Written by: Dr. Arshada Fathin, PharmD (Coimbatore, Tamil Nadu)
Reviewed By: Dr. Seema Satbhai (BAMS, MPH, PhD, Public Health)
Neuromelioidosis, a central nervous system manifestation of melioidosis caused by Burkholderia pseudomallei, has emerged as a serious health concern in Vaniyambadi, Tirupattur district, Tamil Nadu, India. An unusual cluster of cases was identified between July 2022 and April 2023. Importantly, 10 out of 21 patients had undergone some dental procedure, most at the same dental clinic. Out of these 10 cases, 8 patients succumbed to death. This has raised critical questions regarding infection control practices in dental care settings. This article provides an overview of the outbreak, disease pathology, diagnostic considerations, and the role of procedural lapses in precipitating iatrogenic transmission.
Background of the Case
The outbreak of neuromelioidosis in Tamil Nadu centres on a cluster of 21 cases reported between July 2022 and April 2023. These included 11 sporadic infections and 10 distinct sub-cluster epidemiologically linked to a dental clinic in Vaniyambadi, Tirupattur district. The affected patients who visited the clinic presented with severe symptoms shortly after dental treatment.
About Neuromelioidosis
Neuromelioidosis results from infection of the central nervous system by Burkholderia pseudomallei, manifesting primarily as brainstem syndrome. Typical clinical features include facial pain, cranial nerve dysfunction, abscess formation, and necrotizing encephalitis. The infection often spreads along neuronal pathways, such as the trigeminal nerve, leading to rapid neurological decline. Adults within the age range of 26 to 44 years are predominantly affected in endemic regions. Diagnosis relies on isolation of the organism from blood, cerebrospinal fluid (CSF), or affected tissues through culture or polymerase chain reaction (PCR) assays. Molecular tools, including WGS and detection of virulence-associated genes such as bimA, aid in strain typing and epidemiological investigations. Management requires prompt initiation of intravenous antibiotics, commonly ceftazidime or meropenem, followed by prolonged oral eradication therapy, i.e., Co-Trimoxazole, for several months. Delay in recognition and treatment often results in poor clinical outcomes, sometimes death.
The Culprit: Burkholderia pseudomallei
This bacterium typically inhabits soil and water, but in this outbreak, it entered patients directly along nerve pathways by contact with mucous membranes in the mouth during dental treatments. This neurological route led to rapid brain infections rather than the more typical bloodstream spread.
Case Description and Microbiological Findings
The outbreak involved 21 patients with neuromelioidosis in Tamil Nadu, with a median age of 33 years, affecting both males and females. Clinical presentations include facial cellulitis, lymphadenopathy, brainstem involvement, and rapid neurological decline. Among the 10 patients with documented dental procedure exposure, 8 succumbed to the illness within a median period of 17 days post-exposure, indicating a higher fatality rate compared to sporadic cases. The high fatality of the outbreak is indicative of an iatrogenic source of infection. A high-level, authoritative investigation was warranted on an immediate basis.
Investigation by Researchers
It all started when a married couple presented at CMC Vellore with acute-onset fever followed by symptoms of brainstem syndrome. Radiological imaging revealed necrotizing brainstem encephalitis, a finding consistent with neuromelioidosis. The relative reported that both patients had undergone a dental procedure at the dental clinic in Vaniyambadi shortly before illness.
A highly authoritative investigation was carried out which led by researchers from CMC Vellore, ICMR-National Institute of Epidemiology, Chennai, and the Tamil Nadu Directorate of Public Health and Preventive Medicine. The primary objective of the investigation was to understand how the infection spread and confirm whether the source was iatrogenic. The outbreak investigation utilized clinical evaluation, microbiological cultures, environmental sampling and whole-genome sequencing (WGS) of bacterial strain to establish the transmission dynamics and identify the source of infection. The initial investigation pointed to the cases from Tirupattur district experiencing an outbreak after undergoing invasive dental procedures at a local dental clinic and suggested possible contamination during dental procedures.
Identified Deviations in Infection Control – Medication Error and Sterility Breach
Based on an interview with the dentist and investigation findings, the dental clinic involved in the outbreak provided a wide range of services, including fixation of partial dentures, full-mouth prophylaxis, root canal treatments, and tooth extraction. The clinic was staffed by a dentist, nursing personnel, and a receptionist; however, none of the staff had formal training in hospital infection control practices.
Normal saline was supplied in sterile 500 mL plastic bottles and used both for wound irrigation during surgical procedures and for dilution of local anesthetic for infiltration. It was observed that the sterile saline bottles were opened using a non-sterile periosteal elevator. These bottles were then loosely resealed and reused over several days until empty. There was no proper sterilization of equipment between patients.
Such practices deviated significantly from established infection control standards. The repeated use of opened saline bottles without proper aseptic technique, combined with the use of non-sterile instruments to open them, increased the risk of contamination. Indeed, an increase in failed dental procedures and complications was reported concurrent with the emergence of neuromelioidosis cases in the district.
Microbiological analysis supported these findings, as Burkholderia pseudomallei was isolated from one of the in-use saline bottles collected during environmental sampling at the clinic. These breaches in sterile technique and medication handling directly contributed to the iatrogenic transmission of the pathogen to patients during dental procedures.
Recommended Preventive Measures
Based on the outbreak findings, several corrective measures are essential to prevent similar incidents in the future:
Strict use of sterile supplies: Single-use sterile saline bottles should be opened aseptically and discarded after one use. The reuse of opened bottles must be avoided.
Adherence to aseptic technique: All dental procedures must be performed under sterile conditions, employing sterilized instruments and protective barriers such as sterile gloves.
Comprehensive staff training: Dental clinic personnel should receive ongoing training in infection prevention and control protocols, emphasizing proper handling of sterile supplies.
Environmental monitoring: Routine microbial testing of dental unit water lines and fluids should be conducted, particularly in regions endemic for B. pseudomallei.
Immediate investigation of infection clusters: Any unusual increase in post-procedural infections must prompt epidemiological investigation and suspension of implicated materials or practices.
Implementing these measures will reduce the risk of iatrogenic infection and ensure patient safety during dental procedures.
Conclusion: A Wake-Up Call for Infection Control in Outpatient Care
The tragic Neuromelioidosis outbreak in Tamil Nadu is more than just a public health incident. It is a warning about how single lapse in clinical hygiene, such as reusing a contaminated saline bottle, can escalate into a fatal outbreak of a rare and deadly infection. While melioidosis is typically associated with environmental exposure in endemic regions, this event underscores an alarming reality: modern medical settings are not immune to such threats when basic infection control protocols are neglected.
The Vaniyambadi dental clinic case highlights critical vulnerabilities in outpatient care, particularly in resource-limited settings where practices like reusing consumables or improper instrument handling may still occur. In this instance, the use of an unsterile periosteal elevator to repeatedly open a saline bottle facilitated the direct introduction of Burkholderia pseudomallei, a soil-dwelling microorganism, into the oral mucosa, bypassing traditional routes of transmission. The result was an outbreak of neuromelioidosis, a rare neurological manifestation with devastating consequences, including an 80% fatality rate among exposed patients.
The rapid identification of the outbreak source, coordinated by CMC Vellore, ICMR-NIE Chennai, and state health authorities, demonstrates the importance of multisectoral collaboration in outbreak investigation.
For healthcare systems across India and globally, this event serves as a wake-up call. It emphasizes the urgent need to:
Reinforce standard infection prevention protocols in dental and outpatient clinics
Mandate the single-use of consumables like saline bottles
Educate practitioners on rare but deadly infections like melioidosis
Improve clinical waste management and sterilization practices
Establish local microbiology networks for early pathogen detection
Ultimately, this outbreak is an earnest reminder that patient safety must never be compromised for convenience. The lives lost in Vaniyambadi are a tragic testament to what can go wrong, but also a call to action, urging the healthcare community to uphold the highest standards of hygiene, vigilance, and accountability.
This investigation and findings are published in the Lancet Regional Health – Southeast Asia
References
Angel Miraclin Thirugnanakumar, Prabu Rajkumar, Karthik Gunasekaran et al, Neuromelioidosis outbreak in Tamil Nadu, India: an investigation of transmission with genomic insights, The Lancet Regional Health – Southeast Asia 2025;37: 100602, https://doi.org/10.1016/j.lansea.2025.100602
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