Atypical Bacterial
Pneumonia
Dina Abouelkheir
Lecturer of chest medicine-MUH
2015
Why it is called “Atypical”???

The atypical organisms cannot be cultured on standard
media, nor can they be seen on Gram’s stain.
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Have atypical presentation
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Often cause extrapulmonary manifestations
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Intrinsically resistant to all β-lactam agents as most of
the atypical pathogens do not have a bacterial cell wall
Causes of Atypical pneumonia

Bacteria

Respiratory tract viruses
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Mycoplasma
(M.
pneumoniae)
Chlamydophila (C. psittaci,
C. pneumoniae)
Legionella
F. tularensis
Y. pestis
B. anthracis

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Rickettsia

C. burnetii (Q fever)
Other viral agents

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Influenza,
adenovirus,
respiratory syncytial virus,
parainfluenza virus
Varicella-zoster,
measles,
Epstein-Barr virus, CMV,
metapneumovirus, Hantavirus
Fungi

Histoplasma,
Blastomyces,
Coccidioides, Pneumocystis
Epidemiology

Atypical CAPs represent approximately 15% of all
CAPs.
Legionella
Sources of infection include domestic hot and cold water
systems, wet cooling systems, natural spas, humidifiers,
ultrasonic mist machines, respiratory therapy equipment.
- The attack rate is higher in:
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the elderly
tobacco smokers, alcoholism
those with chronic lung disease
diabetes mellitus
ICH
Mycoplasma (M. pneumoniae)
The organism is spread by droplet aerosol
Chlamydophila (C. psittaci, C. pneumoniae)

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C. psittaci may be hosted by many avian species
Psittacine infection is an occupational hazard of
veterinarians, pet-shop workers, zoo staff and poultry
workers.
Clinical Presentation

Fever, chills, pleuritic chest pain

Cough: non-productive or productive of mucoid
sputum only.

Dyspnea

Physical findings of consolidation

Pleural friction rub
Typical and Atypical Presentation of
CAP:
Extrapulmonary Manifistations
Legionella
Bradycardia
Hyponatremia
Diarrhea: 20%
Mental confusion
Glomerulonephritis
Bullous myringitis
Mycoplasma
(painful haemorrhagic
blisters on the ear-drum and external auditory canal)
Splenomegaly
Lymphadenopathy
Maculopapular skin rash
Hepatitis
Palpable splenomegaly
Chlamydia
Endocarditis
Stevens–Johnson syndrome
Erythema nodosum
Bullous myringitis
Steven Johnson Syndrome
Erythema nodosum
Radiology

Patchy reticular or reticulonodular opacities.
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Subsegmental and sometimes segmental atelectasis.

 Hilar adenopathy

 Pleural effusion
Severe Legionella pneumonia. Chest radiograph shows dense
consolidation in both lower lobes.
Legionella pneumonia
Mycoplasma Pneumonia
Chlamydia pneumonia. CXR shows multifocal, patchy
consolidation in the right upper, middle, and lower lobes
Investigations
Sputum microscopy:

The absence of large numbers of organisms in an
adequate sputum sample raises the possibility of
Legionella
pneumophila,
Mycoplasma
pneumoniae, Coxiella burnetii or a viral
pneumonia.
Sputum culture

Legionella spp. → selective charcoal yeast extract
medium. Result is relatively slow, taking about 3
days.
Urine Antigen detection

Legionella spp.
Standard acute and convalescent serological
testing
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Complement-fixing antibody levels in the blood
Enzyme-linked immunosorbent assay (ELISA)
Immunofluorescent tests
PCR
Haematological
measurements
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and
biochemical
White cell count: normal or increased (Legionella )
ESR : raised.
Mild abnormalities of liver and renal function
including proteinuria and microscopic haematuria
Raised LDH and creatine kinase (Legionella )
Hyponatraemia (Legionella )
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IgM cold agglutinins: Mycoplasma
This test is usually done by combining the patient’s
serum with type O red cells in the laboratory. If
clumping is noted, the serum is serially diluted and
the test repeated, the titre reported being the highest
dilution at which clumping occurs at 4°C
complications
Legionella
Mycoplasma
Chlamydia
respiratory failure
√√
rare
rare
Empyema, cavitation
rare
√
Cardiac: pericarditis, myocarditis and
endocarditis
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Neurological :confusion,
memory
impairment, cerebellar ataxia, GBS
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Pancreatitis
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Cellulitis
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Renal failure
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Autoimmune hemolytic anaemia
SIADH
Steven Johnson Syndrome
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Treatment
Can we use
B-LACTAM
ANTIBIOTICS
to treat Atypical
Pneumonia????
Antibiotics:
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Macrolides
Doxycycline
Quinolone
Add on therapy
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Rifampicin (legionella, chlamydia)
Steroids (mycoplasma)
Doses
Erythromycin 500 mg/ 6-hours
Azithromycin 500 mg/24 hours
200 mg for the first dose
Doxycycline
Followed by 100 mg / 12-hours
Ciprofloxacin 400mg/8 hours IV
OR
750 mg orally /12 hours
Levofloxacin 750 mg/24 hours
Moxifloxacin 400 mg/24 hours
Rifampicin
600 mg /12 hours
Duration

It is recommended that treatment is continued for
2–3 weeks for fear that shorter periods may
result
in
delayed
resolution
or
relapse,
particularly in those who are immunosuppressed or
who have extensive disease.
Prevention of Legionella pneumonia

Identification of the sources where epidemics or
case clustering have occurred.

Hot water supplies are usually decontaminated by
hyperchlorination, or by superheating water
supplies to 70–80°C, and by the removal of
rubber washers from shower fittings.