产AmpC酶阴沟肠杆菌耐药的基础与临床

Study on the AmpC producing Enterobacter cloacae and its resistance

目的对四川大学华西医院阴沟肠杆菌产AmpC酶菌株的检出率、耐药性及ampC结构基因序列进行分析,探讨阴沟肠杆菌产AmpC酶菌株的耐药性及临床特点。方法采用琼脂稀释法对临床标本中分离的阴沟肠杆菌进行产AmpC酶株的筛选,用酶粗提物头孢西丁三维试验结合PCR法检测AmpC酶,并测定产AmpC酶菌株对9种抗菌药物的MIC值。对3株高度耐药阴沟肠杆菌产AmpC酶的结构基因和1株敏感菌进行PCR扩增并对产物序列进行分析,测序的菌株与E.cloacaep99进行核苷酸序列比较和推导的氨基酸序列比较。结果阴沟肠杆菌产AmpC酶株的检出率为24.6%。产AmpC酶菌株多呈多重耐药,产AmpC酶耐药菌对9种抗菌药物的耐药率由高至低为头孢西丁、头孢噻肟、阿米卡星、氨曲南、头孢他啶、头孢哌酮/舒巴坦、环丙沙星、头孢吡肟、亚胺培南。阴沟肠杆菌耐药株ampC结构基因的核苷酸序列与E.cloacaep99的同源性为99%,推导的氨基酸序列仅Ala-58→Pro发生点突变。结论四川大学华西医院阴沟肠杆菌产AmpC酶细菌检出率较高。产AmpC酶细菌多呈多重耐药,亚胺培南是治疗产AmpC酶细菌感染的较可靠的药物。阴沟肠杆菌产AmpC酶是其对β-内酰胺类抗生素耐药的原因之一,其ampC结构基因突变可能与其耐药性有关。

Objective To investigate the prevalence of AmpC-producing Entero bacter cloacae isolates in our hospital and analyze the resistance of these stra ins.To study the relationship between drug resistance and the mutant of ampC str ucture gene in nosocomial AmpC-producing Enterobacter cloacae.Methods The AmpC-producing Enterobacter cloacae isolates were isolated from clinical species i n our hospital.The MIC of nine kinds of antibiotics against the AmpC-producing clinical isolates were performed by two fold agar dilution with the standard of NCCLS.AmpC enzyme was examined by cefoxitin three dimension test and PCR amplif ication of ampC structure gene were studied.The nucleotide sequence of ampC enco ding gene that amplified by PCR were detected by automatic sequencer.T heir necleotide sequences and amino acid sequences were compared with that of E.cloacae p99. Results The incidence of AmpC-producing Enterobac ter cloacae were 24.6% . Most of the AmpC-producing strains were multidrug re sistance.The resistance rate of AmpC-producing strains to cefoxitin were 92.8 % , cefotaxime( 78.6% ) , amikacin( 71.4% ) ,aztreonam( 57.1% ) ,cef tazidime( 50.0% ) ,cefoperazone/sulbactam( 42.9% ) ,ciprofloxacin( 21.4% ) ,cefepime( 14.3% ) ,and imipenem( 0) .All AmpC-producing strains were susceptible to imipenem. The sequences of resistant strains showed homolog ous of 99% with E.cloacae p99 and their amino acid sequences had site-direct ed mutagenesis of Ala-58→ Pro.Conclusion The incidence of AmpC-producing st rain was comparatively high.Most of the AmpC-producing strains were multi-dr ug resistance,and imipenem is still the proper antibiotic for treatment of the i nfections caused by AmpC-producing bacteria.AmpC enzyme was one of the cause of Enterobacter cloacae’ s resistance. The mutant of ampC structure gene may be associated with its drug resistance.