Multidrug-resistant (MDR) bacteria pose a serious threat to global health, which may be addressed using bacteriophage therapy. It is important to measure the susceptibility of bacteria to bacteriophages. We used a micromechanical sensor with a microfluidic channel for rapid antimicrobial susceptibility testing (AST). The interior surface of the microfluidic channel was functionalized with a molecule linker to capture the bacterial cells inside the channel. The Escherichia coli response to the bacteriophage PhiX174 and Staphylococcus aureus response to the bacteriophage Phi44AHJD is observed. The micromechanical sensor measured the mechanical fluctuations induced by nano-movements of the bacteria, reflecting their metabolic activity, before and after viral infection. In other words, the time-dependent oscillations of the microchannel can be correlated to the membrane movement in the cells produced by the cell metabolisms. The initial magnitudes of the fluctuations were different in the two bacteria. Bacteria exposure to the bacteriophages induced a sharp reduction of the sensor response, indicating a marked decrease in bacterial metabolic activities. In contrast to E. coli, S. aureus was resistant to Phi44AHJD, and the significant reduction in its metabolic activity may be attributed to transient dormancy due to stress caused by the viral interaction. This technique provides a rapid and accurate assessment of the susceptibility of bacteria to bacteriophages in a small volume of 150 picolitres.

Non-faradaic impedimetric biosensors have received wide interest due to their direct detection approach. The crosslinking layer in these biosensors must be dense to avoid permeation of ions into the electrode to allow direct detection of diseases. Here, we investigated the effect of incubation time of cysteamine crosslinking layer on non-faradaic impedimetric biosensors performances. Two sets of interdigitated gold electrodes were functionalized with cysteamine for 1 and 24 hours. Then, UL83-antibodies were immobilized on the surface via glutaraldehyde for the detection of human cytomegalovirus. The sensitivity of biosensors functionalized with cysteamine for 24 hours were superior to those functionalized with cysteamine for 1 hour (i.e. 0.046 nF/ln(ng/mL) compared to 0.0224 nF/ln(ng/mL)). Probing the cysteamine layer with faradaic-EIS and X-ray photoelectron spectroscopy suggests that the better biosensing performance of biosensors incubated in cysteamine for 24 hours is related to the better coverage of cysteamine at the biosensor surface. Atomic force microscopy analysis also revealed an increase in surface roughness with increasing cysteamine incubation time which resulted in better biosensing performances due to the enlarged surface area.