Precollaborative validation of an amperometric immunosensor for Salmonella

Salmonella is considered an important public health issue and one of the main causes of outbreaks involving several food matrices. The method of Salmonella detection recommended is cultural and it is laborious, presents a high consumption of material, and requires about five days for presumptive results. Immunosensor is an interesting tool for microbiologic analysis that has shown promising and rapid results, although many devices have their performance evaluated only under buffering conditions and few achieve the validation stage. The objective was to perform a precollaborative validation of an electrochemical immunosensor assembled on screen-printed electrodes for the detection of Salmonella sp. in milk. The antibodies were immobilized on the surface by cysteamine self-assembled-monolayer (SAM). The sandwich-type amperometric immunosensor was evaluated for contaminated raw and whole UHT milk and compared to performance with a gold standard reference method (BAM) for microbiological analysis according to AOAC recommendations for a single laboratory. The immunosensor had a qualitative performance and a binary response (positive/ negative) was used based on a cut off established from current electric obtained for the absence of the pathogen. There was no significant difference for the results of the biosensor and the reference method, in the absence and the levels of 10¹ UFC mL^-1 and 10³ UFC mL^-1 of Salmonella Typhimurium for the two types of milk. This result indicates the efficiency of the biosensor in detecting the pathogen into a complex matrix.