内蒙古地区奶牛乳源金黄色葡萄球菌耐药性研究

Study on the Drug-resistance of Staphylococcus aureus Isolated from dairy cow in Inner Mongolia

为了确定内蒙古地区奶牛中乳源金黄色葡萄球菌的耐药表型及其耐药基因的流行情况,采用生化鉴定法结合PCR方法对奶牛乳源金黄色葡萄球菌进行了分离、鉴定。采用微量稀释法测定了15种临床常用抗菌药物对21株金黄色葡萄球菌的最小抑制菌浓度(MICs)。结果显示,分离菌株对青霉素和氨苄西林的耐药率较高,分别为81%和75.5%;对头孢菌素类药物的耐药率也较高,均在60%~70%之间;对大环内酯类和四环素类抗生素的耐药率均在40%~50%之间。乳源金黄色葡萄球菌对3种氟喹诺酮类抗菌药物的耐药率较低,均小于30%;对庆大霉素也比较敏感,耐药率13.2%。以上分离菌株对万古霉素全部敏感。联合用药的药敏试验结果显示,菌株对阿莫西林-克拉维酸高度敏感,耐药率仅9.5%。多重耐药表型结果显示,75.5%的菌株耐2~7种药,24.5%的菌株耐8~13种药。通过PCR方法对奶牛乳源金黄色葡萄球菌所携带的耐药表型及基因进行检测,结果表明,分离菌株中有3种四环素耐药基因组合在流行。分别是tet M+tet L1株(4.76%)和18株分离菌携带bla Z耐药基因,检出率为85.7%。由此可见,内蒙古地区奶牛乳源性金黄色葡萄球菌对15种抗菌药物产生了不同程度的耐药性,且多重耐药情况较为严重;分离菌株中有tet M、tet K、tet L和bla Z耐药基因在流行,分别编码了对四环素类和β-内酰类抗生素的耐药性。

In this study,we deter mined the drug resistance phenotype and prevalence of drug resistance genes in Staphylococcus aureus（ S. aureus） isolated from dairy cows with mastitis in Inner Mongolia. The S. aureus isolates were identified by biochemical and PCR methods. The minimum inhibitory concentrations（ MICs） of the strains to antibiotics commonly used in veterinary clinical were detected by micro-dilution method in vitro. The results showed that the resistance rates of the isolates to penicillin and ampicillin were81% and 75. 5% respectively,and the resistance to cephalosporins was from 60% to 70%. Their resistance rates to macrolides and tetracycline antibiotics were between 40% and 50%. The Staphylococcus aureus strains were more sensitive to 3 kind of fluoride quinolone drugs. The resistance rates were all less than 30%. To gentamicin the resistance rate was low,only about 13. 2%. In addition,all of them were sensitive to vancomycin. The results of the combined administration experiment showed that amoxicillin combined clavulanic acid inhibited the growing of S. aureus isolates significantly and the resistance rate was 9. 5%. Among the strains of S. aureus from diary cow with mastitis. 75. 5% of them were resistant to 2 ~ 7 antimicrobial agents,and 24. 5% of them were resistant to 8 ~ 13 antimicrobial agents. No one strain was sensitive to 15 antimicrobial agents. The resistance genes carried by the S. aureus strains were detected by PCR method. The results confirmed that there were three kinds of resistance gene combinations prevalent in the isolates. They were tet M ＋ tet K（ 2 strains,9. 5%）,tet M ＋ tet L（ 1 strain,4. 76%）,and tet K ＋ tet L（ 1 strain,4. 76%）,respectively.They carried tet M,tet K,tet L and bla Z genes which encoded the resistance to tetracycline and β-lactam antimicrobial drugs