Nisin resistance and its association with the plasmid restriction profile of Leuconostoc lactis strains isolated from spoiled sausage

Abstract

A Mexican company that produces sausages, which has presented outbreaks of microbial deterioration in its packaged product, reported that between Nov. 2006 and Jan. 2007, it presented a product deficit due to deterioration, equivalent to 5.61 tons and approximately 18.82 tons more in the period between Nov. 2007 and Feb. 2008. Scandalous amounts, given the economic decline that caused the company, since only in the last outbreak, it amounted to just under a quarter of a million Mexican pesos, and states that in the 2010 has presented constant outbreaks of a similar scale (Financial report, confidential). Leuconostoc lactis species and other Leuconosoc species have been linked as the cause. A viable strategy is the addition of bioconservatives such as nisin. 15 strains of L. lactis were used that showed potential for deterioration. Their resistance profile to nisin was determined to determine the Nis_R phenotype, plasmids were isolated and genotified by means of plasmid restriction profiles using four restriction endonucleases HindII, ApaI, SmaI and XbaI. It was possible to observe that genetically unrelated strains (by restriction of chromosomal DNA), present closely related plasmid restriction profiles (91.7 % genetic similarity). Finally, given that the plasmid package of the strain that presented the lowest resistance to nisin (87: MIC > 0.2 μg / mL) showed a close genetic relationship (93.2 %) with those obtained from other resistant strains, it was not possible to associate a determined plasmid restriction profile, with the Nis_R phenotype. However, it is possible to suggest the permanence (up to two years) of L. lactis Nis_R strains on company work surfaces and / or the possible transfer of plasmids with information encoded for the Nis_R phenotype.