牛源无乳链球菌耐药性与毒力基因的表达量差异分析

【目的】 研究无乳链球菌对抗菌药物的耐药性，分析无乳链球菌毒力基因与耐药基因的携带情况。【方法】 分别采用微量肉汤稀释法和普通PCR的方法，检测牛源无乳链球菌对16种抗菌药物的耐药性和相关耐药基因及毒力基因，并且采用荧光定量PCR技术对不同菌株的8种毒力基因的表达量差异进行分析。【结果】 （1）无乳链球菌对11种药物的敏感性达到了65%以上，其中敏感性最高的是氟苯尼考（92.4.%）和头孢噻呋（88.4%），对氨苄西林、红霉素、克林霉素的耐药率均达到了50%以上，对磺胺异恶唑的耐药率也达到了45%以上。（2）无乳链球菌耐药基因gyrA、sul1、ermB、ermC的检出率分别为100%、 86.67%、 93.3%、 33.3%，而ermA、sul2、sul3及parC 4种耐药基因未检出。（3）无乳链球菌毒力基因pavA、cfb、fbsA、bibA、cspA、sip、iagA、hylB的检出率为100%，rib检出率为13.3%，bca的检出率为53.3%，cyl E检出率为73.3%；未检测到bac、lmb、scp B这三种毒力基因。（4）不同菌株之间毒力基因的表达量有显著性差异（P<0.05）。【结论】 无乳链球菌对红霉素和克林霉素的耐药率较高，无乳链球菌毒力因子是宿主感染疾病的重要因素。

Differential Expression of Drug Resistance and Virulence Genes in Streptococcus agalactiae Isolated from Cattle

【Objective】 The purpose of this study was to investigate the drug resistance of Streptococcus agalactiae to antibacterial agents and determine the carrying status of virulence gene and drug resistance gene of Streptococcus agalactiae.【Methods】 In this study， microdilution broth method and common PCR were used to detect the resistance of 16 kinds of antibacterial drugs and related drug resistance genes and virulence genes of Streptococcus agalactiae from bovine. Moreover， the expression levels of 8 virulence genes in different strains were analyzed by fluorescence quantitative PCR. 【Results】 （1）The sensitivity of Streptococcus agalactiae to 11 drugs was more than 65%， among which the highest sensitivity was florfenicol （92.4%） and ceftiofur （88.4%）. The resistance rate of Streptococcus agalactiae to ampicillin， erythromycin and clindamycin was more than 50%， and the resistance rate of Streptococcus agalactiae to sulfagan was more than 45%. （2） The detection rates of gyrA， sul1， ermb and ermc were 100%， 86.67%， 93.3% and 33.3% respectively， while erma， sul2， sul3 and parc were not detected. （3） The detection rates of virulence genes pavA， cfb， fbsA， bibA， cspA， sip， iagA， hylB， rib， bca and cylE were 100%. The detection rates of rib， bca and cylE were 13.3%， 53.3% and 73.3%， respectively. However， the bac， lmb and scpB were not detected. （4） Fluorescence quantitative analysis showed that the expression levels of virulence gene was significantly different among different strains （P<0.05）. 【Conclusion】 The resistance rate of Streptococcus agalactiae to erythromycin and clindamycin is high. The virulence factor of Streptococcus agalactiae is an important factor of host infection disease.