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Actinomycosis is
a chronic suppurative disease caused by anaerobic filamentous bacteria
in the order Actinomycetales.
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The disease occurs worldwide
and is mostly seen in tropical regions such
as Asia, Africa, central & south America.
Males are more frequently
affected.
The principal agent of
actinomycosis in humans is Actinomyces israelii - a gram-positive,
branching, anaerobic or microaerophilic bacterium.
This organism occur as
commensals in the mouth and "sulphur" granules are commonly found in
the tonsillar crypts of healthy persons.
The actinomycetes are
ordinarily of low pathogenicity.
Underlying disease and
interruption of mucocutaneous barriers predispose a person to
actinomycosis by providing a medium in which these endogenous
organisms can invade, proliferate and disseminate.
Unlike nocardiosis,
actinomycosis does not occur preferentially in patients with defective
immunity.
Visit:
Nocardiosis
;
Mycetoma .
Patients present
with painless swelling of foot and is usually not associated with fever.
The organism produce chronic
destructive lesions of deep soft tissue and bones, most commonly of the
limbs. Infection commonly occurs in the foot of bare-footed
persons. Primary skin infections may develop after human bites.
Based on the
anatomic site of lesions four clinical forms of actinomycosis are
recognized:
(i) Cervicofacial
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Most commonly involved is the cervicofacial area, where the disease is
often a sequel to dental caries, periodontal disease, or injury to the
oral mucosa, such as tooth extraction. The localized lesion enlarges,
abscesses form, and draining sinus tracts
which ruptures with formation of
sinuses through which “sulfur grains” are discharged.
If untreated, the infection may extend into the mandible, paranasal
sinuses, orbit, cranial bones, and thorax, where it may then disseminate
to the central nervous system, skin, and other bones.
(ii) Thoracic
- Infection
occurs due to aspiration of infective material.
(iii) Abdominal
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Abdominal actinomycosis is
frequently mistaken clinically for advanced malignancy. It may result from
direct extension of a thoracic infection but is more commonly seen as a
consequence of a ruptured appendix or bowel perforation by swallowed
foreign bodies, such as toothpicks or needles.
(iv) Pelvic - It is the most
common complication of Intra-uterine contraceptive devices.
Pathological
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The inflammatory reaction in
actinomycosis is suppurative, with formation of abscesses that contain
one or more granules (organized aggregates of filaments), 30 to 3000
micrometer in diameter, that are bordered by eosinophilic ,club-like,
Splendore-Hoeppli material.
Bacterial stains reveal that the
granules are composed of delicate, branched, gram-positive filaments,
about 1 micrometer in diameter, haphazardly arranged in an amorphous
matrix of uncertain composition.
The filaments may be fragmented and
unlike those of the Nocardia species, are not acid-fast.
Gomori methenamine-silver staining is
also useful for demonstrating the filaments, which are not stained by
the hematoxylin and eosin, periodic acid-Schiff and Gridley stains.
Specific identification requires
culture or immunoflourescence staining because, in tissue sections,
the agents of actinomycosis cannot be distinguished from each other.
Both gram-positive and gram-negative
bacilli and cocci may be found in close association with actinomycete
filaments within a granule, but it is generally believed that these
bacteria are secondary pathogens.
Histologically, there are chronic granulomas
with fibrous stroma and cyst-like spaces containing characteristic granules. Granules are
colonies of organisms. Abscess-like granulomas are seen under epidermis which rupture
forming sinuses.
Treatment:
Penicillin is the drug of choice for
treating actinomycosis. It is speculated that fewer cases are seen today
because of the widespread use of antibacterial antibiotics for treating
minor, unrelated infections.
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