Isolation, identification and characterisation of three novel probiotic strains (Lactobacillus paracaseiCNCM I-4034,Bifidobacterium breveCNCM I-4035 andLactobacillus rhamnosusCNCM I-4036) from the faeces of exclusively breast-fed infants

Abstract

The aim of the present study was to isolate, identify and characterise novel strains of lactic acid bacteria and bifidobacteria with probiotic properties from the faeces of exclusively breast-fed infants. Of the 4680 isolated colonies, 758 exhibited resistance to low pH and tolerance to high concentrations of bile salts; of these, only forty-two exhibited a strong ability to adhere to enterocytesin vitro.The identities of the isolates were confirmed by 16S ribosomal RNA (rRNA) sequencing, which permitted the grouping of the forty-two bacteria into three different strains that showed more than 99 % sequence identity withLactobacillus paracasei,Lactobacillus rhamnosusandBifidobacterium breve, respectively. The strain identification was confirmed by sequencing the 16S–23S rRNA intergenic spacer regions. Strains were assayed for enzymatic activity and carbohydrate utilisation, and they were deposited in the Collection Nationale de Cultures de Microorganismes (CNCM) of the Institute Pasteur and namedL. paracaseiCNCM I-4034,B. breveCNCM I-4035 andL. rhamnosusCNCM I-4036. The strains were susceptible to antibiotics and did not produce undesirable metabolites, and their safety was assessed by acute ingestion in immunocompetent and immunosuppressed BALB/c mouse models. The three novel strains inhibitedin vitrothe meningitis aetiological agentListeria monocytogenesand human rotavirus infections.B. breveCNCM I-4035 led to a higher IgA concentration in faeces and plasma of mice. Overall, these results suggest thatL. paracaseiCNCM I-4034,B. breveCNCM I-4035 andL. rhamnosusCNCM I-4036 should be considered as probiotic strains, and their human health benefits should be further evaluated.