Frequency of Bacteriocin Resistance Development and Associated Fitness Costs in Listeria monocytogenes

Abstract

Bacteriocin-producing starter cultures have been suggested as natural food preservatives; however, development of resistance in the target organism is a major concern. We investigated the development of resistance in Listeria monocytogenes to the two major bacteriocins pediocin PA-1 and nisin A, with a focus on the variations between strains and the influence of environmental conditions. While considerable strain-specific variations in the frequency of resistance development and associated fitness costs were observed, the influence of environmental stress seemed to be bacteriocin specific. Pediocin resistance frequencies were determined for 20 strains and were in most cases ca. 10 ؊6 . However, two strains with intermediate pediocin sensitivity had 100-foldhigher pediocin resistance frequencies. Nisin resistance frequencies (14 strains) were in the range of 10 ؊7 to 10 ؊2 . Strains with intermediate nisin sensitivity were among those with the highest frequencies. Environmental stress in the form of low temperature (10°C), reduced pH (5.5), or the presence of NaCl (6.5%) did not influence the frequency of pediocin resistance development; in contrast, the nisin resistance frequency was considerably reduced (<5 ؋ 10 ؊8 ). Pediocin resistance in all spontaneous mutants was very stable, but the stability of nisin resistance varied. Pediocin-resistant mutants had fitness costs in the form of reduction down to 44% of the maximum specific growth rate of the wild-type strain. Nisin-resistant mutants had fewer and less-pronounced growth rate reductions. The fitness costs were not increased upon applying environmental stress (5°C, 6.5% NaCl, or pH 5.5), indicating that the bacteriocin-resistant mutants were not more stress sensitive than the wild-type strains. In a saveloy-type meat model at 5°C, however, the growth differences seemed to be negligible. The applicational perspectives of the results are discussed.

Two Subpopulations of Listeria monocytogenes Occur at Subinhibitory Concentrations of Leucocin 4010 and Nisin

“…The frequency of genotypic heterogeneity of L. monocytogenes 412 (identical to strain 4140) concerning resistance to nisin and pediocin PA-1 has been thoroughly investigated and shown to be 10 Ϫ4 and 10 Ϫ6 , respectively (20). This low rate of bacteriocin resistance combined with the fact that ⌬pH was dissipated for all single cells at high concentration of bacteriocin makes bacteriocin resistance an unlikely explanation to the bimodal distribution.…”

A Multibacteriocin Cheese Starter System, Comprising Nisin and Lacticin 3147 in Lactococcus lactis, in Combination with Plantaricin from Lactobacillus plantarum

“…To determine the frequency of bacteriocin resistance/tolerance development in L. innocua, freshly prepared 18-h cultures were serially diluted in MRD and spread plated on to GM17 or GM17 containing either 1,000 AU/ml or 320 AU/ml of the appropriate bacteriocin or bacteriocin combination; the latter concentration represents the arbitrary in situ concentration of the bacteriocins in the cheeses. Plates were incubated aerobically at 37°C for up to 48 h, at which time the frequency of bacteriocin resistance/tolerance was calculated as described previously (56). All experiments were performed in triplicate.…”

σBand σLContribute toListeria monocytogenes10403S Response to the Antimicrobial Peptides SdpC and Nisin

“…Nisin creates membrane-spanning pores in the bacterial cell wall, which enable dissipation of the cell's proton motive force (Bruno et al, 1992;Bonnet et al, 2006). Although, in general, nisin has been demonstrated as an effective antilisterial peptide (Benkerroum and Sandine, 1988), some strains of L. monocytogenes have developed resistance to both nisin and pediocin PA-1 (Gravesen et al, 2002a(Gravesen et al, , 2002bGandhi and Chikindas, 2007). L. monocytogenes resistance to nisin is a concern to the segments of the food industry (e.g., dairy and poultry) that currently use this peptide to control pathogen growth (Gandhi and Chikindas, 2007).…”