万古霉素在动物性食品中残留的风险评价

近年来万古霉素滥用导致耐甲氧西林葡萄球菌感染的发生率逐年增高。由于其在饲养过程中使用后可对动物有一定的促生长作用,动物性食品存在生产者非法添加的可能性。为了规范生产者行为、防范风险,本文对万古霉素存在风险加以评价并提出建议。     

Activity of blue green microalgae extracts against in vitro generated Staphylococcus aureus with reduced susceptibility to vancomycin

Blue green microalgae have been identified as one of the promising groups of organism from which biochemically active natural products have been isolated. Aqueous and organic extracts of nine blue green microalgae strains were screened against in vitro generated vancomycin intermediate resistant Staphylococcus aureus (VISA) strains. Aqueous extracts of all the blue green microalgae cultures were found to be inactive, while all the organic (hexane, chloroform and methanolic) extracts of Anabaena virabilis and Anabaena sp. showed activity against VISA strains with MIC of 32-64 mug/ml.     

Isolation and Molecular Characterization of Vancomycin‐Resistant Enterococcus faecium from Swine in Michigan,USA

In 2008, we identified vancomycin‐resistant enterococci (VRE) in Michigan swine, which was the first report of VRE in livestock from North America. Continued sampling in 2009 and 2010 was conducted to determine whether VRE persisted in Michigan. In 2009, swine faecal and feed samples (n = 56), county fair pig barn manure samples (n = 9) and pooled Michigan State Fair pig barn manure samples (n = 18) were screened for VRE. In 2010, swine faecal samples were collected from 26 county fairs (n = 73) and nine commercial swine farms in six states (n = 28). Recovered VRE isolates were molecularly evaluated by polymerase chain reaction, restriction fragment length polymorphism, pulsed‐field gel electrophoresis (PFGE), S1 nuclease digestion and multilocus sequence typing (MLST). Six VRE isolates were identified in 2009 from the State Fair, and another six (8.2%) were recovered from the five county fairs in 2010. All 12 isolates were highly related to the first‐reported VRE from Michigan swine: all were confirmed to be vancomycin‐resistant Enterococcus faecium (VREf) carrying vanA gene on Tn1546 (Type D), were negative for IS1251, hyl and esp gene, carried a 150–160 kb megaplasmid, and have closely similar PFGE patterns with >80% similarity. Classified as ST5, ST6 or ST185 by MLST, all belong to the clonal complex 5, a strain recognized to be circulating among European pigs. This study reveals that VREf are widespread in Michigan swine and persist in the historical absence of the use of agricultural glycopeptides.     

猪源万古霉素耐药肠球菌分离及表型和基因型检测

本研究旨在调查3个猪场不同猪群粪便中万古霉素耐药肠球菌(VRE)的分离率并进行耐药表型、基因型的测定,为万古霉素耐药肠球菌的流行病学提供基础数据。根据美国临床和实验室标准协会(CLSI)推荐的方法进行耐药表型的测定,采用PCR法鉴定肠球菌并进行耐药基因的扩增,比较表型与基因型的一致性。结果从3个猪场250个粪便样本共分离出30株VRE。不同猪场不同猪群的分离率以哺乳仔猪最高,其次为保育仔猪、怀孕母猪和哺乳母猪,以大猪和公猪的分离率最低。耐万古霉素肠球菌均以土霉素的耐药率最高,为93.3%;以氨苄西林的敏感率最高,为80%。耐药基因检测2株为VanA阳性,12株为VanB阳性,7株为VanC1阳性,5株为VanC2/3阳性,4株未扩增出Van基因。本研究显示3个猪场均能分离到耐万古霉素肠球菌,各猪群耐药菌分离率与猪群接触抗菌药物的程度有一定的相关性,分离的VRE对6种抗生素具有不同程度的耐药,耐药表型与基因型基本一致。