3. Definition
• Distinct clinical entity characterized by gradual
onset of constitutional and respiratory symptoms
associated with an unusual radiographic pattern
of pulmonary infection(1940)
• Characterized by constitutional symptoms and
upper and lower respiratory tract involvement
and can have a protracted clinical course with
gradual resolution. The lack of typical findings of
lobar consolidation on chest radiographs, failure
to isolate a pathogen with use of routine
bacteriologic testing methods, and lack of
response to penicillin therapy are also common
features of this group of microorganisms
Atypical Pneumonia: Definition, Causes, and Imaging Features,Nicholas P. Dueck,
RadioGraphicsVol. 41, No. 3, 2019
4. Typical vs atypical pneumonia
Typical pneumonia Atypical pneumonia
Causative organism are typical Causative organism are atypical bacteria,
viruses, fungus, parasites, non infective
caused like chemical, irradiation
Immuno-competant Immuno-suppressed
Clinical and laboratory findings limited to
the lungs
Systemic infectious disease with a
pulmonary component like GI or CNS
Unilateral involvement Bilateral involvement
follow alveolar pattern follow interstial pattern
Neutrophilic infiltrates Lymphocytic infiltrates
Chest x-ray will show lobar or segmental
homogenous opacity in over 80% of
typical bacterial pneumonia.
Chest x-ray will show diffuse patchy or
GGO >>> lobar or segmental homogenous
opacity .
Classically response to BL/BL-BI
combination therapy
These do not have cell wall or are
intracellular. Hence, do not responds to
BL/BL-BI combination therapy
Public health concerns , can cause HAP
Outbreak
5. The atypical pneumonias: clinical diagnosis and importance B.A. Cunha,Clin Microbiol
Infect. 2006; 12: 12–24
6. Atypical Pneumonia: Definition, Causes, and Imaging Features,Nicholas P. Dueck, RadioGraphicsVol. 41, No. 3, 2019
IP: 2-4 weeks
IP: 2-10 days
Pontanic fever
IP:1-2 days
IP: 3-4 weeks
10. Dueck NP. Published Online: April 09, 2021
https://doi.org/10.1148/rg.2021200131
11. Mycoplasma pneumonia Posteroanterior (PA)
chest radiograph shows bronchial wall
thickening and mid and lower lung zone
predominant heterogeneous opacities
involving both lungs symmetrically. There is
relative sparing of the lung apices.
Axial chest CT image (lung window)
obtained at the level of the ventricles shows
diffuse bilateral centrilobular nodules
(arrow), peribronchovascular ground-glass
opacities, and bronchial wall thickening,
findings commonly seen in mycoplasma
pneumonia.
Atypical Pneumonia: Definition, Causes, and Imaging Features,Nicholas P. Dueck,
RadioGraphicsVol. 41, No. 3, 2019
12. Axial chest CT images (lung window)
show multilobar ground-glass opacities
and sublobar consolidation of the right
lower lobe. Bilateral small-volume
pleural effusions are present.
Legionella: chest radiograph shows a right
infrahilar and basilar consolidation
(arrow).
13. Chlamydia pneumonia-PA view chest
radiograph shows a sublobar
consolidation in the left lower lobe
(arrow) with rounded morphology.
Axial chest CT image (lung window) shows
peripheral consolidation and ground-glass
opacities characteristic of lobar pneumonia.
No tree-in-bud micronodules or bronchial
mucoid impaction are depicted.
14. F tularensis: PA chest radiograph
shows subtle left suprahilar and
peripheral left upper lobe nodular
opacities (arrows).
Axial chest CT images (lung windows)
obtained above peripheral solid nodules
(arrows) in the left upper lobe
15. Mycoplasma Pneumoniae Chlamydophila Pneumoniae Legionellae
• Gram staining: Chlamydiae
are gram-negative they are
poorly stained.
• Other stains: Such as
Castaneda, Machiavello or
Giemenza stain are better
method to detect chlamydiae
from samples.The inclusion
bodies can be detected in
cytoplasm.
• DIF is used as for direct
detection of inclusion bodies
in clinical material, can also
be used for culture
confirmation. Sensitive is
good but the specificity is low
(non-specific fluorescence).
• Gram stain :appear as faint
pleomorphic gram-negative
rods or coccobacilli
• Other stains: Silver
impregnation and Giemsa
stains can be used.
• DIF using monoclonal or
polyclonal sera is more
specific but sensitivity is poor
than culture. It is more useful
in advanced stage of disease.
Microscopy
16. Mycoplasma Pneumoniae Chlamydophila Pneumoniae Legionellae
Primary isolation :
•Standard solid medium:
Containing PPLO agar, horse
serum and penicillin.
•Standard liquid medium:
Containing PPLO broth,
glucose and penicillin and
phenol red (indicator).
•Diphasic medium: solid
phase and Liquid phase
•SP-4 medium: contains fetal
bovine serum.
•Hayflick modified medium:
Containing heart infusion
broth
•incubated at 37°C for 5-7
days or sometimes even up to
1- 3 weeks.
•Liquid medium: turbidity and
color change (R TO Y)
•Solid medium: fried egg
appearance, Dienes
phenomenon>>royal blue
•C. pneumoniae call be
isolated from HEp2 or human
fibroblast cell line.
•Incubated at 10% CO2 for 48-
72 hrs.
•Cell lines are stained to
demonstrate the presences of
inclusion bodies
•highly sensitive (80-90%) and
specific (100%)
•Buffered charcoal, yeast
extract (BCYE) agar: incubated
at 37°C in 5% CO2 for 3- 5
days.
•Colonies are round with an
entire edge, glistening,
convex, green or pink
iridescent and have granular
or speckled opalescence
resembling ground glass
•motile, catalase positive and
oxidase negative
•Hippurate hydrolysis test is
positive
•Autofluorescence of colonies
under UV light.
17. Mycoplasma Pneumoniae Chlamydophila Pneumoniae Legionellae
•Antigenic Detection
• Direct immunofluorescence
test
•Capture ELISA assay :use
monoclonal antibodies
against P1 adhesin antigen.
•Antibody Detection
•Specific Antibody Detection
Tests(serum)
•after about 1 week of illness,
and peak at 3-6 weeks and
decline gradually. lgM
elevated in children, lgA
antibody detection(choice).
•lmmunofluorescence assays ,
•Latex agglutinalion assays
•ELISA using protein Pl
antigens
•Non specific Antibody
Detection (obselete)
•Cold agglutination test:
Streptococcus MG tests
•Antibody Detection
•ELISA based formats are also
available using recombinant
LPS antigen.
•Microimmunfluorescence
(MIF) test uses the species
and serovar specific MOMP
(major outer membrane
protein) antigen. Detects IgM
and IgG separately
•Single high titer of >1:512 is
diagnostic, however fourfold
rise of titer at 2-3 weeks
interval is more significant
•Antibody detection:
epidemiologic purpose.
•Indirect immunofluorescent
antibody test and enzyme
immunoassays are available.
A single titer of more than
1:128 or fourfold rise in titer
is considered as significant.
•Urinary antigen: ELISA
detects serogroup I specific
soluble antigens in urine.
Advantages: rapid, cheaper,
easy to perform,highly
sensitive, and specific
•Antigen in urine is detectable
3 days after the onset and
disappears over 2 months.
The test not affected by prior
antibiotic administration
19. Rapid immunochromatographic
assay for the qualitative detection of
IgM antibodies by intecasi( China)
Specimen: serum or plasma
Test result: 15-20 minutes
Storage temperature: 2-30℃
Shelf life: 24 months
Kits per pack: 20/40/50
Sensitivity: 94.83%
Specificity: 96.01%
20.
21. •primer set consists of Amplification of a conserved and mycoplasma-specific 16S
rRNA gene region using two primers.
•highly-sensitive and -specific PCR assay
•LOD;10 CFU/ml
•Samples can be prepared in 10 minutes
•contains primers, Taq polymerase, and dNTPs is included
•20 runs per kit
•35 cycle PCR
26. Mycoplasma Pneumoniae Chlamydophila Pneumoniae Legionellae
•PCR available targeting M.
pneumoniae specific 16S
rRNA gene and P1 adhesin
gene
•NAAT is highly sensitive and
specific, takes less time, and
detects even few copies of
DNA from the sample.
• differentiate the species and
serovars.
•currently the diagnostic
assays of choice for chlamydia
infection as recommended by
the CDC,
• Polymerase chain reaction
(PCR)
•Ligase chain reaction (LCR)
•Transcription-mediated
amplification (TMA)
•PCR
treatment
Oral azithromycin, 500 mg on
day 1, then 250 mg on day 2
to 5 .
Doxycycline
Levofloxacin
Tetracycline or erythromycin
(500 mg four times a day) is
recommended for 14days.
Azithromycin(Choice)
Levofloxacin,
27. Francisella tularensis Coxiella Burnetii
•gram-negative coccobacillus with bipolar
appearance, nonmotile and capsulated
•biosafety level 3 laboratory
•Culture:
•BCG agar (blood cysteine glucose agar)
•CHAB agar (cysteine heart agar
supplemented with 9% heated sheep blood)
• incubated at 37° C for 2-4 days aerobically
.Colonies are blue-gray ,slightly mucoid zone
of β-hemolysis
•catalase positive, oxidase negative and H2 S
positive
•Antibody detection: mainstay
•Agglutination tests (latex and tube
agglutination) and ELISA are available.
•a small pleomorphic gram-negative
coccobacillus. It is extremely fastidious
•biosafety level 3 laboratory.
•cell culture: It can be done using human
embryonic lung fibroblast cell lines
•Antibody detection: most commonly used
•Indirect immunofluorescence assay
:sensitive, specific and method of choice
•In chronic infections, antibodies to phase I
antigens are elevated, whereas in acute rise
of antibodies to phase II antigens.
•lgM :7- 10 days of infection IgG:14-20 days
after infection
•Complement fixation test detects lgG
antibodies to phase II antigens.
28. Francisella tularensis Coxiella Burnetii
•PCR assay: outer-membrane proteins. It can
also differentiate between subspecies
•QpH1 plasmid : acute
•QpRS plasmid: chronic
Treatment
Francisella tularensis Chlamydophila Psittaci Coxiella Burnetii
Gentamicin (choice) given 5
mg/kg for 7- 10days
•Tetracycline is the drug of
choice, given 250 mg four
times a day for at least 3
weeks to avoid relapse.
•Erythromycin (500 mg four
times a day by orally) is given
as alternate.
•Doxycycline (1 00 mg tw ice
daily for 14 days) is the drug of
choice.
•Quinolones are also effective.
It uses human O blood group RBC ('I' antigen) and 1es1 is carried ou1 at 4°C. • : 11 uses killed suspension of Streptococcus MG (group F Streptococcus).
It uses human O blood group RBC ('I' antigen) and 1es1 is carried ou1 at 4°C. • : 11 uses killed suspension of Streptococcus MG (group F Streptococcus).
