Mereghetti L, Quentin R, Marquet-Van Der Mee N, Audurier A
Laboratoire de Microbiologie, Faculté de Médecine de Tours, 37032 Tours Cedex, France.
Appl Environ Microbiol. 2000 Nov;66(11):5083-6. doi: 10.1128/AEM.66.11.5083-5086.2000.
Ninety-seven epidemiologically unrelated strains of Listeria monocytogenes were investigated for their sensitivities to quaternary ammonium compounds (benzalkonium chloride and cetrimide). The MICs for seven serogroup 1/2 strains were high. Three came from the environment and four came from food; none were isolated from human or animal samples. All 97 strains carried the mdrL gene, which encodes a multidrug efflux pump, and the orfA gene, a putative transcriptional repressor of mdrL. The absence of plasmids in four of the seven resistant strains and the conservation of resistance after plasmid curing suggested that the resistance genes are not plasmid borne. Moreover, PCR amplification and Southern blot hybridization experiments failed to find genes phylogenetically related to the qacA and smr genes, encoding multidrug efflux systems previously described for the genus Staphylococcus. The high association between nontypeability by phages and the loss of sensitivity to quaternary ammonium compounds are suggestive of an intrinsic resistance due to modifications in the cell wall.
对97株流行病学上无关联的单核细胞增生李斯特菌菌株进行了对季铵化合物（苯扎氯铵和西曲溴铵）敏感性的研究。7株血清群1/2菌株的最低抑菌浓度（MIC）较高。其中3株来自环境，4株来自食品；均未从人或动物样本中分离得到。所有97株菌株均携带编码多药外排泵的mdrL基因和orfA基因，orfA基因是mdrL的假定转录阻遏物。7株耐药菌株中有4株无质粒，质粒消除后耐药性仍保持，这表明耐药基因不是由质粒携带的。此外，聚合酶链反应（PCR）扩增和Southern印迹杂交实验未能找到与qacA和smr基因在系统发育上相关的基因，qacA和smr基因编码先前在葡萄球菌属中描述的多药外排系统。噬菌体不可分型与对季铵化合物敏感性丧失之间的高度关联提示由于细胞壁修饰导致的固有耐药性。
