Naghmouchi K, Drider D, Kheadr E, Lacroix C, Prévost H, Fliss I
Dairy Research Center STELA, Pavillon Paul Comtois, Université Laval, Québec, Qc, Canada G1K 7P4.
J Appl Microbiol. 2006;100(1):29-39. doi: 10.1111/j.1365-2672.2005.02771.x.
Divergicin M35 is a new class IIa bacteriocin produced by Carnobacterium divergicin M35. The bactericidal activity of this antimicrobial peptide was tested against a set of 11 strains of Listeria monocytogenes isolated from food.
The minimal inhibitory concentration (MIC) was determined by the microdilution method. The strains tested displayed a different level of sensitivity to divergicin M35. L. monocytogenes LSD530, referred to as DivS strain, was the most sensitive and appeared to be inhibited by concentration of divergicin M35 below 0.13 microg ml(-1). The mutant resistant to divergicin M35, called DivM, was obtained from L. monocytogenes LSD530 (DivS) by gradually increasing the amounts of divergicin M35 until 1.3 microg ml(-1). Notably, DivM was stable after 50 generations. DivS parental strain was inhibited by a concentration of 4 microg ml(-1). L. monocytogenes LSD530 was shown to be resistant to divergicin M35 at 1.3 microg ml(-1). Remarkably, in the presence of divalent cations such as Ca(2+), Mg(2+) and Mn(2+), the lethality caused by divergicin M35 was reduced by 0.48, 0.54 and 0.63 log CFU per ml (after 18 h at 30 degrees C), respectively. The total DNA profiles of DivS and DivM were similar. DivS and DivM showed variable sensitivity to antibiotics. The two-dimensional (2-D) electrophoresis of cell wall proteins did not show any significant difference between DivS and DivM strains but their fatty acid composition showed a significant difference in C(16:0) content.
Resistance to divergicin M35 is likely ascribed to modification in cell wall fatty acid composition rather than protein modification.
This study provides original results contributing to understanding of the resistance of L. monocytogenes to divergicin M35, a new class IIa bacteriocin.
双歧菌素M35是由双歧肉杆菌M35产生的一种新型IIa类细菌素。测试了这种抗菌肽对从食品中分离出的11株单核细胞增生李斯特菌的杀菌活性。
采用微量稀释法测定最低抑菌浓度（MIC）。测试的菌株对双歧菌素M35表现出不同程度的敏感性。单核细胞增生李斯特菌LSD530，称为DivS菌株，最为敏感，似乎在双歧菌素M35浓度低于0.13微克/毫升时就受到抑制。通过逐渐增加双歧菌素M35的量直至1.3微克/毫升，从单核细胞增生李斯特菌LSD530（DivS）获得了对双歧菌素M35耐药的突变体，称为DivM。值得注意的是，DivM在50代后仍保持稳定。DivS亲本菌株在4微克/毫升的浓度下受到抑制。单核细胞增生李斯特菌LSD530在1.3微克/毫升时对双歧菌素M35表现出耐药性。值得注意的是，在存在Ca(2+)、Mg(2+)和Mn(2+)等二价阳离子的情况下，双歧菌素M35引起的致死率分别降低了每毫升0.48、0.54和0.63 log CFU（在30℃下培养18小时后）。DivS和DivM的总DNA图谱相似。DivS和DivM对抗生素表现出不同的敏感性。细胞壁蛋白的二维电泳在DivS和DivM菌株之间未显示出任何显著差异，但其脂肪酸组成在C(16:0)含量上存在显著差异。
对双歧菌素M35的耐药性可能归因于细胞壁脂肪酸组成的改变而非蛋白质修饰。
本研究提供了有助于理解单核细胞增生李斯特菌对新型IIa类细菌素双歧菌素M35耐药性的原始结果。
