Download The Islamic University- Gaza Report about Nocardia spp. Prepared

The Islamic University- Gaza
Report about Nocardia spp.
Prepared by
Manal Ghanem El-Astal
Supervised by
Dr. Abdelraouf A. Elmanama
Nocardia is a member of the
family Actinomycetales
Actinomycetales
Actinomycetes
Nocardia
Mycobacteria
Streptomyces
2
(Cont.)
• Both Actinomyces and Nocardia are filmentous
branching bacteria and
• were often confused with fungi before the
fundemental differences between prokaryotes
and eukaryotes were recognized.
• Actinomycetes anaerobic
• Nocardia is Strictly aerobic.
Nocardia spp. Includes
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•
•
•
•
•
•
Nocardia asteroides
Nocardia farcinica
Nocardia nova
Nocardia transvalensis
Nocardia brasiliensis
Nocardia caviae
Nocardia otitidiscaviarum
Route of infection
•
Nocardia spp. are soil saprophytes
•
route of infection can be either
1. By inhalation
2. By direct cutaneous inoculation.
(Cont)
• 90% of nocardial infections are caused by
inhalation of members of the N. asteroides
group
Nocardia asteroides complex
Nocardia farcinica
Nocardia nova
• Other strains represent the remaining 10%
of infections.
(Cont.)
• N. brasiliensis is the most important in tropical
areas.
• It is most often seen as a cutaneous infection
• Can affect individuals with normal immune
function
• 70% of cases of N. brasiliensis are seen in
immunocompromised individuals.
Characteristics of Nocardia
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•
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•
•
•
•
Classically Gram +ve(may be variable)
Strictly aerobic
Filmentous
Branching
weakly acid –fast bacilli
Have mycolic acid in cell wall.
Nocardia has cells that are 1.0 µm wide
and 1.0-2.0 µm long.
Identifecation of Nocardia in
culture media
• Types of samples
Sputum culture
Bronchoscopy
Lung biopsy
Skin biopsy
Brain biopsy
Nocardia can be difficult to
isolate by culture
• Because of over growth by faster- growing
nonpathgenic colonizers that may mask its
presence.
• solid medium that uses paraffin as the sole
source of carbon has been effective for
isolating Nocardia spp. from contaminated
clinical specimens.
Other types of media
• Sheep blood agar
• L.j medium
• Sabouraud dextrose agar
(chloramphenicol should not be added)
Nocardia spp. inhibited by chloramphenicol
Rate of growth time to visible colonies
• May be 2- 4 days.
• May be 2- 4 weeks.
Diagnosis may be difficult . In the clinical
laboratory, routine cultures may be
held for insufficient time to grow
Nocardiae.
The colonial appearance of Nocardia spp.
are extremely variable
• May be smooth and moist, or
• Have”mold- like” verrucous grey – white
waxy,or
• powdery appearance from aerial hyphae.
• Nocardia colonies initially have a dry,
wrinkled, chalk like appearance, adhere to
the agar, and develop white to orange
pigment over time.
• Nocardia colonies have very
distinct,strong mildew oder
that allow experienced
microbiologists to suspect
their presence.
• The colonies of N. brasiliensis (left) and
N. caviae (right) pictured below show the
wide range of colony appearance, even
within the same species:
Nocardia with Gram stain and
acid Fast stain
• Gram variable,
with a “beeded”appearance of alternating
G+ve and G+ve segments along a
filments.
• However , Nocardia grown under
suboptimal conditions sometimes appear
uniformly Gram – negative.
(Cont.)
• Nocardia organisms are classically weakly
modified acid-fast.
• This characteristic may help to distinguish
Nocardia from negative Actinomyces
(which is modified-acid-fast-negative).
(Cont.)
• Nocardia can occasionally appear
modified-acid-fast-stain negative.
• Nocardia grown under suboptimal
conditions will have retarded synthesis of
mycolic acids in their cell wall that, in turn,
compromises the ability of the organisms
to retain Gram stain or modified-acid-fast
stains.
Differentiation of Nocardia
species
• Histologic appearance of Nocardia is
similar to other Actinomycetes family
members,
culture and biochemical testing is
necessary for definitive
diagnosis/identification.
(Cont.)
• The UPMC-Presbyterian Mycology Laboratory
performs
petri-dish cultures with tap water agar (1%) to
differentiate the Nocardias and other aerobic
Actinomycete genera from the rapid growing
mycobacteria.
• (The trace organic material found in tap water
provides sufficient nutrients to support growth)
(Cont.)
• Biochemical tests includes:
1. hydrolysis of casein, tyrosine, and/or xanthine.
2. presence of urease.
3. utilization of rhamnose.
4. positive resistance to lysozyme, and
5. Catalase test.
(Cont.)
Table : Hydrolysis Tests for differentiating Nocardia strains
Casein
hydrolysis
L-tyrosine
hydrolysis
Xanthine
hydrolysis
N.asteroides, N.farcinica,or
N.nova
-
-
-
N.Brasiliensis
+
+
-
N.Otitidis
-
+
-
N.caviae
-
-
+
(Cont.)
Hydrolysis Pattern of casein
• N. brasiliensis (left, below) versus N. caviae (right,
below).
• Generally, casein media is in the lower left, followed
by L-tyrosine(upper left) and xanthine (upper right ).
(Cont.)
• An antibiotic susceptibility test may be
performed for a more precise identification
• N. asteroides group (N. asteroides
complex; N. farcinica; or N. nova) have the
same hydrolysis test
(Cont.)
• The test uses the antibiotic disc diffusion method
and requires 72 hours to complete:
Tobramycin
Cefamandole
or Cefotaxime
Erythromycin
N.asteroides Variable
Resistance
complex
N.farcinica
Resistant
Sensitive
Resistant
Resistant
Resistant
N.nova
Sensitive
Sensitive
Resistant
In general, diagnostic factors are
• Catalase positive.
• Urease positive
• Filamentous morphology.
• Orange-red waxy wrinkled colonies.
• Poorly stained with Gram's stain.
• Have strong mildew odor
• Growth on blood agar
Sites and Sources of Nocardia
• Nocardia spp.found in the environment,
(In soil and in dust particles)
(as saprophytes)
• Nocardia not considered as normal human
flora.
(Cont.)
Nocardia spp.usually occur:
• In recipients of bone marrow and organ
transplants.
• In patients with leukemia, lymphoma, humeral
or leukocyte defects
• After prolonged steroid therapy.
• In patients with connective tissue disorders,
and
• In HIV / AIDS patients.
• Generally :
It occur in immunocompromised patients.
Virulence factors
• Nocrdia spp. grow in nonactivated
macrophage, have intracellular growth,
and have prenvention of
phagolysosome fusion.
Pathogenesity and symptoms
1. Pulmonary Nocardiosis:
”Lung involvement”
Caused by Nocardia asteroides group.
Symptoms include
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Fever
Coughing blood
Weight loss
Night sweats, and
Chest pain
(Cont.)
2. Brain abscess:
Caused by Nocardia asteroides group.
Symptoms include
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Headache
Lethargy
Confusion
Vomiting
Seizures, and
Sudden onset of neurologic problems.
(Cont.)
3. Cutaneous Nocardiosis:
”Skin infection” “Myctoma”
Caused by Nocardia brasiliensis
Symptoms include
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Pustules
Fever
Tender lymphadenitis in the regional lymph
nodes, and
May become chronically infected (myctoma) and
develop draining tracts
(Cont.)
4. Disseminated disease from Nocardia:
It may also involve
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the kidneys
the joints
the heart
the eye, and
the bones.
(Cont.)
• (about 90%) of cases of nocardiosis
involves lung infection, brain abscess, or
disseminated (wide spread) disease from
Nocardia.
• The remaining 10% of cases are localized
to the skin.
(Cont.)
• Nocardia asteroides is an important
opprtunistic Pathogen in patients with
malignancy or receiving
immunosuppressive therapy and
usually responsible for pulmonary
infection.
(Cont.)
• Nocardia brasiliesis, is the primary
pathgen in mycetoma but may
occasionally found in disseminated
disease, particularly in patients with
poor host defense mechanism.
Cutaneous nocardiasis
Mode of transmission of disease
• Nocardia is found in soil.
• The inhalation of Nocardia spores usually
initiates pulmonary nocardiosis.
• The skin form of nocardiosis is contracted
through soil contamination of wounds.
(Cont.)
• There is no evidence for person
to person transmission of
Nocardia.
• Rarely nosocomial post
surgical transmission occurs.
Risk factors
• While individuals with normal immune
systems can acquired this infection, the
main risk factors for nocardiosis are
• Weakened immune system or chronic lung
disease.
• People on chronic steroid therapy,
• Those with cancer,
• Organ or bone marrow transplants, or
• HIV / AIDS are at risk , and
• Males (ratio male: female = 3:1).
Treatment
• Nocardia are not susceptible to penicillin.
• The current drug of choice is sulfonamides.
• Long-term antibiotic therapy (usually with
sulfonamides) for 6 months to a year (or longer
depending on the individual and site involved) is
needed to treat nocardia.
• Chronic suppressive therapy may be needed
(prolonged, low-dose antibiotic therapy).
• In addition, in patients with abscesses caused by this
infection, surgery may be required in order to ensure
adequate drainage.
(Cont.)
• The antimicrobial combination of
trimethoprim-sulfamethoxazole (TMP-SMX)
is the drug of choice.
However
resistance to TMP-SMX is becoming more
common.
(e.g. N. farcinica is more resistant TMP-SMX).
• A new combination drug therapy
(sulfonamide, ceftriaxone, and amikacin) has
shown promise for infections difficult to treat.
Prognosis for Nocardial infection
• About 10% of cases of uncomplicated Nocardia
pneumonia are fatal.
• Prognosis depends on the sites involved.
• The fatality rates increase with disseminated
disease, and brain abscess.
• In addition, the degree of impairment of the
individual's immune system will affect the
outcome.
‫السالم عليكم‬