Harrison's Internal Medicine Chapter 126

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Questions and Answers

What primarily triggers the development of pneumonia according to the described model?

  • A macroaspiration event
  • An inflammatory event leading to cytokine release (correct)
  • A sterile space being invaded by microorganisms
  • An epithelial injury due to a bacterial infection

Which bacteria are specifically mentioned as potentially promoted by the inflammatory response in pneumonia?

  • Haemophilus influenzae and Legionella pneumophila
  • Staphylococcus aureus and Escherichia coli
  • Streptococcus pneumoniae and Pseudomonas aeruginosa (correct)
  • Klebsiella pneumoniae and Mycobacterium tuberculosis

What is pneumonia primarily defined as?

  • An infection of the cardiovascular system
  • An infection of the pulmonary parenchyma (correct)
  • An infection of the gastrointestinal tract
  • An infection of the central nervous system

What role do cytokines and chemokines play in pneumonia development?

<p>They enhance the availability of nutrients and support bacterial growth. (B)</p> Signup and view all the answers

Which classification of pneumonia is not considered for those who have been hospitalized?

<p>Aspiration pneumonia (C)</p> Signup and view all the answers

In cases of community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP), which factor is often a trigger?

<p>A viral infection followed by microaspiration (D)</p> Signup and view all the answers

What significant issue is associated with the category of health care–associated pneumonia (HCAP)?

<p>It has increased the use of broad-spectrum antibiotics. (D)</p> Signup and view all the answers

What phenomenon is described as a feedback loop in the context of pneumonia?

<p>The cycle of inflammation leading to bacterial dominance (B)</p> Signup and view all the answers

What is the main outcome of the innate and adaptive immune responses in pneumonia?

<p>They help contain potential pathogens and prevent pneumonia. (B)</p> Signup and view all the answers

Which of the following risk factors is NOT associated with MRSA and Pseudomonas aeruginosa infections?

<p>Being under the age of 18 (B)</p> Signup and view all the answers

How might an aspiration pneumonia specifically be triggered?

<p>By a macroaspiration event that introduces bacteria directly (C)</p> Signup and view all the answers

Why should the use of the HCAP category be discontinued?

<p>It does not reliably predict infection with resistant pathogens. (A)</p> Signup and view all the answers

What defines aspiration pneumonia?

<p>Infection due to macroaspiration of oropharyngeal or gastric contents (C)</p> Signup and view all the answers

Which of the following describes pneumonia in relation to microorganisms?

<p>It arises from multiple mechanisms including inflammation and feedback loops. (D)</p> Signup and view all the answers

Which type of pneumonia has been misdiagnosed and underestimated despite its significant morbidity and mortality?

<p>Pneumonia (A)</p> Signup and view all the answers

Which of the following is most relevant when assessing pneumonia risk factors?

<p>Individual risk factors for resistant organisms (A)</p> Signup and view all the answers

Which virus is known to complicate influenza virus infection?

<p>S.aureus (B)</p> Signup and view all the answers

What is a potential serious consequence of infections caused by MRSA?

<p>Necrotizing pneumonia (A)</p> Signup and view all the answers

Which of the following is associated with aspiration pneumonia in individuals with poor dentition?

<p>Anaerobes (C)</p> Signup and view all the answers

What are community-associated MRSA strains capable of doing?

<p>Infect healthy individuals with no healthcare association (B)</p> Signup and view all the answers

In which cases is a specific etiology often difficult to determine?

<p>In numerous pneumonia cases (D)</p> Signup and view all the answers

Which type of pneumonia is associated with those typically acquiring it in a hospital setting?

<p>Healthcare-associated pneumonia (HAP) (C)</p> Signup and view all the answers

What is the estimated yearly cost of community-acquired pneumonia (CAP)?

<p>$17 billion (D)</p> Signup and view all the answers

What percentage of hospitalized CAP patients are readmitted within one month of discharge?

<p>18 (D)</p> Signup and view all the answers

Which of the following is NOT a risk factor for community-acquired pneumonia?

<p>Age &lt; 70 years (B)</p> Signup and view all the answers

What is a specific risk factor for pneumonia caused by Legionella?

<p>Severe renal disease (A)</p> Signup and view all the answers

How many cases of CAP occur per 1000 persons per year among adults?

<p>16–23 cases (D)</p> Signup and view all the answers

Which patient history increases the likelihood of CA-MRSA pneumonia?

<p>Skin colonization or infection with CA-MRSA (C)</p> Signup and view all the answers

Which of these factors is associated with increased risk for pneumococcal pneumonia?

<p>Seizure disorders (C)</p> Signup and view all the answers

What clinical manifestation could indicate worsening severity of pneumonia?

<p>High fever (A)</p> Signup and view all the answers

What are some typical symptoms that are compatible with a diagnosis of Community-Acquired Pneumonia (CAP)?

<p>Cough and sputum production (B)</p> Signup and view all the answers

What is the sensitivity of physical examination findings in diagnosing CAP?

<p>58% (C)</p> Signup and view all the answers

Why might chest radiography be necessary in the diagnosis of CAP?

<p>To differentiate CAP from other conditions (D)</p> Signup and view all the answers

What findings on a chest radiograph may indicate increased severity of pneumonia?

<p>Cavitation or multilobar involvement (D)</p> Signup and view all the answers

When is clinical and radiologic assessment usually sufficient for treatment of pneumonia?

<p>For outpatients before treatment is started (C)</p> Signup and view all the answers

Which rapid test can influence initial management decisions in suspected pneumonia cases?

<p>Rapid influenza test (B)</p> Signup and view all the answers

What does a CT scan help diagnose in cases of suspected pneumonia?

<p>Loculated effusion or cavitary cases (A)</p> Signup and view all the answers

Which of the following is NOT a reliable indicator for the etiologic diagnosis of pneumonia?

<p>Family history of illness (C)</p> Signup and view all the answers

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Study Notes

Definition of Pneumonia

  • Pneumonia is an infection of the pulmonary parenchyma, linked to high morbidity and mortality rates despite often being misdiagnosed and mistreated.
  • Common classifications include community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP).
  • Health care–associated pneumonia (HCAP) includes cases with multidrug-resistant (MDR) pathogens, typically linked to HAP, but its predictive value for resistant infections is poor.
  • Risk factors for infection with MRSA and Pseudomonas aeruginosa encompass previous isolation of the organism, hospitalization, and antibiotic treatment within the past 90 days.
  • Aspiration pneumonia occurs due to macroaspiration of oropharyngeal or gastric contents and exists along a continuum between CAP and HAP.

Pathogenesis

  • Pneumonia results from inflammatory events causing epithelial or endothelial injury, leading to the release of cytokines, chemokines, and catecholamines that promote bacterial growth.
  • Inflammatory responses can enhance nutrient availability and bacterial growth, potentially creating positive feedback loops that exacerbate the infection.
  • Community-acquired pneumonia may be triggered by viral infections along with microaspiration of oropharyngeal organisms.

Risk Factors

  • CAP causes over 55,000 deaths annually and contributes to 1.2 million hospitalizations, with 70% of patients treated as outpatients and 30% hospitalized.
  • The incidence rate among adults is approximately 16–23 cases per 1,000 persons per year, peaking at age extremes.
  • Risk factors include alcoholism, asthma, immunosuppression, and age over 70 years. In the elderly, decreased cough/gag reflexes heighten pneumonia risk.
  • Specific risk factors for pneumococcal pneumonia include dementia, heart failure, COPD, and HIV infection.
  • CA-MRSA pneumonia risks are higher in those with skin colonization or following viral infections, while Enterobacteriaceae targets patients with recent hospitalization or antibiotic use.

Clinical Manifestations

  • Symptoms of pneumonia range from mild to severe, including cough, fever, sputum production, and dyspnea, necessitating a thorough patient history for accurate diagnosis.
  • Chest radiography is critical for confirming CAP, with findings that may indicate severity (e.g., cavitation, multilobar disease) and occasionally suggest specific pathogens.
  • Radiographic results may also highlight conditions like S.aureus infections (pneumatoceles) or upper-lobe cavitating lesions due to tuberculosis.

Diagnosis and Treatment

  • Diagnosis often requires comprehensive clinical assessment and radiologic evaluation, as the sensitivity and specificity of physical exams for pneumonia are relatively low (58% and 67% respectively).
  • Rapid point-of-care tests, like those for influenza, can influence treatment decisions by prompting targeted interventions and secondary prevention.
  • Laboratory results are typically not available in time to inform initial management for outpatients; thus, clinical and radiologic findings drive early treatment.

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