Microbiota of two species of commercially important fish in the Amazon region (Belm-Par-Brazil): Butterfly peacock bass (Cichla ocellaris) and piramutaba (Brachyplatystoma vailantii)

Abstract

The Amazon offers great potential for fishery activities but the fish fauna's specific microbiota is not yet known. This paper identified the bacterial flora composition and the influence of this process on the microbiological spoilage in economically important fish species in the Amazon region: butterfly peacock bass (Cichla ocellaris) and piramutaba (Brachyplatystoma vailantii). To this end, microbiological characterization was performed: counts of total mesophilic aerobic bacteria, psychrotrophic bacteria and coliforms at 35 and 45°C. Bacteria were also isolated through seeding in agar surface using violet red bile glucose (VRBG) for enterobacteria strains and Baird-Parker Agar with egg-yolk tellurite for Staphylococcus species, both with incubation at 36°C for 48 h. The bacteria isolated were identified using the API 20E kit (Enterobacteria), and Gram-positive with API Staph (Staphylococci). Finally, the limit temperature for strain growth was tested using spectrophotometry readings at 554 nm at 10 and 15°C at three different times: 0, 3 and 6 h. The mesophilic aerobic bacteria counts for fresh fish samples ranged from 6.03-8.23 log CFU/g for piramutaba and 4.52-7.24 log CFU/g for butterfly peacock bass. The count ranges of psychrotrophic aerobic bacteria found were 6.14-8.56 log CFU/g and 4.52-7.24 log CFU/g for piramutaba and butterfly peacock bass, respectively. They also had an average score above 10 3 MPN/g for total coliforms. Sixteen different strains were isolated. The most predominant were Staphylococcus hominis, Staphylococcus aureus, Stenotrophomonas maltophilia and Enterobacter intermedius. When subjected to temperatures of 10 and 15°C, the strains did not achieve growth for 6 h at a 95% significance level.