Neuro melioidosis is an uncommon but extremely dangerous form of melioidosis, where the bacteria travel to the brain and spinal cord.
Published May 30, 2025 | 7:00 AM ⚊ Updated May 30, 2025 | 7:00 AM
Synopsis: A deadly outbreak of brain infections in Tamil Nadu has been traced to contaminated saline used at a dental clinic, according to a study published in The Lancet Regional Health. Twenty-one patients developed neuro melioidosis, a rare and often fatal condition, with most cases linked to procedures at a single clinic in Vaniyambadi and a half-used saline bottle.
In a disturbing revelation from Tamil Nadu, scientists have traced a series of mysterious and deadly brain infections to contaminated saline used at a dental clinic.
The findings, published in The Lancet Regional Health, detail an outbreak of neuro melioidosis, a rare and often fatal brain infection, with 21 cases reported between July 2022 and April 2023.
The majority of these cases were concentrated in Tirupattur district, with additional cases emerging from Ranipet, Krishnagiri, and Tiruvannamalai districts in northern Tamil Nadu.
Doctors at Christian Medical College (CMC) in Vellore, a major referral hospital in the region, were among the first to raise concerns after multiple patients arrived with alarming symptoms: high fever, facial paralysis, slurred speech, limb weakness, and even coma – classic signs of brainstem involvement.
A critical clue emerged when ten of these patients were found to have recently undergone dental procedures at the same clinic in the town of Vaniyambadi. This common link helped investigators identify a potential iatrogenic (medically induced) source behind the outbreak.
Neuro melioidosis is a severe infection of the central nervous system caused by a bacterium called Burkholderia pseudomallei.
This organism lives in soil and water in tropical regions and normally infects people through skin wounds or by inhaling or ingesting contaminated materials.
Neuro melioidosis is an uncommon but extremely dangerous form of melioidosis, where the bacteria travel to the brain and spinal cord.
It can cause brain abscesses, cranial nerve damage, and inflammation of the brainstem.
In this outbreak, many patients showed a rare and distinctive MRI pattern called the “tunnel sign,” indicating the bacteria had spread along nerve pathways deep into the brain.
Ten of the 21 people diagnosed with neuro melioidosis had recently undergone invasive dental procedures – such as tooth extractions, root canals, and surgical cleaning – at the clinic.
The remaining 11 cases are believed to be sporadic infections likely acquired from environmental exposure – such as contact with soil or contaminated water – showed a much milder progression.
Of the 21 total patients, 9 lost their lives – 8 from the dental clinic group, and 1 from the sporadic group. Most of them within a median of just 16 days from the onset of symptoms like facial numbness, fever, and paralysis.
Among the 12 survivors, 8 have been left with lasting disabilities, including partial paralysis, speech problems, and severe neurological damage. Only four patients have made anything close to a full recovery.
The first red flag was raised in May 2023, when a married couple was admitted to CMC in Vellore with strikingly similar and severe neurological symptoms.
Both had experienced sudden-onset facial paralysis, seizures, and coma shortly after undergoing dental procedures at the same clinic in Vaniyambadi, a small town in Tirupattur district.
Around the same time, local media began reporting a string of unexplained deaths linked to patients who had received treatment at the same clinic.
These developments prompted CMC doctors to notify the district public health authority on 9 May 2023.
A multidisciplinary team comprising epidemiologists, clinicians, microbiologists, and public health officials from the Indian Council of Medical Research (ICMR) and CMC launched a full-scale investigation.
The team followed the World Health Organization’s 10-step outbreak response protocol, combing through medical records, conducting interviews with affected families, and collecting environmental samples from the dental clinic.
What investigators found inside the dental clinic in Vaniyambadi was as alarming as the deaths it was linked to. The clinic, now shut following public outrage, operated with no formal infection control training.
Critical lapses in hygiene were apparent: saline bottles, routinely used to irrigate wounds and dilute local anaesthetics during dental procedures, were being reopened with unsterile instruments, left partially exposed, and reused across multiple patients over several days.
Environmental samples from the now-closed clinic confirmed their worst fears: a half-used saline bottle tested positive for Burkholderia pseudomallei, the deadly bacterium that causes neuro melioidosis.
This strain of Burkholderia pseudomallei, which carries a gene variant called bimABm, is known to enhance the bacteria’s ability to spread through nerve tissue, reaching critical areas like the brainstem.
The same variant has been seen in previous cases from Australia and India, suggesting it may already be more widespread than previously believed.
Genetic sequencing later confirmed that this strain was identical to the one found in the brain tissue of one of the deceased patients, leaving little doubt that the clinic’s practices were directly responsible.
Doctors believe the bacteria entered the patients’ bodies through nerve endings in the face, particularly the trigeminal and facial nerves, during these invasive procedures.
From there, the bacteria likely travelled directly into the brainstem, a part of the brain that controls vital functions such as breathing and heart rate. This direct “trans-neural” route of infection explains the unusually fast and devastating progression of the disease in these patients.
The presence of Burkholderia pseudomallei in both clinical and environmental samples from Tamil Nadu raises serious public health concerns.
While B. pseudomallei infections are not new to India, this outbreak marks the first documented case where a dental clinic was identified as the direct source of neuro melioidosis, a form of the disease that primarily attacks the brain.
What makes the situation even more alarming is that this bacteria was found to be resistant to many commonly used antibiotics.
Only intravenous meropenem, a high-grade antibiotic typically reserved for severe infections, showed effectiveness. Yet in many cases, patients died before doctors could make the right diagnosis or begin the appropriate treatment.
Diagnosing nerve melioidosis proved to be extremely difficult. Traditional tests like cerebrospinal fluid cultures were often negative.
In most cases, the bacteria could only be detected from brain tissue samples or blood cultures – tests that are not always readily available or performed in smaller clinics.
Experts say the outbreak is a stark reminder of how deadly lapses in basic hygiene and infection control can be – not just in large hospitals, but in everyday healthcare settings like dental clinics.
Reusing instruments or leaving saline bottles exposed may seem like minor oversights, but in this case, they triggered a deadly chain of events.
The findings also suggest a deeper issue: highly virulent strains of B. pseudomallei may already be circulating silently in parts of India, especially in regions where the bacterium is found naturally in soil and water.
Without greater awareness, improved diagnostics, and stricter hygiene protocols, experts warn, more such outbreaks could follow – and go undetected until it’s too late.
(Edited by Dese Gowda)
