Metabolite-Mediated Bacterial Antibiotic Resistance Revealed by Surface-Enhanced Raman Spectroscopy

A prompt on-site, real-time method to detect bacterial antibiotic resistance is crucial for controlling the spread of resistance. Herein, we report the use of surface-enhanced Raman spectroscopy (SERS) for the monitoring of bioactive metabolites produced by ampicillin-resistant Pseudomonas aeruginosa strains and identification of mechanisms underlying antibiotic resistance. The results indicate that the blue-green pigment pyocyanin (PYO) dominates the metabolite signals and is significantly enhanced upon exposure to subminimal inhibitory concentrations of ampicillin. PYO accumulates during exponential growth and subsequently either diffuses into the culture medium or is consumed in response to nutrient deprivation. The SERS spectra further reveal that the production of some intermediate substances such as polysaccharides and amino acids is minimally impacted and that nutrient consumption remains consistent. Moreover, the intensity changes and peak shifts observed in the SERS spectra of non-PYO-producing ampicillin-susceptible Escherichia coli demonstrate that exogenously added PYO enhances E. coli tolerance to ampicillin to some extent. These results indicate that PYO mediates antibiotic resistance not only in the parent species but also in cocultured bacterial strains. The metabolic SERS signal provides new insight regarding antibiotic resistance with promising applications for both environmental monitoring and rapid clinical detection.

Automated summary

In this study, surface-enhanced Raman spectroscopy (SERS) was used to monitor the bioactive metabolites produced by ampicillin-resistant Pseudomonas aeruginosa strains and investigate the mechanisms underlying antibiotic resistance. The results showed that the blue-green pigment pyocyanin (PYO) dominated the metabolite signals and was significantly enhanced in the presence of subminimal inhibitory concentrations of ampicillin. The SERS spectra also revealed minimal impact on the production of intermediate substances and consistent nutrient consumption. Furthermore, exogenously added PYO enhanced the tolerance of ampicillin-susceptible Escherichia coli to some extent, indicating that PYO mediates antibiotic resistance in both the parent species and cocultured bacterial strains. The metabolic SERS signal provides new insights into antibiotic resistance and has promising applications in environmental monitoring and rapid clinical detection.