OR05

1:Centre National de Référence des Mycobactéries et de la Résistance aux Antituberculeux (CNR MyrMA); 2:AP-HP Nord, site Bichat; Université Paris Cité, IAME, Inserm UMR1137, Paris, France; 3:Eau de Paris, Direction de la Recherche et du Développement pour la Qualité de l’Eau, R&D Biologie, Ivry sur Seine, France; 4:APHP Sorbonne Université, INSERM, Centre d'Immunologie et des Maladies Infectieuses, Paris, France

Nontuberculous mycobacteria (NTM) are emerging pathogens causing pulmonary and extrapulmonary diseases, including healthcare-related infections. Although water is one of the main infection sources, isolating NTM from water samples is rarely done due to the NTM fastidious growth and lack of a standardised method. We set a protocol for NTM cultivation, measured its repeatability (n=20 experiments, 5 for each condition), reproducibility (n=20, 5 for each condition), and performed an inter-laboratory comparison (n=6) using sterile and tap water samples spiked with slowly growing (M. avium) and rapidly growing (M. chelonae) NTM, plus artificial contamination (Pseudomonas aeruginosa). We investigated water-related NTM infections using this protocol from 2014 to 2024. The protocol showed good repeatability, reproducibility, and recovery yield (range: 67–131%) for quantifying NTM in artificial samples. The inter-laboratory agreement was 83%. It was consistent with different growth media and temperatures. The addition of P. aeruginosa did not affect NTM recovery. We used the protocol in 13 investigations, involving 24 patients. NTM were detected in 12/13 investigations (92%, 23 patients) with NTM species being the same as patients’ isolates in 7/12 (54%, 18 patients). Water was identified as a source of infection in 6/7 investigations (86%, 15 patients) based on matching genotypes. This study provides a standardised protocol for detecting and quantifying NTM colonies in tap water, which allows identifying the source of clinical infections. With an increase in NTM infections, using this method in mycobacteriology and in environmental laboratories would lead to better prevention measures.