L8 Goodlet Community-Acquired Pneumonia Information

Community-Acquired Pneumonia Information

Instructor Information

  • Kellie J. Goodlet, PharmD, FCCP, BCIDP, BCPS, BCTXP
    Associate Professor of Pharmacy Practice
    Midwestern University - Glendale

Objectives

  • Understand basic pathophysiology of community-acquired pneumonia (CAP) and risk factors for infection

  • Identify patient signs/symptoms and clinical tests used to support a diagnosis of CAP

  • List the etiologic organisms implicated in CAP

  • Recommend an appropriate antibiotic treatment regimen based on bacterial resistance patterns and patient-specific factors

  • Counsel patients on what to expect with treatment, including medication adverse effects

Patient Case: GR

  • Patient Profile: 49-year-old male admitted with chief complaint of poor review on risotto

  • Past Medical History:

    • Psoriasis, treated with infliximab

    • Asplenia due to a “paring knife incident”

    • Hypertension

  • Signs/Symptoms:

    • Difficulty breathing

    • Shortness of breath (SOB)

    • Subjective fever

    • Chills

    • Productive cough

  • Physical Exam:

    • Alert & Oriented (A&O)

    • Decreased breath sounds on right side (R > L)

    • Rales/crackles in the right lower lobe

  • Social History:

    • Nonsmoker

    • Consumes 1-2 glasses of wine daily

  • Vital Signs:

    • Temperature: 101.5°F

    • Heart Rate: 110 beats per minute

    • Blood Pressure: 125/72 mmHg

    • Respiratory Rate: 28 breaths per minute

  • Laboratory Results:

    • CBC

    • BMP

Definition of Community-Acquired Pneumonia (CAP)

  • Defined as an acute lower respiratory tract infection occurring in patients who do not meet the criteria for:

    • Hospital-acquired pneumonia (HAP)

    • Ventilator-associated pneumonia (VAP)

  • Patients present with pneumonia from the community.

  • Note: “HCAP” (healthcare-associated pneumonia) is no longer considered a distinct clinical entity.

Pathogen Transmission

  • Major Routes:

    • Aspiration:

    • Oropharyngeal flora

    • Gastric contents

    • Airborne:

    • Mycobacterium tuberculosis

    • Fungi

    • Legionella spp.

    • Viruses

    • Hematogenous Spread:

    • Endocarditis

    • Intravenous (IV) catheter

    • Septic joint

    • Trauma/Surgery

    • Direct Extension from Contiguous Sites:

    • Entamoeba histolytica

    • Influenza, RSV

Host Defenses Against Pneumonia

  • Upper Respiratory Defenses:

    • Anatomical Structures: Swallowing and expulsion of particles

    • Nasal Hair: Traps and expels pathogens

    • Normal Flora: Outcompete pathogens

    • Mucus: Acts as a protective barrier, enhanced by ciliary movement

  • Lower Respiratory Defenses:

    • Anatomical Structure: Sharp angles of bronchi preventing particle entry

    • Mucociliary Apparatus: Cilia and mucus trap and expel pathogens

    • Antibodies: Primarily IgA, IgM, IgG present in the respiratory tract

    • Complement Proteins and Proteases: Aid in pathogen clearance

    • Alveolar Macrophages: Phagocytose and destroy pathogens

Risk Factors for Community-Acquired Pneumonia

  • Increased Age:

    • Adults over 65 years of age

  • Existing Respiratory Conditions:

    • Asthma

    • Chronic Obstructive Pulmonary Disease (COPD)

  • Lifestyle Factors:

    • Smoking

    • Alcoholism

  • Comorbid Diseases:

    • Congestive Heart Failure (CHF)

    • Diabetes Mellitus

    • Chronic Liver Disease

  • Immunosuppression:

    • HIV

    • Organ Transplant

    • Neutropenia

    • Asplenia

  • Other Factors:

    • Dysphagia

    • Epilepsy

    • Malnutrition or being underweight

    • Regular contact with children

    • Medications:

    • Corticosteroids

    • Antipsychotics

    • Immunosuppressants

    • Proton Pump Inhibitors (PPIs)

      • pH = 2 suppresses bacterial colonization

      • pH = 7 increases bacterial colonization, increasing aspiration risk

Diagnosis: Clinical Manifestations of CAP

  • Common Findings:

    • Elevated white blood cell count (WBC): >

    • 12,000 cells/mm³

    • Presence of a "left shift" (>10% bands)

    • Poor oxygen saturation as measured by pulse oximetry

    • Lung Auscultation:

    • Crackles (rales)

    • Diminished breath sounds

  • Associated Symptoms:

    • General signs of infection

    • Respiratory signs and symptoms

    • Other nonspecific symptoms

Diagnosis: Radiographic Findings

  • Chest X-ray (CXR) Findings:

    • Evidence of lung inflammation with consolidation

    • New or worsening consolidation

    • Diagnostic constraints: A "junk-y" CXR is not diagnostic and requires ruling out other conditions (CHF, COPD, etc.)

Diagnosis: Cultures and Other Laboratory Tests

  • Blood Cultures: 1-20% positive in CAP cases

  • Sputum and Respiratory Cultures:

    • Smear with Gram stain

    • Bronchoscopy/BAL

    • Tracheal aspirate

    • Brush border samples

  • Serology Tests: for pathogens like Mycoplasma and Chlamydia, including viral agents

  • Urinary Antigen Tests:

    • Legionella pneumophila

    • Streptococcus pneumoniae

  • Respiratory PCR Panel Tests

Diagnosis: Sputum Culture

  • Common Usage:

    • Sputum is a typical specimen type for determining pathogens

  • Quality Control Measures:

    • Expect PMNs (polymorphonuclear cells) indicating infection presence

    • Should show few or no squamous epithelial cells, excessive numbers can lead to rejection of sample

Common Pathogens in Community-Acquired Pneumonia

  • Typical Respiratory Pathogens:

    • Streptococcus pneumoniae

    • Haemophilus influenzae

    • Moraxella catarrhalis

    • Staphylococcus aureus (MSSA)

    • Legionella pneumophila

    • Chlamydia pneumoniae

    • Mycoplasma pneumoniae

  • Notable Points:

    • Streptococcus pneumoniae is the most common bacterium associated with CAP

    • Emphasize memorization of six key bacteria

Streptococcus pneumoniae

  • Characteristics:

    • Gram-positive cocci (groups in pairs or short chains)

    • Alpha-hemolytic encapsulated

  • Clinical Relevance:

    • Most common clinical presentation of pneumonia

    • Responsible for up to 400,000 hospitalizations annually in the U.S.

    • Leading causative pathogen in up to 36% of adult CAP cases

    • Case-fatality rate: 5-7%, increases up to 50% among elderly patients

Resistance Patterns of Streptococcus pneumoniae

  • β-Lactam Resistance:

    • Alteration in penicillin-binding proteins (PBPs): creates a “square peg in a round hole” problem affecting drug efficacy

Implications for Therapy

  • Study Observations:

    • A multi-national study evaluated the impact of discordant β-lactam therapy on mortality among patients with S. pneumoniae bacteremia

    • Study Setup:

    • Day 0: Blood culture positive for S. pneumoniae → initiate β-lactam therapy

    • Day 2: Categorize therapy

    • Day 14: Assess mortality rates

  • Findings:

    • 793 S. pneumoniae isolates were evaluated

    • Non-susceptibility to penicillin (PCN) observed in approximately 25% of cases

    • 119 isolates were intermediate, 76 were resistant, and 13 were highly resistant

    • 398 patients received β-lactam monotherapy, with 93.1% receiving concordant therapy

    • Rates of treatment failure correlated with factors like immunosuppression and prior antibiotic therapy

Overcoming β-Lactam Resistance

  • Therapeutic Strategies:

    • Administering adequate concentrations may help to force the drug through altered PBPs

    • Recap that if S. pneumoniae is sensitive to all β-lactams (except cefuroxime), therapy may proceed accordingly

Resistance to Macrolides in S. pneumoniae

  • Surveillance Insights from a 6-Year CDC Study:

    • Demonstrated significant resistance rates to macrolides:

    • Erythromycin: 35.3% resistant

    • Clarithromycin: 35.2% resistant

    • Azithromycin: 35.2% resistant

    • Resistance linked to treatment failures across all patient age groups, highest rates in children aged 0-2 years

Fluoroquinolone Resistance in S. pneumoniae

  • Current Resistance Rates:

    • Fluoroquinolone (FQ) resistance remains rare (~1-2% resistant)

    • When present, resistance may worsen patient outcomes

  • Patient Study Indicators:

    • Linkage of levofloxacin resistance to 30-day mortality findings in observational cohorts

Haemophilus influenzae and Moraxella catarrhalis

  • Microbiological Characteristics:

    • H. influenzae: Gram-negative coccobacillus

    • M. catarrhalis: Gram-negative diplococcus

  • Resistance Considerations:

    • Approximately 20-30% of H. influenzae and 95% of M. catarrhalis are β-lactamase positive

    • Recommendations: Not to use standard penicillin empiricism but rather β-lactamase inhibitors or advanced cephalosporins

Atypical Bacteria in CAP

  • Definition and Treatment:

    • Atypicals refer to bacteria that cannot be cultured using standard media or visualized using Gram staining

    • Present with intrinsic resistance to cell wall-active antibiotics requiring designated antibiotic classes, including fluoroquinolones, macrolides, and tetracyclines

  • Identification Issues:

    • Cannot predict atypical PNA based on clinical or radiographic features alone

Treatment: Determining Site of Care

  • Approaches:

    • Treatment settings can vary from outpatient to inpatient care (ward or ICU)

  • Pneumonia Scores:

    • Pneumonia Severity Index: Guideline-preferred

    • CURB-65

Outpatient CAP Therapy Summary

  • Antibiotic Recommendations:

    • Respiratory Fluoroquinolone:

    • Levofloxacin 750 mg PO daily

    • Moxifloxacin 400 mg PO daily

    • OR

    • β-Lactam:

    • Amoxicillin/clavulanate 2 g PO BID

    • Cefpodoxime 200 mg PO BID

    • Azithromycin 500 mg PO daily for coverage of resistant S.pneumo

    • Doxycycline 100 mg PO BID

  • Considerations for Severe Cases:

    • Previous hospitalization or prior antibiotics increase risk for drug-resistant organisms

Inpatient CAP Therapy Summary

  • General Strategy:

    • Aim to initiate β-lactam-containing regimens for CAP presenting with severe symptoms.

  • Example Regimens:

    • Ceftriaxone 1 g IV Q24H

    • Ampicillin/sulbactam 3 g IV Q6H

    • Alongside azithromycin or respiratory fluoroquinolone depending on antibiotic allergies

Adjunctive Corticosteroids for CAP

  • Rationale:

    • Addressing inflammation due to pathogens contributes to CAP morbidity/mortality

  • Guideline Recommendations (2025 ATS):

    • Severe CAP:

    • Suggested systemic corticosteroids

    • Non-severe CAP:

    • Recommended against systemic corticosteroids

Administration Route: IV vs. PO

  • Oral vs. IV Administration:

    • Use oral administration for antibiotics with adequate bioavailability in hemodynamically stable patients

    • IV preferred for less bioavailable antibiotics, transitioning to oral for step-down therapy as patient clinically improves

Specifics on Coverage for Pseudomonas and MRSA

  • Coverage Considerations:

    • Routine empiric coverage is not recommended without prior history of Pseudomonas or MRSA pneumonia

    • Strategy to escalate based on identified risk factors:

    • Non-severe CAP: No routine coverage

    • Severe CAP: Follow guidelines based on risk factors present

Culture Follow-up and Management

  • Daily Culture Review:

    • Positive blood cultures indicate pathogens but negative results do not rule out infection

  • De-escalation Strategy:

    • Adjust antibiotic therapy based on culture results and clinical progress, including atypical organism coverage

Procalcitonin (PCT) as a Biomarker

  • Definition:

    • PCT is an acute-phase reactant specific to bacterial infections

    • Rapidly rises with bacterial infection and drops upon control of the infection

    • May aid in guiding antibiotic initiation or discontinuation

Follow-Up Management for CAP

  • Clinical Response Monitoring:

    • Initial clinical response should extend over a total of 3-5 days of active antibiotics

    • Expect improvements by days 2-3 post-therapy initiation

    • Clarify that a CXR may still show infiltrate post-treatment resolution

Adverse Effects of Common CAP Antibiotics

  • Macrolides & Doxycycline:

    • Macrolides: Taste perversion, ototoxicity, hepatotoxicity, QTc prolongation

    • Doxycycline: Photosensitivity, esophageal irritation, and teeth/bone accumulation with prolonged use

  • Fluoroquinolones:

    • Monitor for significant toxicities including:

    • Tendon rupture risks with advanced age and steroid use, QT prolongation, hypoglycemia, and central nervous system effects

Review of Patient Case GR and Treatment Decisions

  • CXR showed right lower lobe infiltrate, started on empiric antibiotics (Ceftriaxone 1 g IV Q24H, Doxycycline 100 mg PO BID)

    • Which organism most likely causing GR’s pneumonia?

    • Likely to be identified from sputum as Gram(+) diplococcus

Summary of Community-Acquired Pneumonia Management

  • CAP is a diagnosis based on clinical symptoms correlated with radiographic findings:

    • Infiltrate presence on CXR or positive sputum screening not definitive without symptoms

  • ABX regimens must actively cover six key pathogens and address resistance concerns for effective treatment outcomes:

    • Ensure thorough assessment to adapt therapy as needed based on pathogen profiles and patient health status.

Notable References

  • Guidelines:

    • 2025 Community-Acquired Pneumonia (ATS)

    • 2019 Community-Acquired Pneumonia (ATS, IDSA)

  • Primary Literature:

    • Procalcitonin systematic review and its importance

    • Assessing Doxycycline’s role in reducing C. difficile infectious risk

Questions Section

  • End remarks suggest no cure for the common cold but possibly a pneumonia diagnosis for patients, prompting further dialogue toward treatment decisions.