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