A rapid method for detection of catalase-positive and catalase-negative bacteria based on monitoring of hydrogen peroxide evolution at a composite peroxidase biosensor

The rapid detection of catalase-positive and catalase-negative bacteria in complex culture media has been accomplished by monitoring of hydrogen peroxide consumption or generation with a graphite–Teflon–peroxidase–ferrocene composite electrode. Escherichia coli and Streptococcus pneumoniae have been used as model catalase-positive and catalase-negative bacteria, respectively. Hydrogen peroxide evolution was amperometrically measured at 0.00 V. Experimental conditions, including the working solution composition, the incubation time and the hydrogen peroxide concentration, were optimized. The reusability of the biosensor was improved by placing a nylon membrane on the bioelectrode surface to prevent fouling caused by the bacterial medium. The developed methodology allowed the detection of E. coli and S. pneumoniae at concentration levels of approximately 2 × 10 6 and 2 × 10 5 cfu/mL, in assays taking 10 and 15 min, respectively, without any pre-concentration step or pre-enrichment procedure.