Diversity and probiotic characterisation of yeast isolates in the bovine gastrointestinal tract.

The use of yeasts as a feed supplement for cattle can promote animal development and performance. However, for the positive results to be consistent, strains with probiotic properties must be selected. The objective of this study was to isolate and identify yeasts present in the bovine feces and evaluate their probiotic potential together with strains previously isolated from the rumen (preliminary study). A total of 193 isolates were studied, including 139 isolates (19 species) from fecal samples from 11 different animals (Bos taurus and Bos indicus) and 54 strains previously isolated from rumen fluid (Bos taurus). The yeast population in the feces ranged from 3.51 to 4.99 log CFU/g, with Candida pararugosa being the most abundant (isolated from the feces of six samples analysed). Isolates were selected that had negative results in the safety tests (hemolytic activity, DNAse, and gelatinase) and had percentages greater than 35 and 70% for hydrophobicity and auto-aggregation, respectively. In addition, selected isolates had percentages greater than 77.7 and 74.7% for coaggregation with pathogenic strains of Escherichia coli and Clostridium perfringens, respectively. The isolates with percentage growth at 39 °C greater than 64.6% and viability greater than 96.7% were selected for survival testing under bovine gastrointestinal conditions. After the tests, the seven best isolates were selected, belonging to the species Candida pararugosa (L60, CCMA 928 and CCMA 930) and Pichia kudriavzevii (L97, L100, CCMA904, CCMA 907). The selected isolates were exopolysaccharide producers. Based on the results of the evaluated properties, the seven selected isolates were classified as potential probiotics for cattle.

In vitro selection of autochthonous bacterium with probiotic potential for the neotropical fish piauçu Megaleporinus microcephalus / [Seleção in vitro de bactéria autóctone com potencial probiótico para o peixe neotropical piauçu Megaleporinus macrocephalus]

The study aimed to isolate, identify, and apply in vitro tests on bacteria with autochthonous probiotic potential isolated from fifteen healthy specimens of Megaleporinus macrocephalus. The strains were selected from the intestinal tract of fish and inoculated in the Petri plate containing Sharp Man Rogosa Agar (MRS) for (48 hours at 35ºC). They were isolated based on a test of catalase, Gram stain, tolerance to different gradients NaCl (1, 2 and 3%), pH (4, 5, 6, 8 and 9) values and bile salts (2.5 and 5%), in addition to the inhibition zone against pathogens. Of the 42 strains isolated, ST1 and ST9 had higher values (p<0.05) for total viable cells (31.80±0.07 and 32.51±0.05 CFU/mL × 108) respectively. In the resistance tests, strains ST1 and ST9 presented the best results, with emphasis on ST9 in the gradients of pH, high values of bile salts and larger inhibition zones against Aeromonas hydrophila and Aeromonas jandaei. The strains with the best results in the tests, ST1 and ST9, were identified by the MALDI-TOF-MS method as Enterococcus faecium. Thus, the isolated E. faecium bacteria, may be recommended as for probiotic use in farming the M. macrocephalus.

O presente estudo visou isolar, identificar e aplicar testes in vitro em bactérias com potencial probiótico, autóctones, isoladas de 15 espécimes saudáveis de Megaleporinus macrocephalus. As cepas foram selecionadas do trato intestinal dos peixes e inoculadas em placas de Petri contendo Man Rogosa Sharped Agar (MRS), por 48 horas, a 35ºC. Foram isoladas com base em teste de catalase, coloração de Gram, tolerância a diferentes gradientes de NaCl (1, 2 e 3%), valores de pH (4, 5, 6, 8 e 9) e sais biliares (2,5 e 5%), além do halo de inibição contra patógenos. Das 42 cepas isoladas, ST1 e ST9 apresentaram maiores valores (P<0,05) para células viáveis totais (31,80±0,07 e 32,51±0,05 UFC/mL × 108), respectivamente. Nos testes de resistência, as cepas ST1 e ST9 apresentaram os melhores resultados, com destaque para ST9 nos gradientes de pH, altos valores de sais biliares e maiores halos de inibição contra Aeromonas hydrophila e Aeromonas jandaei. As cepas com melhores resultados nos testes, ST1 e ST9, foram identificadas pelo método de MALDI-TOF-MS como Enterococcus faecium. Assim, a bactéria isolada Enterococcus faecium, pode ser recomendada para uso probiótico na criação do M. macrocephalus.