Atypical
Pneumonia
BY
Annerie Hattingh
26/08/09
Introduction:
• Pneumonia caused by atypical pathogens
• Typical pathogens usually includes:
- Strep. pneumonia
- Haemophilus pneumonia
- Klebsiella pneumonia
• Does not respond to the usual antibiotics
• Causes a milder form of pneumonia (hence the term
“walking pneumonia”)
• Characterized by a more drawn out coarse of
symptoms
Introduction:
• Legionella + SARS are exceptions to the above –
both can be very severe infections
• Typical pneumonia can come on more quickly + with
more severe early sx
• The arbitrary classification of typical vs. atypical
pneumonia is of limited clinical value
• Literature now shows that a primary pathogen may
co-exist with a secondary one, further blurring this
distinction
Introduction:
Causes:
“Classical” atypical pneumonias:
1.) Mycoplasma pneumonia
2.) Chlamydia pneumonia
3.) Legionella pneumonia
Introduction:
Causes:
Other micro-organisms that cause similar patterns
of presentation:
1.) Chlamydia psittaci (exposure to birds)
2.) Coxiella burnetti (presenting as Q fever)
3.) Viral pneumonias - Influenza A
- SARS
- RSV
- Adenoviridae
- Varicella pneumonitis
Epidemiology:
• It is thought that the 3 main atypical pathogens
might be implicated in up to 40% of CAP
• The precise incidence is not known
• Often not identified in clinical practice due to lack of
readily available, reliable standardized tests to
confirm dx
• By age 20, 50% of people in the USA have detectable
levels of Antibodies to Chlamydia
pneumonia
Risk Factors:
• Mycoplasma + Chlamydia spread by person-toperson contact
- spread most common in closed populations e.g.
schools, offices + military barracks
• Legionellae found most commonly in fresh water +
man-made H2O systems
Risk Factors:
- sources of contaminated H2O includes:
* showers
* condensers
* whirlpools
* cooling towers
* respiratory equipment
* air conditioning systems
Risk Factors:
• Other risk factors include:
- young, healthy people
- cigarette smoking
- lung disease (like COPD)
- weakened immune system (e.g. chronic steroid
use or HIV)
Presentation:
Mycoplasma pneumonia:
• Gram neg bacteria with no true cell wall
• Frequent cause of CAP in adults + children
• Prevalence in adults with pneumonia 2 – 30%
• Tends to be endemic, occurring @ 4-7yr intervals
Presentation:
Mycoplasma pneumonia:
Clinical Features:
• Symptomatic / asymp
• Gradual onset (over few days – weeks)
• Prodrome of “flu-like” symptoms
Presentation:
Mycoplasma pneumonia:
Clinical Features:
• Including: - headache
- malaise
- fever
- non prod. Cough
- sore throat
Presentation:
Mycoplasma pneumonia:
Clinical Features:
• Objective AbN on physical exam are minimal in
contrast to the pt’s reported symptoms
• Present like many of common viral illnesses BUT
persistence + progression of sx help to mark it out
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
•
Can involve: CNS, Blood, Skin, CVS, Joints, GIT
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
Neurological compl.
- Aseptic meningitis
- Cerebellar ataxia
- Transverse myelitis
- Peripheral neuropathy
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
•
•
•
•
Neurological manifestations are infrequent
Usually found in kids, if seen
Associated with increased morbidity + mortality
Antecedent resp. infection not always present
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
Hematological compl.
• Hemolytic anemia
• IgM antibodies to erythrocyte membrane I antigen
are present
• Produces a cold agglutinin response that leads to
hemolysis
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
Dermatological compl.
Include rashes such as:
1. Erythema multiforme
2. Erythema nodosum
3. Urticaria
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
Cardiac involvement:
1. Pericarditis
2. Myocarditis
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
Joint involvent: (occationately described)
1. Arthralgia
2. Arthritis
Presentation:
Mycoplasma pneumonia:
Extrapulm. Manifestations/Complications:
GIT symptoms:
1. N + V
2. Diarrhea
3. Pancreatitis (rarely)
Presentation:
Chlamydia:
•
Genus Chlamydia includes 3 species that infect
humans: - C. psittaci
- C. trachomatis
- C. pneumonia
•
Small, coccoid, Gram neg bacteria that resemble
rickettsiae
Presentation:
Chlamydia:
Chlamydia trachomatis - seen in newborn infants
during delivery
- has been ass. with
pneumonia in adults
Presentation:
Chlamydia:
Chlamydia psittaci:
•
Ornithosis is a systemic infection often acc. by
pneumonia
•
Common in birds + some domestic animals
•
Pet shop employees + poultry workers @ risk
•
Other systems involved: CNS
(meningoencephalitis) + CVS (cult. neg.
endocarditis)
Presentation:
Chlamydia pneumonia:
•
•
•
•
•
•
Prevalence varies by yr + geographic setting
Causes 5-15% of all CAP
Repeat infection is common
Gradual onset which may show improvement
before worsening again
Incubation 3-4 weeks
Initial non-specific URTI Sx lead to bronchitic/
pneumonic features
Presentation:
Chlamydia pneumonia:
•
•
•
•
•
Most infected remains quite well + asymptomatic
Can cause prolonged, acute bronchitis with
prod. cough
Hoarseness + headache are common features
Fever relatively uncommon
Sx may drag on for weeks/months despite course
of appropriate antibiotics
Presentation:
Chlamydia pneumonia:
•
•
1.
2.
3.
Clinical severity usually caused by a secondary
pathogen or co-existing illness e.g. diabetes
Complications:
Sinusitis, otitis media
New onset asthma after acute infection
Endocarditis, myocarditis
Presentation:
Legionella pneumonia:
•
•
•
•
•
Aerobic, motile, non-encapsulated, Gram neg
bacilli
Tends to be the most severe of the atypical
pneumonias
Focal outbreaks centered around poorly
maintained air conditioning / humidification
systems
Incubation 2-10 days
Initial mild headache, myalgia leading to fever,
chills + rigors
Presentation:
Legionella pneumonia:
•
•
•
•
•
Minimally prod. cough
Dyspnoea, pleuritic pain + hemoptysis are not
uncommon
Extra pulmonary legionellosis is rare but can be
severe
CVS most common extrapulm. site causing
myocarditis, pericarditis + endocarditis
Also pancreatitis, peritonitis, glomerulonephritis +
focal neurological deficit
Diagnosis:
•
CXR findings are usually non-specific and difficult
to distinguish from other pneumonias
•
Chest signs on examination minimal
•
Rx of suspected atypical pneumonias should be
empirical
•
Cultures + serologic tests are not routinely
available in laboratories
Diagnosis:
• A 53yr old patient with severe
Legionella pneumonia.
• CXR shows dense
consolidation in both lower
lobes.
Diagnosis:
• A 40yr old patient with
Chlamydia pneumonia.
• CXR shows multifocal, patchy
consolidation in the right
upper, middle and lower lobes.
Diagnosis:
• A 38yr old patient with
Mycoplasma pneumonia.
• CXR shows a vague, ill
defined opacity in the left lower
lobe.
Mycoplasma
pneumoniae
Legionella pneumophila
Chlamydophila
(Chlamydia)
pneumoniae
Blood tests
May be raised WCC or rarely
evidence of haemolytic
anaemia. ESR may be
elevated. Serology titres
and complement fixation
tests/ELISA can help to
confirm the diagnosis.
FBC may show left shift. Severe
cases may have DIC evident on
FBC/INR. Hyponatraemia may occur
due to syndrome of inappropriate
ADH secretion. Urea/creatinine can
be raised if complicated by renal
failure or dehydration. LFTs often
non-specifically deranged. CK may
be elevated in rhabdomyolysis.
Serological tests on blood or urine
may be used to confirm diagnosis.
Usually non-specific and
unhelpful. Serology titres
or polymerase chain
reaction tests may be
used to confirm the
diagnosis.
CXR
Usually single lower-lobe
bronchopneumonia pattern
with lobar consolidation
rare. Other possible
patterns include atelectasis,
nodular infiltration akin to
TB/sarcoidosis, hilar
adenopathy and rarely
pleural effusion.
50% have pleural effusion. Patchy
alveolar infiltrates may be seen. CXR
can take up to 4 months to return to
normal and may initially progress
despite therapy.
Usually lower-lobe single
subsegmental infiltrate.
Pleural effusion found in
up to a quarter of cases.
Can progress to ARDS.
CXR changes may take up
to 3 months to resolve.
Cause of
pneumonia:
ABGs may be checked to assess respiratory function in acute, severe cases of community-acquired pneumonia.
Similarly, blood cultures should be taken to aid subsequent microbiological diagnosis. In cases of atypical
pneumonia where there is evidence of focal or global cerebral impairment, an LP should be considered.
Management:
•
Severe cases should be admitted
•
Atypical pneumonias usually Rx as for other
CAP, at least initially
•
No evidence that routinely giving antibiotics active
against atypical organisms leads to better
outcomes in non-severe CAP
Management:
•
•
•
•
•
Macrolides, such as Erythromycin, Clarithromycin
+ Azithromycin have been shown to be effective in
the Rx of all 3 organisms
Erythromycin tends to be less well tolerated + only
few trails demonstrates its efficacy in the Rx of
Legionella
Severe Legionella infections may require
rifampicin + a macrolide
Tetracycline, Doxycycline + Fluoroquinolones are
also effective
Recommened duration of therapy usually 2-3
weeks
THE END
QUESTIONS??
References:
1.
2.
3.
4.
Shakeel Amanullah: Atypical Bacterial Pneumonia;
eMed. March 2008.
www.patient.co.uk: Atypical Pneumonias; Jan. 2007.
www.thirdage.com: Encyclopedia – Atypical
Pneumonia (Mycoplasma and Viral) (Walking
Pneumonia); May 2008.
Rosen’s Emergency Medicine Online: Community
Acquired Pneumonia