TABLE 5.
Impact of Raman spectra normalization methods
| Antibiotic | Class | % Correct predictiona |
||||
|---|---|---|---|---|---|---|
| No normalization | Vector normalization | 1,003 cm−1 | 1,445–1,455 cm−1 | 2,900–3,100 cm−1 | ||
| Chloramphenicol | PROT | 46.9 | 93.9 | 81.6 | 89.8 | 89.8 |
| Clindamycin | PROT | 23.6 | 83.6 | 61.8 | 58.2 | 87.3 |
| Gentamicin | PROT | 16.0 | 69.3 | 60.0 | 36.0 | 73.3 |
| Kanamycin | PROT | 13.0 | 63.0 | 40.7 | 37.0 | 61.1 |
| Streptomycin | PROT | 30.6 | 71.4 | 71.4 | 71.4 | 71.4 |
| Tetracycline | PROT | 11.3 | 75.5 | 34.0 | 37.7 | 67.9 |
| Ciprofloxacin | DNA | 62.3 | 47.8 | 47.8 | 36.2 | 34.8 |
| Nalidixic acid | DNA | 88.1 | 67.8 | 52.5 | 71.2 | 67.8 |
| Trimethoprim | DNA | 81.1 | 64.2 | 64.2 | 67.9 | 62.3 |
| Amoxicillin | CW | 63.9 | 41.0 | 57.4 | 42.6 | 42.6 |
| Ampicillin | CW | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Cefotaxime | CW | 61.4 | 38.6 | 40.4 | 40.4 | 38.6 |
| Rifampin | RNA | 0.0 | 3.5 | 3.5 | 3.5 | 1.8 |
| Rifapentine | RNA | 78.0 | 66.1 | 59.3 | 72.9 | 66.1 |
| Rifaximin | RNA | 80.0 | 80.0 | 86.2 | 83.1 | 78.5 |
| Overall accuracy (%) | 43.8 | 57.7 | 50.7 | 49.9 | 56.2 | |
| Randomb | 20.0 | 20.0 | 20.0 | 20.0 | 20.0 | |
a
Percentage of correct PC-DA prediction of antibiotic class for the spectra representing each antibiotic excluded from the training data set. Raman signal intensities were normalized using vector normalization and with respect to the signal intensity of the phenylalanine band at 1,003 cm−1, the signal intensity of the C-H band at 1,450 cm−1, and the signal intensity of the C-H stretching vibration region at 2,900 to 3,100 cm−1.
b
The probability of correct classifications by random assignment.