Nisin-resistant (Nis(r)) Listeria monocytogenes and Nis(r) Clostridium botulinum are not resistant to common food preservatives

Nisin-resistant (Nis(r)) strains of Clostridium botulinum and Listeria mono cytogenes may arise as nisin becomes more widely used as an additional safe ty barrier in minimally-processed foods. The sensitivity of Nis(r) L. monoc ytogenes ATCC 700301 and ATCC 700302 and toxigenic Nis(r) C. botulinum 169B to low pH, salt, sodium nitrite, and potassium sorbate was assayed using d iscontinuous gradients in broth and compared to the parental witd-type stra ins. The nisin-resistant strains did not have intrinsic resistance to low p H, sodium chloride, potassium sorbate, or sodium nitrite. In no case were t he Nis(r) L. monocytogenes and C. botulinum strains examined more resistant to inhibitors than the parental strains.