摘要

抗生素抗性微生物病原体的持续增加已成为全球主要的公共健康威胁之一。尽管迄今为止采取了所有的努力和行动，仍然观察到抗生素耐药性（AR）和多重抗生素耐药性（MAR）菌株的增殖，包括食源性病原体。据报道，这种趋势最近也发现了单核细胞增生李斯特菌菌株，该菌株尽管对临床相关抗菌素极为敏感，据报道对抗生素的耐受性增加，特别是从食物链中回收的菌株。在这项研究中，我们比较了MAR（n = 8），AR（n = 18）和抗生素易感性（AS，n = 11）来自食物和临床来源的单核细胞增生李斯特氏菌菌株在不同环境胁迫条件下存活的能力， （58℃），酸性胁迫（1％v / v乳酸，pH 3.5）和渗透胁迫（37％w / v NaCl）。还研究了MAR和AR菌株中抗生素活性外排的存在及其对单核细胞增生李斯特菌耐受不同抗菌化合物的作用，即：过氧化氢;有机酸（醋酸，柠檬酸和乳酸）;乳酸链球菌素;苯扎氯铵（BC）;和亚硝酸钠。虽然在暴露于高温（58℃）的37个菌株的存活中没有观察到显着差异，但总体而言，在酸和盐暴露后，临床菌株的平均对数减少在统计学上低于观察到的食物来源菌株的平均对数减少;但与AS菌株相比，耐受两种或三种抗生素的食物和临床菌株对酸（乳酸1％v / v）和渗透胁迫（37％w / v NaCl）的敏感性明显较低。使用EtBr-琼脂车轮法，可以在26个MAR和AR分离物中的三个中检测外排泵，包括一个对照菌株;这些菌株的主动外排被证明与氟喹诺酮耐药性有关，并且可能挤出BC和过氧化氢。造成单核细胞增生李斯特菌耐药性与酸或盐胁迫可能相关的机制尚未明了。

The ongoing rise of antibiotic resistant microbial pathogens has become one of the major public health threats worldwide. Despite all the effort and actions taken so far, a proliferation of antibiotic resistant (AR) and multi-antibiotic resistant (MAR) strains is still observed, including in foodborne pathogens. This trend has been also noted recently for isolates ofListeria monocytogenes, a species that, although remaining largely sensitive to clinically relevant antimicrobials, has been reported to develop increased tolerance to antibiotics, particularly in isolates recovered from the food-chain. In this study we compared the ability of MAR (n = 8), AR (n = 18) and antibiotic susceptible (AS, n = 11) L. monocytogenes strains from food and clinical origin to survive to different environmental stress conditions, including temperature (58 °C), acidic stress (1% v/v lactic acid, pH 3.5), and osmotic stress (37% w/v NaCl). The presence of antibiotic active efflux among MAR and AR strains, and its role on L. monocytogenes tolerance to different antimicrobial compounds was also investigated, namely; hydrogen peroxide; organic acids (acetic, citric and lactic); nisin; benzalkonium chloride (BC); and, sodium nitrite. While no significant differences were observed in the survival of the 37 strains exposed to high temperature (58 °C), overall the mean logarithmic reduction of clinical strains was statistically lower after acid and salt exposure than that observed for strains of food origin; but both food and clinical strains resistant to two or three antibiotics were significantly less susceptible to acid (lactic acid 1% v/v) and osmotic stresses (37% w/v NaCl) when compared to AS strains. Using the EtBr-agar Cartwheel method, it was possible to detect efflux pumps in three of the 26 MAR and AR isolates, including one control strain; the active efflux in theses isolates was proven to be associated with fluoroquinolone resistance, and possible extrusion of BC and hydrogen peroxide. The mechanisms responsible for the possible correlation between resistance to antibiotics and to acid or salt stress in L. monocytogenes have yet to be understood.

https://www.sciencedirect.com/science/article/pii/S0168160517300405