Pulmonary infections (Pneumonia)

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Pulmonary infections (Pneumonia)

• Pneumonia can be very broadly defined as any
  infection in the lung

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Pulmonary infections

• Respiratory tract infections are more frequent
  than infections of any other organ and account
  for the largest number of workdays lost in the
  general population, why?
• The epithelium of the lung is exposed to liters
  of contaminated air
• Nasopharyngeal flora are aspirated during sleep
• Underlying lung diseases render the lung
  parenchyma vulnerable to virulent organism.

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Pulmonary infections

• Upper respiratory tract infection are common,
  caused mainly by viruses (common cold,
  pharyngitis)
• Infection of the lung by virus, mycoplasma,
  bacteria and fungi account for enormous amount of
  morbidity and mortality.

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Pathogenesis of pneumonia

• Each day, the respiratory tract is exposed to
  more
• than 10,000 liters of air containing hazardous
  dust,
• Chemicals and microorganisms.
• Particle gt 10 mm deposited in nose.
• Particle 3-10 mm impacted in trachea and bronchi.
• Particle 1-3 mm (bacteria) deposited in terminal
  airways and alveoli.
• Smaller particles lt 1 mm may remain suspended in
  air.
• Normal lung is free from bacteria.

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Pathogenesis of pneumonia

• Pneumonia can result whenever
• defense mechanisms are impaired
• the resistance of the host in general is lowered.

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Pulmonary host defenses

• Upper airways
• Nasopharynx
• Oropharynx

Nasal hair, turbinates, mucociliary apparatus,
IgA secretion
Saliva, sloughing of epithelium, local complement
production, interference from resident flora

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Pulmonary host defenses

• Upper airways
• Conducting airways (trachea and bronchi)

Cough, epiglottic reflexes, sharp angled branches
of the airways, mucociliary apparatus,
Immunoglobulin (IgM, IgG, and IgA) secretion
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Pulmonary host defenses

• Upper airways
• Conducting airways (trachea and bronchi)
• Lower respiratory tract

Alveolar lining fluid ( surfactant,
immunoglobulin, complement and fibronectin),
Cytokines (IL-1, TNF), alveolar macrophages,
polymorphonuclear leukocyte, cell mediated
immunity
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Pathogenesis of pneumonia

• Impaired defense mechanisms
• Loss or suppression of the cough reflex,
• as a result of coma, anesthesia, neuromuscular
  disorders, drugs, or chest pain.
• Injury to the mucociliary apparatus,
• by either impairment of ciliary function or
  destruction of ciliated epithelium e.g. cigarette
  smoke, inhalation of hot or corrosive gases,
  viral diseases, or genetic disturbances
• Interference with the phagocytic or bactericidal
  action of alveolar macrophages
• by alcohol, tobacco smoke, anoxia, or oxygen
  intoxication
• Pulmonary congestion and edema
• Accumulation of secretions
• e.g. cystic fibrosis and bronchial
  obstruction
• Defect in innate immunity
• Include neutrophil, complement, humoral and cell
  mediated immune defects

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Pathogenesis of pneumonia

• Defects in innate immunity (including neutrophil
  and complement defects) and humoral
  immunodeficiency lead to an increased incidence
  of infections with pyogenic bacteria.
• Cell-mediated immune defects lead to increased
  infections with intracellular microbes such as
  mycobacteria ,herpesviruses and Pneumocystis
  jiroveci.
• Several exogenous aspects of lifestyle interfere
  with host immune defense mechanisms and
  facilitate infections.
• Examples
• cigarette smoke compromises mucociliary clearance
  and pulmonary macrophage activity
• alcohol not only impairs cough and epiglottic
  reflexes, thereby increasing the risk of
  aspiration, but also interferes with neutrophil
  mobilization and chemotaxis.

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Pathogenesis of pneumonia

• General factors that affect resistance
• chronic diseases
• immunologic deficiency
• treatment with immunosuppressive agents
• leukopenia
• unusually virulent infections.

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Pathogenesis of pneumonia

• One type of pneumonia sometimes predisposes to
  another, especially in debilitated patients.
• Portal of entry for most pneumonias is the
  respiratory tract, hematogenous spread from one
  organ to other organs can occur.
• Many patients with chronic diseases acquire
  terminal pneumonias while hospitalized
  (nosocomial infection).

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Pathogenesis of pneumonia

• Pneumonia can be acute or chronic
• The histologic spectrum may vary from
  fibrinopurulent alveolar exudate to mononuclear
  interstitial infiltrates to granulomatous
  inflammation

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Bacterial pneumonia

• Bacterial invasion of lung parenchyma evoke
  exudation of fibrinpurulent fluid in the alveoli
  and solidification.
• Classification may be made according to causative
  agent or gross anatomic distribution of the
  disease.

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Anatomic distribution of pneumonia

• Bronchopneumonia
• -Represent an extension from preexisting
• bronchitis or bronchiolitis.
• -Extremely common tends to occur in two
• extremes of life.
• Lobar pneumonia
• - Acute bacterial infection of a large
• portion of a lobe or entire lobe.
• -Classic lobar pneumonia is now infrequent.

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Lobar pneumonia - 90-95 are caused by
pneumococci (type 1,3,7 2) - Rare
agents K. pneumoniae staphylococci -
streptococci H. influenzae - Pseudomonas and
Proteus

• Bronchopneumonia
• most common agents are
• Streptococcus pneumonea,
• Haemophilus Influenza,
• Pseudomonas Aeroginosa
• coliform bacteria.

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• Overlap of the two patterns often occur.
• Identification of clinical pattern is more
  important.

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Etiology of pneumonia Community-Acquired Acute
Pneumonia

• Bacterial
• Can follows viral URT infection
• Sudden onset of high fever, chills, pleuritic
  chest pain and productive cough, may be with
  hemoptysis
• Streptococcus pneumoniae is the most common cause
  of Community-Acquired Acute Pneumonia
• Frequently affected pt. are those with
• Underlying chronic disease e.g. DM, COPD, and
  congestive heart failure
• Congenital or acquired immune deficiency
• Decreased or absent splenic function
• Other causative organisms are
• Haemophilus influenzae, Moraxella catarrhalis,
  Staphylococcus aureus, Legionella pneumophila,
  Enterobacteriaceae (Klebsiella pneumoniae) and
  Pseudomonas spp.

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Staphylococcus aureus

• S. aureus is an important cause of secondary
  bacterial pneumonia in children and healthy
  adults after viral respiratory illnesses (e.g.,
  measles in children and influenza in both
  children and adults).
• Staphylococcal pneumonia is associated with a
  high incidence of complications, such as lung
  abscess and empyema.
• Staphylococcal pneumonia occurring in association
  with right-sided staphylococcal endocarditis is a
  serious complication of intravenous drug abuse.
• It is also an important cause of nosocomial
  pneumonia

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Haemophilus influenzaeBoth

• encapsulated and unencapsulated forms are
  important causes of community-acquired
  pneumonias.
• The former can cause a particularly
  life-threatening form of pneumonia in children,
  often following a respiratory viral infection.
• Adults at risk for developing infections include
  those with chronic pulmonary diseases such as
  chronic bronchitis, cystic fibrosis, and
  bronchiectasis
• H. influenzae is the most common bacterial cause
  of acute exacerbation of COPD.

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Pseudomonas aeruginosa

• it is associated with infections in cystic
  fibrosis,
• P. aeruginosa is most commonly seen in nosocomial
  
• Pseudomonas pneumonia is also common in persons
  who are neutropenic, usually secondary to
  chemotherapy in victims of extensive burns and
  in those requiring mechanical ventilation.
• P. aeruginosa has a propensity to invade blood
  vessels at the site of infection with consequent
  extrapulmonary spread

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Morphology of pneumoniaCommunity-Acquired Acute
Pneumonia

• Lobar or bronchopneumonia may occur.
• The lower lobes or the right middle lobe are most
  frequently involved.
• Widespread fibrinosuppurative consolidation.

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Community-Acquired Acute Pneumonia Stages of
pneumonia

1. Congestion lobes are heavy, red and boggy
   histologically, vascular congestion can be seen
   with proteinaceous fluid, scattered neutrophils
   and many bacteria in the alveoli.
2. Red hepatization alveolar spaces are packed
   with neutrophils, red cells, and fibrin, pleura
   fibrinous or fibrinopurulent exudate.
3. Gray hepatization lung is dry, gray and firm
   and the fibrinous exudate persists within the
   alveoli.
4. Resolution exudates within the alveoli are
   enzymatically digested.

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Community-Acquired Acute Pneumonia Morphology of
pneumonia
Congestion vascular congestion can be seen with
proteinaceous fluid, scattered neutrophils and
many bacteria in the alveoli. Red hepatization
alveolar spaces are packed with neutrophils, red
cells, and fibrin, pleura fibrinous or
fibrinopurulent exudate
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Community-Acquired Acute Pneumonia Stages of
pneumonia
Gray hepatization fibrinous exudate persists
within the alveoli.
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Community-Acquired Acute Pneumonia Stages of
pneumonia
Resolution exudates within the alveoli are
enzymatically digested.
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Clinical features

• Abrupt onset of high fever, shaking chills, and
  cough productive of mucopurulent sputum
  occasional patients may have hemoptysis.
• When fibrinosuppurative pleuritis is present, it
  is accompanied by pleuritic pain and pleural
  friction rub

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Complications of pneumonia

• Tissue destruction (abscess).
• Empyema.
• Organization of alveolar exudate solid
  fibrinous tissue.
• Bacteremic dissemination may lead to meningitis,
  arthritis or infective endocarditis.

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Community-Acquired Acute Pneumonia Dx Rx

• Examination of Gram-stained sputum smear is
  helpful in diagnosis
• Blood culture is more specific (only ve in 20
  to 30 of pt.)
• Pneumococcal pneumonia respond to penicillin Rx

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• Acute Pneumonias
• S. pneumoniae (pneumococcus) is the most common
  cause of community-acquired acute pneumonia
• Other common causes of acute pneumonias in the
  community include
• H. influenzae and Moraxella catarrhalis (both
  associated with acute exacerbations of COPD)
• S. aureus (usually secondary to viral
  respiratory infections),
• K. pneumoniae (observed in chronic alcoholics),
• P. aeruginosa (seen in individuals with cystic
  fibrosis, in burn patients and in neutropenics),
• L. pneumophila, seen particularly in individuals
  who have undergone organ

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Community-Acquired Atypical PneumoniaPrimary
atypical pneumonia

• Pt. Usually present with flulike symptoms with
  pharyngitis evolved into laryngitis,
  trachiobronchitis and pneumonia with little
  sputum and no lung consolidation
• Mycoplasma pneumoniae, Chlamydia spp. (C.
  pneumoniae, C. psittaci, C. trachomatis)
• Coxiella burnetti (Q fever)
• Viruses respiratory syncytial virus,
  parainfluenza virus (children) influenza A and B
  (adults) adenovirus and SARS virus
• Mycoplasma pneumoniae is associated with
  production of IgM antibody ( this react with red
  cells having I antigen leading to
  hemagglutination of cooled blood)

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Community-Acquired Atypical Pneumonia Primary
atypical pneumonia

• Circumstances that favor extension to lower
  respiratory tract
• malnutrition
• Alcoholism
• underlying debilitating disease.

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Community-Acquired Atypical PneumoniaPrimary
atypical pneumonia

• Acute febrile respiratory disease characterized
• by patchy inflammatory infiltration by lymphocyte
  and plasma cells
• largely confined to the alveolar septa and
  pulmonary
• interstitium- (Interstitial pneumonitis).

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Community-Acquired Atypical Pneumonia Primary
atypical pneumonia

• Gross
• Pneumonic involvement may be patchy, or involve
  whole lobes bilaterally or unilaterally.
• Affected areas are red-blue congested.
• Micro

• Predominant interstitial inflammatory reaction.
• Alveolar septa are widened and edematous with
  mononuclear inflammatory infiltrate (and
  neutrophils in acute cases only).
• Intra-alveolar proteinaceous material with pink
  hyaline membrane lining the alveolar walls
  (diffuse alveolar damage).

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Community-Acquired Atypical Pneumonia Primary
atypical pneumonia

• Clinical course
• Extremely variable course.
• URTI? life-threatening infection.
• Commonly
• - bronchopneumonia.
• - mycoplasma lobar pneumonia.
• Identification of the organism is difficult.
• Treatment antibiotic.
• Prognosis in uncomplicated pt. is good

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Severe Acute Respiratory Syndrome (SARS)

• first appeared in November of 2002 in China
• Between fall of 2002 and spring of 2003, there
  were more than 8,000 cases of SARS, including 774
  deaths
• SARS begins with a dry cough, malaise, myalgias,
  fever and chills
• A third of patients improve and resolve the
  infection, but the rest progress to severe
  respiratory disease with shortness of breath,
  tachypnea, and pleurisy and nearly 10 of
  patients die from the illness
• Caused by coronaviruses, however the SARS virus
  differs from previously known coronaviruses in
  that it infects the lower respiratory tract and
  spreads throughout the body.

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Summary

• Atypical pneumonias are characterized by
  respiratory distress out of proportion to the
  clinical and radiologic signs, and inflammation
  that is predominantly confined to alveolar septa,
  with generally clear alveoli.
• The most common causes of atypical pneumonias
  include those caused by M. pneumoniae, viruses,
  including influenza types A and B, C. pneumoniae,
  and C. burnetti (Q fever).

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Nosocomial pneumonia

• Nosocomial Pneumonia
• Hospital acquired Pneumonia
• Common in pt. with sever underlying conditions
  e.g. immunosuppression, prolonged antibiotic
  therapy, intravascular catheter and pt. with
  mechanical ventlator
• Organism include
• Gram-negative rods belonging to
  Enterobacteriaceae (Serratia marcescens,
  Escherichia coli, Klebsiella spp.), Pseudomonas
  spp. and Staphylococcus aureus (usually
  penicillin-resistant)

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Aspiration pneumonia

• Aspiration Pneumonia
• Occur in debilitated patients or those who
  aspirated gastric contents
• Chemical injury due gastric acid and bacterial
  infection including
• Anaerobic oral flora (Bacteroides, Prevotella,
  Fusobacterium, Peptostreptococcus), admixed with
  aerobic bacteria (Streptococcus pneumoniae,
  Staphylococcus aureus, Haemophilas influenzae,
  and Pseudomonas aeruginosa)
• A necrotizing pneumonia with fulminant clinical
  course, common complication (abscess) and
  frequent cause of death.

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Chronic pneumonia

• is most often a localized lesion in an
  immunocompetent person, with or without regional
  lymph node involvement.
• There is typically granulomatous inflammation,
• may be due to bacteria
• (e.g., M. tuberculosis) or
• fungi
• (Histoplasma capsulatum, Coccidioides immitis,
  Blastomyces )
• In the immunocompromised, there is usually
  systemic dissemination of the causative organism,
  accompanied by widespread disease.
• Tuberculosis is by far the most important entity
  within the spectrum of chronic pneumonias.

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The pneumonia syndromes

• Community-Acquired Acute Pneumonia
• Community-Acquired Atypical Pneumonia
• Nosocomial Pneumonia
• Aspiration Pneumonia
• Chronic Pneumonia
• Pneumonia in the Immunocompromised Host

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Pneumonia in the Immunocompromised Host

• Cytomegalovirus
• Pneumocystis jiroveci
• Mycobacterium avium-intracellulare
• Invasive aspergillosis
• Invasive candidiasis
• "Usual" bacterial, viral, and fungal organisms

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Pneumocystis Pneumonia

• P. jiroveci (formerly known as P. carinii), an
  opportunistic infectious agent long considered to
  be a protozoan, is now believed to be more
  closely related to fungi.
• Serologic evidence indicates that virtually all
  persons are exposed to Pneumocystis during the
  first few years of life, but in most the
  infection remains latent.
• Reactivation and clinical disease occurs almost
  exclusively in those who are immunocompromised
  (AIDS)

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Pneumocystis Pneumonia
Microscopically, involved areas of the lung
demonstrate a characteristic intra-alveolar
foamy, pink-staining exudate with HE stains
Silver stain demonstrates cup-shaped cyst walls
within the exudate
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Pneumocystis Pneumonia

• Fever, dry cough, and dyspnea occur in 90 to 95
  of patients, who typically demonstrate bilateral
  perihilar and basilar infiltrates.
• Hypoxia is frequent pulmonary function studies
  show a restrictive lung defect.
• The most sensitive and effective methods of
  diagnosis
• to identify the organism in bronchoalveolar
  lavage fluids or in a transbronchial biopsy
  specimen.
• immunofluorescence antibody kits and PCR-based
  assays have also become available for use on
  clinical specimens

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Lung abscess

• A localized suppurative process within the
  pulmonary parenchyma
• features tissue necrosis and marked acute
  inflammation
• Posssile causes aerobic and anaerobic
  streptococci, Staphylococcus aureus, and many
  gram negative organisms
• Can follow aspiration ( one abscess of Rt. lung)
• occur as complication of pneumonia ( multiple)
• Abscess is filled with necrotic suppurative
  debri

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Lung abscess
Clinical Features - Prominent cough producing
copious

amount of foul- smelling purulent sputum -
Change in position evoke paroxysm of cough
- Fever malaise and clubbing of fingers
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Chest X- ray
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• Chest radiograph of a patient who had
  foul-smelling and bad-tasting sputum, an almost
  diagnostic feature of anaerobic lung abscess.

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Lung abscess
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Lung abscess

• Complications
• Pleural involvement (empyema) formation
  resulting from a bronchopleural fistula
• massive hemoptysis, spontaneous rupture into
  uninvolved lung segments
• non-resolution of abscess cavity
• Bacteremia could result in brain abscess and
  meningitis
• with antibiotic therapy 75 of abscess resolve