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ACTINOMYCOSIS
Actinomycosis is a chronic granulomatous infection occurring in human
beings. It is charaterised by the development of indurated swellings, mainly
in the connective tissue, suppuration and the discharge of ‘sulphur
granules’. The lesion often points towards the skin, leading to multiple
sinuses.
Actinomycosis in human beings is an endogenous infection. The actinomyces
species are normally present in mouth, intestine and vagina as commensals.
Trauma, foreign body or poor oral hygiene may favour tissue invasion.
A.israelii is the most common causative agent. However, other actinomycetes
such as A.naeslundi, A.viscosus, A.odontolyticum and A.meyeri may sometimes
be responsible. Actinomycosis is usually a co-operative disease, the
actinomyces being accompanied by other associated bacteria which may enhance
the pathogenic effect.
Actinomycosis occurs in four main clinical forms: 1) cervicofacial with
indurated lesions on the cheek and submaxillary regions;2) thoracic, with
lesions in the lung that may involve the pleura and pericardium and spread
outwards through the chest wall; 3) abdominal where the lesion is usually
around the cecum, with the involvement of the neighbouring tissues and the
abdominal wall. 4) Pelvic. Many cases of pelvic actinomycosis have been
reported in association with the use of intrauterine devices.
Laboratory diagnosis:
The diagnosis is made by demonstrating actinomycetes in the lesions by
microscopy and by isolation in culture. High index of suspicion is required
for isolation of this organism in culture. The specimen to be collected is
pus. In pulmonary disease, sputum, is collected. ‘Sulphur granules’ are
crushed between slides and stained by gram stain and examined. The granules
are, in fact, bacterial colonies and will be found to consist of a dense
network of thin Gram positive filaments, surrounded by a peripheral zone of
swollen radiating club shaped structures, presenting a sun ray appearance.
Sulphur granules or pus containing actinomycetes are washed and inoculated
into thioglycollate liquid medium or streaked on brain-heart infusion agar
and incubated anaeroically at 37`C. In thioglycollate medium A. israelii
grows as fluffy balls at the bottom of the tube. On solid media A. israelii
produces small ‘spidery colonies’ in 48-72 hours that become heaped up,
white and irregular or smooth, large colonies in 10 days. Other species have
different type of colonies. Nocardia resemble Actinomycetes morphologically
but are aerobic and also weakly acid fast.
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