Electroacoustic Biosensor Systems for Evaluating Antibiotic Action on Microbial Cells

Abstract

Antibiotics are widely used to treat infectious diseases. This leads to the presence of antibiotics and their metabolic products in the ecosystem, especially in aquatic environments. In many countries, the growth of pathogen resistance to antibiotics is considered a threat to national security. Therefore, methods for determining the sensitivity/resistance of bacteria to antimicrobial drugs are important. This review discusses the mechanisms of the formation of antibacterial resistance and the various methods and sensor systems available for analyzing antibiotic effects on bacteria. Particular attention is paid to acoustic biosensors with active immobilized layers and to sensors that analyze antibiotics directly in liquids. It is shown that sensors of the second type allow analysis to be done within a short period, which is important for timely treatment.

Keywords: acoustic biosensors; acoustic delay lines; antibiotic resistance/sensitivity; bacterial cells; piezoelectric resonators.

Figure 1

Main groups of antibacterial drugs.

Figure 2

Main mechanisms of bacterial MDR.

Figure 3

Current methods for antimicrobial susceptibility testing: PCR—polymerase chain reaction; qPCR—quantitative polymerase chain reaction; NGS—next-generation sequencing; MALDI-TOF MS—matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Figure 4

Schematic diagram of a biosensor.

Figure 5

Classification of acoustic sensors.

Figure 6

Schematic representation of a SAW sensor for monitoring the state of a biofilm deposited on the sensor surface after exposure to an antibiotic.

Figure 7

Schematic representation of a quartz resonator with E. coli cells deposited on its surface to evaluate antibiotic effects on them.

Figure 8

(a) General scheme of a sensor based on a resonator with a lateral electric field for evaluating antibiotic-resistant and antibiotic-sensitive microbial strains directly in a liquid. (b) Frequency dependencies of the real part of the electrical impedance of the sensor when an antibiotic is added to resistant (left) and sensitive (right) E. coli cells.

Figure 9

(a) Scheme for the compact acoustic analyzer. (b) Frequency dependenciesof the sensor’s electrical impedance modulus (Z) for a suspension of E. coli cells without (blue curve) and after (pink curve) CAP addition.

Figure 10

(a) The general design of a slot-mode sensor in an acoustic delay line for examining antibiotic-resistant and antibiotic-sensitive microbial strains directly in a liquid. (b) Frequency dependencies of the insertion loss of the slot-mode sensor for a suspension of microbial cells insensitive (left) and sensitive (right) to the antibiotic. Black and pink colors correspond to cell suspension before and after adding antibiotic, respectively.