Publication Date:
2016-10-03
Description:
We introduce a label-free spectroscopic method to classify subtypes of quinolone-nonsusceptible Escherichia coli ( E. coli ) isolates obtained from human blood cultures. Raman spectroscopy with a 30-nm gold-deposited, surface-enhanced Raman scattering (SERS) substrate was used to evaluate three multilocus sequencing typing (MLST)-predefined groups including E . coli ATCC25922, E . coli ST131:O75, and E . coli ST1193:O25b. Although there was a coffee-ring effect, the ring zone was selected at the ideal position to screen E. coli isolates. Strong Raman peaks were present at 1001–1004 cm −1 (C C aromatic ring breathing stretching vibrational mode of phenylalanine), 1447–1448 cm −1 (C H 2 scissoring deformation vibrational mode), and 1667 cm −1 (amide I α -helix). Although the three MLST-predefined E . coli isolates had similar Raman spectral patterns, a support vector machine (SVM) learning algorithm-assisted principal component analysis (PCA) analysis had superior performance in detecting the presence of quinolone-nonsusceptible E. coli isolates as well as classifying similar microbes, such as quinolone-nonsusceptible E . coli ST131:O75 and E . coli ST1193:O25b isolates. Therefore, this label-free and nondestructive technique is likely to be useful for clinically diagnosing quinolone-nonsusceptible E. coli isolates with the MLST method.
Print ISSN:
1059-910X
Electronic ISSN:
1097-0029
Topics:
Natural Sciences in General
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