摘要
      食物来源的葡萄球菌科物种具有严重的抗微生物耐药性，尤其是金黄色葡萄球菌，是对公众健康的主要威胁。干酪多球菌（M.caseolyticus）是葡萄球菌科的一员，在动物的发酵产物和致病过程中发挥着至关重要的作用。在我们之前的研究中，在耐多药金黄色葡萄球菌中发现了几种金黄色葡萄菌抗生素耐药性岛状msr（SaRImsr）。在这项研究中，新的SaRImsr，SaRImsr-III从金黄色葡萄球菌中产生。另一种新的类似SaRImsr的病毒进一步出现在来自食物的干酪分枝杆菌中。对这些分离株的流行率和遗传环境进行了调查和表征，以了解这些新的SaRImsr菌株的分布和传播。所有SaRImsr阳性的金黄色葡萄球菌分离株都表现出多药耐药性（MDR）表型，其中鉴定了一系列抗微生物耐药性基因（ARGs）和毒力因子基因（VFs）。此外，在这些分离株的染色体中鉴定出三种携带mef（D）–msr（F）的SaRImsr类型，即SaRImsr-I（15.1kb）、SaRImsr-II（16-17kb）和SaRImsrIII（18kb）。SaRImsr-（I-III）含有一个位点特异的整合酶基因int和操纵子mef（D）-msr（F）。SaRImsr III在mef（D）和msr（F）下游具有额外的orf3或f4-IS30布置。此外，SaRImsr样和大环内酯抗性转座子Tn6776形成了一种新的镶嵌结构，并共存于一个干酪分枝杆菌分离物中。在这种镶嵌结构中，大环内酯类抗性基因mef（D）–msr（F）在SaRImsr样中不存在，而在Tn6776中鉴定出一个操纵子mef（F）–msr（G）。将SaRImsr-（I-III）和SaRImsr样结构插入染色体中编码30S核糖体蛋白S9的rpsI基因中。使用两步PCR证实了SaRImsr III、SaRImsr-like、操纵子mef（D）-msr（F）和orf3-orf4-IS30排列的切除和环化。本研究首次报道了从零售食品中分离出的MDR金黄色葡萄球菌携带新的SaRImsr III和含有新马赛克结构的干酪分枝杆菌。类似的SaRImsr型抗性岛在葡萄球菌科物种中的发生和繁殖需要持续监测和调查。
Abstract
Food-derived Staphylococcaceae species with severe antimicrobial resistance, especially Staphylococcus aureus, is a major threat to public health. Macrococcus caseolyticus (M. caseolyticus) is a member of the Staphylococcaceae family which plays a vital role in fermented products and disease causation in animals. In our previous study, several Staphylococcus aureus antibiotic-resistant island msr (SaRImsr) were found in multidrug-resistant S. aureus. In this study, novel SaRImsr, SaRImsr-III emerged from S. aureus. Another novel SaRImsr-like further emerged in M. caseolyticus from food. These isolates' prevalence and genetic environment were investigated and characterized to understand the distribution and transmission of these novel SaRImsr strains. All SaRImsr-positive S. aureus isolates exhibited a multidrug resistance (MDR) phenotype, within which a series of antimicrobial resistance genes (ARGs) and virulence factor genes (VFs) were identified. In addition, three SaRImsr types, SaRImsr-I (15.1 kb), SaRImsr-II (16–17 kb), and SaRImsr-III (18 kb) carrying mef(D)–msr(F), were identified in these isolates' chromosomes. SaRImsr-(I-III) contains a site-specific integrase gene int and operon mef(D)-msr(F). SaRImsr-III has an additional orf3-orf4-IS30 arrangement downstream of mef(D) and msr(F). Moreover, the SaRImsr-like and macrolide-resistant transposon Tn6776 forming a novel mosaic structure coexisted in one M. caseolyticus isolate. Within this mosaic structure, the macrolide-resistant genes mef(D)–msr(F) were absent in SaRImsr-like, whereas an operon, mef(F)–msr(G), was identified in Tn6776. The SaRImsr-(I-III) and SaRImsr-like structure were inserted into the rpsI gene encoding the 30S ribosomal protein S9 in the chromosome. Excision and cyclisation of SaRImsr-III, SaRImsr-like, operon mef(D)-msr(F), and orf3-orf4-IS30 arrangements were confirmed using two-step PCR. This study is the first to report MDR S. aureus harbouring novel SaRImsr-III and M. caseolyticus containing novel mosaic structures isolated from retail foods. Similar SaRImsr-type resistant islands' occurrence and propagation in Staphylococcaceae species require continuous monitoring and investigation.

https://www.sciencedirect.com/science/article/abs/pii/S0168160522004925