Quantification of Staphylococcus epidermidis using a wireless, mass-responsive sensor

A remote-query (wireless, passive) magnetoelastic sensor is utilized for the quantification of Staphylococcus epidermidis (S. epidermidis). The sensor is fabricated by coating a thin nutrient gelatin medium film on a ribbon-like magnetoelastic sensor; the consumption of the nutrient by S. epidermidis during its growth and reproduction decreases the mass loading on the sensor, in turn increasing the resonance frequency of the liquid-immersed magnetoelastic sensor. The proposed sensor is used to detect S. epidermidis in the range of 3 × 103 to 2 × 107 cells ml−1. The proposed sensor shows little response to bacteria which cannot liquefy gelatin, e.g. Escherichia coli, exhibiting a certain selectivity to gelatin-liquefying bacteria.