National Food Institute, Technical University of Denmark, Søltofts Plads, Bldg. 221, DK-2800 Kgs. Lyngby, Denmark.
Antimicrob Agents Chemother. 2011 Sep;55(9):4064-71. doi: 10.1128/AAC.00460-11. Epub 2011 Jul 11.
The human food-borne pathogen Listeria monocytogenes is capable of persisting in food processing plants despite cleaning and sanitation and is likely exposed to sublethal biocide concentrations. This could potentially affect susceptibility of the bacterium to biocides and other antimicrobial agents. The purpose of the present study was to determine if sublethal biocide concentrations affected antibiotic susceptibility in L. monocytogenes. Exposure of L. monocytogenes strains EGD and N53-1 to sublethal concentrations of Incimaxx DES (containing peroxy acids and hydrogen peroxide) and Triquart Super (containing quaternary ammonium compound) in four consecutive cultures did not alter the frequency of antibiotic-tolerant isolates, as determined by plating on 2× the MIC for a range of antibiotics. Exposure of eight strains of L. monocytogenes to 1 and 4 μg/ml triclosan did not alter triclosan sensitivity. However, all eight strains became resistant to gentamicin (up to 16-fold increase in MIC) after exposure to sublethal triclosan concentrations. Gentamicin-resistant isolates of strains N53-1 and 4446 were also resistant to other aminoglycosides, such as kanamycin, streptomycin, and tobramycin. Gentamicin resistance remained at a high level also after five subcultures without triclosan or gentamicin. Aminoglycoside resistance can be caused by mutations in the target site, the 16S rRNA gene. However, such mutations were not detected in the N53-1-resistant isolates. A combination of gentamicin and ampicillin is commonly used in listeriosis treatment. The triclosan-induced resistance is, hence, of great concern. Further investigations are needed to determine the molecular mechanisms underlying the effect of triclosan.
人类食源性病原体李斯特菌能够在食品加工厂中存活下来，尽管经过了清洁和消毒，但仍可能暴露于亚致死浓度的杀菌剂下。这可能会影响细菌对杀菌剂和其他抗菌剂的敏感性。本研究的目的是确定亚致死浓度的杀菌剂是否会影响李斯特菌对抗生素的敏感性。将 EGD 和 N53-1 两种李斯特菌菌株连续暴露于亚致死浓度的 Incimaxx DES（含有过氧酸和过氧化氢）和 Triquart Super（含有季铵化合物）中，通过在两倍 MIC 的平板上进行抗生素药敏试验，并未改变抗生素耐药分离株的频率。八种李斯特菌菌株连续暴露于 1 和 4μg/ml 三氯生中，并未改变三氯生的敏感性。然而，所有八种菌株在接触亚致死浓度的三氯生后，对庆大霉素（MIC 增加了 16 倍）的敏感性降低。N53-1 和 4446 菌株的庆大霉素耐药分离株对其他氨基糖苷类药物（如卡那霉素、链霉素和妥布霉素）也具有耐药性。即使在没有三氯生或庆大霉素的情况下进行五次传代培养后，庆大霉素耐药性仍保持在较高水平。氨基糖苷类药物的耐药性可能是由于靶位（16S rRNA 基因）的突变引起的。然而，在 N53-1 耐药分离株中并未检测到这种突变。庆大霉素和氨苄西林的组合常用于李斯特菌病的治疗。因此，三氯生诱导的耐药性非常令人担忧。需要进一步研究确定三氯生作用的分子机制。
