Evaluation of the Wider System, a New Computer-Assisted Image-Processing Device for Bacterial Identification and Susceptibility Testing

The Wider system is a newly developed computer-assisted image-processing device for both bacterial identification and antimicrobial susceptibility testing. It has been adapted to be able to read and interpret commercial MicroScan panels. Two hundred forty-four fresh consecutive clinical isolates (138 isolates of the family Enterobacteriaceae, 25 nonfermentative gram-negative rods [NFGNRs], and 81 gram-positive cocci) were tested. In addition, 100 enterobacterial strains with known β-lactam resistance mechanisms (22 strains with chromosomal AmpC β-lactamase, 8 strains with chromosomal class A β-lactamase, 21 broad-spectrum and IRT β-lactamase-producing strains, 41 extended-spectrum β-lactamase-producing strains, and 8 permeability mutants) were tested. API galleries and National Committee for Clinical Laboratory Standards (NCCLS) microdilution methods were used as reference methods. The Wider system correctly identified 97.5% of the clinical isolates at the species level. Overall essential agreement (±1 log(2) dilution for 3,719 organism-antimicrobial drug combinations) was 95.6% (isolates of the family Enterobacteriaceae, 96.6%; NFGNRs, 88.0%; gram-positive cocci, 95.6%). The lowest essential agreement was observed with Enterobacteriaceae versus imipenem (84.0%), NFGNR versus piperacillin (88.0%) and cefepime (88.0%), and gram-positive isolates versus penicillin (80.4%). The category error rate (NCCLS criteria) was 4.2% (2.0% very major errors, 0.6% major errors, and 1.5% minor errors). Essential agreement and interpretive error rates for eight β-lactam antibiotics against isolates of the family Enterobacteriaceae with known β-lactam resistance mechanisms were 94.8 and 5.4%, respectively. Interestingly, the very major error rate was only 0.8%. Minor errors (3.6%) were mainly observed with amoxicillin-clavulanate and cefepime against extended-spectrum β-lactamase-producing isolates. The Wider system is a new reliable tool which applies the image-processing technology to the reading of commercial trays for both bacterial identification and susceptibility testing.

Wider系统是一款全新研发的计算机辅助图像处理设备，可同时用于细菌鉴定（Bacterial Identification）与抗菌药物敏感性试验（Antimicrobial Susceptibility Testing）。该设备已完成适配，可读取并判读商用MicroScan检测板（MicroScan panels）。本研究共纳入244株连续分离的新鲜临床菌株，其中包括138株肠杆菌科（Enterobacteriaceae）菌株、25株非发酵革兰阴性杆菌（Nonfermentative Gram-negative Rods，NFGNR）以及81株革兰阳性球菌。此外，本研究还纳入了100株已知β-内酰胺耐药机制的肠杆菌科菌株，其中包括22株携带染色体型AmpC β-内酰胺酶（chromosomal AmpC β-lactamase）的菌株、8株携带染色体型A类β-内酰胺酶（chromosomal class A β-lactamase）的菌株、21株产广谱β-内酰胺酶与IRT β-内酰胺酶的菌株、41株产超广谱β-内酰胺酶（extended-spectrum β-lactamase）的菌株以及8株通透性突变株。本研究以API鉴定条与美国临床实验室标准化委员会（National Committee for Clinical Laboratory Standards，NCCLS）微量稀释法作为参考方法。Wider系统可在物种水平上准确鉴定97.5%的临床菌株。针对3719株菌株-抗菌药物组合的整体基本一致性（±1个log₂稀释度）为95.6%，其中肠杆菌科菌株为96.6%、非发酵革兰阴性杆菌为88.0%、革兰阳性球菌为95.6%。最低基本一致性出现在肠杆菌科菌株与亚胺培南配对（84.0%）、非发酵革兰阴性杆菌与哌拉西林（88.0%）及头孢吡肟（88.0%）配对，以及革兰阳性菌株与青霉素配对（80.4%）时。按照NCCLS标准判定的分类错误率为4.2%，其中极严重错误率为2.0%、严重错误率为0.6%、轻微错误率为1.5%。针对携带已知β-内酰胺耐药机制的肠杆菌科菌株，8种β-内酰胺类抗生素的基本一致性与判读错误率分别为94.8%与5.4%。值得注意的是，其极严重错误率仅为0.8%。3.6%的轻微错误主要出现在阿莫西林-克拉维酸与头孢吡肟针对产超广谱β-内酰胺酶菌株的检测中。Wider系统是一款可靠的新型工具，其将图像处理技术应用于商用检测板的判读，可同时完成细菌鉴定与药敏试验。