Spontaneous Nisin-ResistantListeria monocytogenesMutants with Increased Expression of a Putative Penicillin-Binding Protein and Their Sensitivity to Various Antibiotics

Abstract

A concern regarding the use of bacteriocins, as for example the lantibiotic nisin, for biopreservation of certain food products is the possibility of resistance development and potential cross-resistance to antibiotics in the target organism. The genetic basis for nisin resistance development is as yet unknown. We analyzed changes in gene expression following nisin resistance development in Listeria monocytogenes 412 by restriction fragment differential display. The mutant had increased expression of a protein with strong homology to the glycosyltransferase domain of high-molecular-weight penicillin-binding proteins (PBPs), a histidine protein kinase, a protein of unknown function, and ClpB (putative functions from homology). The three former proteins had increased expression in a total of six out of 10 independent mutants originating from five different wild-type strains, indicating a prevalent nisin resistance mechanism under the employed isolation conditions. Increased expression of the putative PBP may affect the cell wall composition and thereby alter the sensitivity to cell wall-targeting compounds. The mutants had an isolate-specific increase in sensitivity to different beta-lactams and a slight decrease in sensitivity to another lantibiotic, mersacidin. A model incorporating these observations is proposed based on current knowledge of nisin's mode of action.

Cytokines activate genes of the endocytotic pathway in insulin-producing RINm5F cells

“…The 5′ end was modified with a phosphate group while the last nucleotide at the 3′ end was ligated to an amino extension protection group on carbon 7. The sequences of the SD adaptor were 5′-GCGATGAGTCCTGAC-3′ (upper strand) and 5′-CGGTC-AGGACTCAT-3′ (lower strand) [23]. Ligation of adaptors to cDNA restriction fragments has four possible outcomes: (EP-SD, SD-EP, EP-EP, and SD-SD).…”

Activity and Export of Engineered Nisin-(1-22) Analogs

“…An interesting candidate antibiotic is the antimicrobial peptide nisin A ( Figure 1) [1]. Although nisin has been widely used for a long time as a food-preservative in a broad range of products [2,3], resistance is limited [4,5]. Nisin is produced by Lactococcus lactis and exerts antimicrobial activity against a broad range of Gram-positive bacteria.…”

Antilisterial Activity on Poultry Meat of Amylolysin, a Bacteriocin from Bacillus amyloliquefaciens GA1

“…This bacteriocin has been attributed GRAS status and is used commercially as a food preservative in more than 40 countries [8]. However, its inactivation in certain types of food and the emergence of nisin-resistant strains point out the need for the characterisation of new bacteriocins or bacteriocin-like compounds to overcome these problems [5,15,18].…”