A new ultrasonic signal amplification method for detection of bacteria

Abstract

A new method is presented that increases the sensitivity of ultrasound-based techniques for detection of bacteria. The technique was developed for the detection of catalase-positive microorganisms. It uses a bubble trapping medium containing hydrogen peroxide that is mixed with the sample for microbiological evaluation. The enzyme catalase is present in catalase-positive bacteria, which induces a rapid hydrolysis of hydrogen peroxide, forming bubbles which remain in the medium. This reaction results in the amplification of the mechanical changes that the microorganisms produce in the medium. The effect can be detected by means of ultrasonic wave amplitude continuous measurement since the bubbles increase the ultrasonic attenuation significantly. It is shown that microorganism concentrations of the order of 10 5 cells ml -1 can be detected using this method. This allows an improvement of three orders of magnitude in the ultrasonic detection threshold of microorganisms in conventional culture media, and is competitive with modern rapid microbiological methods. It can also be used for the characterization of the enzymatic activity.

Mechanism modeling for phase fraction measurement with ultrasound attenuation in oil–water two-phase flow

“…In oil-water two-phase flow, ultrasound attenuation mainly depends on the viscous and thermal loss of the fluids. When ultrasound with a certain intensity propagates through the mixture, sound intensity is weakened at the receiving end [28]. This attenuation rate changes with the phase distributions and fractions at the same time.…”

Contact and non-contact ultrasonic measurement in the food industry: a review

“…The presence of bacteria, microorganisms, and fungi in food products are among the types of chemical contamination. Shukla et al [64] utilized a contact ultrasonic measurement to detect the presence of bacteria. They proposed an ultrasonic signal amplification technique that can increase the sensitivity and accuracy of measurement.…”