In vitro inhibition activity of nisin A, nisin Z, pediocin PA-1 and antibiotics against common intestinal bacteria

Aims: To evaluate the sensitivity of 21 common intestinal bacteria to six antibiotics and three broad-spectrum bacteriocins (nisins Z and A and pediocin PA-1). Methods and Results: Neutralized cell-free culture supernatants containing active bacteriocins, and antibiotics were tested with the agar diffusion test and the disc-diffusion method, respectively. The tested intestinal strains showed high sensitivity to most antibiotics except for streptomycin and oxacillin. Nisins A and Z (8 mu g per well) had similar activity spectra and inhibited all Gram-positive intestinal bacteria at different levels (except Streptococcus salivarius), with bifidobacteria (except Bifidobacterium breve and Bif. catenulatum), Collinsella aerofaciens and Eubacterium biforme being the most sensitive strains, but they were not active against Gram-negative bacteria. Surprisingly, none of the tested strains were inhibited by pediocin PA-1 (16 mu g per well). Conclusion: Pediocin PA-1 which is very active against Listeria spp. and other food pathogens did not inhibit major intestinal species in the human intestine in contrast to both nisins A and Z. Significance and Impact of the study: Our data suggest that pediocin PA-1 has potential to inhibit Listeria within the intestinal microbiota without altering commensal bacteria.