Caracterização da microbiota cultivável do muco externo de astronotus ocellatus e avaliação do perfil de susceptibilidade antimicrobiana dos isolados

Abstract

Astronotus ocellatus is a fish native to the Amazon basin with great commercial appeal in ornamental aquariums. Part of its popularity lies in its large size, strong markings, robustness, and tolerance to disease and changes in parameters. These characteristics make it not only a desirable animal for enthusiasts but also a potential invasive agent, carrying native pathogens to exotic regions. Together, these aspects make this species of interest for the study of its external commensal microbiota, tracking not only its composition something unprecedented in the literature but also its resistance to several classes of antibiotics. This study aimed to map the commensal microbiota of the external mucus of Astronotus ocellatus from the lateral opercular regions. Six young animals with an average size and weight of 49 g were selected and kept in a recirculation system with controlled parameters. The samples were processed through culture and microbiological testing, and the microbiota analysis was performed using the Maldi-Tof methodology. Antibiogram assays were also performed on the identified species. 101 isolates and 29 species/genera were identified: Aeromonas jandaei, Aeromonas veronii, Bacillus altitudinis, Bacillus cereus, Bacillus megaterium, Citrobacter braakii, Citrobacter freundii, Gordonia hongkongensis, Janibacter melonis, Kocuria carniphila, Kocuria sp, Microbacterium paraoxydans, Micrococcus flavus, Mycobacterium fortuitum, Nocardia farcinica, Nocardia niwae, Nocardia nova, Nocardia spp, Paracoccus spp, Plesiomonas shigelloides, Pseudomonas aeruginosa, Pseudomonas alcaligenes, Pseudomonas sp, Solibacillus selvas, Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus simulans. Differences in microbial diversity between the lateral and opercular regions were assessed using the nonparametric Kruskal–Wallis test. For the Richness index, a significant difference was observed between the regions (H1 = 8.52; p = 0.004). Similarly, the Shannon index also showed a significant difference (H1 = 8.34; p = 0.004), indicating greater diversity in the lateral region compared to the operculum. For the antibiogram, tests were performed on 29 isolates; the antibiotics used were: ampicillin, ciprofloxacin, Florfenicol, Gentamicin, Penicillin G, Sulfatrozim, and Tetracycline, and the ATCCs 25922 E. coli and 25923 S. aureus. Ampicillin and Penicillin G demonstrated the highest resistance rates, at 72% and 83%, respectively. Sulfazotrim and Tetracycline showed intermediate resistance rates, at 28% and 34%, and susceptibility rates of 59% and 52%, respectively. Gentamicin, Ciprofloxacin, and Florfenicol showed good sensitivity rates, with susceptibility rates of 90%, 83%, and 79%, respectively. The results suggest a high microbiological diversity associated with the external mucus of A. ocellatus and the importance of understanding these microbial communities for monitoring the health of native fauna, given that there are significant resistance rates to several antibiotics, which should be monitored for significant impacts on environmental research, one health, and environmental preservation.