Wake Pulm Lower Respiratory Tract Infections

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Lower Respiratory Tract Infections
Overview

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Inflammatory processes involving airways, lung parenchyma, &/or pleural space

Etiologic causes extremely numerous & varied

Wide host spectrum (young → elderly; healthy → immunocompromised)

Inhalation or aspiration of microbes into endobronchial tree major route of infection

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Types of Lower Respiratory Tract Infections

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1. Bronchiolitis

2. Bronchitis

3. Pneumonia

4. Lung abscess

5. Pleural empyema

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Bronchitis

(definition and classification)

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Inflammation of the bronchial mucosa, resulting in a productive cough, with minimal or no fever & no evidence of pneumonia by PE or CXR

Classification:
- Acute bronchitis (Normal hosts)
- Acute exacerbations of chronic bronchitis (Pts with underlying lung disease)

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Acute Bronchitis

Etiology

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Mostly viral (Rhino, flu, paraflu, adeno, RSV)

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Acute Bronchitis

Epidemiology

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Fall, Winter, Spring

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Acute Bronchitis

Clinical features

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Productive cough

low grade fever

Normal lung exam

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Acute Bronchitis

Lab features

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WBC usually normal

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Acute Bronchitis

Diagnosis

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Based on clinical setting & features

occasionally CXR

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Acute Bronchitis

Therapy

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Antibiotics RARELY indicated

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Pneumonia

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Microbial infection of lung parenchyma characterized by:
- Fever
- Dyspnea
- Cough with production of purulent sputum
- Infiltrates on CXR

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Pneumonia Classification

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Community-acquired pneumonia (CAP)

Healthcare-associated pneumonia (HCAP)
- Hospital-acquired pneumonia (HAP)
- Ventilator-associated pneumonia (VAP) = 80-85% of HAP

Pneumonia in the compromised host

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Community Acquired Pneumonia

Epidemiology

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4 million cases/yr in US; annual attack rate 12-15/1000 adults.

15-20% of pts require hospitalization (600,000 pts).

Of those pts hospitalized with CAP, ~10% will die.

Aggregate cost > $4 billion.

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Hospital Acquired Pneumonia

Epidemiology

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Develops in 0.5% to 1.0% of all hospital admissions.

Rates in ICU are 15% to 20% and, for mechanically ventilated pts, 18% to 60%.

For pts with VAP, crude mortality may be 50% to 90%.

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Stepwise approach to diagnosis in the patient with possible pneumonia

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1. Presumptive clinical diagnosis

2. Confirmed clinical diagnosis

3. Presumptive etiologic diagnosis

4. Definitive etiologic diagnosis

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Presumptive clinical diagnosis

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Applicable Sources of Data:
- History (symptoms)
- Findings on lung exam

Important Diagnostic Clues:
- Fever/chills, cough, purulent sputum
- Dullness, rales, bronchial breath sounds

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Confirmed clinical diagnosis

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Applicable Sources of Data:
- Sputum examination
- CXR

Important Diagnostic Clues:
- Gross purulence
- Infiltrate(s)

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Presumptive etiologic diagnosis

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Applicable Sources of Data:
- Epidemiology
- Clinical Settings
- Clinical features
- Sputum stains/smears

Important Diagnostic Clues:
- Nosocomial vs. community
- Normal vs. Abnormal Host
- Typical vs. atypical
- Organism types/morphologies

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Definitive etiologic diagnosis

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Applicable Sources of Data:
- Cultures
- Serologies
- Immunodiagnostics

Important Diagnostic Clues:
- Specific organism(s) implicated

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Approach to dx of Pneumonia

Epidemiologic Background of Disease

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1. Exposure history

2. Travel history

3. Unusual contacts

4. Recent hospitalization or ATB Rx

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Brucella

Pneumonia Epidemiologic Assocations

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Exposure to cattle, goats, pigs

Abattoir worker or veterinarian

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Melioidosis

Pneumonia Epidemiologic Assocations

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SE Asia

Australia

Central/S. America

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Plague

Pneumonia Epidemiologic Assocations

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Exposure to ground squirrels, prairie dogs, rats

Typically in SW

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Psittacosis

Pneumonia Epidemiologic Assocations

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Exposure to birds (parakeets, parrots, turkeys)

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Coccidioidomycosis

Pneumonia Epidemiologic Assocations

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Travel to San Joaquin Valley or arid SW

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Histoplasmosis

Pneumonia Epidemiologic Assocations

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Exposure to bat droppings or bird droppings

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Approach to dx of Pneumonia

Clinical Setting of Disease

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1. Community vs hospital-acquired

2. Age of host

3. Predisposing conditions

4. Host immune deficits

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Common causes of community-acquired pneumonia

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S. pneumoniae

Anaerobes

Legionella

Mycoplasma

Chlamydophilia

Viruses

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Infrequent causes of community-acquired pneumonia

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H. influenzae

K. pneumoniae

Staph. aureus

Enterobacter

E. Coli

Pseudomonas

Nocardia

M. tuberculosis

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Rare causes of community-acquired pneumonia

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Proteus

Salmonella

Yersinia pestis

Strep. pyogenes

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healthcare-associated or hospital-acquired pneumonia is typically caused by ...

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S. aureus and GNRs such as Pseudomonas

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Community-acquired pneumonia is most often due to ...

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selected typical and atypical bacteria (eg, S. pneumoniae, M. pneumoniae, Chlamydophila pneumoniae) or viruses

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Post-influenza

puts patient at risk for this pathogen:

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S. pneumoniae

S. aureus

H. influenzae

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Altered consciousness/ esophageal dysmotility

puts patient at risk for this pathogen:

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Oral flora

(anaerobes/aerobes)

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Alcoholism

puts patient at risk for this pathogen:

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Oral flora

S. pneumoniae

S. aureus

Klebsiella

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Chronic Lung Disease

puts patient at risk for this pathogen:

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S. pneumoniae

H. influenenzae (nontypeable)

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Cystic Fibrosis

puts patient at risk for this pathogen:

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P. aeruginosa

S. aureus

Stenotrophomonas

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Hypogammaglobulinemia

puts patient at risk for this pathogen:

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S. pneumoniae

H. influenzae type B

ENCAPSULATED BACTERIA

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Depressed cell-mediated immunity

puts patient at risk for this pathogen:

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Typical and atypical mycobacteria

Fungi (crypto, endemic mycoses)

Viruses (CNV, VZV, HSV, measles)

Pneumocystis jirovecii

Toxoplasma gondii

INTRACELLULAR PATHOGENS

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Decrease in the number of fulling functional granulocytes

puts patient at risk for this pathogen:

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(Neutrophil deficiencies)

Oral bacterial flora

Enterobacteriaceae

Pseudomonas aeruginosa

Aspergillus

- Pyogenic extracellular bacteria (early)

- Filamentous fungi (late)

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Complement defects

puts patient at risk for this pathogen:

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Streptococcus pneumoniae

H. influenzae type B

ENCAPSULATED BACTERIA

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Approach to dx of pneumonias

Clinical features of disease

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1. Tempo of onset

2. Typical vs atypical sxs/signs

3. Extrapulmonic signs

4. Radiographic pattern

5. Special considerations

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Etiologic Agents of TYPICAL Pneumonias

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Streptococcus pneumoniae

Klebsiella pneumoniae

Haemophilus influenzae

Moraxella catarrahalis

[Legionella pneumophila]

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Etiologic Agents of ATYPICAL Pneumonias

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Mycoplasma pneumoniae

Chlamydophila pneumoniae

Chlamydophila psittaci

Coxiella burnetii

Legionella pneumophila

Non-pneumophila Legionella species

Viruses

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What are the characteristics of TYPICAL Pneumonias

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sudden in onset and are characterized by high spiking fevers, severe rigors, cough productive of purulent sputum, leukocytosis (WBC count >15,000), and lobar infiltrates on CXR.

The prototypical causative pathogen would be S. pneumoniae.

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What organism is suspected with:
Lobar consolidation?

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Pyogenic extracellular bacteria (S. pneumo, GNRs)

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What organism is suspected with:
Interstitial infiltrates?

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Viruses

Mycoplasma

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What organism is suspected with:
Cavitation without air-fluid level?

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TBC

fungi

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What organism is suspected with:
Consolidation + pleural effusion?

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S. pneumo

Staph

GNRs

anaerobes

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What organisms are foung in oropharyngeal colonization (incidence)?

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S. aureus 35-40%

S. pyogenes (GABHS) 0-9%

S. pneumoniae 0-50%

N. meningitidis 0-15%

H. influenzae 5-20%

Gram-negative bacteria 2%

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Sputum

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Potential for Oropharyngeal contamination --> Deeply expectorated specimen not spit!!

Prompt transport to lab

Good Gram stain

Assessment of adequacy of specimen (WBCs vs squames)

Interpretation by experienced observer

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How often is there a confirmation of the cause of pneumonia?

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< 50% of patients

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What are the most useful diagnostic tests for pneumonia?

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the most useful diagnostic tests are sputum & blood cultures and selected antigen screens on urine

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What is the gold standard for clinical diagnosis of pneumonia?

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abnormal CXR

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Laboratory Aspects of Pneumonias

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WBC count: increase WBC with bands (bacterial).

Serologies: 4 x increase. Retrospective. “Difficult to culture” pathogens.

Antigen detection: Encapsulated pathogens. Sputum (false +’s), blood, urine.

DNA probes: Culture identification; limited role for direct probe of clinical specimens.

PCR: Wave of future; evolving.

Skin testing: Tuberculosis.