Abstract
Colibacilosis is one of the major diseases of calves, causing huge losses. The aim in this study was to characterize and select lactic bacteria with probiotic potential from Nellore calves raised in northern Minas Gerais. Stool samples from six healthy calves were collected, with three days old and again at three months of age. After isolation, bacteria were enumerated and submitted to morphological and biochemical characterization with API 50 CH test, pH and acid resistance to bile salts and antagonist activity in vitro for three strains of Escherichia coli. The population of lactic acid bacteria was greater (p < 0.05) in feces of the calves at colostrum phase. For resistance to chloric acid, 92.3% of isolates from newborn calves resisted pH 4.0, presenting higher resistance than the isolates from calves at three months of age. In the antagonism test, the isolates Be4 1m, Be1 2b and Be6 2a were presumptively identified as Lactobacillus salivarius, L. crispatus and L. pentosus, respectively, and produced average inhibition zones greater than 10 mm of diameter and showed resistance acid pH and bile salts, indicating potential probiotics.
Highlights
A colibacilose é caracterizada como doença bacteriana infectocontagiosa ocasionada por cepas patogênicas de Escherichia coli enterotoxigênica (ETEC)
The aim in this study was to characterize and select lactic bacteria with probiotic potential from Nellore calves raised in northern Minas Gerais
The isolates Be4 1m, Be1 2b and Be6 2a were presumptively identified as Lactobacillus salivarius, L. crispatus and L. pentosus, respectively, and produced average inhibition zones greater than 10 mm of diameter and showed resistance acid pH and bile salts, indicating potential probiotics
Summary
Foram amostrados seis bezerros hígidos e contemporâneos da raça Nelore (Bos indicus) nascidos em uma fazenda de Montes Claros, norte de Minas Gerais. O crescimento foi avaliado após seis horas e em seguida foram inoculados 50 μL desse meio acidificado em placas contendo ágar MRS. Discos de papel de filtro com 6 mm de diâmetro, impregnados com o caldo MRS contendo um dos 26 isolados de bactérias láticas cultivadas a 37 oC durante 48 h, foram aplicados sobre a superfície do ágar para verificar formação de halos de inibição após o período de incubação de 48 h (Chaves et al, 1999). Os isolados de Lactobacillus spp. que apresentaram resultado positivo no teste de antagonismo anterior, foram inoculados na superfície do ágar MRS, proporcionando o crescimento da colônia no formato circular com diâmetro médio de 0,4 mm.
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