Fig. 1. Resonant frequency change as the antibody functionalized PEMC sensor was exposed to E. coli O157:H7 inoculated beef samples flowing at a rate of 3.2 mL/min and temperature of 22 °C. The E. coli samples were harvested for 2 and 4 h from a flask and a Stomacher bag culture. The Stomacher bag contains finely blended meat and the flask unblended beef, both samples were filtered to remove large beef particles.

Fig. 2. Resonant frequency change as a function of time for the binding of E. coli O157:H7 to antibody derivatized PEMC sensor from broth (B) samples flowing at 1 mL/min and was initially inoculated with 25 pathogens. The samples were harvested 2, 4, and 6 h. The response labeled control was an antibody functionalized sensor immersed in broth samples in which no E. coli O157:H7 was initially added.

Fig. 3. Resonant frequency change as a function of time for the binding of E. coli O157:H7 to antibody derivatized PEMC sensor from meat (M) samples flowing at 1 mL/min and was initially inoculated with 25 pathogens. The experiments were carried out at 22 °C. Samples were harvested 2, 4, and 6 h. The control was an antibody functionalized sensor immersed in samples in which no E. coli O157:H7 was initially added.

Fig. 4. PEMC sensor response to attachment and release of E. coli O157:H7. Panel A: the attachment and release from the 2 h meat (M) sample. The total frequency change due the binding and unbinding were, respectively, 21 ± 2 and 23 ± 2 Hz. Panel B: the binding and release of E. coli O157:H7 from the 6 h meat sample. The steady state resonant frequency change during the attachment and the release of the bacteria was 70 ± 2 Hz. In both experiments the flow rate of the sample was 1 mL/min.

Fig. 5. Response to E. coli O157:H7 spiked irradiated meat (Mx) samples at 1 mL/min. Panel A: response to samples at 2 h, 4 h, and 6 h. The control was an antibody functionalized sensor immersed in irradiated meat sample in which no E. coli O157:H7 was added. Panel B: response to two different sets of irradiated meat-E.coli O157:H7 samples. The samples 25Mx-2 sample contained more meat particles and appeared optically more dense than 25Mx-1.

E. coli concentration in various samples using plating and the pathogen modeling

k_obs values as a function of E. coli O157:H7 incubation time