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Aims: Twenty lactic acid bacteria strains were isolated from human faeces and tested by MTT assay for stimulation or inhibition of the proliferation of Vero and myeloma cells. Methods and Results: None of the strains significantly affected the proliferation of Vero cells. However, two isolates (HN1 and HA8) showed a strong inhibition of myeloma cell proliferation (16·7 and 5·0%, respectively) by MTT assay. Conclusions: Both strains have an anti‐proliferative effect on a tumoral cell line. Significance and Impact of the Study: The beneficial effect of LAB cancer therapy has been linked to their ability for immunomodulation.

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Ten strains of lactic acid bacteria were isolated from a dry fermented sausage and tested for stimulation or inhibition of the viability of Vero and myeloma cells. They did not significantly affect the viability of Vero cells but two isolates (CBL/H and CBL/K) showed a strong and moderate inhibition of the myeloma cell viability (at 10 8 CFU mL )1 , 17.6 and 33.2%, respectively, survival of myeloma cells). The isolates were identified as Lactobacillus sakei by DNA sequencing of the 16S rRNA products of a polymerase chain reaction. No protective effect was found, at the concentrations used, against cytotoxicity of N-nitrosamines. To test the effect of L. sakei CBL/H and CBL/K on cytokine production [tumour necrosis factor alpha (TNF-a), interleukin-1b (IL-1b) and interleukin-8 (IL-8)], the human macrophage cell line (THP-1) was cultured in the presence and absence of lipopolysaccharide (LPS). Lactobacillus sakei CBL/H and CBL/K induced IL-1b and IL-8 release when cells were stimulated with and without LPS. However there was TNF-a release only in the presence of the LPS.

The protective effect of a Lactobacillus salivarius strain from human faeces (HA8) was evaluated against the cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA) and N-nitrosopiperidine (NPIP) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. L. salivarius HA8 strain showed a moderate protective effect against NPYR and weak against NDBA and NPIP. No protective effect against cytotoxicity of NDMA was observed at the bacterial population used. To test the effect of L. salivarius HA8 on cytokine production (interleukin-1␤ (IL-1␤), interleukin-8 (IL-8) and tumour necrosis factor alpha (TNF-␣)), the human macrophage cell line (THP-1) was cultured in the presence and absence of lipopolysaccharide (LPS). L. salivarius HA8 induced IL-1␤, IL-8 and TNF-␣ releases when cells were stimulating with and without LPS.