2. introduction
Actinomycetes are heterogeneous group of filamentous bacteria. so
they grow as branching filaments that fragments into bacteria like
bacilli.
Although superficially resembling fungi. Actinomycetes true
bacteria because:
1-They are prokaryotic cells
2- They are susceptible to antimicrobial antibiotics
3- They stain with bacterial stains, this are gram- positive
bacteria, generally anaerobic Some members that are present in
this group can cause various disease .Has been source of taxonomic
instability, Medically important genera are 3 groupsActinomyces
NocardiaStreptomyces
3. Nocardia
Definition :
The genus Nocardia is an aerobic actinomycete, catalase-
positive, gram-positive bacillus, with a branching
filamentous form that can cause pulmonary infection (most
common), primary cutaneous infection and also
dissemination to other sites. Typically, Nocardia is an
opportunistic pathogen that primarily affects
immunosuppressed patients.
4. Species of Nocardia
The most important species of nocardia:
-Nocardia. asteroides is the most common Species , it cause
nocardia human infection cutaneous infection with abscess
formation of sites infection, also cause meningitis with
brain abscesses and arthritis
-Nocardia. brasiliensis cause pneumonia and lung absces
-Nocardia caviae cause actinomycotic mycetoma
5. Morphology of Nocardia
Gram positive,an aerobic, rod-shaped bacteria. It forms
partially acid-fast beaded branching filaments (acting as
fungi, but being truly bacteria). non motile , spore
forming.
6. Transmission methods
When soil or water carrying nocardiosis bacteria gets
into the skin through a cut or scrape (traumatic
inoculation) When a hospitalized patient is infected
from contaminated medical equipment or from
bacteria getting into a wound after surgery (hospital-
acquired infection).
Most Nocardia infections are acquired by inhalation of
the bacteria.
7. pathogenesis
Nocardiosis is a disease caused by bacteria found in
soil and water. It can affect the lungs, brain, and
skin.Primary cutaneous nocardiosisCellulitic and
sporotrichosis forms ActinomycetomaDisseminated
disease (most common secondary to pulmonary
involvement)It is most common in people with
weakened immune systems who have difficulty
fighting off infections
9. Diagnosis
1 -Nocardia is typically weakly acid-fast after traditional carbol-fuchsin staining
and positive on modified acid-fast staining due to the presence of mycolic acid in
the cell wall.
Nocardia has a “beaded” appearance on acid-fast staining.Nocardia is catalase-
positive and urease positive.
2 -Culture
Norcardia species will grow on most non selective media the colonies have
a white or cotton ball appearance because of the presence of abundant aerial
filaments more rapidly growing increased by the use of selective media such as
Thayer - Martin agar with antibiotics .Growth of Nocardia species typical colonies
are usually seen after 3-5 days.
10. Treatment
People with nocardiosis may need to take
multiple antibiotics given for several
months—or even up to a year or more.
Sometimes abscesses or wound infections
need to be surgically drained.
