无乳链球菌的耐药性及对利奈唑胺不敏感的机制分析

Resistance and mechanism mediated Streptococcus agalactiae unsusceptible to linezolid

目的监测我国主要城市三级甲等医院住院患者分离的无乳链球菌的耐药状况,分析不同标本来源的无乳链球菌的药敏结果及1株无乳链球菌对利奈唑胺不敏感的机制.方法定点收集全国各个医院147株无乳链球菌,由中心实验室统一用平皿二倍稀释法测定抗菌药物最低抑菌浓度(MIC)、分析药敏结果.参照美国临床和实验室协会(CLSI)或欧洲药敏委员会(EUCAST)2021标准判定细菌敏感率、耐药率.通过聚合酶链反应(PCR)和序列比对分析利奈唑胺不敏感无乳链球菌对利奈唑胺的耐药机制.结果无乳链球菌对多数菌药物的敏感率较高,对大环内酯类、克林霉素和喹诺酮类耐药率较高;尿标本来源菌株对大多数药物的耐药率略高于生殖道标本来源菌株.在147株无乳链球菌株中,利奈唑胺MIC_(50)与MIC_(90)均为1 mg·L^(-1),发现1株无乳链球菌利奈唑胺MIC值为8 mg·L^(-1),对利奈唑胺不敏感.该菌株poxtA、cfr、cfr(B)、cfr(C)阴性,未检出核糖体L蛋白突变,但携带optrA基因和23SrRNA V结构区突变.结论从整体来看,无乳链球菌对多数抗菌药物较敏感,但其耐药情况不容忽视.尤其是无乳链球菌对利奈唑胺耐药应引起重视,在临床治疗中,应关注此类菌株的治疗效果,给予合适的药物治疗.

Objective To monitor the drug resistance of Streptococcus agalactiae isolated from inpatients in tietiary hospitals in major cities in China,and analyze the drug sensitivity of Streptococcus agalactiae and the resistance mechanism to linezolid.Methods A total of 147 strains were collected from hospitals all over the country.The minimum inhibitory concentration(MIC)of antibiotics and drug sensitivity results were determined by double dilution method in the central laboratory.The bacterial sensitivity rate and drug resistance rate were determined according to the 2021 standard of American Clinical and Laboratory Association(CLSI)or European Commission on drug susceptibility(EUCAST).The resistance mechanism of linezolid insensitive Streptococcus agalactiae was analyzed by polymerase chain reaction(PCR)and sequence alignment.Results Overall,Streptococcus agalactiae were susceptible to most of antibacterial agents and highly resistant to macrolides,clindamycin and fluoroquinolones;the resistance of strains collected from urine were more serious.Among 147 strains of Streptococcus agalactiae,the MIC;and MIC;of linezolid were 1 mg·L^(-1),and a strain of Streptococcus agalactiae was found to be unsusceptible to linezolid with MIC value of 8 mg·L^(-1).The strain was negative for poxt A,cfr,cfr(B)and cfr(C)and did not carried the ribosomal protein mutation,but carried optr A gene and mutation of 23SrRNA V structure area.Conclusion The resistance of Streptococcus agalactiae should not be ignored and in clinical treatment,we should pay attention to the therapeutic effect of such strains and give appropriate drug treatment.