Melioidosis

Melioidosis is a life-threatening infection caused by the Gram-negative environmental saprophyte Burkholderia pseudomallei, endemic to Southeast Asia, northern Australia, and increasingly recognized in the southern United States and other tropical regions. [1-2] Often called "the great mimicker," it has protean clinical manifestations ranging from localized skin ulcers to fulminant septic shock with multi-organ abscesses, and carries a mortality of 9–70% depending on resources and time to diagnosis. [1][3] The following figure from the NEJM illustrates the pathogenesis and clinical spectrum of disease:

• Exposure history: Contact with soil or surface water in endemic regions (Southeast Asia, northern Australia, southern US, South America, Africa); occupational exposure (farming, construction, military); recreational muddy/wet environments [1-2]
• Travel history: Any travel to or residence in tropical/subtropical regions, even decades prior — latency with reactivation up to 62 years has been documented [4]
• Onset and timing: Acute (<2 months, ~89% of cases) vs. chronic (≥2 months, ~11%); seasonal peak during monsoon/wet season (80% of cases) [5-6]
• Symptom characterization: Fever (present in ~76%), productive cough ± hemoptysis, dyspnea, pleuritic chest pain, localized swelling/abscess, dysuria, bone/joint pain, neurologic deficits [4][7]
• Important negatives: Ask about weight loss, night sweats (mimics TB); prior episodes of melioidosis; near-drowning events (aspiration route) [4][8]

• Septic shock — occurs in ~21% of cases and is the strongest predictor of mortality [5][7]
• Rapidly progressive bilateral pneumonia with respiratory failure requiring mechanical ventilation (~16%) [5]
• Bacteremia without evident focus — suggests disseminated disease [4]
• Neurologic signs: Brainstem encephalitis with cranial nerve palsies (especially CN VII), myelitis, altered mental status [4][9]
• Multi-organ abscess formation (lungs, liver, spleen, prostate) [4][9]
• Hemoptysis with cavitary lung disease [10]
• Failure to respond to standard empiric antibiotics for community-acquired pneumonia/sepsis — a critical clue, as common empiric regimens do not cover B. pseudomallei [4]

Intensive Phase (IV, ≥10–14 days)

• First-line: IV ceftazidime (50 mg/kg up to 2 g q6–8h) [4][11]
• Severe/ICU: IV meropenem (25 mg/kg up to 1 g q8h) or imipenem [4-5]
• Adjunctive TMP-SMX may be added for deep-seated infections [8]

Eradication Phase (oral, ≥3 months, often 3–6 months)

• First-line: Oral TMP-SMX (TMP 6–8 mg/kg/day in two divided doses) [4][11-12]
• Alternative (children, pregnancy): Amoxicillin-clavulanate — associated with higher relapse rates [4][12]

Intrinsic Resistance (do NOT use)

• Penicillin, ampicillin, 1st/2nd-gen cephalosporins, aminoglycosides (gentamicin, tobramycin, streptomycin), polymyxins [4]
• Ertapenem, tigecycline, and moxifloxacin have limited activity [4]

Cautions

• ~25% of patients on TMP-SMX ± doxycycline develop adverse drug reactions; switching to amoxicillin-clavulanate increases relapse risk [12]
• Median time to fever defervescence is 9 days — slow response is expected and does not necessarily indicate treatment failure [9]

• No specific dietary triggers for melioidosis
• Hydration: Aggressive IV fluid resuscitation in septic patients per standard sepsis protocols
• Alcohol cessation: Hazardous alcohol use is a major independent risk factor (present in ~40% of cases) and should be addressed [5]
• Long-term: Optimize glycemic control in diabetic patients, as diabetes is the single most important comorbidity [1][5]

• Respiratory: Cough (productive), hemoptysis, dyspnea, pleuritic chest pain
• GU: Dysuria, perineal pain, urinary retention (prostatic abscess in ~20% of males in Australia) [4]
• MSK: Joint pain/swelling (septic arthritis), bone pain (osteomyelitis) — ~4% of cases [4]
• Neuro: Facial weakness, diplopia, limb weakness, gait disturbance (brainstem encephalitis/myelitis) [4]
• Skin: Localized ulcers, subcutaneous nodules, pustules, cellulitis [13]
• GI: Abdominal pain (hepatic/splenic abscesses), diarrhea
• Constitutional: Fever, rigors, night sweats, weight loss, fatigue [7]
• Head/neck (pediatric): Parotid swelling — up to 40% of pediatric cases in Thailand/Cambodia [4][9]

• Collateral: Occupational exposure (farming, rice paddies, construction), recreational soil/water contact, military service in endemic areas, recent natural disaster or flooding exposure [2][14]
• Family history: No hereditary predisposition, but household members with similar environmental exposures may also be at risk
• Social context: Socioeconomic disadvantage, rural residence in endemic areas, homelessness, injection drug use [2]
• Immigration/travel: Detailed lifetime travel history is essential — reactivation can occur decades after leaving an endemic area [4][8]

• Diabetes mellitus — present in ~45% of cases; the single most important risk factor [1][5][15]
• Hazardous alcohol use — ~40% of cases [5]
• Chronic kidney disease [8][16]
• Chronic lung disease (including COPD, cystic fibrosis) [8][16]
• Immunosuppression: Corticosteroid use, malignancy, thalassemia [1][15]
• Male sex (~63% of cases) [5]
• Age 40–60 years (median age ~50) [5][14]
• Occupational/environmental: Farming, soil/water contact, wet season exposure [2][14]
• 84% of patients have ≥1 underlying comorbidity; only 2% of fatalities had no identified risk factor [5]

• Tuberculosis — the most common mimic, especially chronic melioidosis with upper lobe cavitary disease [8][16]
• Community-acquired pneumonia (Klebsiella, Staphylococcus, Streptococcus) — acute pneumonic presentation [3]
• Lung abscess / empyema from other organisms
• Malignancy — chronic melioidosis with mass-like lesions can mimic lung cancer or lymphoma [16-17]
• Deep fungal infections: Histoplasmosis, coccidioidomycosis, penicilliosis
• Other tropical infections: Leptospirosis, typhoid fever, scrub typhus
• Visceral abscess from other causes: Amebic liver abscess, pyogenic liver abscess
• Mycotic aneurysm — rare but described with B. pseudomallei [18]

Key distinguishing feature: Failure to respond to standard empiric antibiotics (which lack B. pseudomallei coverage) in a patient with risk factors and endemic exposure should raise immediate suspicion. [4][17]

• Diabetes mellitus — screen HbA1c in all suspected cases; poorly controlled diabetes worsens outcomes [7][15]
• Prior melioidosis — recurrence in ~1 in 16 patients, often within the first year; ~75% are relapse, ~25% reinfection [4]
• Chronic renal disease, chronic liver disease, chronic lung disease [8][16]
• Immunosuppressive therapy or malignancy
• Splenectomy or functional asplenia
• Surgical history: Prior abscess drainage, prostatectomy
• Substance use: Alcohol use disorder, IV drug use

Vital Signs

• [5][7]

Focused Exam

• Lungs: Crackles, bronchial breath sounds, decreased breath sounds (consolidation, effusion, abscess)
• Abdomen: Hepatomegaly, splenomegaly, RUQ/LUQ tenderness (hepatic/splenic abscesses) [4][19]
• Skin: Localized ulcers with surrounding erythema, subcutaneous abscesses, pustules, cellulitis, disseminated papular/pustular lesions [4][13]
• Head/neck: Parotid gland swelling (children in SE Asia), cervical lymphadenopathy [9][20]
• GU: Perineal tenderness, prostatic tenderness/boggy prostate on DRE (prostatic abscess) [4]
• MSK: Joint effusion, warmth, limited ROM (septic arthritis); bony tenderness (osteomyelitis) [4]
• Neuro: Cranial nerve palsies (especially CN VII), limb weakness, flaccid paraparesis (myelitis), cerebellar signs [4][9]

• Blood cultures (×2 minimum) — the gold standard; positive in ~56% of cases [4-5]
• Sputum culture — alert the microbiology lab to suspect B. pseudomallei to avoid misidentification [4][8]
• Throat swab culture — useful adjunct in endemic settings [8]
• Urine culture — especially in GU presentations
• Wound/abscess aspirate culture
• CBC: Leukocytosis or leukopenia; thrombocytopenia in severe sepsis
• CMP: Hyponatremia (common), elevated creatinine (renal impairment), hyperglycemia/new diabetes diagnosis [21]
• LFTs: Elevated if hepatic abscesses present
• Lactate, ABG: Metabolic acidosis in septic shock [21]
• HbA1c: Screen for undiagnosed or poorly controlled diabetes in all cases
• CRP/Procalcitonin: Elevated; nonspecific but useful for monitoring
• PCR for B. pseudomallei: More rapid than culture but less sensitive, especially on blood [4]
• Serology (IHA): Limited diagnostic value — background seropositivity >50% in endemic areas; not adequate for confirming diagnosis [4]

First-line

• Chest X-ray: Acute — diffuse nodular infiltrates, alveolar consolidation (often multilobar/bilateral), rapid cavitation; chronic — upper lobe infiltrates with cavities mimicking TB, often sparing the apices [8][22]
• Pleural effusion/empyema in ~21% of acute cases [22]

Gold Standard / Advanced

• CT chest: Better delineates lung abscesses, cavitation, mediastinal lymphadenopathy [19][23]
• CT abdomen/pelvis (or ultrasound): Recommended in all cases to search for internal-organ abscesses — liver, spleen, prostate, kidney [4][19]
  • Multiple small discrete abscesses in liver and spleen simultaneously are highly suggestive of visceral melioidosis [19]
  • "Honeycomb" appearance described in large hepatic abscesses [24]
• MRI: For musculoskeletal involvement (osteomyelitis, septic arthritis) or neurologic melioidosis (brainstem encephalitis) [19]

When imaging is unnecessary

• [5]

• Ashdown selective agar: Specialized culture medium that enhances B. pseudomallei recovery from non-sterile sites [1]
• MALDI-TOF mass spectrometry: Increasingly used for rapid identification, though databases must include B. pseudomallei [1]
• Latex agglutination test: Rapid bedside test for colony identification
• Indirect hemagglutination assay (IHA): Titer ≥1:160 suggestive but not confirmatory in endemic areas [25]
• Fine-needle aspiration (FNA) of abscesses with inoculation into blood culture bottles — improves diagnostic yield, especially for head/neck lesions [20]
• Prostate-specific antigen (PSA): May be elevated with prostatic abscess; DRE and imaging guide diagnosis

• No melioidosis-specific ECG findings; direct cardiovascular involvement by B. pseudomallei is rare [18]
• Indications for ECG: All patients with sepsis/septic shock — standard sepsis workup
• Findings in sepsis context: Sinus tachycardia (most common), QT prolongation, new atrial fibrillation/flutter — all associated with worse outcomes in sepsis generally [26]
• Rare cardiovascular complications: Pericardial involvement (~6% of acute pulmonary cases), mycotic aneurysm [18][22]

Clinical Summary

Melioidosis is a potentially fatal tropical infection with an extraordinarily diverse clinical spectrum. It should be suspected in any patient with sepsis, pneumonia, or deep-seated abscesses who has risk factors (diabetes, alcohol use, CKD) and relevant environmental/travel exposure to endemic regions. [1][4][15]

Severity Stratification

• Mild/localized: Skin abscess, localized soft tissue infection without bacteremia — mortality <1% [5]
• Moderate: Pneumonia without shock, single organ abscess — mortality ~10–15%
• Severe: Bacteremic pneumonia, septic shock, multi-organ abscesses, neurologic involvement — mortality 20–50% depending on resources [5][7]

Typical vs. Atypical

• Typical: Febrile adult with diabetes presenting with community-acquired pneumonia during wet season in endemic area
• Atypical: Chronic cavitary lung disease mimicking TB; parotid abscess in a child; brainstem encephalitis; reactivation decades after exposure in a non-endemic country [4][8]

• Septic shock, ARDS, multi-organ failure
• Relapse (~6–10% even with full treatment; 16% within 10 years in Thailand) [9][12]
• Mycotic aneurysm (rare) [18]
• Chronic osteomyelitis

Initial Stabilization (ED)

• Standard sepsis resuscitation: IV fluids, vasopressors if needed, supplemental O₂/intubation
• Obtain cultures (blood ×2, sputum, urine, wound) before antibiotics — alert microbiology lab to suspect B. pseudomallei [4][8]

Intensive Phase (minimum 10–14 days IV)

• Ceftazidime 50 mg/kg (max 2 g) IV q6–8h — first-line [4][11]
• Meropenem 25 mg/kg (max 1 g) IV q8h — preferred for ICU patients, severe disease, or treatment failure [4-5]
• Consider adjunctive TMP-SMX for deep-seated infections (bone, CNS, prostate) [8]

Eradication Phase (minimum 3 months, up to 6 months oral)

• TMP-SMX (TMP 6–8 mg/kg/day divided BID) [4][11-12]
• Alternative: Amoxicillin-clavulanate (children, pregnancy) — higher relapse risk [12]

Adjunctive

• Abscess drainage: Surgical or percutaneous drainage of all drainable collections (liver, spleen, prostate, soft tissue) [1][4]
• Septic joint washout [4]
• Glycemic optimization in diabetic patients
• Alcohol cessation counseling

Admission Criteria (all suspected/confirmed cases should be admitted):

• Any bacteremia, pneumonia, or deep-seated organ involvement
• Sepsis or septic shock — ICU admission (~24% require ICU) [5]
• Need for IV antibiotics (minimum 10–14 days)
• Mechanical ventilation required in ~16% [5]

Observation

Specialist Consultation Triggers

• Infectious Disease — mandatory for all cases; directs antibiotic therapy and duration [5]
• Surgery/IR — for abscess drainage (hepatic, splenic, prostatic, soft tissue)
• ICU/Critical Care — septic shock, respiratory failure, multi-organ dysfunction
• Neurology/Neurosurgery — brainstem encephalitis, cerebral abscess, myelitis

Discharge Criteria

• Clinical improvement, afebrile, tolerating oral medications
• Transition to oral eradication therapy (TMP-SMX)
• Infectious disease follow-up arranged

Follow-up Timing

• Weekly clinic visits initially after discharge, then monthly during eradication therapy [5]
• Follow-up continued ideally ≥6 months after completion of therapy [5]
• Repeat imaging to document resolution of abscesses

Adherence

• half of patients do not complete eradication therapy[5]

Return Precautions — seek immediate care for

• Recurrence of fever, chills, or rigors
• New or worsening cough, dyspnea, hemoptysis
• New swelling, abscess, or skin lesion
• Neurologic symptoms (facial weakness, limb weakness, confusion)
• Abdominal pain (concern for new visceral abscess)
• Medication side effects (rash, GI intolerance from TMP-SMX)

Expected Recovery

• Slow clinical response is typical — median fever defervescence is 9 days on appropriate IV therapy [9]
• Recurrent melioidosis occurs in ~1 in 16 patients, most within the first year [4]
• Lifelong awareness needed in patients from endemic areas, as reactivation from latency is possible [4][8]

1. Human Melioidosis. — Gassiep I, Armstrong M, Norton R. Clinical Microbiology Reviews. 2020.

2. Burkholderia Pseudomallei and Melioidosis. — Meumann EM, Limmathurotsakul D, Dunachie SJ, Wiersinga WJ, Currie BJ. Nature Reviews. Microbiology. 2024.

3. Melioidosis: A Neglected Cause of Community-Acquired Pneumonia. — Virk HS, Mukhopadhyay C, Wiersinga WJ. Seminars in Respiratory and Critical Care Medicine. 2020.

4. Melioidosis. — Wiersinga WJ, Currie BJ, Peacock SJ. The New England Journal of Medicine. 2012.

5. The Darwin Prospective Melioidosis Study: A 30-Year Prospective, Observational Investigation. — Currie BJ, Mayo M, Ward LM, et al. The Lancet. Infectious Diseases. 2021.

6. Global Burden of Melioidosis in 2015: A Systematic Review and Data Synthesis. — Birnie E, Virk HS, Savelkoel J, et al. The Lancet. Infectious Diseases. 2019.

7. Improving the Clinical Recognition, Prognosis, and Treatment of Melioidosis Through Epidemiology and Clinical Findings: The Sabah Perspective. — Hussin A, Nor Rahim MY, Dalusim F, et al. PLoS Neglected Tropical Diseases. 2023.

8. Melioidosis: An Important Cause of Pneumonia in Residents of and Travellers Returned From Endemic Regions. — Currie BJ. The European Respiratory Journal. 2003.

9. Melioidosis. — White NJ. Lancet. 2003.

10. Locally Acquired Melioidosis Linked to Environment — Mississippi, 2020–2023. — Petras JK, Elrod MG, Ty MC, et al. The New England Journal of Medicine. 2023.

11. Treatment of Melioidosis. — Meumann EM, Rajahram G, Woolley SD, Smith S, Gassiep I. Infectious Disease Clinics of North America. 2026.

12. Trimethoprim-Sulfamethoxazole Versus Trimethoprim-Sulfamethoxazole Plus Doxycycline as Oral Eradicative Treatment for Melioidosis (MERTH): A Multicentre, Double-Blind, Non-Inferiority, Randomised Controlled Trial. — Chetchotisakd P, Chierakul W, Chaowagul W, et al. Lancet. 2014.

13. Cutaneous Melioidosis: An Updated Review and Primer for the Dermatologist. — Schwartzman G, Reddy SA, Berg SH, Currie BJ, Saavedra AP. Journal of the American Academy of Dermatology. 2023.

14. Missing Links of Melioidosis in India: A Cross-Sectional Analysis of Case Reports, Agrometeorological and Socioeconomic Factors. — Jha S, Mittal M, Prasad LR, et al. Scientific Reports. 2025.

15. Melioidosis. — Wiersinga WJ, Virk HS, Torres AG, et al. Nature Reviews. Disease Primers. 2018.

16. Management of Accidental Laboratory Exposure to Burkholderia Pseudomallei and B. Mallei. — Peacock SJ, Schweizer HP, Dance DA, et al. Emerging Infectious Diseases. 2008.

17. Pitfalls and Optimal Approaches to Diagnose Melioidosis. — Kingsley PV, Arunkumar G, Tipre M, Leader M, Sathiakumar N. Asian Pacific Journal of Tropical Medicine. 2016.

18. ACCF/­AHA/­CDC Conference Report on Emerging Infectious Diseases and Biological Terrorism Threats. Task Force I: Direct Cardiovascular Implications of Emerging Infectious Diseases and Biological Terrorism Threats. — Baddour LM, Zheng ZJ, Labarthe DR, O'Connor S. Journal of the American College of Cardiology. 2007.

19. Spectrum of Imaging Findings in Melioidosis. — Muttarak M, Peh WC, Euathrongchit J, et al. The British Journal of Radiology. 2009.

20. Fine-Needle Aspiration to Improve Diagnosis of Melioidosis of the Head and Neck in Children: A Study From Sarawak, Malaysia. — Mohan A, Podin Y, Liew DW, et al. BMC Infectious Diseases. 2021.

21. Bacteraemic Melioidosis Pneumonia: Impact on Outcome, Clinical and Radiological Features. — Mukhopadhyay A, Lee KH, Tambyah PA. The Journal of Infection. 2004.

22. Pulmonary Melioidosis: Clinical-Radiologic Correlation in 183 Cases in Northeastern Thailand. — Dhiensiri T, Puapairoj S, Susaengrat W. Radiology. 1988.

23. Clinical-Radiological Features and Diagnostic Modalities for Mediastinal Melioidosis. — Nyanti LE, Lee SSY, Shanmugam V, et al. The International Journal of Tuberculosis and Lung Disease : The Official Journal of the International Union Against Tuberculosis and Lung Disease. 2023.

24. Radiological Manifestations of Melioidosis. — Lim KS, Chong VH. Clinical Radiology. 2010.

25. Clinical Presentation and Treatment of Melioidosis in the Head and Neck Region. — Mahawerawat K, Kasemsiri P. The Journal of Laryngology and Otology. 2018.

26. Association of Electrocardiogram Abnormalities With Clinical Outcomes in Emergency Department Sepsis Patients. — Kotruchin P, Chuehongthong M, Tangpaisarn T, et al. The Western Journal of Emergency Medicine. 2026.