<b>Aquatic microbiota diversity in the culture of Nile tilapia (<i>Oreochromis niloticus</i>) using bioflocs or periphyton: virulence factors and biofilm formation

Abstract

The following research isolated and identified the main bacterial groups present in the culture of juvenile Nile tilapia in the presence of bioflocs and/or periphyton. The strains were also tested for the production of exoenzymes, indicative of potential virulence factors, and ability to form biofilm. The water samples were taken from tilapia cultured in the presence of bioflocs (T1), in the presence of bioflocs and periphyton (T2), from traditional culture (T3) and from culture in the presence of periphyton (T4). In the growth and selection of the bacterial groups, pour plate method was used, along with the following media: Plate Count Agar (PCA - DIFCO), Aero Pseudo Selective Agar (GSP - Himedia) and Nutrient Agar (AN - Merck). 46 strains were isolated in the following distribution: T1 (n = 12); T2 (n = 10); T3 (n = 14) and T4 (n = 10). Among the isolates, the most frequent genera were: Pseudomonas spp., Aeromonas spp., Staphylococcus spp., Bacillus spp., Mycobacterium spp., Micrococcus spp., and Corybacterium spp. Bacterial isolates in treatments T1 and T3 tested positive for five virulence profiles each, while those isolated from T2 and T4 for two and three virulence profiles, respectively. Treatments in bioflocs and periphyton (T2) or only periphyton (T4) yielded bacteria of less pathogenic potentials. In relation to the fish growth, T1 and T4 resulted in a higher final weight.

Study on floc characteristics and bacterial count from biofloc‐based genetically improved farmed tilapia culture system

“…In contrary, Silva et al. (2016) reported dominance Aeromonas sp in the BFT water of Nile tilapia culture using molasses as carbon source and they stated that beneficial microorganisms can eliminate the Aeromonas bacteria from the culture system. The supremacy of biofloc‐associated planktonic organisms and beneficial bacteria could be the reason for reduction in Aeromonas in the present study.…”

A produção científica mundial sobre a tecnologia bioflocos na tilapicultura como propulsora do desenvolvimento sustentável

“…Os resultados corroboram com a afirmação de que BFT contribui para otimizar a utilização dos recursos naturais e proporcionar melhor desempenho econômico. Silva et al (2016) isolaram e identificaram os principais grupos bacterianos existentes na criação de tilápia na fase juvenil na presença de bioflocos ou perifíton e o seu potencial patogênico. Com resultado, esses autores identificaram que os tratamentos com bioflocos e perifíton ou só perifiton possuíam bactérias com menor potencial patogênico em relação aos outros tratamentos.…”

The Occurrence of Bacteria of the Genus &lt;i&gt;Aeromonas&lt;/i&gt; spp. in &lt;i&gt;Oreochromis niloticus&lt;/i&gt; (Tilapia) and in the Water of Amateur Sport Fish Ponds and Sensitiveness to Antimicrobials

“…However, several environmental issues, such as an increase in the population growth of specific bacteria of natural water microbiota, wastes from feeding, and a possible proliferation of microorganisms resistant to antimicrobials used indiscriminately, have been detected. Several bacteria related to fish pathology have been reported, among which may be mentioned Aeromonas spp., a pathogenic bacterium harmful to fish and humans [3].…”