Determination of the distribution of mycobacterial species in aquarium fish in Samsun province

Fish tuberculosis is a progressive disease caused by bacterial species called non-tuberculous mycobacteria (NTM) belonging to the Mycobacteriaceae family, occurs in both freshwater and saltwater fish, and is generally chronic, granulomatous, sporadic, and has zoonotic potential. The aim of the present study was to reveal the presence of mycobacterial species in aquarium fish in the pet shops in Samsun province. For this purpose, a total of 151 aquarium fish belonging to 36 different species in Samsun province, were collected between January 2022 and October 2022. Tissue samples taken from the internal organs of the fish were first subjected to decontamination process, and then the presence of acid fast bacille (AFB) was revealed by Erlich Ziehl-Neelsen (EZN) staining in the prepared smears. Decontaminated homogenates were inoculated into Lowenstein-Jensen medium for microbiological culture. Molecular identification of the obtained isolates was carried out by sequence analysis of the hsp65 (heat shock protein) gene region. With EZN staining, AFB were detected in 28 (18.54%) of the fish samples. After culture, a total of 50 mycobacterial isolates were obtained from 43 fish (28.47%). The sequences obtained from each isolate were compared with the hsp65 gene region sequences of the other mycobacteria species previously deposited in GenBank, and the obtained sequences were deposited in the GenBank database. As a result of these analyses, 24 of 50 isolates were identified as Mycobacterium sp. (48%), 16 isolates were identified as Mycobacteroides chelonae (32%), 8 isolates were identified as Mycobacterium gordonae (16%), and 2 isolates were identified as Mycobacteroides abscessus (4%). The species identified in this study can cause infection in both aquarium fish and humans. Therefore, it should be taken into consideration by breeders, hobbyists, and health professionals that aquarium fish may be a potential source of mycobacteria for humans.