This study was performed to investigate the distribution of macrolide and tetracycline resistance genes of 48 Streptococcus suis clinical isolates.The microdilution test was used to determine the susceptibility of 48 clinical S.suis isolates to nine antibiotics according to the National Committee for Clinical Laboratory Standards.PCR was used to detect the macrolide resistance genes ermA/B/C,mefA/E,msrD,mphB,23S rRNA,L4,L22,tetracycline resistance genes tetM,tetO,tetL,tetK and transposon related genes int,xis.The resistance rate to macrolides of 31 isolates of S.suis serotype 2 was 3.23%.Of 17 isolates of S.suis serotype 9,the resistance rate to erythromycin was 88.24%,and were all 70.59% to Tylosin,Phosphate Tilmicosin and Azithromycin.All of the clinical isolates were resistant to tetracycline,and sensitive to penicilin,amoxicillin,ceftriaxone sodium and ampicillin.ErmB gene,which accounted for 75%(12/16),was the main resistant gene,while both mefA/E and msrD genes accounted for 25%(4/16).Of 16 macrolide resistant strains,the detection rates of tetM,tetO,int and xis were 25%(4/16),62.5%(10/16),31.25%(5/16)and 31.25%(5/16),respectively.All of the macrolide resistant strains were negative to ermA,ermC,mphB,tetL and tetK,and have not been found the mutation of 23S rRNA,L4 and L22.

就国产硫酸头孢喹肟对昆明种小鼠的急性毒性和亚慢性毒性进行了研究,用改良寇式法测得硫酸头孢喹肟原料药对小鼠口服LD50大于5 000 mg/kg,其混悬液制剂对小鼠腹腔注射LD50为844.03 mg/kg,LD50的95%可信限为802.05~887.56 mg/kg。亚慢性毒性试验设1/2LD50、1/4LD50、1/8LD50的高、中、低3个剂量组,另设空白对照组,连续28 d腹腔注射给药,用药28 d后剖杀各组小鼠。统计学分析表明,各组间的体重变化和脏器系数比较无显著性差异;血常规检测结果表明,高剂量组的红细胞计数和血小板略微下降,但与对照组比较差异不显著(P>0.05);血液生化指标结果表明,高剂量组的尿素氮(UN)和肌酐与对照组比较有升高的趋势,但差异也不显著(P>0.05),其他各组小鼠的测定值均在正常值范围内;病理组织学检查除高剂量组肾脏的肾小囊略有变化外,其余组织未见异常明显的变化,说明硫酸头孢喹肟对血常规和血清生化指标影响很小。国产硫酸头孢喹肟按临床剂量使用毒性低,应用安全。