摘要
目的了解北京协和医院临床分离产ESBLs大肠埃希菌的耐药性及所产ESBLs的等电点和基因型特征。方法对2002年11-12月间北京协和医院临床分离的22株产ESBLS大肠埃希菌采用琼脂平皿对倍稀释法测9种抗菌药的MIC；接合试验研究ESBLs基因是否定位于质粒，并对接合于进行MIC测定和ESBLs确证；等电聚焦电泳检测各菌株及其接合子所产B内酰胺酶的等电点；以PCR通用引物对接合子扩增blaTEM，blaSHV，blaCTX-M基因后测序以确定基因亚型。结果产ESBLs的22株大肠埃希菌仅1株（4．5％）对头孢噻肟敏感，远低于对头孢他啶的敏感率（86．4％，19株），对氨曲南，头孢吡肟，头孢哌酮-舒巴坦，头孢米诺，亚胺培南的敏感率从50％～100％，对环丙沙星和加替沙星的敏感率均较低（9．1％和22．7％）。接合实验获得16株接合子，所有接合子均确证产ESBLs，接合子对上述7种β内酰胺类药物的药敏谱与供体菌相似，而对环丙沙星和加替沙星则全部敏感。接合子和供体菌所产的β内酰胺酶等电点主要为5．4，7．6和8．2，且这些酶均能被克拉维酸抑制。8株接合子扩增出blaTEM基因，将其中1株测序发现其与blaTEM1（GenBank accession no．AY293072）100％同源；3株接合子扩增出blaCTX-M-3组基因，将1株测序发现其与blaCTX-M-3（GenBank accession no．AY485338）100％同源；13株接合子扩增出blaCTX-M-14组基因，将1株测序发现其与blaCTX-M-14（GenBank accession no．AF462398）100％同源。16株接合子均未扩增出blaSHV基因和blaCTX-M-5组基因。结论我院2002年11-12月间产ESBLs的大肠埃希菌中有TEM及CTX-M酶的流行，这些酶特别是CTX—M酶的存在导致大肠埃希菌对大多数口内酰胺类药物耐药，对头孢噻肟高度耐药尤为明显。
Objective This study was designed to investigate the resistance in ESBLs producing Escherichia coli strains isolated from patients in our hospital and to identify the isoelectric points of β-lactamases and the subtype of ESBLs encoding gene. Methods The MICs of 9 antimicrobials against 22 ESBLs-producing E. coli strains were determined by 2-fold agar dilution method. Conjugation test was used to locate ESBL encoding genes. Transconjugants were characterized by MICs and ESBLs confirmation test, The pIs of the β-lactamases were determined by isoelectric focusing electrophoresis. The TEM-type, SHV- type and CTX M type encoding genes were amplified by PCR. DNA sequencing was used to determine the subtype of these β- lactamases. Results The susceptibility rate to cefotaxime was 4.5%, which was obviously lower than that to ceftazidime （86. 4%）. The susceptibility rate to aztreonam, cefepime, cefoperazone-sulbactam, cefminox and imipenem ranged from 50% to 100%. The susceptibility rate to both ciprofloxacin and gatifloxacin was low （9. 1% and 22. 7%）. Sixteen transconjugants were acquired. All transconjugants were confirmed to produce ESBLs and their resistance patterns were similar to donors except the resistance to ciprofloxacin and gatifloxacin. The pIs of β-lactamases produced by transconjugants and donors were ：mainly 5.4, 7.6 and 8.2. These enzymes could be inhibited by clavulanic acid. BlaTEM genes were detected by PCR amplification in 8/16 transeonjugants, blacrxm3 subgroup genes in 3/16 transconjugants, and blaCTX-M-4 subgroup genes in 13/16 transeonjugants. No blasHv or blac-rxM-s subgroup genes were amplified. Conelusions There was prevalence of TEM-type and CTX-M-type β lactamases in E. coli strains isolated in our hospital from November to December in 2002. These enzymes especially CTX-M enzymes in E, coli strains are responsible for resistance to a number of β-laetams, especially cefotaxlme.
出处
《中国感染与化疗杂志》
CAS
2006年第1期1-6,共6页
Chinese Journal of Infection and Chemotherapy
