Septic arthritis of knee due to Burkholderia pseudomallei : a case report

Introduction

Burkholderia pseudomallei, a Gram-negative obligatory aerobic non-spore forming bacillus causes melioidosis. In 1911, Captain Alfred Whitmore and his assistant, CS Krishnaswami, diagnosed this condition in Burma.

The bacillus grows as a soil saprophyte in stagnant water and rice fields, and infection spreads through abrasions on the skin or via inhalation. ¹ Patients with diabetes mellitus, chronic renal failure, alcoholism, cirrhosis or those who are immunocompromised are more susceptible.^2,3 No association with human immunodeficiency virus (HIV) has been reported yet. It may present at any age, though it most commonly presents in the third and fourth decades.

It can be localised or disseminated at presentation (with or without septicaemia).^4,5 Abscesses in multiple organs—including the lungs, liver, spleen, parotids and skeletal muscles—are found. Musculoskeletal melioidosis seems rare in India, but many cases of soft-tissue infection have been found.

Clinically, the disease may present as polyarthritis, Gram-negative sepsis, pyogenic bacterial infection or with tuberculosis (TB). The chance of recurrence persists after inadequate clearance of septic foci. Sequelae include severe pneumonia, septicaemia, osteomyelitis, arthritis or septic emboli. The diagnosis may not be thought of unless a high suspicion is entertained both by clinician and microbiologist. Histopathology may show necrotising granulomata that mimic TB. ⁶ The bacillus is normally sensitive to ceftazidime, amoxy-clavulanic acid, co-trimoxazole and doxycycline.

Case report

We report a case of a 50-year-old man presenting with left knee pain, swelling and high-grade fever of seven days’ duration. The pain was insidious in onset, severe in intensity, without any diurnal variation nor radiation. On examination, he was very pale. There was swelling, mild warmth over the knee but no skin changes or sinuses. Tenderness was present over the joint line, and prepatellar and suprapatellar regions. The range of motion was in the range of 0°–30°.

He was known to suffer with diabetes. Investigations proved anaemia (Hb = 66 g/L) and a high erythrocyte sedimentation rate (60 mm/h). Serology for HIV/HBsAg/HCV was normal. Radiograph of the left knee was normal. Ultrasound scan of the knee joint showed a suprapatellar and parapatellar effusion with thickened synovium and so pointed to septic arthritis of the knee.

Percutaneous drainage of the knee was established and continuous irrigation started. A blood transfusion was administered to correct the anaemia, and glycaemic levels optimised using subcutaneous insulin. Systemic antibiotics were initiated (Cefuroxime) until the pus culture report was received. A left knee arthrotomy by a medial parapatellar approach was then carried out and thorough debridement of the joint cavity ensured (Figures 1–3).

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Figure 1.

Intraoperative picture during arthrotomy.

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Figure 2.

Tissue defect over medial aspect of the knee.

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Figure 3.

Tissue defect closure after flap.

Culture of pus drained revealed Burkholderia pseudolmallei sensitive to cotrimoxazole, ceftazidime, ceftriaxone, cefotaxime and ampicillin-sulbactam. For definitive therapy, we started intravenous ceftazidime (acute phase = three weeks) and oral doxycycline and co-trimoxazole (eradication phase = five weeks) for two months. A prolonged and combination antibiotic therapy is usually recommended as B. pseudomallei is notorious for its recalcitrant nature, giving it the name ‘the Vietnam time bomb’. ⁷

However, symptoms of painful swelling and high-grade fever persisted. Further pus culture sensitivity and a TB polymerase chain reaction (PCR) test were obtained. B. pseudomallei was again isolated but the TB PCR was negative.

Despite breakdown of the wound around the proximal medial aspect of the knee, the swelling and pain and fever subsided. After one month of regular dressing and wound care, a gastrocnemius flap coverage was carried out.

With intensive physiotherapy, the range knee motion improved to a range of 0°–80°. At the 30-week follow-up, a full range of motion was recovered with no recurrence of infection (Figure 4).

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Figure 4.

Postoperative site and range of motion.

Discussion

Melioidosis is relatively rare but increasingly reported. The bacillus is widespread and is found in the soil of almost all the states of India, though more frequently in the southern states. It is underreported in India because of a lack of awareness of disease, a low index of suspicion and an under-recognition of the disease. It should be suspected on isolation of a Gram-negative bacillus, which is oxidase positive, bipolar staining and which is gentamicin resistant.

It mostly affects the respiratory system although soft-tissue abscesses are common. It occurs in persons with concurrent diabetes, renal failure, thalassemia or immunocompromised status. It is introduced into the body by inoculation via the skin or by inhalation. Sexual transmission and vertical transmission at birth have also been reported.^8,9 It is not a zoonosis. The highest concentration of the organism is found on the surface water of wet rice fields.

The clinical presentation is quite variable. There are acute or chronic forms of a rheumatoid nature. Melioidosis should be entertained as a differential diagnosis in atypical presentations, especially if the patient is from an endemic area. In musculoskeletal melioidosis, the diagnosis is usually made by microbial culture. Blood cultures are rarely positive. B. pseudomallei is sensitive to ceftazidime, amoxy-clavulanic acid, chloramphenicol, tetracycline and co-trimoxazole.^10,11 Imipenem is also quite effective, especially in septicaemia. ¹²

Conventional quadruple antibiotic therapy was used earlier in the literature, but it caused toxicity. Definitive therapy of initial intravenous antibiotics was used followed by combination oral drugs because we felt that this condition was slow to respond and difficult to treat with known recurrences, ⁷ complicated by the fact that the patient was diabetic.

The disease may take two weeks to subside. Regular antibiotics used for arthritis are seldom beneficial. The literature reports a 10% relapse even after 20 weeks of treatment. However, the relapse rate increases to 30% if the duration of treatment is < 8 weeks. ¹³ The distribution and frequency of musculoskeletal melioidosis is probably underestimated. Its prevention in rice-producing areas is difficult. Vaccination is not an option. Awareness of this infection, with its full spectrum of presentation is indispensable to help early detection, isolation of the organism and proper disease management.