 2, 3

• Equally effective alternative: Levofloxacin 750 mg IV daily OR moxifloxacin 400 mg IV daily as monotherapy 2, 3
• Administer first antibiotic dose in the emergency department—delayed administration beyond 8 hours increases 30-day mortality by 20-30% 2, 3
• Obtain blood cultures and sputum cultures before initiating antibiotics in all hospitalized patients 2, 3
• Switch to oral therapy when patient is hemodynamically stable, clinically improving, able to take oral medications, and has normal GI function—typically by day 2-3 2, 3

Inpatient Treatment - ICU/Severe CAP

Mandatory combination therapy: ceftriaxone 2 grams IV daily PLUS azithromycin 500 mg IV daily OR respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily). 2, 3

• Monotherapy is inadequate for severe disease 2, 3
• For Pseudomonas risk factors (structural lung disease, recent hospitalization with IV antibiotics within 90 days, prior P. aeruginosa isolation): Use antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg IV daily 2, 3
• For MRSA risk factors (prior MRSA infection, recent hospitalization with IV antibiotics, post-influenza pneumonia, cavitary infiltrates): Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours 2, 3

Duration of CAP Treatment

Treat for minimum of 5 days and until patient is afebrile for 48-72 hours with no more than one sign of clinical instability. 1, 2, 3

• Typical duration for uncomplicated CAP: 5-7 days 1, 2, 3
• Extend to 14-21 days ONLY for: Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 2, 3
• Do not extend therapy beyond 7 days in responding patients without specific indications—this increases resistance without improving outcomes 2, 3

Clinical Stability Criteria for Discontinuation

Patient must meet ALL of the following:

• Temperature ≤37.8°C (100°F) 2
• Heart rate ≤100 beats/min 2
• Respiratory rate ≤24 breaths/min 2
• Systolic blood pressure ≥90 mmHg 2
• Oxygen saturation ≥90% on room air 2
• Ability to maintain oral intake 2
• Normal mental status 2

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COPD Exacerbation with Bacterial Infection

Limit antibiotic treatment to 5 days when managing COPD exacerbations with clinical signs of bacterial infection. 1

• Clinical signs of bacterial infection: Increased sputum purulence PLUS increased dyspnea and/or increased sputum volume 1
• Do not extend beyond 5 days even if patient has underlying COPD 1
• If pneumonia is confirmed (not just exacerbation), follow CAP guidelines above 2

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Urinary Tract Infections (UTIs)

Uncomplicated Cystitis in Women

Use short-course antibiotics with one of the following regimens: 1

• Nitrofurantoin: 5 days 1
• Trimethoprim-sulfamethoxazole (TMP-SMZ): 3 days 1
• Fosfomycin: Single dose 1

Uncomplicated Pyelonephritis

Base treatment on antibiotic susceptibility: 1

• Fluoroquinolones: 5-7 days 1
• TMP-SMZ: 14 days 1
• Choice depends on local resistance patterns and susceptibility testing 1

Renal Impairment Considerations

• Loading doses of antimicrobials are NOT affected by renal function—always give full loading dose for severe infections 2
• Maintenance dosing and frequency must be adjusted based on creatinine clearance 2
• Failure to adjust maintenance doses leads to drug accumulation and toxicity 2

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Cellulitis (Nonpurulent)

Use 5-6 day course of antibiotics active against streptococci, particularly for patients able to self-monitor with close primary care follow-up. 1

• This applies to nonpurulent cellulitis without purulent drainage or abscess 1
• Shorter courses are as effective as traditional 10-14 day regimens 1

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Critical Implementation Strategies

Facility-Specific Guidelines

• Develop clinical practice guidelines for common infections based on local epidemiology and resistance patterns 1
• Incorporate guidelines into electronic order sets with dissemination strategy 1
• Monitor antibiotic utilization and effectiveness at the local level 4, 5

Educational Approaches

• Combine education with other stewardship strategies (prospective audit and feedback) for sustained improvement 1
• Education alone results in non-sustainable improvements—must be paired with active interventions 1

Diagnostic Stewardship

• Obtain blood and sputum cultures before initiating antibiotics in all hospitalized patients with suspected pneumonia 2, 3
• Use urinary antigen testing for Legionella pneumophila in severe CAP or ICU patients 3
• Rapid diagnostics can address fear of uncovered pathogens and support narrowing therapy 6

De-escalation Strategy

• Reassess antibiotic regimen at 48-72 hours based on clinical response and culture results 2, 3
• If patient not improving with appropriate antibiotics, reassess for other causes rather than defaulting to longer duration 1
• Narrow spectrum based on culture results when available 6, 7

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Common Pitfalls to Avoid

Pneumonia-Specific Pitfalls

• Never use macrolide monotherapy in hospitalized patients—provides inadequate coverage for typical bacterial pathogens 2, 3
• Avoid cefuroxime, cefepime, or carbapenems as first-line empiric therapy unless specific risk factors for Pseudomonas or MRSA present 2, 3
• Do not delay first antibiotic dose—administer in emergency department for hospitalized patients 2, 3
• Avoid indiscriminate fluoroquinolone use in uncomplicated outpatient CAP due to resistance concerns and serious adverse events (tendinopathy, peripheral neuropathy, CNS effects) 2, 3

General Stewardship Pitfalls

• Do not automatically extend therapy beyond clinical stability—longer courses increase resistance without benefit 1
• Avoid prescribing antibiotics "to prevent resistance"—prolonged use actually causes resistance through selection pressure 1
• Do not ignore recent antibiotic exposure—select different antibiotic class if used within past 90 days 2, 3
• Avoid broad-spectrum antibiotics without documented risk factors for resistant organisms 2, 3

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Special Populations

Penicillin-Allergic Patients

• For CAP: Use respiratory fluoroquinolone (levofloxacin or moxifloxacin) 2, 3
• For severe CAP with cephalosporin allergy: Use respiratory fluoroquinolone PLUS aztreonam 2, 3

Elderly or Debilitated Patients

• Classify as having comorbidities—use combination therapy even in outpatient setting 2, 3
• Lower threshold for hospitalization using PSI or CURB-65 score 2, 3
• Assess for volume depletion and consider IV fluids 2

Patients on Immunosuppressive Therapy

• Tyrosine kinase inhibitors or other immunosuppression constitutes comorbidity requiring combination therapy 2
• Do not automatically escalate to broad-spectrum without documented risk factors 2
• Obtain cultures before initiating antibiotics to allow targeted therapy 2, 3

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Monitoring and Follow-Up

Inpatient Monitoring

• Assess clinical response at day 2-3 (fever resolution, lack of radiographic progression) 1, 2
• Monitor temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation at least twice daily 2
• If no improvement by day 2-3: Obtain repeat chest radiograph, CRP, white cell count, additional microbiological specimens 2

Outpatient Follow-Up

• Clinical review at 48 hours or sooner if clinically indicated 2, 3
• Schedule 6-week follow-up for all hospitalized patients 2, 3
• Chest radiograph at 6 weeks ONLY for: persistent symptoms, physical signs, or high risk for malignancy (smokers, age >50 years) 2, 3