Low-cost multichannel system with disposable pH sensors for monitoring bacteria metabolism and the response to antibiotics

Abstract

Antibiotic resistant bacteria are an important threat to human and animal health. Accurate antibiotic susceptibility test results are essential in medical control. We present a low-cost, simple, and rapid multichannel system for the registration of bacteria pH changes in time and the phenomena used to follow the microbial metabolic activity to evaluate the response to antibiotics. Small size silicon chips covered with a thin layer of Ta₂O₅ were employed as all-solid-state pH-sensors. The pH measurements were performed in 1 mL samples in Eppendorf tubes in which a liquid junction was formed by a rapidly wettable polymer pin. The tubes were fixed in a thermostatic bath filled with KCl with incorporated standard Ag/AgCl reference electrode. This system design permits the prevention of the reference electrode contact with the bacteria containing solution and eliminates the need for its cleaning and sterilization. The presented system was successfully applied for monitoring the response of Escherichia coli (E. coli), used as a model bacterium, to ampicillin, tetracycline, and kanamycin antibiotics in undiluted culture medium in just 5 hr. The proposed sensor fabrication cost is very low which permits disposable use.

Keywords:

• Antibiotic resistance
• bacteria metabolism
• pH-sensor
• potentiometry

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the European Commission WATERWORKS 15 ERA-NET under Grant SMARTECOPONIC number PCIN-2017-031; by Spanish Council of Scientific Research (CSIC) under INTRAMURAL Grant number 201850E071. C. Ocaña acknowledges support from MICINN (Spain) in the form of Juan de la Cierva fellowship grant.