Melioidosis: Symptoms, Types, Causes and Treatment

Melioidosis is an infectious disease that has long challenged doctors and scientists due to its complex presentation, broad spectrum of symptoms, and significant risk to vulnerable populations. Caused by the bacterium Burkholderia pseudomallei, this disease is most common in tropical climates such as Southeast Asia and northern Australia—but as awareness grows, cases are increasingly recognized worldwide. Understanding melioidosis is crucial, not just for healthcare providers in endemic regions but globally, as international travel and climate change alter the patterns of infectious diseases.

Symptoms of Melioidosis

Melioidosis often confounds doctors with its chameleon-like ability to mimic other infections. The symptoms range from mild, localized ailments to life-threatening sepsis. Recognizing these symptoms early can be lifesaving, particularly for people with underlying health issues.

Symptom	Presentation	Commonality	Source
Fever	High, persistent	Very common	1 2 3
Pneumonia	Cough, breathlessness	Frequent	1 2 4
Abscesses	Liver, spleen, skin	Common	1 2 4
Neurological	Headache, seizures	Rare but severe	3 4
Skin Lesion	Ulcer, nodule	10–20% of cases	5 4 7
Sepsis	Rapid progression	Severe cases	1 2 6

Table 1: Key Symptoms

Overview of Symptom Profiles

Symptoms vary based on the type and severity of infection, the patient’s health, and the site of bacterial entry. The initial presentation can be misleading, often resembling other diseases such as tuberculosis or common bacterial infections, making laboratory confirmation essential for diagnosis 1 4 8.

Respiratory Manifestations

Pneumonia is among the most common forms, presenting with high fever, cough, chest pain, and difficulty breathing. In severe cases, respiratory failure may require intensive care 1 2 4. Melioidosis-related pneumonia can be acute, subacute, or chronic, sometimes mimicking tuberculosis or other forms of pneumonia 7.

Abscess Formation

A hallmark of melioidosis is the tendency to cause abscesses in diverse organs—especially the liver, spleen, lungs, skeletal muscle, skin, and prostate 1 2 4. These abscesses may be multiple and can be detected via imaging or aspiration. Parotid abscesses are particularly notable in children in Southeast Asia 2.

Neurological and Uncommon Symptoms

Central nervous system involvement is rare but serious, manifesting as headache, seizures, cranial nerve deficits, and in some cases, encephalomyelitis or brain abscesses. CNS melioidosis is associated with high mortality and often affects the brainstem and frontal lobes 3 4. Unusual presentations such as vascular aneurysms, joint pain, or focal seizures have also been documented 4.

Skin and Soft Tissue Involvement

Cutaneous melioidosis appears in 10–20% of cases, often as ulcers, nodules, or cellulitis. Skin involvement may be the only sign in some patients, particularly those exposed through broken skin 5 7.

Types of Melioidosis

Melioidosis presents in several clinical forms, each with distinct features. Understanding these types helps guide diagnosis and management, as well as prognosis.

Type	Description	Risk/Outcome	Source
Acute	Rapid onset, severe sepsis	High mortality	1 2 6
Chronic	Prolonged, mild symptoms	May mimic TB	1 7
Localized	Skin/soft tissue focus	Better prognosis	5 4
Disseminated	Multiple organ abscesses	Severe, systemic	1 2 4
CNS	Neurological symptoms	Rare, serious	3 4

Table 2: Forms of Melioidosis

Acute Melioidosis

This is the most dangerous form, characterized by sudden onset of fever, rapidly progressive pneumonia, septic shock, and multiple organ failure. Without prompt intervention, the mortality rate can be extremely high—up to 50% in some regions 1 2 6.

Chronic Melioidosis

Chronic cases develop over months or years, often presenting with vague symptoms such as weight loss, cough, and low-grade fever. These cases are sometimes mistaken for tuberculosis or malignancy 1 7. Chronic infection may smolder for years before reactivating, especially if the immune system becomes compromised 1 7.

Localized Melioidosis

Localized infection typically appears as a skin ulcer, nodule, or abscess, often at the site of inoculation. These cases have a better prognosis and may resolve spontaneously or with oral antibiotics 5 4.

Disseminated Melioidosis

Disseminated disease involves spread to multiple organs, usually with abscess formation in the lungs, liver, spleen, prostate, and sometimes bone or joints. This type often follows bacteremia and is associated with severe sepsis and high mortality 1 2 4.

Central Nervous System (CNS) Melioidosis

CNS involvement is rare but critical. Patients may experience fever, headache, seizures, cranial nerve palsies, and focal neurological deficits. Imaging may reveal brain abscesses or encephalomyelitis, often with rim-enhancing lesions 3 4. Early recognition is vital due to the high risk of death.

Causes of Melioidosis

Melioidosis is caused by the bacterium Burkholderia pseudomallei, an environmental organism with unique characteristics that make it a formidable pathogen.

Cause	Details	Risk Groups	Source
Bacterium	B. pseudomallei	All ages, especially adults	1 2 6
Environmental	Wet soil, stagnant water	Farmers, outdoor workers	1 6 7
Entry Route	Inhalation, skin, ingestion	Open wounds, inhalation	1 7
Risk Factors	Diabetes, alcohol, kidney/lung	Immunocompromised	1 2 6

Table 3: Causes and Risk Factors

The Bacterial Agent

Burkholderia pseudomallei is a Gram-negative bacillus found in wet soils, particularly in rice paddies, stagnant water, and moist environments in tropical regions 1 2 6. It is a resilient saprophyte, capable of surviving in harsh conditions and evading immune responses.

Environmental Exposure

Most infections occur through direct contact with contaminated soil or water, particularly via skin abrasions, inhalation of dust or aerosols, or sometimes ingestion 1 6 7. Occupations such as farming, construction, and gardening, especially in endemic areas, carry higher risk.

Modes of Transmission

• Percutaneous Inoculation: The most common route; bacteria enter through cuts or abrasions.
• Inhalation: Especially during severe weather events like cyclones, where contaminated water or dust is aerosolized 7.
• Ingestion: Less common, but possible through contaminated water 1 7.

Host Risk Factors

Certain underlying conditions dramatically increase susceptibility:

• Diabetes Mellitus: The most significant risk factor, likely due to impaired immune function 1 2 6.
• Chronic Kidney or Lung Disease: Weakened immunity increases vulnerability 1.
• Alcohol Abuse: Associated with impaired neutrophil function 1 2.
• Other Immunocompromised States: HIV/AIDS, cancer, steroid therapy, and other causes of immune suppression 1 2 6.

Pathogenesis

The bacterium has evolved mechanisms to evade immune defenses, such as a type III secretion system, enabling survival within phagocytes. This contributes to persistent infection and relapse 6. Notably, repeated exposure does not seem to confer immunity, and there is no effective vaccine available yet 6.

Treatment of Melioidosis

Treating melioidosis is challenging and requires a prolonged, multi-phase approach. Timely intervention can dramatically improve outcomes, but access to appropriate care remains an issue in many endemic regions.

Phase	Treatment(s)	Duration	Source
Intensive	IV ceftazidime/carbapenem	10–14+ days	2 11 13
Eradication	Oral trimethoprim-sulfamethoxazole, doxycycline, or amoxicillin-clavulanate	12–20 weeks	2 11 12 13
Alternatives	Amoxicillin-clavulanate (children, pregnancy)	Varies	2 11 13
Supportive	Abscess drainage, ICU care	As needed	4 11 13

Table 4: Melioidosis Treatment Overview

Phases of Therapy

Treatment is divided into two main phases to reduce mortality and prevent relapse:

• Intensive (Acute) Phase: Hospital-based intravenous antibiotics for 10–14 days or longer, depending on disease severity and organ involvement 2 11 13.
• Eradication (Maintenance) Phase: Prolonged oral antibiotics for at least 12–20 weeks, crucial to prevent relapse 2 11 13.

First-Line Medications

• Ceftazidime: Considered the gold standard for acute therapy. Carbapenems (e.g., meropenem) are reserved for severe, resistant, or treatment-refractory cases 2 11 13.
• Trimethoprim-sulfamethoxazole (TMP-SMX): The drug of choice for the oral eradication phase, often combined with doxycycline 2 11 12 13.
• Amoxicillin-clavulanate: Preferred in children, pregnant women, or patients intolerant of first-line drugs 2 11 13.

Duration and Adjustments

• Intensive Phase: Typically 10–14 days, but can be extended (up to 4 weeks or more) in cases with deep-seated abscesses, osteomyelitis, or CNS involvement 12 13. Recent guidelines recommend tailoring the duration based on disease severity and clinical response 12.
• Eradication Phase: At least 12–20 weeks; shorter courses risk relapse 2 10 13. However, studies suggest that relapse is rare when intensive therapy is adequate, even if eradication therapy is incomplete 10 12.

Supportive and Adjunctive Care

• Abscess Drainage: Surgical or image-guided drainage of abscesses is often required, especially for deep-seated infections 4 11 13.
• Supportive Care: Intensive care for septic shock, organ support, and management of complications is essential in severe cases 1 2 13.

Challenges and Future Directions

• Drug Resistance: Resistance is rare, but monitoring is necessary, especially for TMP-SMX 13.
• Resource Limitations: In many endemic areas, cost and access to medications remain barriers to optimal care 11 13.
• Vaccine Development: Research continues, but no vaccine is available yet 6.
• Relapse and Recrudescence: Prolonged and tailored therapy, with surgical management of persistent foci, helps minimize recurrence 10 12 13.

Conclusion

Melioidosis is a complex, potentially fatal disease that demands awareness, early diagnosis, and rigorous treatment. Its protean nature means it can mimic many other illnesses, making clinical suspicion and laboratory confirmation crucial, especially in those with risk factors like diabetes or chronic disease.

Key Takeaways:

• Melioidosis symptoms are highly variable, ranging from mild skin lesions to fulminant sepsis and multi-organ failure.
• Several clinical types exist, including acute, chronic, localized, disseminated, and rare CNS forms.
• Caused by Burkholderia pseudomallei, infection is most common through contact with contaminated soil or water, particularly in at-risk populations.
• Treatment involves a two-phase regimen: intensive intravenous antibiotics followed by prolonged oral therapy, often with surgical intervention for abscesses.
• Early detection and tailored therapy significantly improve outcomes, but resource limitations and lack of a vaccine remain challenges.

By improving recognition, investing in diagnostic and treatment infrastructure, and supporting research, we can reduce the burden of this enigmatic and dangerous disease.