Occurrence and detection of AmpC beta-lactamases among Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis isolates at a Veterans Medical Center
Occurrence and detection of AmpC beta-lactamases among Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis isolates at a Veterans Medical Center
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DOI：
10.1128/jcm.38.5.1791-1796.2000
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发表时间：
2000-05-01
影响因子：
9.4
通讯作者：
Thomson, KS
中科院分区：
文献类型：
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作者：
Coudron, PE;Moland, ES;Thomson, KS
AmpC β-内酰胺酶是头孢菌素酶，其赋予对多种β-内酰胺药物的耐药性，并由此可能产生严重的治疗问题。虽然报道频率越来越高，但大肠埃希菌、肺炎克雷伯菌和奇异变形杆菌中AmpC β-内酰胺酶的真实发生率仍不清楚。我们测试了这三个物种的总共1,286个连续的非重复分离株，发现总的来说，45个（3.5%）产生的头孢西丁区直径小于18 mm（筛选阳性），16个（1.2%）通过等电聚焦显示AmpC条带。根据种属划分，683 E. coli、371 K. 232株奇异变形杆菌和232株肺炎链球菌分别有13株（1.9%）、28株（7.6%）和4株（1.7%）表现出带直径减小，分别有11株（1.6%）、4株（1.1%）和1株（0.4%）表现出AmpC条带。头孢西丁耐药性转移到所有，但8（E。coli）。我们还描述了一个三维提取物测试，这是用来检测表型分离，港口AmpC β-内酰胺酶。在45株头孢西丁耐药菌株中，三维提取物试验准确鉴定了所有16株AmpC生产菌和29株（97%）中的28株（97%）为非AmpC生产菌。有趣的是，后一组中的大多数（86%）菌株是K。肺炎分离株。这些数据证实，在我们的机构，E。coli，K. pneumoniae和P. mirabilis具有质粒介导的AmpC酶。
AmpC beta-lactamases are cephalosporinases that confer resistance to a wide variety of beta-lactam drugs and that may thereby create serious therapeutic problems. Although reported with increasing frequency, the true rate of occurrence of AmpC beta-lactamases in Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis remains unknown. We tested a total of 1,286 consecutive, nonrepeat isolates of these three species and found that, overall, 45 (3.5%) yielded a cefoxitin zone diameter less than 18 mm (screen positive) and that 16 (1.2%) demonstrated AmpC bands by isoelectric focusing. Based on the species, of 683 E. coli, 371 K. pneumoniae, and 232 P. mirabilis isolates tested, 13 (1.9%), 28 (7.6%), and 4 (1.7%), respectively, demonstrated decreased zone diameters and 11 (1.6%), 4 (1.1%), and 1 (0.4%), respectively, demonstrated AmpC bands. Cefoxitin resistance was transferred for all but 8 (E. coli) of the 16 AmpC producers. We also describe a three-dimensional extract test, which was used to detect phenotypically isolates that harbor AmpC beta-lactamase. Of the 45 cefoxitin-resistant isolates, the three-dimensional extract test accurately identified all 16 AmpC producers and 28 of 29 (97%) isolates as non-AmpC producers. Interestingly, most (86%) isolates in the latter group were K. pneumoniae isolates. These data confirm that, at our institution, E. coli, K. pneumoniae, and P. mirabilis harbor plasmid-mediated AmpC enzymes.