A 60-year-old man from Sherpur, Bangladesh, was admitted to BIRDEM hospital on July 20, 2023, with a 34-day history of fever, loss of appetite, and over three weeks of upper chest pain. On hospital admission, the patient had severely restricted movement in the left hip, which was mildly warm but showed no swelling. His vital signs (body temperature, pulse, respiratory rate, and blood pressure) were normal, and he was on oral antihypertensive medications. He had type 2 diabetes for over 20 years and hypertension for 8 years. He also had a history of pulmonary tuberculosis 20 years ago, which was cured after treatment. According to his clinical history, the patient was in good health until five weeks ago when he developed a continuous fever, with night time temperatures reaching 103°F-104°F, along with chills and rigors. He also experienced a burning sensation while urinating, which could be indicative of urinary tract infection (UTI). He consulted a physician, who, after a primary examination, recommended routine tests for the fever. The Complete Blood Count (CBC) showed normal (haemoglobin: 12.4 g/dl, leucocytosis: 12,300/cu mm with 75 % neutrophils) with elevated ESR (105 mm), and CRP (48 mg/l). The WIDAL test was negative, and random blood sugar was 16.2 mmol/L. He was initially treated with cefixime and ceftriaxone for seven days, but his condition did not improve. He was then admitted to Sherpur District Hospital and treated for UTI with intravenous Meropenem for eight days. He recovered from the urinary tract infection, but his fever persisted. He then developed upper chest pain and visited BIRDEM Hospital, a specialized diabetes care facility in Dhaka. After clinical evaluation, he was diagnosed with pyrexia of unknown origin, acute kidney injury, diabetes, and hypertension. He was initially treated with intravenous Ceftazidime 1 g twice daily for the first four days. Two days after admission, his fever subsided, but he developed severe pain in the left hip joint and inguinal region, along with swelling in the left inguinal area and upper chest pain. The hip pain progressively confined him to bed, with no pain in other joints.

Blood, sputum, and urine samples were collected on admission for routine tests and culture. The blood culture showed B. pseudomallei colonies on blood and MacConkey agar, with gram-negative bacilli and bipolar staining. On Ashdown media, the colonies were wrinkled and deep pink to purple. The bacteria were sensitive to meropenem, ceftazidime, amoxicillin-clavulanic acid, cotrimoxazole, and doxycycline, but resistant to gentamicin, amikacin, and colistin. Immunochromatography tests for malaria and kala-azar were negative.

The CBC showed elevated white blood cell count with increased polymorphonuclear leukocytes, along with high ESR, CRP, serum AST, ALT, blood sugar, and HbA1c levels (Table 1). Urine analysis showed 0–2 WBCs/HPF, 0–3 epithelial cells/HPF, 0–2 RBCs/HPF, presence of glucose and albumin, and acetone negative. Urine culture showed no growth. X-rays of the chest and hip, Magnetic Resonance Imaging (MRI) of the left hip, and an inguinal ultrasound were performed. MRI findings indicated septic arthritis in the left hip joint, showing altered signal intensities in the femoral head, neck, and surrounding muscles, with joint space widening and mild fluid accumulation (Fig. 1, Supplementary Figure 1). Multiple mildly enlarged lymph nodes were noted in both inguinal regions, with no bone abnormalities (Supplementary Figure 2). The chest X-ray was normal (Supplementary Figure 3). The chest pain might be a result of lung involvement associated with pneumonia. Ultrasound showed a few enlarged lymph nodes in the left inguinal region, the largest measuring 15 × 7 mm, with no hernia, mass, or fluid collection.

The phylogenetic tree of B. pseudomallei (Fig. 2) shows that the genome sequence from the clinical isolate (strain B0557 – red branch) obtained from this patient clusters with other Bangladeshi strains and it is within the major clade of East and Southeast Asia strains (red dotted circle), but unfortunately no other detailed disease information exists for those isolates besides causing melioidosis. While such extensive case information is lacking for strain B0557’s near neighbours, including a comprehensive tree will enable a future lookback if more isolates are gathered in the future with or without septic arthritis.

After confirming B. pseudomallei infection, the patient received intravenous meropenem (1 g every 12 h) for four weeks, followed by oral cotrimoxazole and doxycycline (100 mg every 12 h) for six months. He was referred to orthopaedics and physical medicine for hip joint pain and rehabilitation exercises. His pain gradually subsided, inflammatory markers normalized, and WBC count returned to normal by day 13 (Supplementary Table 1). Under close follow-up, he fully recovered after seven months, with no joint pain or complications. Follow-up blood cultures were negative.

The patient, a former businessman, had been homebound for the past five years. A day before symptom onset, he was exposed to soil and water while farming. He had also cared for a sick cow over four months, which died a month after his melioidosis diagnosis. He had no travel history in the past year and no history of smoking, alcohol, or drug use.