Syn
: Rangoon
Beggar’s Disease and Whitmore’s Disease.
Melioidosis is an
uncommon infectious disease caused by Burkholderia pseudomallei
, a small gram-negative
bacillus in the soil and surface water of Southeast Asia and other
tropical areas.
Visit:
Glanders
Although melioidosis is endemic in Southeast Asia,
there have been scattered infections of humans and animals in South
and Central America, Africa, Turkey, Australia, and Guam.
During the
conflict in Vietnam, several hundred French, Vietnamese and American
servicemen acquired melioidosis.
The organism flourishes in wet
environments, such as rice paddies and marshes.
The skin is the usual
portal of entry, and organisms enter through preexisting lesions,
including penetrating wounds and burns.
Man may also be infected by
inhaling contaminated dust or aerosolized droplets. The association of melioidosis with drug addiction implies transmission by contaminated
needles and syringes.
The incubation period varies up to
months and possibly years.
The clinical course may be chronic, subacute or acute.
The acute illness presents as a pulmonary
infection, with sudden onset, high fever, chills, malaise, myalgia,
and a cough that may produce blood-stained mucopurulent sputum.
The
severity of pulmonary involvement varies from a mild tracheo-bronchitis
to an overwhelming cavitary pneumonia.
Splenomegaly, hepatomegaly, and
jaundice are sometimes present.
The diarrhea may be as severe as in
cholera.
Fulminating septicemia, shock, coma,
and death may develop in spite of antibiotic therapy.
Acute septicemic melioidosis
causes discrete abscesses throughout the body.
These occur most
frequently in the lungs, liver, spleen, lymph nodes, and bone marrow,
but any organ may be involved.
Small, firm, and yellowish lesions are
sharply delimited from surrounding normal tissue and are often bounded
by a narrow hemorrhagic margin. The small foci may coalesce into
larger abscesses.
Image1 ;
Image2 ;
Image3 ;
Image4 .
Microscopically, the centers of
the abscesses are necrotic and contain neutrophils in a fibrin mesh.
A
narrow necrotic rim containing histiocytes forms the boundary of the
abscess. Necrosis is prominent feature of even the very early lesions,
a finding that probably reflects toxin production by
Burkholderia
pseudomallei.
Large numbers of bacteria are seen in
the abscesses, but seldom in the surrounding tissue.
Subacute melioidosis mimics
tuberculosis and is characterized by fever, cough, and pneumonia.
Melioidosis also occurs as a self-limited febrile disease lacking
specific features.
Some 20% of people living in endemic areas have
antibodies against
Burkholderia
pseudomallei.
Chronic melioidosis is a localized
suppurative infection involving lungs, skin, or bones.
Clinically and radiologically it may resemble tuberculosis.
Complications include osteomyelitis, psoas or subcutaneous abscesses, and lymphadenopathy.
Chronic melioidosis may follow a mild acute illness, or it may lie
dormant for months or years, only to appear suddenly- hence the
colloquial name , “Vietnamese time bomb”.
Chronic melioidosis is usually
localized to a single organ, most often the lung.
The lesions have a
necrotic center surrounded by a granulomatous reaction and a perimeter
of fibrous tissue.
The central necrotic zone may be suppurative or
caseous.
In the lymph nodes stellate abscesses resemble lesions of
lymphogranuloma venereum, cat scratch disease, and tularemia.
Bacteria
are seldom seen in chronic lesions, even though cultures may be
positive.
Diagnosis is made by serologic tests or
culture. The cultures must be handled carefully, since
laboratory-acquired infection is possible. Tetracycline is the
treatment of choice.
|
