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 de vice for both bacterial identification and antimicrobial susceptibility tes ting. It has been adapted to be able to read and interpret commercial Micro Scan panels. Two hundred forty-four fresh consecutive clinical isolates (13 8 isolates of the family Enterobacteriaceae, 25 nonfermentative gram-negati ve rods [NFGNRs], and 81 gram-positive cocci) were tested. In addition, 100 enterobacterial strains with known beta-lactam resistance mechanisms (22 s trains with chromosomal AmpC beta-lactamase, 8 strains with chromosomal cla ss A p-lactamase, 21 broad-spectrum and IRT beta-lactamase-producing strain s, 41 extended-spectrum beta-lactamase-producing strains, and 8 permeabilit y mutants) were tested. API galleries and National Committee for Clinical L aboratory Standards (NCCLS) microdilution methods were used as reference me thods. The Wider system correctly identified 97.5% of the clinical isolates at the species level. Overall essential agreement (+/-1 log(2) dilution fo r 3,719 organism-antimicrobial drug combinations) was 95.6% (isolates of th e family Enterobacteriaceae, 96.6%; NFGNRs, 88.0%; gram-positive cocci, 95. 6%). The lowest essential agreement was observed with Enterobacteriaceae ve rsus imipenem (81.0%), NFGNR versus piperacillin (88.0%) and cefepime (88.0 %), and gram-positive isolates versus penicillin (80.4%). The category erro r 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 beta-lactam antibiotics against isolates of the family Enterobact eriaceae with known beta-lactam resistance mechanisms were 94.8 and 5.4%, r espectively. Interestingly, the very major error rate was only 0.8%. Minor errors (3.6%) were mainly observed with amoxicillin-clavulanate and cefepim e against extended-spectrum beta-lactamase-producing isolates. The Wider sy stem is a new reliable tool which applies the image-processing technology t o the reading of commercial trays for both bacterial identification and sus ceptibility testing.