, Listeria monocytogenes, Staphylococcus #CP-690550 ic50 randurls[1|1|,|CHEM1|]# spp. and Streptococcus spp. using the deferred antagonism assay and thus observed for other purified pediocin-like bacteriocins and mutacins [2, 7, 8, 13, 19, 22, 27]. However, some of the strains tested, particularly

Listeria spp., were less sensitive to the activity of purified mutacin F-59.1 than to the producer strain itself [8]. This may be due to the production by S. mutans 59.1 of more than one mutacin in solid medium having activity against Listeria spp.. Also, resistance to pediocin-like bacteriocins in Listeria species has already been reported and can be physiologically or genetically acquired [28, 29]. Low levels of resistance are caused by alterations in membrane lipid composition while high resistance levels involved the loss of a mannose permease component [30, 31]. Nisin resistance is also reported and is related to membrane composition [32] or alterations in the cell wall

[33]. Our results show that nisin-resistant learn more Listeria strains were still sensitive to the lantibiotic mutacin D-123.1. Lipid II-targeted lantibiotics that are too short to form a pore across the bilayer membrane can still maintain their antibacterial activity to be able to kill the nisin-resistant strains In a similar manner, mutacin D-123.1 could act by trapping lipid II from the septum, blocking peptidoglycan synthesis and leading to cell death [34]. Moreover, activity of mutacin D-123.1 against antibiotic-resistant Enterococcus spp. and Staphylococcus spp. stresses its potential as a new antibiotic. Weak activity of mutacins F-59.1 and D-123.1 were observed against their respective producing strains (S. mutans 59.1 and 123.1) as compared to the highly sensitive strain M. luteus ATCC 272, which suggests that the respective strains are able to produce specific self-immunity factors. Bacteriocin biosynthesis genes are generally 5FU co-transcribed with a gene encoding a cognate immunity

protein ensuring protection of the producing cell against the lethal activity of the bacteriocin they produce [4]. Pediocin-like bacteriocins were identified in a wide variety of Gram positive bacteria such as Bacillus spp., Carnobacterium spp., Enterococcus spp., Lactobacillus spp., Leuconostoc spp., Listeria spp. [2, 13]. While high heterogeneity has been observed in the genetic determinants coding for production of mutacins [12, 35], this is the first report of a pediocin-like mutacin produced by S. mutans, which further extends the distribution of pediocin-encoding genes as well as the antibacterial spectra of S. mutans against pathogens sensitive to class IIa bacteriocins. From the two genomes of S.