Abstract：
The presence of methicillin-resistant or -susceptible S. aureus in pig nostrils has been known for a long time, but the occurrence of extended-spectrum beta-lactamase (ESBL)-producing E. coli has hardly been investigated. Here, we collected 25 E. coli recovered from nasal samples of 40 pigs/10 farmers of four farms. Nine ESBL-producing isolates belonging to ST48, ST117, ST847, ST5440, ST14914 and ST10 were retrieved from seven pigs. All blaESBL genes (blaCTX-M-32,blaCTX-M-14,blaCTX-M-1,blaCTX-M-65, and blaSHV-12) were horizontally transferable by conjugation through plasmids belonging to IncI1 (n=3), IncX1 (n=3) and IncHI2 (n=1) types. IncI1-plasmids displayed different genetic environments: i) IS26-blaSHV-12-deoR-IS26, ii) wbuC-blaCTX-M-32-ISKpn26 (IS5), and iii) IS930-blaCTX-M-14-IS26. The IncHI2-plasmid contained the genetic environment IS903-blaCTX-M-65-fipA with multiple resistance genes associated either to: a) Tn21-like transposon harbouring genes conferring aminoglycosides/beta-lactams/chloramphenicol/macrolides resistance located on two atypical class 1 integrons with an embedded ΔTn5393; or b) Tn1721-derived transposon displaying an atypical class 1 integron harbouring aadA2-arr3-cmlA5-blaOXA-10-aadA24-dfrA14, preceding the genetic platform IS26-blaTEM-95-tet(A)-lysR-floR-virD2-ISVsa3-IS3075-IS26-qnrS1, as well as the tellurite resistance module. Other plasmids harbouring clinically relevant genes were detected, such as a ColE-type plasmid carrying the mcr-4.5 gene. Chromosomally encoded genes (fosA7) or integrons (intI1-dfrA1-aadA1-qacE-sul1/intI1-IS15-dfrA1-aadA2) were also identified. Finally, an IncY plasmid harbouring a class 2 integron (intI2-dfrA1-sat2-aadA1-qacL-IS406-sul3) was detected but not associated with a blaESBL gene. Our results evidence that pig nostrils might favour the spread of ESBL-E. coli and mcr-mediated colistin-resistance. Therefore, enhanced monitoring should be considered, especially in a sector where close contact between animals in intensive farming increases the risk of spreading antimicrobial resistance.
摘要：
猪鼻孔中存在耐甲氧西林或易感的金黄色葡萄球菌，但是产超广谱β-内酰胺酶（ESBL）的大肠杆菌的发生几乎没有被研究。这里,我们从4个农场的40头猪/10个农民的鼻腔样本中收集了25个大肠杆菌。从7头猪中回收了9个产生ESBL的分离株，分别属于ST48，ST117，ST847，ST5440，ST14914和ST10。所有blaESBL基因（blaCTX-M-32，blaCTX-M-14，blaCTX-M-1，blaCTX-M-65和blaSHV-12）均可通过属于IncI1（n=3）的质粒偶联水平转移，IncX1(n=3)和IncHI2(n=1)类型。IncI1-质粒表现出不同的遗传环境：i）IS26-blaSHV-12-deoR-IS26，ii）wbuC-blaCTX-M-32-ISKpn26（IS5），和iii)IS930-blaCTX-M-14-IS26。IncHI2质粒包含遗传环境IS903-blaCTX-M-65-fipA，具有多个抗性基因，这些基因与以下任一者相关：a）Tn21样转座子具有赋予氨基糖苷/β-内酰胺/氯霉素/大环内酯抗性的基因，位于两个非典型1类整合子上，具有一个嵌入的ΔTn5393；或b）Tn1721-frongen-T23-检测到其他携带临床相关基因的质粒，例如携带mcr-4.5基因的ColE型质粒。还鉴定了染色体编码基因（fosA7）或整合子（intI1-dfrA1-aadA1-qacE-sul1/intI1-IS15-dfrA1-aadA2）。最后,检测到含有2类整合子（intI2-dfrA1-sat2-aadA1-qacL-IS406-sul3）的IncY质粒，但与blaESBL基因无关。我们的结果表明，猪鼻孔可能有利于ESBL-E的传播。大肠杆菌和mcr介导的粘菌素抗性。因此,应考虑加强监测，特别是在集约化养殖中动物之间的密切接触增加了传播抗菌素耐药性的风险的部门。
