Pulmonary Infections :PNEUMONIAS
Factors in Pathogenesis Microbial factors
Capsule (pneumococcus) IgA protease (pneumococcus,
neisseria) Others – ciliostatic factor…etc
Host factors Impaired host defence
Hypogammaglobulinaemia, phagocytic or ciliary dysfunction, neutropenia, lymphopenia
Anatomical defects Bronchus obstruction,
bronchiectasis Genetic factors
Impairment of defense mechanisms leading to pulmonary infections :
1- Loss or suppression of cough reflex : coma , general anasthesia
neuromuscular disease, kyphoscoliosis, drugs.
2- Injury to mucociliary blanket : smoke, viral, alcohol, gases,
obstruction, cystic fibrosis
3- Decrease in macrophage function : alcohol, smoking phagocyte killing
defects
4- Impaired immune system : chronic diseases, acquired or
congenital immune deficiency, aging
5- Existing pulmonary disease: atelectasis, edema, COPD
6- Unusually virulent infecting organism
Definition of Pneumonia :
Pathological : Infection of lung parenchyma distal
to the terminal bronchioles.
ClinicalConstellation of symptoms & signs with at least one opacity on chest x-
ray
Diagnosis :
History Examination : percussion,
auscultation Blood picture Isolation of microbe :
sputum blood culture pleural fluid serology
Chest X ray
COMMUNITY-ACQUIRED BACTERIAL ACUTE PNEUMONIASStreptococcus PneumoniaeHaemophilus InfluenzaeMoraxella CatarrhalisStaphylococcus AureusKlebsiella PneumoniaePseudomonas AeruginosaLegionella Pneumophila
COMMUNITY-ACQUIRED ATYPICAL (VIRAL AND MYCOPLASMAL) PNEUMONIASMorphology.Clinical Course.Influenza InfectionsSevere Acute Respiratory Syndrome (SARS)
NOSOCOMIAL PNEUMONIAASPIRATION PNEUMONIALUNG ABSCESS
Etiology and Pathogenesis.CHRONIC PNEUMONIA
Histoplasmosis, MorphologyBlastomycosis, MorphologyCoccidioidomycosis, Morphology
PNEUMONIA IN THE IMMUNOCOMPROMISED HOSTPULMONARY DISEASE IN HUMAN IMMUNODEFICIENCY VIRUS INFECTION
PULMONARY INFECTIONS
Patterns of pneumonia :
LOBAR PNEUMONIA BRONCHOPNEUMONIA INTERSTITIAL MILIARY ( usually TB)
Lobar Pneumonia
Downloaded from: Robbins & Cotran Pathologic Basis of Disease (on 30 April 2008 02:55 PM)
© 2007 Elsevier LOBAR PNEUMONIA
Bronchopneumonia
Bronchopneumonia
Classification of pneumonias
• Community- Acquired Acute Pn.• Community- Acquired Atypical Pn.• Nosocomial Pneumonia• Aspiration Pneumonia• Chronic Pneumonia• Pneumonia in the
Immunocompromised host
Community-Acquired Pneumonia Risk factors
Dependent on organism Alcoholism, asthma,
immunosuppression, age >70, smoking, COPD, dementia, seizures, CHF etc
Aetiology Bacteria, fungi, viruses, parasites Common – s. pneumoniae, h.
influenzae, s. aureus, m. pneumoniae, c.
pneumoniae, influenza, adenoviruses, respiratory syncytial virus
A -Acute Bacterial Pneumonias
Pathology : CONSOLIDATION Hardening of lung parenchyma due to presence of exudate in alveolar
spaces.
Pneumococcal Pneumonia :
Commonest community acquired pn.
Healthy adults, more with predisposing
conditions Acute onset of fever, cough, rust
coloured sputum & chest pain. Pathology: Usually LOBAR
There are 4 stages of evolution :
CONGESTION 1-2 days RED HEPATIZATION 2-4 days GREY HEPATIZATION 4-8 days RESOLUTION 8-9 days
1- Congestion
Heavy red lungs Severe vascular congestion Intra alveolar exudate with few neutrophils Watery sputum Bacteria +++
2- Red hepatization Firm airless , liver-like lung Fibrinopurulent pleuritis Intra alveolar exudate : organisms
++ cells: * erythrocytes * neutrophils * fibrin * rusty sputum
3- Grey hepatization :
Dry grey brown cut surface ↑ intra alveolar fibrin &
macrophages Disintegrating neutrophils & ↓
RBC’s 4- Resolution : Enzymatic digestion of exudate resorption, phagocytosis ,
sometimes with residual adhesion
Stages of Bacterial Pneumonia
Bronchopneumonia
Patchy consolidation involving one or several lobes
Usually affects dependent lower & posterior portions of lung
Neutrophilic exudate centred in bronchi & bronchioles with centrifugal spread to adjacent alveoli
Clinical Manifestations
Typical Symptoms : Fever Cough Expectoration of sputum Pleuritic chest pain Chills, rigors SOB
Clinical Manifestations
Physical signs Tachypnoea
Single most useful sign for assessing severity: RR >30 bpm
Dullness to percussion Friction rub
B- Interstitial Pneumonia (Atypical)
A group of pneumonias ( Pneumonitis ) caused by community /hospital acquired
atypical bacteria or nonbacterial agents: Mycoplasma Pneumoniae Viruses - Resp.syncitial virus,
measles parainfluenza, adenoviruses,
CMV….. Chlamydia - Psittacosis Rickettsiae
Pathology Inflammatory process predominantly
involving the interstitium May be patchy of diffuse
Alveolar septa contain infiltrate of lymphocytes, macrophages, plasma cells
Little exudate in alveoli
Interstitial Pneumonia
- Clinical picture : insidious onset minimal
dry cough, minimal expectoration, minimal WBC’s , no Consolidation - Radiological picture : Transient ill
defined patches, mainly in lower lobes - In case of viruses , viral inclusions are
seen - In mycoplasma: cold agglutinin present
Diffuse Alveolar Damage, with formation of hyaline membranes in severe cases.
VIRAL PNEUMONIAS
Frequently “interstitial”, NOT alveolar
Hospital-Acquired (Nosocomial) Pneumonia
Pneumonia occurring at least 48 hrs after admission & not incubating at the time of admission
Epidemiology 5-10% of all hospital discharges
on medical & surgical wards Incidence 6-20 X higher among
mechanically ventilated patients
Pathogenesis
Poor infection control measures Prolonged & inappropriate use of
antibiotics spread of antibiotic resistant virulent organisms
Endotracheal intubation Serves as direct bacterial conduit Prevents effective coughing Damages tracheal epithelium Accumulation of oropharyngeal
secretions
Aetiology
Causative organisms Mostly gram-negative bacilli
P. aeruginosa, K. pneumoniae
Gram positive :S. aureus is the most common cause of nosocomial pneumonia in the US
Nosocomial Pneumonias :
Pseudomonas aeruginosa pneumonia
Bronchopneumonia , high mortality Patients : neutropenic cancer
patients , burn patients, ventilator associated…
Pathology : abscess formation & empyema with prominent vascular invasion vasculitis , hemorrhage & necrosis (Necrotizing Pneumonia )
Klebsiella pneumonia:
Bronchopneumonia or lobar. Gelatinous sputum nonresolution Risk : COPD, alcoholics, old,
malnourished
CYSTIC FIBROSIS patients with pneumonia are presumed to have PSEUDOMONAS until proven otherwise
Staphylococcal pneumonia : Severe abscessing broncho -
pneumonia with destruction.
Risk : children - cystic fibrosis or postviral Adults - COPD , IV drug addicts
Aspiration Pneumonia : Aspiration from oropharyngeal
secretion, acid gastric contents Patient : weak , with depressed
sensation &control of hypopharynx, repeated vomiting e.g. post anasthesia & paralysed patient
Mixed bacterial infection + Acid Chemical damage + consolidation
Severe Necrotizing Pneumonia
Lipid Pneumonia : Exogenous : inhalation of lipid
containing nasal drops , laxatives…etc Reaction is foreign body
granulomatous
Endogenous: secondary to bronchial
obstruction specially by tumor Reaction is patchy
bronchopneumonia with accumulation of lipid in macrophages
Complications of bacterial pneumonias :
1- Pleural effusion & pyothorax 2- Non resolution and organization of exudate fibrosis 3- Abscess formation 4- Bacteremic dissemination meningitis , arthritis , infective endocarditis 5- Empyema : accumulation of pus in pleural cavity which is followed by adhesions 6- Atelectasis 7- Vascular invasion infarction, cavitation, empyema, bronchopleural fistula
Empyema
Lung Abscess: Localized area of suppuration within the lung
Pathogenesis : 1- Aspiration of infective material 2- Post pneumonic 3- Bronchial obstruction 4- Infection in existing cavities or
cysts 5- Septic embolism 6- Bacteremic seeding
Morphology of abscess :
- Variable size , may be single or multiple ,
depending on mode of development. * Aspiration - Usually solitary , RL more than
LB * Postpneumonic- Usually multiple, more
basal *Hematogenous - usually multiple & any site
- Culture of pus : mixed aerobic / anaerobic
- Histology - suppuration , surrounded by fibrous wall with chronic inflammatory cells
Lung Abscess
Fate & complications of lung abscess:
1- Healing by fibrosis leaving a sterile cavit2- Rupture with partial drainage of material
*Radiological picture Air- Fluid level *Rupture into pleura Empyema *Rupture into
bronchusBronchopneumonia3- Bronchopleural fistula Pneumothorax4- Septic emboli5- Lung hemorrhage from vessels in fibrous
wall
CHRONIC PNEUMONIAS
CHRONIC Pneumonias
USUALLY NOT persistances of the community or nosocomial bacterial infections, but CAN BE, at least histologically
Often SYNONYMOUS with the 4 classic fungal or granulomatous pulmonary infections infections
If you see pulmonary granulomas, think of a CHRONIC process, often years
Include :
Tuberculosis Histoplasmosis Blastomycosis Coccidiodomycosis
1- Histoplasmosis,Coccidiodomycosis, & Blastomycosis
Usually normal host, also immunocompromised
Presentation & pathology very similar to T.B. Acute primary pulmonary infection Chronic cavitary pulmonary infection Disseminated miliary infection
Lesion is granuloma with necrosis & giant cells
Identify the organisms
Spores in bird or bat droppings Histoplasma CAPSULATUM Tiny organisms live in macrophages MANY other organs can be affected
HISTOPLASMOSIS
Spores in soil Blastomyces DERMATIDIS Large distinct SPHERULES MANY other organs can be affected,
especially SKIN
BLASTOMYCOSIS
Spores in soil Coccidioides IMMITIS Tiny organisms live in macrophages MANY other organs can be affected
COCCIDIOMYCOSIS
INFECTIONS in immunocompromised
patient
1- Candidiasis :
Common superficial oral or vaginal mucosal infection or skin
Maybe invasive in special patients AIDS , renal transplant, neutropenia ,
heart valvular diseases … Findings include abscesses in
kidney , lungs , heart ,brain, GIT….etc
Selective involvement of esophagus in AIDS
2-Cryptococcosis :
Opportunistic infection specially in
AIDS Gelatinous organisms, initiates
minimal inflammation Pulmonary, CNS, Disseminated
disease Usually inhalation to lung, spread to
meninges in gelatinous masses
3- Aspergillosis :
1- Invasive pulmonary aspergillosis : Immunocompromised host
Multifocal necrotizing pneumonia
May invade BV dissemiation with
vasculitis, occlusion,& infarction
2-Aspergilloma : ( mycetoma) growing in existing cavities , specially in TB & bronchiectasis
3-Allergic bronchopulmonary aspergillosis:
Asthmatic attack or hypersensitivity pneumonitis : Transient pulmonary infiltrates,
eosinophilia Ig E
ASPERGILLOMA
4 - Mucormycosis:
Hyphae localized in nose brain In lung localized cavity or miliary Immunocompromised host, specially
in diabetics
5- Pneumocystis carinii pneumonia :
? Protozoa, ? Fungus Majority of humans show positive
serology , but no disease Opportunistic infection in AIDS , often
with CMV (reactivation) Clinical picture : fever,dry
cough ,dyspnea, hypoxia, restrictive lung disease Radiology : bilateral & basal infiltrates
Pathology :
Interstitial lymphocytic infiltration Pink frothy exudate in alveoli Cysts or trophozoites in exudate Diagnosis : Organism best detected by special
stains & PCR on the following samples : Bronchoalveolar lavage Transbronchial biopsy
Pneumocystis pneumonia
Silver Stain (+)
Methenamine SILVER stain for Pneumocystis Carinii
Clinical Picture :
Fever, dry cough, dyspnea, hypoxia
Chest X ray : Bilateral perihilar & Basilar
nodular infiltrates Restrictive pulmonary function
defects Recurrences are common
6- Cytomegalovirus ( CMV )
Transplacental spread to fetus,or children:
CNS, pulmonary….etc Normal people : infectious
mononucleosis Immunocompromised : Transplants
&AIDS Commonest pathogen in AIDS
patients Necrotizing Interstitial Pneumonia
with inclusions. May progress to ARDS
Retinitis Gastrointestinal ulcerations &
diarrhea
7-Mycobacterium avium intracellulare
Atypical Mycobact. usually affect birds,
Common in advanced AIDS while M.hominis common in early AIDS Morphology :
Atypical microgranulomas Minimal caseation
Pulmonary Disease in HIV : Bacterial pneumonias are commoner &
more serious than in immunocompetent patients
Type of infection depends on CD4 counts: >200cells/mm³: bacterial pneumonia & secondary TB <200cells/mm³: pneumocystis carinii <50cells/mm³: CMV & M.avium
Kaposi Sarcoma, lymphoma & lung CA are more frequent in AIDS