阴沟肠杆菌耐药及ampC基因表达状况研究

目的 了解144株阴沟肠杆菌的耐药现状及ampC基因的表达。方法 通过纸片扩散法检测阴沟肠杆菌的药敏情况。聚合酶链反应（PCR）法检测ampC基因，克隆测序分析其特异性，并根据耐药表型对ampC基因表达状况进行分析。结果 144株阴沟肠杆菌对亚胺培南的敏感率高达98.6%，对头孢吡肟和头孢哌酮/舒巴坦的敏感率分别为65.9%和63.9%，但对阿莫西林/克拉维酸，头孢呋辛和头孢噻肟等抗菌药物的敏感率较低。120株ampC基因阳性（占83.3%)，其中36株高水平表达（占30.0%),45株诱导表达（占37.5%),未表达或低水平表达的有39株（占32.5%)，有56株合并产超广谱β-内酰胺酶（ESBLs)（占46.7%)，单纯诱导产AmpC酶的菌株除对阿莫西林/克拉维酸和头孢呋辛敏感率低外，对其他抗菌药物的敏感率均在90%以上；而单纯高产AmpC酶的菌株仅对亚胺培南和头孢吡肟的敏感率在85%以上，如合并产ESBLs，则对头孢吡肟的敏感率下降。结论 阴沟肠杆菌耐药状况严重。明确ampC基因的表达状况有助于临床抗菌药物的选用。

Status of resistance and ampC gene expression in Enterobacter cloacae

Objective To investigate the status of the resistance and the ampC gene expression of Enterobacter cloacae . Methods Disk diffusion tests were performed to detect the susceptibility of antimicrobial agents against Enterobacter cloacae . PCR and verificated amplified ampC gene by DNA sequencing were used to confirm its specificity. ampC gene expression was analyzed according to antimicrobial agent sensitive phenotype. Results The sensitive rates of 144 strains to Imipenam, Cefepime and Cefoperazone/sulbactam were 98.61%, 65.97% and 63.89%, respectively. The sensitive rates of 144 strains to other antimicrobial agents were lower. 120 out of 144 strains were found to be positive by PCR for ampC gene. The PCR product showed high homology to the GenBank ampC sequence. Hyperexpressing strains, hyperinducible strains and unexpressing or lower level expressing strains accounted for 30.00% (36/120), 37.50% (45/120) and 32.50% (39/120), respectively. 56 out of 120 strains (46.67%) also produced ESBLs. The hyperinducible strains were highly sensitive to all antimicrobial agents except Amoxicillin/clavulanic acid and Cefuroxime, while the hyperexpressing strains were only sensitive to Imipenam and Cefepime. But the sensitivity to Cefepime descended if the strains also produced ESBLs. Conclusions The resistant status of Enterobacter cloacae is severe. To clear out the expression status of ampC gene is helpful to select the antimicrobial agents in the treatment of clinical infection.