Fig 5. Antimicrobial-induced bacterial spectral changes at 106 and 104 cfu/mL can be detected for a levofloxacin-resistant E. cloacae BAA2341 samples before and after incubation with 8 μg/mL levofloxacin for 4 hours at 35°C.
A sample of bacteria incubated in saline under the same temperature for the same duration was prepared as positive control and ATR spectra were acquired. The bacteria peak intensities in the before and after incubation spectra as well as from the positive control spectrum did not vary significantly, which were confirmed by the cell culture results and matches with the levofloxacin-resistance nature of this bacteria strain.