[Preparation and use of fish fillet infusion as a basic medium for culturing bacteria]

The authors present the first results on the utilization of fish infusion (IFP) as a basic medium for the cultivation of bacteria. The infusion was obtained from a common marine fish, corvina (Micropogonias furnieri) according to the technique used in the preparation of beef infusion broth. Streptococcus pyogenes, S. pneumoniae, Neisseria meningitidis, Campylobacter jejuni, Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis were cultured in liquid and solid media prepared with IFP as well as in recommended standard media. Solid media used for cultivation of S. pyogenes, S. pneumoniae, N. meningitidis and C. jejuni were supplemented with 5% of defibrinated sheep blood and for the latter, substances recommended to increase aerotolerance were included in solid and liquid media. All of these strains grew on the media prepared with IFP except S. pneumoniae when cultured in IFP diluted 1:2 with a sodium chloride solution. Only S. pyogenes produced colonies smaller than those of the standard medium. No more differences were detect in the observation of colony morphology. The growth of E. coli, K. pneumoniae, S. marcescens, P. aeruginosa, S. aureus and B. subtilis was measured in liquid media after 8 hours. In solid media, the growth index was expressed by dividing the number of colonies produced in IFP-agar and Nutriente Agar by the number of colonies on Trypticase soy agar plates. Some differences were observed in colonial size and morphology when compared with those generated in standard media. The average value obtained from the analyses of total proteins by biuret reaction in twelve batches of IFP was 5.03 mg/ml. The experiments showed that culture media prepared with IFP supported the growth of bacterial strains used in this work. It suggests that fish infusion has promising conditions of being an alternative substrate for cultural purposes.