Pulmonary infections

PULMONARY INFECTIONS
(PNEUMONIAS)
SUNIL KUMAR.P
Haematology & Transfusion Medicine
2/19/2018 1SUNIL KUMAR.P

• Introduction
• Definition
• Classification
• Etiology ( causes )
• Pathogenesis

INTRODUCTION
• Acute & Chronic pulmonary infections are
common at all ages and are frequently cause
of death.
• They are generally caused by a wide variety of
microorganisms such as ……
• a. Bacteria
• b. Viruses
• C. fungi and Mycoplasma

Examples of Acute Pulmonary
infections are….
• 1.Pneumonias
• 2.Lung Abscess
• 3.Fungal Infections
• Chronic Pulmonary Infections :
• Pulmonary Tuberculosis

PNEUMONIA

DEFINITION
• Pneumonia is defined as acute inflammation
of the lung parenchyma distal to the terminal
bronchioles .

• The term “Pneumonia” and “ Pneumonitis”
are often used synonymously for
inflammation of the lungs.
Consolidation : Meaning solidification is the
term used for gross and radiologic appearance
of the lungs in pneumonia.

CLASSIFICATION OF PNEUMONIA
• On the basis of the anatomic part of the lung
parenchyma involved, pneumonias are
traditionally classified as………..
• 1. Anatomical Classification
• 2.Etiological Classification

1 : Anatomical classification.
• A – lobar pneumonia .
• The consolidation involves all or part of lobe
• B – Bronchopneumonia
• the consolidation involves scattered lobules
• C - Interstitial pneumonia .
• As in viral pneumonia where inflammatory .
• Infiltrate involve mainly interstitial tissue
between alveoli.

2.Etiologic Classification of
Pneumonias

Causes of infectious pneumonia

Uncommon

PATHOGENESIS
2/19/2018 SUNIL KUMAR.P 20

PATHOGENESIS
• The microorganisms gain entry into the lungs
by one of the following four routes.
• 1.Inhalation of microbes present in the air
• 2. Aspiration of organisms from the
nasopharynx or oropharynx.
• 3.Haematogenous spread from adjoining site
of infection.
• 4. Direct spread from an adjoining site of
infection.

Conti……….
• The lower respiratory tract is normally sterile by
• -Physiologic defense mechanisms including
• -Mucociliary clearance
• -Properties of normal secretion such as secretory
immunoglobulin A IgA
• - Clearing of air way by coughing
• Immunologic defense mechanism of lung limit invasion
by pathogenic organisms
• Includes macrophages are present in alveoli and
bronchioles secretory IgA and others immunoglobulins

• Failure of these defense mechanisms and presence of
certain predisposing factors result in pneumonias.
• These conditions are as under.
• 1. Altered consciousness . Eg: CVA, Cranial Trauma.
• 2.Depressed cough and glottic reflexes . Eg. Old age ,
pain from trauma.
• 3.Impaired Mucociliary transport.
• 4.Impaired alveolar macrophage function
• 5.Endobronchial Obstruction.
• 6.Leukocyte dysfunction.

BACTERIAL PNEUMONIA
• Bacterial infection of the lung parenchyma is
the most common cause of the pneumonia
• or
• Consolidation of one or both the lungs .

• Two types of bacterial pneumonias are
distinguished
• - Lobar pneumonia
• Broncho ( Lobar ) Pneumonia …… each with
different etiological agent and morphological
changes.

• Another type distinguished by some workers
separately is confluent pneumonia involves
larger areas in both the lungs irregularly ,
while others consider this as a variant of
bronchopneumonia.

Lobar pneumonia
• Lobar pneumonia is an acute bacterial
infection of a part of a lobe or even two lobes
of the lungs

ETIOLOGY
• Based on the etiologic microbial agent causing
lobar pneumonia, following types of lobar
pneumonia are described

• 1.Pneumococcal pneumonia
• 2.staphyloccal pneumonia
• 3.Sreptococcal pneumonia
• 4.Pneumonia by gram negative aerobic
bacteria.

MORPHOLOGICAL FEATURES
• Laennec’s original description divide lobar
pneumonia into 4 sequential pathologic
phases….

• 1.Stage of congestion( initial Phase )
• 2. Red Hepatisation ( Early consolidation )
• 3. Grey Hepatisation (Late consolidation)
• 4.Resolution
• However these classic stages seen in untreated
cases are found much less often nowadays due to
early institiution of antibiotic therapy.

• In lobar pneumonia as the name suggest, part
of a lobe , a whole lobe, or two lobes are
involved, some times bilaterally.
• The lower lobes are affected most commonly.

1. Stage of congestion initial phase
• The initial phase represents the early acute
inflammatory response to bacterial infection
and lasts for 1 -2 days

• Gross Examination :
• - The affected lobe is enlarged
• - Heavy
• - Dark red
• - Congested .
• _ Cut surface exudes blood –stained frothy
fluid.

• Microscopic / Histological :

Pulmonary infections

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