华北地区部分省(市)奶牛乳房炎乳中链球菌耐药表型和耐药基因研究

Study on Streptococcus resistant phenotypes and resistance genes in dairy cow mastitis in four provinces in North China

为了解华北地区4个省(市)奶牛乳房炎乳中链球菌的感染情况及对常用抗生素的耐药性,试验采用EN液体培养基、5%绵羊鲜血琼脂培养基、触酶试验、6.5%NaCl试验、七叶苷试验i马尿酸钠试验和CAMP试验对2016年华北地区240批次乳房炎奶牛乳样进行链球菌的分离鉴定和分型;采用纸片扩散法对2016年华北地区分离出的链球菌进行药敏试验,对华北地区上下半年及4个省(市)链球菌的药敏情况进行对比;并通过PCR扩增技术研究链球菌的耐药基因,计算链球菌表型耐药率与所携带相关耐药基因的阳性率,比较两者的相符率。结果表明:共分离得到致病性链球菌28株,总分离率为11.67%,其中无乳链球菌7株、停乳链球菌5株和乳房链球菌16株;链球菌分离株对苯唑西林和青霉素G表现出完全耐药;对四环素类药物耐药性较高,强力霉素和四环素的耐药率分别为85.71%和82.14%;对氯霉素类药物高度敏感,敏感率为92.86%;对喹诺酮类和氨基糖苷类药物耐药性较低,平均耐药率分别为8.93%和10.20%;除磺胺类药物外,其他类药物耐药率下半年均低于上半年;在4个省(市)中,天津市链球菌分离株对各类抗生素的平均耐药率高于其他省(市);经PCR扩增检测,耐药基因阳性率在7.14%~26.79%之间,整体检出率较低,耐药基因与耐药表型相符率在0~100%之间,其中氯霉素相符率为0,并不能完全拟合。说明2016年我国华北地区链球菌总检出率较低,乳房链球菌为主要致病菌,链球菌分离株表现出不同程度的耐药性,且多为多重耐药,耐药基因与耐药表型的相符率较低。

To understand the infection of Streptococcus mutans in cows in four provinces in North China and their resistance to commonly used antibiotics,Streptococcus was isolated and classified from 240 batches of mastitis milk samples in North China in 2016 using EN liquid medium, 5% sheep blood agar medium, thiolase test, 6.5% NaCl test, aesculin test, sodium hippurate test and CAMP test.The drug sensitivity test of Streptococcus isolated in North China in 2016 was conducted by paper diffusion method, and the drug sensitivity of Streptococcus isolated in North China in the first and second half of 2016 in 4 provinces(cities) were compared. The resistance gene of Streptococcus was studied by PCR amplification and agarose gel electrophoresis. The coincidence rate between the drug resistance rate of Streptococcus phenotype and the positive rate of drug resistance genes was calculated. The results showed that 28 strains of pathogenic Streptococcus were isolated, the total ceparation rate was 11.67%, including 7 strains of Streptococcus agalactiae, 5 strains of Streptococcus dysgalactiae and 16 strains of Streptococcus uberis.The Streptococcus isolates were completely resistant to oxacillin and penicillin G. The resistance to tetracycline was higher, the drug resistance rates of doxycycline and tetracycline were 85.71% and 82.14%.Highly sensitive to chloramphenicol, with a sensitivity rate of 92.86%.Resistance to quinolones and aminoglycosides was low, with drug resistance rates of 8.93% and 10.20% respectively. Except for sulfonamides, the drug resistance rate of other drugs in the second half of the year is lower than that in the first half. Among the four provinces(cities). PCR amplification showed that the positive rate of drug resistance genes was between 7.14% and 26.79%, the overall detection rate was low, and the coincidence rate between drug resistance genes and drug resistant phenotypes was between 0 and 100%, among which the coincidence rate of chloramphenicol was 0,drug resistance genes and drug resistance phenotypes are not completely matched.It showed that the total detection rate of Streptococcus in North China was low in 2016, and Streptococcus uberis was the main pathogenic bacteria, Streptococcus isolates showed varying degrees of drug resistance, and most were multiple drug resistant,the correlation rate of drug resistance genotype and phenotype was low.