Figure 1.
NIR profiles obtained for antibiotic-treated susceptible cells and for healthy growing cells.
A) NIR profiles for E. coli were recorded during growth (Ec-Growth) and in the presence of 2.5 µg/ml, 5 µg/ml, and 12.5 µg/ml of gentamicin; B) NIR profiles for S. aureus were recorded during growth (Sa-Growth) and in the presence of 4 µg/ml and 20 µg/ml of vancomycin. Medium without cells (Control) was used as a negative control.
Figure 2.
NIR profiles obtained for chemically stressed bacteria.
Bacterial suspension was incubated in the presence of 0.5% Triton X-100 (blue curves) or 10 mM H2O2 (red curves). Medium without cells (Control) was used as a negative control (black curves). A) 8.2×105 cfu/ml E. coli in LB B); 6.8×105 cfu/ml S. aureus in TSB.
Figure 3.
NIR profiles obtained for heat-shocked bacteria.
A) E. coli (2.4×105 cfu/ml) heat-shocked for 30 min at 45°C and re-suspended in LB; B) S. aureus (3.6×105 cfu/ml) heat-shocked for 30 min at 48° and re-suspended in TSB. Media without cells (Control) were used as a negative control (black curves).
Figure 4.
NIR profiles obtained for clinical isolates with antibiotic resistance.
A) A clinical isolate of E. coli resistant to ciprofloxacin (CIP) was incubated in the presence of 45 µg/ml of CIP (blue curve) and 15 µg/ml of gentamicin to which it is susceptible (red curve). B) A clinical isolate of S. aureus (MRSA, Iberian isolate) was incubated in the presence of 400 µg/ml of methicillin (blue curve) and 8 µg/ml of vancomycin to which it is susceptible (red curve). Medium without cells (Control) was used as a negative control (black curve).
Table 1.
The survival of S. aureus and E. coli treated with vancomycin and gentamicin.
Table 2.
The mean NIR values* for antibiotic-treated E. coli and S. aureus.
Figure 5.
Photograph of the BioSense differential impedance sensing platform.
The platform is comprised of an impedance analyzer (A) and a two-chamber test cassette (B, top view). The cassette is loaded into a drawer located on the face of the analyzer that extends and retracts and is designed to hold the cassette during the measurement.