This document discusses several types of pneumonia including nosocomial, aspiration, and lung abscess pneumonia. It provides details on causative organisms, pathophysiology, clinical features, diagnosis and treatment. Key points include: - Nosocomial pneumonia is associated with immunosuppression, antibiotics, and respirators. Common organisms are E. coli, Pseudomonas aeruginosa, and S. aureus. - Aspiration pneumonia results from gastric content aspiration and is characterized by necrotizing inflammation. Causative organisms include a mixture of oral aerobes and anaerobes like Bacteroides and S. pneumoniae. - Lung abscesses develop most commonly from aspiration or

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Nosocomial or hospital acquired pneumonias
Pulmonary infections acquired in the course of a
hospital stay.
Associated with :
Immunosuppression , Antibiotic therapy
Respirators (MC source of infection).
Etiology: organisms in descending order
E.coli
Pseudomonas aeruginosa (respirators)
S.aureus (usually penicillin resistant)

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Aspiration pneumonia
Due to aspiration of gastric contents.
Resulting pneumonia:
Partly chemical and Partly bacterial (from the
oral flora).
Characterized by
Necrotizing inflammation with fulminant
course.
Complication: lung abscess formation.
Causative Organisms : Mixture of aerobes and
anaerobes
Anaerobes from oral cavity : Bacteroides
Fusobacterium, Peptococcus spp.
Aerobes : S. pneumoniae and S. aureus

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Predisposing Conditions for Aspiration
Unconscious state
Alcoholic intoxication
Repeated vomiting
Anaesthesia
Partial drowning

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Aspiration Pneumonia (vegetable matter )

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Lung abscess
Refers to microbial infection resulting in:
Necrosis of lung tissue with
formation of cavities containing
Necrotic debris (pus) .

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Lung abscess : Pathophysiology
Most lung abscesses develop as a complication
of
1. Aspiration of oropharyngeal material: MCC
From Carious teeth , Infected sinuses or
tonsils, vomitus
Seen in-Acute alcoholism, Coma Anesthesia
2. Bacterial pneumonia
3. Septic embolism
From Infective endocarditis
4. Bronchogenic carcinoma (bronchial obstruction)
Obstruction impaired drainage
atelectasis good soil for bacteria to grow.

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Lung abscess
Microbiology:
Staphylococcus aureus (#1), Pseudomonas,
Klebsiella
90% have Anaerobic bacteria ( oropharynx)
Clinical features:
Spiking fever***
Cough with sputum production, night sweats
and weight loss.
Expectorated sputum characteristically is foul
smelling and bad tasting***.

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Lung abscess: Morphology
Gross findings:
Location and number: depends on mode of development
of abscess
Due to aspiration  Right lung , single
Standing up : RLL – post segment
Supine : RLL – superior segment.
Right sided position : RML, post seg of RUL.
Pneumonia  basal, multiple
Septic emboli  multiple, any region.
Microscopic findings:
Abscess cavity: Neutrophils, +/- necrotic debris
May drain  air fluid level on X ray***

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Lung abscess

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Sheet of neutrophils
with necrotic debris
Lung abscess

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Complications
1. Enlargement of abscess rupture into
airway exudate drained  air-fluid level
on X ray.
2. Abscess:
1. rupture in to pleura  broncho-pleural
fistula  pneumothorax , empyema.
2. embolization brain abscess, meningitis

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Lung abscess
Diagnosis:
1. Chest radiograph:
Iregularly shaped cavity with an air – fluid
level inside.
2. Cause confirmed by microbiologic
investigation.
Differential diagnosis:
1. Cancer of lung
2. Cavitary tuberculosis
Treatment:
includes anti-anaerobic drug and lasts 2-4
months.

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Chronic pneumonias
Histoplasma capsulatum
Blastomyces dermatidis
Coccidioides immitis
Nocardia
Actinomyces
Mycobacterium tuberculosis

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Histoplasma capsulatum
An intracellular fungus that infects macrophages.
Causes: Histoplasmosis
Most common systemic fungal infection.
Acquired by inhalation of spores from dust
particles contaminated with bird droppings.
Associated with bats, birds and cave
exploration.
Caves – “Spelunker’s disease”
S/S: Chills, fever. Cough, headache and
pneumonia.
Produces granulomatous inflammation with
calcification ( tree bark appearance).

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Histoplasma capsulatum
Endemic areas in US:
Midwest (Ohio and Mississippi river
valleys)***
Morphology
Yeast forms in macrophages****

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Tree Bark appearance :Histoplasma granuloma of
the lung.

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Histoplasma capsulatum yeast forms in macrophages

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Blastomyces dermatitidis
Causes = Blastomycosis
Two major clinical forms ( mostly occurs in
males)
1. Pulmonary blastomycosis
2. Cutaneous blastomycosis
Endemic areas:
Central US, Minnesota, S. Canada, Africa
(almost same range as histoplasma but extends
up, into Canada)
Found in moist soil with decomposing wood
Morphology:
Organism in tissue exhibits broad-based
budding

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Blastomycosis
Broad-based Budding

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Coccidioides immitis
Causes: Coccidioidomycosis
Acquired by inhaling arthrospores in dust in the
Southwest or San Joaquin valley in California.(=
San Joaquin Valley fever).
Increased incidence after earthquakes.
Presents with flu like symptoms
Cough, fever, arthralgia and rash
Morphology:
Tissue form is SPHERULE
Filled with small endospores.

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Coccioidomycosis spherule in tissue
Spherule
Endospores

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Pneumonia in the immunocompromised
host
Usually occurs in patients with:
AIDS
Bone marrow transplant and
Organ transplant recipients.
The common opportunistic pathogens:
Cytomegalovirus
Pneumocystis carinii
Mycobacterium avium - intracellulare
Aspergillus fumigatus
Candida albicans

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Relationship between CD4+ T cell count and
type of infecting organism in AIDS patients
CD4+ count >200/cub.mm (N: >500)
Usual bacterial pathogens
M. tuberculosis hominis
CD4+ count <200/cub.mm
P. carinii
CD4+ count <50/cub.mm
MAI complex
CMV

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Pneumocystis carinii
Most common initial AIDS defining infection
Occurs if CD4 helper T cell count <200/microlit
Gross :Lungs are dry and consolidated
Micro:
Frothy (“cotton candy”) exudate within
alveoli.
Cysts and trophozoites of P carinii.
C/F : low grade fever, dyspnea and tachypnea
Chest X ray: diffuse alveolar and interstitial
infiltrates
Diagnosis: Bronchoalveolar lavage and lung biopsy
Stain well with GMS stain

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Frothy (“cotton candy”) exudate
Pneumocystis carinii
GMS stain

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Cytomegalovirus
Enlarged alveolar
macrophages,
pneumocyte and
endothelial cells
contain basophilic
intranuclear
inclusions
surrounded by a
halo