Prevalence and drug resistance profiles of nontuberculous mycobacteria isolated from Iranian fish pond waters

Nontuberculous mycobacteria (NTM) infection is considered one of the most severe waterborne diseases. NTMs are widespread in fish pond water, which may serve as a significant exposure pathway for NTM infections, raising substantial concerns for public health. Consequently, the purpose of this study was to investigate the presence of NTM and determine their drug resistance in 120 fish pond waters (FPW). Totally, 120 water samples were gathered from FPW. After being filtered through a 0.45 μm membrane, the samples were decontaminated with 0.005% cetylpyridinium chloride and subsequently cultured on two Lowenstein-Jensen media. The cultures were incubated at 25 °C and 37 °C for a period of 8 weeks. The identification of different NTM species was conducted using molecular tests targeting the hsp65, rpoB, and 16 S rDNA genes. The identification of NTM isolates included several species: M. marinum, M. chelonae, M. fortuitum, M. mucogenicum, M. lentiflavum, M. abscessus, M. gordonae, M. porcinum, M. kansasii, M. conceptionense, M. simiae, M. phocaicum, M. xenopi, and M. neoaurum. The NTM counts across the 110 water samples ranged from 10 to over 1,000 CFU/1,000 mL, with a median of 400 CFU/1000 mL. Furthermore, we documented two cases of skin infections attributed to M. marinum and M. chelonae, with the source of infection traced back to NTM-contaminated FPW. In conclusions, the study revealed that a significant proportion of FPWs were contaminated with NTM, presenting a potential health risk to humans. This study highlights the critical importance of implementing rigorous water quality control measures in fish breeding ponds, with a particular focus on ensuring the absence of NTM.