Abstract
We report a case of melioidosis with splenic abscesses caused by Burkholderia pseudomallei in an urban-dwelling, 54-year-old Taiwanese man. The patient presented with prolonged fever and abdominal pain. A splenectomy was performed, followed by successful treatment with ceftazidime and amoxicillin-clavulanate. The patient recovered fully.
Introduction
Melioidosis, an endemic infection in southeast Asia and northern Australia, is caused by the Gram-negative bacillus Burkholderia pseudomallei, which inhabits damp soil and fresh water in many tropical areas. 1–3 Symptoms include fever, headache, chills, nausea, vomiting and joint pain. Abscesses, characteristic of melioidosis, typically occur in the lung, liver, spleen, skeletal muscle, prostate, neck and skin; the lung is most commonly involved. 1,4 Pneumonia, common in adults, is associated with a high mortality rate. Risk factors include diabetes mellitus, pre-existing renal disease and occupational exposure. 1,5 The incidence of septic shock approaches 40% of cases and the mortality rate is 26% to 80%. 6
We describe a patient with melioidosis who had several splenic abscesses but no respiratory involvement or any known exposure to contaminated soil or water. The patient was treated successfully by splenectomy, followed by ceftazidime and amoxicillin-clavulanate.
Case history
A 54-year-old man who lived in an urban area of southern Taiwan was examined in our gastroenterology unit after one week of fever, poor appetite, general malaise and abdominal pain. He had been administered metformin hydrochloride (500 mg twice daily) for five years for type 2 diabetes mellitus. The patient had not travelled to other regions. He had no diarrhoea, dysuria, jaundice or episodes of unconsciousness.
On admission, his temperature was 37.8°C, respiration rate 20/min, pulse rate 76/min and blood pressure 120/80 mmHg. Endoscopic examination revealed acute erosive gastritis; no ulcer or active bleeding was observed. He did not appear anaemic or icteric. His throat was normal, he had no cervical lymphadenopathy, his respiratory and cardiovascular functions were normal and he had no neurological, skin or muscle abnormalities.
The patient's haemoglobin level was 9.5 g/dL; white blood cell count was 8200/mm3 with 62% neutrophils, 26% lymphocytes and 12% monocytes; and the platelet count was 281,000/mm3. Biochemical test results were: blood urea nitrogen 15 mg/dL; creatinine level 1.6 mg/dL; glucose level 153 mg/dL; blood glutamic oxaloacetic transaminase activity 68 units/L; glutamic pyruvic transaminase activity 75 units/L; and serum sodium 127 mmol/L. Carcinoembryonic antigen, α-fetoprotein, Ca19-9 and serum concentrations of potassium and calcium were normal.
The patient was treated with cefazolin (1.0 g every 8 h). His fever diminished initially and his condition improved for two days. However, abdominal pain then developed in the entire left upper quadrant and his symptoms were gradually aggravated. Sonography, three days following admission, showed multiple, poorly-demarcated, hypoechoic lesions in the spleen. Computed tomography (CT) on the same day showed multiple low-attenuated areas in the spleen that resembled abscess-like regions (Figure 1). As a result of a possible splenic abscess, the parenteral antibiotic treatment was changed to ceftriaxone sodium (1.0 g every 12 h). Seven days after admission, the patient developed peritonitis with intermittent fever spikes. A splenectomy was performed; examination of the spleen revealed multiple abscesses (Figure 2) as suggested by the CT scans. Pathologic examination confirmed splenic abscess and cultivation of a pus sample yielded B. pseudomallei.
Computerized tomography of the spleen. Multiple abscesses with sizes in the range of 1 to 5 cm are apparent as indicated by the arrow
An image of the spleen obtained after surgery. The spleen measures about 10.5 × 10 × 4 cm and shows multiple abscesses
Postoperatively, the patient was treated with ceftazidime (2.0 g every 8 h) for 2 weeks, followed by oral administration of Augmentin (500 mg amoxicillin – 125 mg clavulanate; 1 tablet 3 times daily). The patient was discharged in good condition 20 days later (28 days after admission). Oral antibiotic therapy was maintained for eight weeks following discharge. The patient recovered without further complications and a one-year follow-up examination was normal.
Discussion
Melioidosis is acquired by inoculation or inhalation. Exposure to contaminated soil and muddy water of ponds and rice paddies may be the most common source of infection. 1 The present case may represent a different route of acquisition: the patient was a downtown urban dweller, had not traveled to regions where soil and water contact may have occurred and did not have the common respiratory involvement. A recent report also describes an Indian agricultural worker with diabetes who had no history of travel, but became infected with B. pseudomallei and developed multiple splenic abscesses and an abscess in his foot. 7 Clearly, diabetes is a risk factor 5 and diabetic patients may be substantially more susceptible to infection by B. pseudomallei. Furthermore, the haemoglobin level in our patient at admission was substantially lower (i.e., 9.5 g/dL) than normal (14 to 18 g/dL), which may have enhanced his susceptibility.
The spleen is the most common extrapulmonary visceral organ involved by melioidosis, 1 with multiple abscesses being the norm. 7 The most common sonographic appearance consists of small (≤2 cm), discrete, multiloculated lesions, with a target-like appearance, probably due to early central necrosis of the affected tissue and prominent fibrin content. The sonographic findings for intra-abdominal organ abscesses in melioidosis are not specific. 8 CT is the most accurate modality for imaging the spleen. The hallmark CT indication of an abscess is a low-attenuation area with an enhancing rim when intravenous contrast is given, with gas sometimes being evident in the lesion. 9
Although B. pseudomallei is Gram-negative, it can be or become resistant to antibiotics, including aminoglycosides, first- and second-generation cephalosporins, macrolide, rifamycin and colistin. Typically, B. pseudomallei is susceptible to ampicillin/sulbactam, chloramphenicol, tetracycline, Bactrim (sulphamethoxazole-trimethoprim), third-generation cephalosporins and carbapenem. 10 Ceftazidime treatment is associated with a 50% lower overall mortality than conventional treatment (chloramphenicol, tetracycline and trimethoprim-sulphamethoxazole) and is, therefore, recommended as the treatment of choice for severe melioidosis. 2,10 Initial parenteral treatment with ceftazidime reduces the risk of relapse in patients with severe diseases or associated conditions or in immunocompromised patients. 2
Conclusion
This case brings out several important points. Even for patients who live in urban environments, where there is expected to be a low burden of B. pseudomallei, melioidosis is possible and should be considered when pulmonary, visceral or other abscesses are identified. Infection should also be considered in diabetic patients and even in those with low haemoglobin levels. Treatment with ceftazidime and amoxicillin-clavulanate should be started immediately upon a suspicion of infection with B. pseudomallei.