The review, authored by Singaravel Vijayapoopathi of the Saveetha Institute of Medical and Technical Sciences in Chennai, synthesizes epidemiological, genomic, diagnostic and therapeutic evidence on neuromelioidosis, with particular focus on India. Tertiary-care studies from southern India have reported neurological involvement far above the commonly cited global range. One retrospective series covering 2017 to 2023 identified 13 neurological cases among 82 culture-confirmed melioidosis patients, a proportion of 15.8 percent, with mortality among those neurological cases reaching 38.5 percent. The author is careful, however, to caution against reading these numbers as proof that the bacterium is more neurotropic in India. Referral of severe neurological cases to specialist centres, selection bias, differing case definitions, variable access to neuroimaging and uneven microbiological capacity can all inflate the apparent proportion. Standardized, prospective multicentre studies will be needed before genuine geographic differences can be established.

The watershed moment for the field came during 2022 and 2023, when an outbreak in northern Tamil Nadu documented 22 probable cases across four districts, resulting in eight deaths. Epidemiological tracing revealed something startling: the source was contaminated saline used in a dental-care setting. This single finding reframed melioidosis, long regarded as an exclusively environmental infection acquired through contact with soil and water, as a pathogen capable of causing healthcare-associated clusters. Whole-genome sequencing of outbreak isolates identified sequence type ST1553, and the bimA Bm allele was detected in three clonal isolates comprising two clinical samples and one recovered from an in-use contaminated saline bottle. Core-SNP phylogenetic analysis supported the epidemiological evidence for a common source linked to dental treatment, demonstrating how high-resolution genomics can reconstruct an outbreak, attribute its source and confirm transmission relationships that conventional investigation alone might miss.

That genomic detective work sits within a broader story about the bacterium’s population structure. Burkholderia pseudomallei exhibits extensive genomic diversity, with distinct Australasian, Southeast Asian and South Asian lineages shaped by long-term environmental adaptation and recombination. Among the best-characterized genetic factors associated with neurological disease is the Burkholderia intracellular motility A gene, or bimA. The conventional bimA Bp allele is widely distributed, whereas the B. mallei-like bimA Bm variant occurs more frequently among Australian isolates and has been strongly associated with an increased propensity for neurological melioidosis. Experimental work indicates that strains carrying the bimA Bm variant show enhanced persistence and dissemination to the brain and spinal cord. At the cellular level, BimA promotes intracellular survival, actin-dependent motility and cell fusion, and disrupting the gene reduces intracellular survival and cytotoxicity in human neuroblastoma cells. Still, the review stresses that bimA Bm should be regarded as a neurotropism-associated marker rather than an independent predictor, since host susceptibility, inoculation route and bacterial background all matter. A standardized core-genome multilocus sequence typing scheme incorporating 4,221 core-genome targets now offers a reproducible framework for international molecular surveillance.

How the bacterium actually reaches the brain is one of the most fascinating chapters of its biology. Burkholderia pseudomallei may enter the central nervous system through the bloodstream from pulmonary, cutaneous or systemic infection, or, remarkably, by crawling directly along cranial nerves, particularly the olfactory and trigeminal pathways. Experimental and clinical evidence strongly supports this latter route, sometimes called the trigeminal highway, which allows the bacterium to bypass the blood-brain barrier and establish infection in the brainstem. Once inside, the pathogen deploys an arsenal of virulence strategies: type III secretion systems inject effector proteins into host cells, subverting immune signalling, while BimA-mediated actin polymerization enables the bacterium to propel itself from cell to cell, hiding from extracellular immune defences. The result is a spectrum of lesions including brain abscesses, brainstem encephalitis, myelitis and venous sinus thrombosis, accompanied by neuronal apoptosis, mitochondrial dysfunction and inflammatory oedema that can drive relentless progression even under aggressive antimicrobial therapy.

Diagnosis remains the Achilles heel of neuromelioidosis care. Clinically, patients present with fever, headache, altered sensorium, seizures, cranial nerve palsies, limb weakness or ataxia, a constellation that closely mimics tuberculous meningitis, viral encephalitis, demyelinating disease or malignancy. In children, misdiagnosis as tuberculosis is particularly common. Magnetic resonance imaging can reveal ring-enhancing abscesses, brainstem encephalitis or spinal microabscesses, with the so-called tunnel sign serving as a radiological hallmark, but imaging is not pathogen-specific. Culture remains the reference standard, yet cerebrospinal fluid cultures may be negative despite active central nervous system infection, especially when disease is localized within abscesses or antibiotics have already been started. The review emphasizes that a negative CSF culture should never be treated as sufficient to exclude the diagnosis; blood cultures, pus, tissue and aspirates from focal lesions may provide the critical evidence. Some presentations even mimic acute disseminated encephalomyelitis, raising the danger that corticosteroids prescribed for presumed demyelination could delay lifesaving antimicrobials.

Advanced diagnostics are beginning to close this gap. Real-time PCR targeting type III secretion system loci and lateral-flow antigen detection targeting capsular polysaccharide have shown high diagnostic accuracy in comparative evaluations, whereas automated biochemical systems are less reliable for species identification. MALDI-TOF mass spectrometry can provide rapid species-level identification when validated spectral databases are available, and during the Tamil Nadu outbreak isolates were confirmed with VITEK MS alongside conventional biochemistry and PCR. Serology, particularly the indirect haemagglutination assay, is constrained by variable sensitivity, poor standardization and high background seropositivity in endemic populations, with documented cross-reactivity between B. pseudomallei and B. mallei. Metagenomic next-generation sequencing offers an unbiased approach for unexplained meningoencephalitis when routine tests fail, and prospective evidence shows it can identify pathogens missed by conventional testing, though experience specifically in neuromelioidosis remains limited and it is best viewed as an adjunct rather than a replacement for culture.

Treatment demands patience and precision. Central nervous infection requires an intravenous intensive phase with ceftazidime or, preferably for severe and CNS disease, meropenem, often combined with trimethoprim-sulfamethoxazole for deep-seated infection. The revised Darwin treatment guideline recommends a minimum intensive phase of approximately eight weeks for CNS involvement, followed by an oral eradication phase of roughly six months to prevent relapse. Although randomized trials have supported shorter twelve-week eradication therapy for uncomplicated melioidosis, very few CNS cases were included, so those findings cannot be extrapolated. Source control matters too: a systematic review found adjunctive abscess drainage was used in more than half of documented CNS melioidosis cases. Supportive management of seizures, raised intracranial pressure and rehabilitation for persistent deficits, together with antimicrobial susceptibility testing and careful stewardship, complete the therapeutic package.

The public health lessons extend well beyond any single clinic. Diabetes mellitus consistently emerges as the most powerful risk factor, affecting nearly half of patients, followed by chronic kidney disease, alcoholism and monsoon-season occupational exposure, and more than 90 percent of India’s published melioidosis cases have been reported in just the past decade, suggesting both heightened recognition and long-underappreciated endemicity. A nationwide review collated more than 210 cases from Tamil Nadu alone, with overall mortality of about 22 percent and a male-to-female ratio of three to one. The review argues for strengthened laboratory networks, standardized specimen-referral pathways, environmental monitoring of soil and water after floods, rigorous infection-prevention practices around clinical fluids, and integrated One Health surveillance linking human, environmental and genomic data. Longer-term priorities include rapid decentralized diagnostics, host-directed therapies, and vaccine development, since no licensed human melioidosis vaccine currently exists. What the Tamil Nadu experience ultimately demonstrates is that an environmental pathogen, a vulnerable population and a lapse in infection control can converge to produce an outbreak nobody was watching for, and that only coordinated clinical, genomic and environmental surveillance can ensure the next one is caught in time.

Subject of Research: Neuromelioidosis caused by Burkholderia pseudomallei, including its epidemiology, genomic determinants of neurotropism, diagnosis, treatment and public health implications in Tamil Nadu, India

Article Title: Neuromelioidosis in endemic regions: epidemiology, genomic insights, diagnosis, treatment, and public health lessons from Tamil Nadu

Article References: Singaravel Vijayapoopathi (2026). Neuromelioidosis in endemic regions: epidemiology, genomic insights, diagnosis, treatment, and public health lessons from Tamil Nadu. Journal of Emergency and Disaster Medicine, 2(1), Article 21. https://doi.org/10.1007/s44467-026-00024-x

Image Credits: AI Generated

DOI: 10.1007/s44467-026-00024-x

Keywords: neuromelioidosis, melioidosis, Burkholderia pseudomallei, Tamil Nadu, bimA, whole-genome sequencing, outbreak investigation, central nervous system infection, healthcare-associated transmission, One Health, mNGS, antimicrobial stewardship