A traveller presenting with severe melioidosis complicated by a pericardial effusion: a case report

Background Burkholderia pseudomallei, the etiologic agent of melioidosis, is endemic to tropic regions, mainly in Southeast Asia and northern Australia. Melioidosis occurs only sporadically in travellers returning from disease-endemic areas. Severe clinical disease is seen mostly in patients with alteration of immune status. In particular, pericardial effusion occurs in 1-3% of patients with melioidosis, confined to endemic regions. To our best knowledge, this is the first reported case of melioidosis in a traveller complicated by a hemodynamically significant pericardial effusion without predisposing disease. Case presentation A 44-year-old Caucasian man developed pneumonia, with bilateral pleural effusions and complicated by a hemodynamically significant pericardial effusion, soon after his return from Thailand to Switzerland. Cultures from different specimens including blood cultures turned out negative. Diagnosis was only accomplished by isolation of Burkholderia pseudomallei from the pericardial aspirate, thus finally enabling the adequate antibiotic treatment. Conclusions Melioidosis is a great mimicker and physicians in non-endemic countries should be aware of its varied manifestations. In particular, melioidosis should be considered in differential diagnosis of pericardial effusion in travellers , even without risk factors predisposing to severe disease.


Background
Melioidosis is a great mimicker and on clinical grounds it is often impossible to differentiate it from other acute and chronic bacterial infections. Definite diagnosis relies on isolation and identification of its causative agent, Burkholderia pseudomallei [1,2]. In different endemic regions, pericardial effusion occurs in 1-3% of patients with melioidosis [1]. We present a case of severe melioidosis with a hemodynamically significant pericardial effusion in a traveller returning to a non-endemic region.

Case presentation
A 44-year-old Caucasian man from Switzerland developed fever and productive cough, two weeks after returning from north-eastern Thailand, were he had stayed from December 2008 until February 2009. The general practitioner treated the patient for community-acquired pneumonia with amoxicillin-clavulanate for seven days. After initial improvement, the patient became febrile and dyspneic again.
On admission the patient was febrile (38.3°C), had a tachycardia of 130 beats/minute, a blood pressure of 120/78 mmHg, and a respiratory rate of 40/min.
Although the patient showed jugular venous distention, neither Kussmaul's sign nor hepatomegaly or peripheral oedema were observed.
A chest radiograph showed bilateral pleural effusions and an enlarged cardiac silhouette. Computed tomography (CT) of the chest confirmed bilateral pleural effusions, with atelectasis of the inferior lobes, mediastinal lymphadenopathy and a prominent pericardial effusion. Abdominal CT showed a small intra-abdominal fluid collection.
Echocardiography confirmed a hemodynamic relevant pericardial effusion with diastolic compression of the right ventricle and a leftventricular ejection fraction of 55%. After pericardiocentesis and aspiration of 700 ml of a clear yellowish fluid the right ventricular function normalized, the leftventricular ejection fraction raised to 65%, and the QRS voltage normalized.
Pleural effusion (1.07 G/l leucocytes, 33% monocytes/ macrophages, 54% lymphocytes, 13% polymorphonuclear neutrophil leucocytes; LDH 144 U/l with normal range of LDH in serum <265 U/l ,and with a pleural fluid/serum-quotient of 0.4 for LDH and 0.4 for total protein, respectively) was negative on Gram-and Ziehl-Neelsen stains and negative by Polymerase Chain Reaction Assay for Mycobacterium tuberculosis complex. Cultures remained negative for bacteria, including mycobacteria and fungi. Cultures of two sputum samples from the same day yielded normal upper respiratory tract flora. Four sets of blood cultures taken on four consecutive days remained sterile and urine was negative for Legionella antigen.
The patient received ceftazidime 2 g every 6 hours for 2 weeks followed by maintenance treatment for three months with doxycycline, trimethoprim-sulfamethoxazole and leucovorine. The patient fully recovered after four months and suffered no relapse in the two years follow-up.

Discussion
Our patient developed signs of respiratory illness within the usual incubation period for melioidosis of 1-21 days, shortly after leaving northeastern Thailand, an endemic region for this illness. As Switzerland is not among those countries, where autochthonous cases of melioidosis have been reported [1], the patient probably acquired the infection during his stay in Thailand.
Pneumonia results from haematogenous spread of B. pseudomallei to the lung following inoculation through exposure to muddy soils or surface water or alternatively by inhalation, as the two main modes of infection [1,8].
Although melioidosis occurs in all age groups, severe clinical disease, such as septicaemic pneumonia, is seen mostly in patients with alteration of immune status, e.g. diabetes, chronic renal failure or alcoholism [8]. Our patient had neither a clinical risk factor for melioidosis nor any other underlying disease.
Epidemiologic considerations are very important in the management of pericardial effusion, as in developed countries acute idiopathic pericarditis and idiopathic pericardial effusion are the most common etiologies, whereas in some underdeveloped geographic areas tuberculous pericarditis is the leading cause of pericardial effusion [9]. In a systematic analysis of 106 pericardial fluid samples from France, a non-endemic country for melioidosis, B. pseudomallei was not among the detected bacterial agents [10]. Even in endemic regions, pericardial effusion caused by B. pseudomallei is a rare phenomenon. In the Darwin prospective melioidosis study from tropical Australia only four of 540 documented cases had pericarditis, three of them with pulmonary infection [11]. In a 10-years retrospective study from Thailand only 12 domestic cases of melioidosis complicated by cultureconfirmed pericarditis were found. One-third of these patients had underlying diseases and two-third showed evidence of bacteremia with secondary seeding in the pericardium [12]. In areas where tuberculosis and melioidosis are endemic, complicating pericarditis may only be differentiated by pericardial fluid culture and findings of pericardial biopsy [12].
As bacteremia could not be detected in our patient, B. pseudomallei might have gained access into the pericardium through the mediastinal lymph nodes in the course of pneumonia, known from patients with tuberculosis [13]. Cultures from different specimens remained negative for B. pseudomallei. Only culture of pericardial fluid grew the causative agent, possibly due to the use of blood culture bottles as primary culture medium. Blood culture bottles are superior in performance to traditional platedmedium methods for detection of microorganisms from sterile body fluids [14]. Detection of B. pseudomallei from nonsterile specimens such as sputum samples, can be hampered by the overgrowth and masking of B. pseudomallei by commensal flora, if selective culture media are not used, that are more common in medical laboratories situated in countries where the disease is endemic [1].
The initial empiric therapy with orally given amoxicillin-clavulanate was certainly inadequate as an intensive phase therapy for melioidosis [1,2]. However, this may have been responsible for the absence of growth of B. pseudomallei in other samples, especially in blood culture. This may also explain why the patient did not develop a septic shock as recently reported to be very common in patients with primary pneumonia combined with positive blood culture [15]. The detection of B. pseudomallei in the pericardial aspirate finally enabled the adequate, although delayed antibiotic treatment, 22 days after onset of illness.

Conclusions
Melioidosis is a great mimicker and physicians in nonendemic countries like Switzerland should be aware of its varied manifestations. In particular, melioidosis should be considered in the differential diagnosis of pericardial effusion in travellers, even in the absence of risk factors predisposing to severe disease. To our best knowledge, this is the first reported case of melioidosis in a traveller complicated by a hemodynamically significant pericardial effusion.