Electrochemical sensor for the determination of enterotoxigenic Escherichia coli in swine feces using glassy carbon electrodes modified with multi-walled carbon nanotubes

• An electrochemical sensor for enterotoxigenic E. coli in swine feces was developed.
• Electrochemical oxidation of the E. coli was carried out on a modified GC electrode.
• The ETEC F4 detection is performed through an irreversible oxidative signal by SWV.
• A similar behavior was found with both live and inactivated bacteria.
• The method is fast, simple, and economical to quantify E. coli in swine feces.

Enterotoxigenic Escherichia coli F4 (K88) (ETEC F4) is one of the main etiologic agents involved in neonatal and post-weaning diarrhea in pigs, which generates significant economic losses due to high mortality and morbidity.An electrochemical sensor based on glassy carbon electrodes modified with a dispersion of multi-walled carbon nanotubes plus 1% Nafion™ is proposed to detect and quantify ETEC F4 in stool samples of pigs. The preparation of samples was made by dilution in phosphate buffer solutions (PBSs), followed by centrifugation and inactivation of the supernatant in autoclave. An irreversible oxidation peak was observed by cyclic voltammetry at a potential close to 0.69 V. The best response was obtained for an optimum pre-concentration time of 10 min under forced convection conditions. The electrochemical response performed by square wave voltammetry was obtained in 1/5000 fecal samples in PBS spiked with ETEC F4. A peak current vs. ETEC F4 concentration plot was constructed from successive additions of suspensions of ETEC F4 inactivated by autoclave. The limit of detection (LOD), the limit of quantitation (LOQ) and the relative standard deviation were 6 × 104 CFU mL− 1, 2 × 105 CFU mL− 1 and 20%, respectively. The developed electrochemical method is simple, fast and economical to quantify ETEC F4 in swine stool samples, making it useful for diagnosis monitoring in production facilities.