Antimicrobial spectrum of Bifidobacterium animalis subsp. lactis INL1 and the influence of drying on functionality

SOUZA T; ZACARIAS MF; CARMONA D; VIEIRA L; REINHEIMER, J.A.; VINDEROLA C.G.

Buenos Aires

Congreso; XII Congreso Argentino de Microbiología.; 2010

Introduction: Bifidobacterium animalis subsp. lactis INL1 is a strain isolated from human breast milk with resistance to technological processes of interest for the dairy industry such as freezing, freeze-drying, spray-drying and mild heating (50°C). The functional properties of this strain, to be considered as a probiotic (immunomodulation capacity, antimicrobial activity, etc.), are under study. Recent studies suggest that technological treatments like those described above could modify cell functionality of probiotic bacteria without affecting cell viability. Aim: To study the in vitro antimicrobial capacity of B. lactis INL1 against enteropathogenic indicators and the in vivo effect of freeze-drying and spray-drying on its immune properties, estimated as the capacity to enhance s-IgA production in intestinal fluid and proliferation of Küpffer cells in liver. Materials and Methods: For the study of antimicrobial activity, the well-diffusion and agar-spot assays were compared using the following pathogens: Salmonella enterica subsp. enterica serovar Typhimurium FUNED, Vibrio cholerae LEFM, Shigella sonnei ATCC 11060, Shigella flexneri LEFM, Enterococcus faecalis ATCC 19433, Listeria monocytogenes ATCC 15313, Escherichia coli ATCC 25922 and Clostridium perfringens type A ATCC 3624. Swiss NIH mice received, by daily gavage and for 10 consecutive days, 10% skim milk (control group) or 108 CFU of B. animalis subsp. lactis INL1 as fresh, spray-dried or freeze-dried cultures in 10% skim milk. Liver was removed for Küpffer cells count by histological examination and small intestinal fluid was used for determination of s-IgA contents by capture-ELISA. Results: An antimicrobial activity against V. cholerae, S. flexneri and E. coli was detected using the agar-spot assay but not by well-diffusion assay. Only the oral administration of bifidobacteria as fresh culture significantly increased (P < 0.05) the number of Küpffer cells (45.9±8.6 cel.+/100 hepatocytes) when compared to control mice (30.2±2.5 cel.+/100 hepatocytes). Administration of bifidobacteria as fresh (59.9±16.7 pg/ml), freeze-dried (29.3±3.1 pg/ml) and spray-dried (25.6±0.7 pg/ml) cultures significantly increased the concentration of s-IgA in the intestinal fluid when compared to control mice (18.6±1.1 pg/ml). Conclusions: In vitro antimicrobial activity against some pathogenic bacteria was detected for the strain studied only by the agar-spot assay. The reason why one methodology was effective compared to the other one remains unknown but should be taken into account for other studies. B. animalis subsp. lactis INL1 displays in vivo immunomodulatory properties, being this capacity significantly modified by the technological treatments applied to the strain. It was confirmed that plate counts may offer just a partial view of cell functionality since technological treatments affected the immunomodulating capacity of the strain without this fact being noticed by enumeration of viable cells by plate counts.