Abscesses due to Melioidosis: A case-based review

Highlights

• •Melioidosis can involve any part of the body, often together. Since inhalation and percutaneous inoculation routes are the common modes of transmission, lung and skin are the most common sites of involvement.
• •While some patients present acutely with sepsis and multi-organ failure, others present with a subacute to chronic course characterised by abscess formation.
• •Pulmonary, osteoarticular and genitourinary abscesses have high rates of concomitant bacteremia, as opposed to central nervous system and cutaneous sites.
• •The antimicrobial treatment of abscesses due to melioidosis begins with an intensive phase of meropenem or ceftazidime, followed by an eradication phase with cotrimoxazole.
• •Abscess drainage is recommended for prostatic involvement but may be required on a case-to-case basis for abscesses at other sites as well.

Abstract

Melioidosis is caused by percutaneous inoculation or inhalation of Burkholderia pseudomallei, predominantly among individuals with risk factors (diabetes mellitus, immunosuppression, etc.) from endemic areas of South Asia, Southeast Asia and Northern Australia. While some patients present acutely with sepsis and multi-organ failure, others present with a subacute to chronic course characterised by abscess formation. We present nine representative cases, each with an abscess at a separate site (lung, skin, bone/ joint, prostate, parotid gland, liver, spleen, brain and orbits). Using these cases as examples, we reviewed the literature on abscesses in various organs.

Graphical abstract

Introduction

Melioidosis, caused by Burkholderia pseudomallei, a gram-negative facultative intracellular bacterium, is endemic to South Asia (including India), Southeast Asia and Northern Australia (Cheng and Currie, 2005). It is caused by exposure to contaminated soil or surface water by percutaneous inoculation, inhalation or, rarely, ingestion (Cheng and Currie, 2005). Predisposing factors for melioidosis involve various forms of immunosuppression, including uncontrolled DM, chronic alcohol use disorder and other chronic diseases, such as chronic renal failure (Cheng and Currie, 2005). The lung is the most commonly involved organ, but any organ can be involved, ranging from skin to bone to viscera (Cheng and Currie, 2005). While some patients present with sepsis and multi-organ failure, others present with a subacute to chronic course characterised by abscess formation (Cheng and Currie, 2005). The clinical picture of these abscesses is variable, with a broad range of differential diagnoses (Cheng and Currie, 2005). Correctly identifying these patients is crucial to achieving favourable outcomes. Using real cases as examples in our review, we aim to explore the various organs that can have abscesses due to B.pseudomallei.

Case series

We present nine representative cases (after taking informed consent), each with an abscess at a separate site (Table 1). Many patients had abscesses at multiple sites. Most of our patients presented to our hospital from June to October (The season of heavy rainfall in South India). All except one of the patients had poorly controlled Diabetes Mellitus (DM). The duration of illness at presentation ranged from 1 week to 3 months. Apart from the growth of B. pseudomallei from pus/tissue specimens of the affected site, four patients had concurrent bacteraemia. All patients were successfully treated with intensive intravenous meropenem or ceftazidime therapy for 2–4 weeks, followed by an eradication phase that included either cotrimoxazole or amoxicillin-clavulanic acid for 4–6 months.

Table 1.

Demography, risk factors, presenting features, diagnostics and treatment of patients with abscesses due to B. pseudomallei.

Sn	Age range	Gender	Occupation	Site of abscess	HBA1C (%)	DOI (days)	Presenting features	Culture positivity	IP	EP	Outcome
1	50	M	FO	Extradural	11.2	7	Fever, headache	Tissue, Pus	Caz for 2 wks	Ctx for 4 mo	Recovered
2	52	M	FO	Orbital		10	Fever, eye swelling	Blood	Mer for 2 wks	Ctx for 4 mo	Recovered
3	36	M	FO	Lung, parotid	10	20	Fever, facial swelling	Blood, tissue	Mer for 4 wks	Ctx for 4 mo	Recovered
4	71	M	Retired*	Lung, skin	11	30	Fever, cough, left arm swelling	BAL, pus	Caz for 2 wks	Ctx for 4 mo	Recovered
5	41	M	Fisherman	Pericardial	8.2	14	Fever, cough	Pericardial fluid	Mer for 2 wks	Amx-Clav + Doxy for 4 mo	Recovered
6	39	M	Civil Engineer*	Lung, liver, spleen, skin	11.2	15	Fever, cough	Blood	Mer for 2 wks	Ctx for 4 mo	Recovered
7	42	M	Software Engineer*	Bone, prostrate	9	20	Fever, weight loss	Bone biopsy	Mer for 3 wks	Ctx for 4 mo	Recovered
8	34	M	FO	Liver	9.2	15	Fever, abdominal pain	Blood, pus	Mer for 3 wks	Ctx for 4 mo	Recovered
9	42	M	FO	Brain	6.7	90	Fever, headache	Pus	Caz for 4 wks	Ctx for 6 mo	Recovered

^⁎Involved in the farming in their local garden/farm

Abbreviations: Sn: Serial number, Age range (in years), M-Male, FO- Farming and other outdoor work, HBA1C- Glycosylated haemoglobin in percentage, DOI- Duration of illness at presentation, IP- Intensive phase, Mer- Meropenem, Caz- Ceftazidime, wks- weeks, EP- Eradication phase, Ctx-cotrimoxazole, mo-months.

Discussion

Melioidosis presenting as an abscess can have a broad range of differential diagnoses, such as tuberculosis, fungal infections or other bacterial infections due to ubiquitous bacteria such as Staphylococcus aureus or Klebsiella pneumoniae. It is important to suspect melioidosis early and start empirical treatment to avoid poor outcomes. Patients coming from endemic areas, especially after heavy rains or severe weather events, should be suspected of melioidosis (Cheng and Currie, 2005). In the Darwin study, for every 100 mm increase in rainfall, the incidence of melioidosis increased by 14 % (Cheng and Currie, 2005). Patients who are exposed to soil or surface water because of their occupation are at increased risk (Cheng and Currie, 2005). All our patients were involved in farming, fishing, or both. This explains the predominance of middle-aged males in our series, similar to large prospective cohorts (Currie et al., 2021). Diabetes mellitus is the most common risk factor for melioidosis, especially when it is uncontrolled (Cheng and Currie, 2005; Currie et al., 2021; Suputtamongkol et al., 1999). All except one of our patients was diabetic. It must be noted that although these risk factors are more common in patients with melioidosis, they are frequently seen with other infectious etiologies.

Melioidosis can involve any part of the body, often together. Since inhalation and percutaneous inoculation routes are the common modes of transmission, lung and skin are the most common sites of involvement (Table 2). Bones, joints, genitourinary and central nervous systems are other sites that can be involved (Table 2). The predominant manifestation in most extra-pulmonary sites is the development of abscesses (Cheng and Currie, 2005). Clinically, a melioidosis patient presenting with abscesses is usually stable at presentation and not in shock (Currie et al., 2021). This contrasts with patients presenting with acute onset community-acquired pneumonia, where the patient is commonly in shock at presentation (Nisarg et al., 2024). None of our patients were clinically unstable at presentation.

Table 2.

Summary of organ involvement and associated bacteremia due to melioidosis in two big cohort studies.

Sn	Site of involvement	Darwin 30-year cohort study (n = 1148)		Thailand cohort study (n = 1352)
		Total (%)	Bacteremia (%)	Total (%)	Bacteremia (%)
1	Lung	52	62	42	76
2	Cutaneous (skin and soft tissue)	17	7	23	54
3	Osteoarticular	4	68	9	78
4	Genitourinary	12	58	13	88
5	CNS	2	21	1	64

Abbreviation: CNS- Central Nervous system.

Isolation of the organism via bacterial culture is the gold standard for diagnosis. Blood culture should be performed in all patients as it can be positive in 40–70 % of the cases (Gassiep et al., 2020). In a study of 71 melioidosis patients, automated blood cultures were positive within 24 h in 62.5 % of the patients with bacteremia (Tiangpitayakorn et al., 1997). Almost all patients with bacteremia were positive by 48 h in that study (Tiangpitayakorn et al., 1997). Bacteremia in melioidosis differs with the involved site, with pulmonary, osteoarticular and genitourinary sites having high rates of concurrent bacteremia. In contrast, Central Nervous System (CNS) and cutaneous sites have a low percentage of bacteremia. Table 2 shows the most common sites of involvement in two major cohorts and the rate of bacteremia associated with each site of involvement. For example, of all melioidosis cases in the Darwin cohort, 52 % had lung involvement, and of those with lung involvement, 62 % had bacteremia (Table 2). B.pseudomallei grows well in routine culture media. For non-sterile sites, selective media containing gentamicin and colistin can be used (Gassiep et al., 2020). It displays a “bipolar safety pin” appearance on Gram stain, but this may be seen in other gram-negative bacteria as well (Gassiep et al., 2020). On culture media, it appears as wrinkled colonies, which are non-lactose fermenting and oxidase-positive (Gassiep et al., 2020). Unless there is concurrent bacteremia, melioidosis in a patient with an abscess is difficult to diagnose without invasive procedures (Currie et al., 2021). In a resource-limited setting, this can be challenging (Cheng and Currie, 2005). It is, therefore, pertinent for treating clinicians to be aware of the various clinical and radiological features of melioidosis at various sites.

The antimicrobial treatment of abscesses due to melioidosis begins with an intensive phase of meropenem or ceftazidime, followed by an eradication phase with cotrimoxazole. Observational studies have shown some advantages of using carbapenems (over ceftazidime) in critically ill adults or those with neurological involvement (Stephens et al., 2016). It must be noted that randomized controlled trials have shown no difference in mortality between the two drugs (Simpson et al., 1999). Some authors recommend adding cotrimoxazole during the intensive phase, but randomized controlled trials do not support this (Chierakul et al., 2005). For the eradication phase, doxycycline or amoxicillin-clavulanate can be used as alternatives to cotrimoxazole. Alternative agents should be used only when cotrimoxazole cannot be used, as these agents are possibly less effective than cotrimoxazole (Rajchanuvong et al., 1995; Currie et al., 2000). The minimum duration of the intensive phase is two weeks. Some authors suggest a longer duration (of up to 4–6 weeks) in non-pulmonary melioidosis. A retrospective cohort study showed that a shorter duration of the intensive phase was associated with relapse (Pitman et al., 2015). The eradication phase of three months or more is recommended. In a study that compared the eradication phase of ≤2 months with ≥3 months, the relapse rate was significantly lower with a longer duration of therapy (Limmathurotsakul et al., 2006). Eradication therapy may be extended in the presence of a delayed or poor response, especially in CNS or osteoarticular melioidosis. Some authors recommend abscess drainage for only prostatic involvement (Morse et al., 2009). In routine clinical practice, drainage may be required on a case-to-case basis, especially for neurological melioidosis. Below, we discuss the clinical features, diagnosis and management of abscesses in different organs in separate headings (Table 3).

Table 3.

Summary of abscesses at various sites: Epidemiological, clinical and radiological findings along with treatment and outcome of melioidosis at various sites.

Site of involvement	Epidemiological characteristic	Clinicoradiological features	Treatment duration	Outcome
Lung	Most common organ	-Multilobar involvement in acute -Upper lobe involvement in chronic	IP-2 weeks EP-12 weeks	Poor outcomes in acute
Cutaneous	-Percutaneous inoculation or haematogenous dissemination	-Abscesses, cellulitis, ulcers	IP-2 weeks EP-12 weeks	Low mortality
Osteoarticular	History of trauma	-Lower limb bones and joints -Multifocal involvement possible	Surgical debridement if there is a high risk of relapse	-Low mortality -Relapse
Brain	Common in North Australia	-Frontoparietal macro abscesses -Microabscesses along the corticospinal tract	Longer duration	Low mortality
Parotid	More common in children	Unilateral	Longer duration	Low mortality
Pericardial	Uncommon	Similar to TB pericarditis	Longer duration	Less data
Hepatosplenic	Higher rates in Southeast Asia	-Multiseptate multilocular abscess -honeycomb, necklace sign -Multiple abscesses in the spleen	Longer duration	Low mortality
Prostrate	-Ingestion of contaminated water -Higher rates in Southeast Asia	-Peripheral involvement -PSA negative	Surgical drainage (if >1cm)	Low mortality

Abbreviation: IP- Intensive phase, EP- Eradication phase, TB- Tuberculosis, PSA- Prostate-specific antigen.

Lung abscess

Pulmonary involvement in melioidosis is common and is associated with a poor outcome (Currie et al., 2021; Currie et al., 2000). The increase in cases after heavy storms suggests that inhalation is the primary route of lung involvement (Limmathurotsakul et al., 2013). An alternate view suggests transmission is commonly percutaneous, and the bacteria reaches the lung by a haematogenous route (Currie et al., 2000). In a study from Northern Australia, the patient recalled a percutaneous inoculation event in 25 % of the cases (Currie et al., 2000). Lung involvement secondary to B. pseudomallei bacteremia can have features similar to septic emboli (peripheral nodules), whereas lung involvement through inhalation is likely more central. The radiological pattern of lung involvement also differs between acute vs subacute or chronic melioidosis. In acute fulminant melioidosis, the lower lobe is involved in 55 % of the cases (Meumann et al., 2012). Multi-lobar involvement is also not uncommon (30 %) in acute cases (Meumann et al., 2012). Chronic pulmonary melioidosis is predominantly restricted to single lobes and preferentially involves the upper lobe (Meumann et al., 2012). Abscesses are more common in patients with subacute or chronic cases. In a series from Thailand, 7 % of the subacute/ chronic cases had lung abscesses (Reechaipichitkul, 2004).

The clinical and radiologic picture is often indistinguishable from pulmonary tuberculosis or invasive fungal infections. Computed tomography scans may also show a reversed halo sign in uncontrolled diabetics, mimicking pulmonary mucormycosis (Fig. 1) (Gupta et al., 2024). They can have centrilobular nodules, but hilar adenopathy is rare (Meumann et al., 2012; Gupta et al., 2024). Melioidosis is also known to cause pleural or pericardial effusion (like in Case 5). In a large series from Thailand, pleural and pericardial effusion was seen in 15 % and 3 %, respectively, of the subacute/ chronic melioidosis cases (Reechaipichitkul, 2004). Like case 5, in endemic areas, pericardial abscess due to melioidosis is difficult to differentiate from tuberculosis pericarditis (Fig. 2).

Fig. 1.

Lung window coronal images: Consolidation patch in the right upper lobe with central clearing (suggestive of reverse halo sign).

Fig. 2.

Contrast-enhanced computed tomography (axial and coronal) image of the thorax: Pericardial abscess with associated pericardial thickening (white arrow) is seen.

Cutaneous abscesses

Since percutaneous inoculation is thought to be the main transmission route, cutaneous abscesses at the inoculation site (with or without reported trauma) are not uncommon. In the Darwin cohort, cutaneous abscesses were the second most common cause, seen in 13 % of the melioidosis patients (Currie et al., 2021). In addition to direct inoculation, skin involvement can occur secondary to haematogenous dissemination. In a review, close to 50 % of cutaneous melioidosis had involvement of other sites (Fertitta et al., 2019). Skin involvement presents most commonly as abscesses, cellulitis and ulcers (Fertitta et al., 2019). Lower limbs are most commonly involved (Fertitta et al., 2019). In endemic areas, melioidosis should be considered as a differential diagnosis for skin lesions, especially in the presence of risk factors or a history of trauma. Case 4 had both pulmonary and cutaneous melioidosis. He had a history of trivial trauma at the site of the development of the localised collection, which could be the possible route of entry (Fig. 3). Similarly, Case 6 developed a foot abscess and suppurative lymphadenitis following localised trauma.

Fig. 3.

Cutaneous abscess: Seen in a patient's left arm after minor trauma. Pus culture was positive for melioidosis.

Osteoarticular abscess

Bone and joint involvement in melioidosis are seen in 1 % and 3 % of the cases, respectively (Currie et al., 2021). They can be isolated or part of systemic involvement (Gupta et al., 2021). Lower limb bones (tibia, femur, etc.) and joints (knee, ankle, etc.) are more commonly affected (Shetty et al., 2015). Our case 7 presented with prolonged fever without localisation. A whole-body PET-CT subsequently showed a prostate abscess and distal osteomyelitis of the left femur. In a large series of osteoarticular melioidosis, 27.5 % of the patients with septic arthritis had adjacent bone osteomyelitis. This was also associated with recurrence. Multifocal involvement of bone and joint is not uncommon in published studies (80 foci were involved in 50 patients) and is also associated with recurrence (Shetty et al., 2015). In a previous series of osteoarticular melioidosis, concomitant myositis was seen in 36 % of the patients, which can help differentiate it from other differential diagnoses (tuberculosis, brucellosis, and other pyogenic infections) (Gupta et al., 2021). Most bone-involvement patients have a subacute course and relatively low mortality (Nisarg et al., 2024). The duration of treatment is not well defined and usually requires 4–6 weeks of intensive and 3–6 months of the eradication phase. Surgical debridement and longer regimens are preferred in patients with a higher chance of recurrence (multifocal involvement, adjacent bone and joint involvement).

Prostrate abscess

Prostatic abscesses are common in melioidosis and are detected frequently in male patients with melioidosis (Morse et al., 2009). In a large prospective cohort, significant alcohol use disorder was associated with prostate involvement in melioidosis (Morse et al., 2009). Most patients present with urinary tract symptoms at presentation, but more than half do not have prostatic pain or tenderness (Morse et al., 2009). Prostate abscesses due to melioidosis can have multiple sites of involvement and are commonly bacteremic (Morse et al., 2009). Escherichia coli, Staphylococcus aureus and tuberculosis are common differentials (Morse et al., 2009). A soft clue of differentiating prostatic abscess from melioidosis when compared to other etiologies is the fact that abscesses in melioidosis are more peripheral (like in Case 7) as they are a result of bacteremic spread rather than prostatic abscesses with a urinary source (Fig. 4). Since the peripheral prostate is involved in melioidosis, prostate-specific antigens may not be elevated. It is possible to detect a silent abscess through imaging. Therefore, routine radiological screening should be performed to rule out a prostatic abscess in male patients, especially if urine culture is positive for B.pseudomallei. Abscesses at other sites may respond to medical therapy alone. Still, most experts believe that prostatic abscesses of >1 cm should be drained as they have viable bacteria, and antimicrobials penetrate poorly, increasing the risk of recurrence after therapy(14).

Fig. 4.

Coronal and Axial sections of PET-CT: Uptake in the prostate (white arrow) and distal femur (white arrow).

Parotid abscess

Parotid gland involvement has been very infrequent in the Darwin cohort, whereas, in Thailand and Malaysia, it is reported to be a common manifestation, especially in children (Currie et al., 2021). In these regions, parotid involvement has been postulated to be more frequent because of a possible transmission via the ingestion of contaminated water (Limmathurotsakul et al., 2013; West et al., 2010). In a large study by Dance et al., unilateral parotid involvement was seen in 6 % of all melioidosis patients (Dance et al., 1989). Most patients with parotitis were children without apparent immunosuppression in that study (Dance et al., 1989). Patients with parotid gland involvement may rupture into the auditory canal or develop paralysis of the 7th lower motor neuron (Dance et al., 1989). Recent reports of parotid involvement have emerged from South Asia as well (Mohanty et al., 2020). Our case 3 had parotid gland involvement with necrotising fasciitis and subsequent spread to the neck spaces (Fig. 5, Fig. 6). His condition improved after surgical drainage of pus and appropriate antibiotic treatment.

Fig. 5.

Parotid abscess: Right-sided cheek swelling is seen.

Fig. 6.

Contrast-enhanced computed tomography image of the face: Enlarged right parotid gland with surrounding inflammatory changes (white arrow) is seen.

Hepatosplenic abscess

Melioidosis is one of the most important causes of pyogenic liver and spleen abscesses in endemic areas (Apisarnthanarak et al., 2011). Most of these are associated with bacteraemia. Liver abscesses in tropical regions can have multiple differential diagnoses- amoebic, pyogenic (Klebsiella pneumoniae, E. coli, etc.), tubercular and parasitic (toxocariasis, fascioliasis, etc.). In a study that compared liver abscesses due to melioidosis with other etiologies, multiseptated, multiloculated hypodense lesions (Honeycomb sign, CT Necklace sign) in the liver were found to be indicative of melioidosis (Apisarnthanarak et al., 2011). Additionally, the concurrent presence of hepatic and splenic lesions (usually small and multiple) was more specific for melioidosis (Apisarnthanarak et al., 2011). Our case 6 had a concurrent involvement of the liver and spleen (Fig. 7), while Case 8 had a typical honeycomb liver abscess (Fig. 8).

Fig. 7.

Contrast-enhanced computed tomography images of the abdomen: Ill-defined hypodense lesion in the spleen with surrounding inflammatory changes.

Fig. 8.

Ultrasound image of the liver: A well-defined hypoechoic lesion with a honeycomb appearance.

CNS abscess

Neurological involvement in melioidosis was seen in 2 % of the patients in the Darwin cohort (Currie et al., 2021). Neurological involvement can be in the form of a brain abscess (similar to Case 9), encephalomyelitis, meningitis or an extradural collection (haematoma or abscess) (similar to Case 1) (Fig. 9, Fig. 10). In a large cohort, brain abscess was the most common form of neurological involvement in melioidosis (Gora et al., 2022). Seeding from the blood usually results in brain abscesses, and direct invasion from the nasal mucosa is thought to cause encephalomyelitis (Naik et al., 2023). Extradural abscess (or haematoma), like in our case, if associated with skull bone osteomyelitis and scalp abscess, is more likely to be associated with trauma and percutaneous inoculation (Hsu et al., 2016). The haematogenous spread leads to the involvement of the frontoparietal lobe through the middle cerebral artery (Raj et al., 2022). Besides macroabscesses, microabscesses are also common in melioidosis (Raj et al., 2022). Microabscesses along the corticospinal tract (tunnel sign) have been described as pathognomonic for melioidosis (Raj et al., 2022). Ocular involvement in the form of preseptal orbital cellulitis in melioidosis is possible (Yaisawang et al., 2018). Bacteremia and simultaneous involvement of surrounding structures are common (Yaisawang et al., 2018). Our case 2 had poorly controlled diabetes, pansinusitis, and orbital cellulitis complicated by a subperiosteal abscess (Fig. 11). Mucormycosis is a close differential of case 2, and urgent microscopy to look for aseptate hyphae is crucial in such a scenario.

Fig. 9.

Axial CT scan of the brain: Extradural abscess (thin arrow) and scalp abscess (thick arrow) is seen.

Fig. 10.

Coronal computed tomography image of the brain: A ring-enhancing lesion is seen in the right occipital lobe (arrow).

Fig. 11.

Axial and coronal non-contrast computed tomography images of the brain and face: A&B: Axial sections showing diffuse soft tissue swelling in the left temporal region with a small collection in the left orbit in the extra-conal location (white arrow). C&D: Coronal sections showing diffuse soft tissue swelling in the left temporal region with a small collection in the left orbit in the extra-conal location on the superolateral aspect (white arrow).

Limitations

This case series represents melioidosis cases with abscesses at different sites. However, the sites presented in this series are not all-inclusive and are not meant to mirror the current epidemiological situation exactly.

Conclusion

Melioidosis should be considered as a differential diagnosis in all cases of abscess in endemic areas, especially among patients with risk factors. Imaging is essential to localize deep visceral abscesses, and certain features like honeycombing can help make an early suspicion of melioidosis. Microbiological diagnosis is important to optimise management. While blood culture is helpful, patients with localized abscesses may not have bacteremia and invasive sampling may be required. Abscesses due to B. pseudomallei have a good prognosis with appropriate antimicrobial therapy.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

Data will be made available on request.