Human Melioidosis, Malawi, 2011

Thembi Katangwe, Janet Purcell, Naor Bar-Zeev, Brigitte Denis, Jacqui Montgomery, Maaike Alaerts, Robert Simon Heyderman, David A.B. Dance, Neil Kennedy, Nicholas Feasey¹, and Christopher Alan Moxon¹

Author affiliations: Queen Elizabeth Central Hospital, Blantyre, Malawi (T. Katangwe, N. Bar-Zeev, N. Kennedy, C.A. Moxon); University of Malawi College of Medicine, Blantyre (J. Purcell, N. Bar-Zeev, B. Denis, J. Montgomery, M. Alaerts, R.S. Heyderman, N. Feasey, C.A. Moxon); Liverpool School of Tropical Medicine, Liverpool, UK (R.S. Heyderman, J. Montgomery, C.A. Moxon); University of Liverpool, Liverpool (N. Bar-Zeev, N. Feasey, C.A.Moxon); Mahosot Hospital, Vientiane, Lao People’s Democratic Republic (D.A.B. Dance); University of Oxford, Oxford, UK (D.A.B. Dance); Wellcome Trust Sanger Institute, Cambridge, UK (N. Feasey)

Abstract

A case of human melioidosis caused by a novel sequence type of Burkholderia pseudomallei occurred in a child in Malawi, southern Africa. A literature review showed that human cases reported from the continent have been increasing.

Melioidosis is widely distributed in tropical and subtropical regions, but data are lacking on this disease in sub-Saharan Africa. We report a case of melioidosis caused by a novel sequence type in a 16-month-old boy from rural Malawi. Increasing reports of melioidosis from Africa indicate a need for further investigation.

Case Report

A 16-month-old boy was seen at Queen Elizabeth Central Hospital (QECH), Blantyre, Malawi, in March 2011 with fever of 18 days’ duration, poor feeding, subcutaneous lesions of 15 days’ duration, and edema of the hands and feet. He had received intravenous (IV) benzylpenicillin and gentamicin for 4 days at a local health center before being referred for persistent fever.
The family lived in a remote village in the Shire Valley near the Malawi–Mozambique border at a latitude of –15°S; daytime temperature average was 27°–29°C, and natural flooding occurs from October through April. The boy’s parents were subsistence maize farmers and kept goats and pigs.
On arrival at QECH, the child was irritable and pale; temperature was 38.7°C, weight 9.8 kg (weight-for-age z score −1.14), and height 79 cm (weight-for-height z score −1.06). He had bilateral dactylitis with arthritis of the metacarpophalangeal and interphalangeal joints of the lateral 3 fingers. Numerous rubbery, tender subcutaneous nodules of ≈2 cm diameter were palpable on the face, thorax, and limbs. Overlying hyperpigmentation and weepy ulcerations occurred over some nodules. There was cervical and inguinal lymphadenopathy but no hepatosplenomegaly. Symmetric bipedal pitting edema extended to the knees. Neurologic, cardiovascular, and respiratory examinations revealed no abnormalities.
Laboratory results were as follows: blood glucose 7.8 mmol/L (reference 3.5–7.7 mmol/L), hemoglobin 4.6 g/dL (reference 9.7–15.1 g/dL), leukocyte count 31.9 × 10³/µL (reference 3.9–10.7 × 10³/µL), and erythrocyte sedimentation rate 95 mm/h (reference 3–13 mm/h). Blood smear showed poikilocytes with some tear drops and reticulocytes and was negative for malaria parasites. HIV test (Unigold; Trinity Biotech, Bray, Ireland) and VDRL (Venereal Disease Research Laboratory) test for syphilis were negative. Radiographs of the hand showed bilateral osteolytic reactions in the lateral 3 fingers. Chest radiograph and abdominal ultrasound indicated no abnormalities.
Culture (BacT/Alert PF; bioMérieux, Marcy l’Etoile, France) of blood taken on admission and aspirate of pus from a subcutaneous nodule grew white, oxidase-positive colonies of gram-negative rods, and the biochemical profile (API 20NE; bioMérieux) strongly suggested Burkholderia pseudomallei (1556575: B. pseudomallei [98.3% identity]). The API profile from the pus isolate (1156154) initially suggested Chromobacterium violaceum, a recognized misidentification of B. pseudomallei, by API profiling (1). Antimicrobial susceptibility by disk diffusion indicated resistance to gentamicin and susceptibility to co-amoxiclav; colistin disk testing was unavailable. Because B. pseudomallei has not been reported from Malawi, we sought to confirm the isolate by real-time PCR, targeting the highly specific type III secretion system (2). DNA was extracted by using a Wizard Genomic Purification kit (Promega, Madison, WI, USA), and real-time PCR was performed on an Applied Biosystems 7900HT (Applied Biosystems, Foster City, CA, USA) by using a technique modified for SYBR green detection (2). This PCR confirmed the identity of the organism as B. pseudomallei. Whole-genome sequencing (WGS) was performed by using the MiSeq Personal Sequencer (Illumina, San Diego, CA, USA), which enabled multilocus sequence typing (MLST) (3) and revealed a novel allelic combination (1,3,3,1,5,1,1). This sequence type (ST) has been submitted to the MLST database (http://bpseudomallei.mlst.net/

) and has been assigned MLST ST1008, part of clonal complex 1.
The boy was given chloramphenicol for empiric treatment of systemic bacterial infection before the isolate was identified. In light of the anthropometric values, anorexia, fecal morphology, and symmetric pedal edema, acute kwashiorkor was diagnosed, and nutritional rehabilitation was begun. Pedal edema and anorexia improved after 48 hours. At 96 hours, B. pseudomallei infection was diagnosed, and treatment was changed to IV ceftazidime. Fever abated by day 7, and after 30 days of IV ceftazidime, the nodules had involuted and the dactylitis and arthritis had resolved. At the family’s request, the child was discharged on a 6-month regimen of cotrimoxazole, rather than the planned 6-week IV regimen for osteomyelitis.
Four weeks after discharge, the child remained well with no fevers and no new lesions; clinical anemia had resolved, and repeat radiographs showed that the hands were within normal limits. He was then lost to follow-up.