Respiratory Infections: Infectious Disease Pathology. Respiratory System. Froberg. Katelyn Rogers.
11.08.09.
Pneumonia
Distributions
Lobar Pneumonia
Onset1, Cause2,
Bacteria3
1.Abrupt
2.Primary
3.Pneumococcus
Histological
Characteristics
*Alveolar infiltrates –
neuts (not patchy)
Epidemiology
Pathology
Cough Symptoms
Diagnosis
<4 yo or
elderly
M>F
CAP
*Congestion
*Red hepatization (alveolar
influx of serum & RBCs). Looks
~ liver. Pink proteinaceous
fluid.
*Gray hepatization (alveolar
influx of WBCs)
*Resolution
Productive
*X-ray - consolidation
*Rapid dissemination:
Patients can tell you
the exact moment they
got sick, often seen w/
Strep pneumoniae.
Bronchial Pneumonia
1.Insidious
2.Secondary (COPD)
3.Mixed (esp gram-)
*Alveolar infiltrates –
neuts adjoining small
airways.
*Patchy alveolar
involvement
M=F
HAP, HCAP
*Focal distribution surrounding
airways (lobular)
*Nodules/nidus of inflam
*Anthracotic pigment marks
*Purulent exudate
Productive
X-ray – nodular, fluffy,
patchy distribution, bc
ctrd around airways
Interstitial Pneumonia
(should be called
pneumonitis)
1.Insidious
2.Primary
3.Viral/Mycoplasma
Dry
X-ray – lacy, takes
severe case to see.
Opportunistic
Bacterial Resp Infs
Gram
+/-
Morphology1
& Stain2
Pathology &
Histology
Pathogenesis
Transmission
Clinical
Diagnosis
Legionnaire’s Disease
-
1.Rod
2.Dieterle’s
Silver Stain
Intracell replication in mac:
-prevent acidification of
phagosome
-block phagosome-lysosome
fustion
Air-conditioning
units &
contaminated water
(chlorine resistant)
*Healthy indls: mild, selflimited pneumonia
*Compromised: serious
to fatal pneumonia
X-ray: Lobar
Pseudomonas
-
1.Rod, aerobe
*Fibrinopurulent
pneumoniae –
mononuc
phagocytes
(leukocytosis –
nucleorrhexis)
*~neuts, but macs
*Lobar pattern
*Consolidation,
Bronchiectasis
*Dilated
peripheral airways
*Green/yellow
*Blue vasculitis of
denuded bv wall.
M=F
CAP
*Exotoxin A (~diptheria toxin
blocks prot synth)
*PLC (lyses rbcs & degrades
surfactant)
*Colonizes airways
*Risk factors: CF,
neutropenia, severe
burns.
*Pneumoniabronchial
pluggingbronchiectasis
& pulm fibrosis (10 yo)
*3rd cause of
HAIvasculitissepsis
1
*Leading cause of HAP
Gram
+/-
Morphology
Pathology & Histology
Pathogenesis
Clinical
Rod
Edema, orgs grown on surface.
WBC = lymphocytosis
Attaches to resp mucosal cilia & kills cell
by cytotoxin (blocks signal transduction)
Corynebacterium
Diptheriae (Diptheria)
+
Rod
Hemophilus Influenzae
(“Bully of the Pharynx”)
-
Rod
*Purulent
*Toxin myocardial fiber necrosis &
peripheral nerve damage
*Diptheritic memb: fibrin + dead cells
+ bact  liver to necrotic
*Red cells = dead
*Narrowing of glottis
*Mucosal pustules (bact + neut
infiltrate) & small abscesses.
Orgs grow on surf of colonized larynx &
trachea  phage coded exotoxin  kills
mucosa. Purulent resp = “pseudomemb”
(dead mucosa + PMNs + fibrin) 
detachment  aspirationdeath.
NO INVASION.
Encapsulated (5%-type b) form evades
phagoctyosis causing illnesses.
Erosive, acute
laryngotracheitis,
edema  “whoop”
Leathery
pseudomemb
covers pharynx,
larynx, & trachea is
fatal.
Bordetalla Pertussis
(Whooping Cough)
Virulence Factors:
*Polysaccharide capsule
*Capsule is a polymer of polyribitol
phospate
*Produces IgA protease
*Endotoxin (LPS)
Mycoplasma & viruses
(Atypical Pneumonia)
fungi
*Interstitial pneumonitis:
mononuclear cells (lymphs & macs)
confined to interstitium
*Alveolar walls widened &
edematous, no consolidation unless
secondary bact infection
M. pneumoniae most common
-bacteria minus cell wall
Viruses have to be w/in the cell to cause
dx.
Sudden onset, sore
throat, hoarseness,
stridor.
Capsulated forms:
*Pharyngolaryngitis &
epiglottis
(swollen,red); edema
 resp death
*Meningitis –
previously most
common cause in
<5yo.
*Pneumonia
*Bacteremia
(really all are
emergencies)
Uncapsulated forms:
*Local Pharyngitis
*Otitis media
Treatment1 &
Prevention2
1.Antibiotics
2.DPT vaccine
early
2. DPT vaccine
1.Antibiotics
2.PRPconjugated
protein vaccine
 decd
meningitis.
(Does not
prevent
infection by
encapsulated
forms)
Esp teens, fever,
nonproductive
cough, cold
agglutinins (IgM)
2
3