CHENNAI: Eight people died of neuromelioidosis — a bacterial infection of the brain — that they got from a dental clinic in Vaniyambadi town of Tamil Nadu’s Tirupattur district in 2023, a study published in The Lancet has revealed.The outbreak, which hasn’t been reported by any govt agency, has been linked to unsterile dental practices, according to an investigation by a team of doctors from multiple organisations including CMC Vellore, ICMR-NIE and Tamil Nadu Directorate of Public Health.The study said an unsterile surgical instrument called a periosteal elevator was used to open a saline bottle, which was then loosely resealed. Reuse of its contents by the clinic led to at least 10 people contracting the infection and eight of them dying, pegging the fatality rate at 80%, said the first author of the study, Dr Angel Miraclin Thirugnanakumar of the neurological sciences department at CMC.“The rapid and high fatality may be because the bacteria in the saline travelled directly along nerve pathways when used to clean the patients’ mouth during procedures, rather than through the bloodstream, a common route for such infections,” the researcher concluded. Whole genome sequencing showed that the bacteria has a gene that aggressively attacks the brain.Neuromelioidosis is a severe infection of the central nervous system, that includes the brain and the spinal cord, caused by bacterium Burkholderia pseudomallei which is found in contaminated soil and water in tropical and subtropical regions. Symptoms include fever and headache followed by slurred speech, visual distortion and in some cases facial palsy.Between July 2022 and April 2023, the researchers identified 21 cases of neuromelioidosis (including 10 patients who went to the dental clinic) and total nine deaths. The fatality rate among the remaining 11 patients who didn’t go to the dental clinic was 9%. Of the total 21 patients, 17 were in Tirupattur district, two in Ranipet, and one each in Tiruvannamalai and Krishnagiri. The patients who succumbed after their visit to the dental clinic had a quicker death since the infection date. It took 16 days from symptom onset to death and nine days from hospitalisation among patients who went to the clinic compared to 56 and 38 days respectively in case of the lone fatality not linked to the dental clinic.State public health officials said the study would help identify such cases to understand the epidemiology and initiate micro-containment measures. “We have stopped the spread with corrective measures. It’s also a reminder for healthcare providers to be aware of infection control measures,” said director of public health Dr T S Selvavinayagam.On May 9, 2023, CMC notified an increase in neuromelioidosis cases and said some of them were linked to the dental clinic. On May 13, 2023, health officials held a meeting with healthcare facilities and other stakeholders in Tirupattur and neighbouring districts. Soon, a team of doctors investigated the cluster to describe the clinical and epidemiological characteristics and identify the source of infection, said co-author Prabu Rajkumar from the ICMR-NIE.“But before doctors could visit the dental clinic to pick samples, the clinic was disinfected, the water supply was cut off, and the clinic was closed following public outcry,” the authors wrote. However, scientists identified B. pseudomallei from the saline bottle sample. There was no contamination in unopened saline bottles. More samples were tested, and whole genome sequencing was done for further verification.Analysis showed head and neck involvement, such as inflammation of a salivary gland (parotid gland), inner lining of cheeks (buccal mucosa), along with enlargement or swelling of one or more lymph nodes (lymphadenopathy), was common in cases not linked to the dental clinic. But those with dental exposure showed rapid progression, presenting with facial cellulitis and soft tissue abscess, probably because the contaminated saline was ingested.