Methicillin Resistant Staphylococcus aureus (MRSA) is one of the most important threats of nosocomial infections in many regions of the world and Vancomycin Resistant Enterococcus (VRE) is an emerging pathogen that develops full resistance against third-generation glycopeptide antibiotics. Conventional methods for identification of MRSA and VRE generally depend on culturing, which requires incubation of biological samples at least 24-72 hours to get accurate results. These methods are time consuming and necessitate optical devices and experts for evaluation of the results. On the other hand, early diagnosis and initiation of appropriate treatment are necessary to decrease morbidity and mortality rates. Thus, new diagnostic systems are essential for rapid and accurate detection of biological analytes at the point of care. This study presents design, fabrication, and implementation of MEMS based micro electrochemical sensor (&micro / ECS) to detect the methicillin resistance in Staphylococcus aureus and vancomycin resistance in Enterococcus species. To the best of our knowledge, the developed sensor is the first &micro / ECS which utilizes on-chip reference (Ag), working (Au), and counter (Pt) electrodes together with a microchannel to detect MRSA and VRE. The characterization of the designed sensor was achieved analyzing the interactions of the buffer solutions and solvents with the electrodes and Parylene C film layer by using optical and electrochemical methods. Specific parts of genes that are indicators of antimicrobial resistances were used in order to detect the resistances with high selectivity and sensitivity. Thus, synthetic DNA and bacterial PCR product were used as target probes in redox marker based detection and enzyme based detection, respectively. In order to enhance the hybridization, folding structures of the capture probe were investigated by using mfold Web Server. In redox marker based detection, the hybridization of DNA was indirectly detected by using Hoechst 33258 as redox marker with differential pulse voltammetry. The cross reactivity of the tests were performed by using different target probes of femA genes of S. aureus and S. epidermis, which are the major genes detected in methicillin detection assays. Consequently, amplification of signal by using horseradish peroxidase and TMB/H2O2 as substrate was achieved in order to enhance detection sensitivity. The sensor could detect 0.01 nM 23-mer specific part of mecA gene with redox marker based detection and 10 times diluted PCR product with enzyme-based detection in about six hours including the steps of sample preparation from whole blood. This sensor with its compatibility to MEMS fabrication processes and IC technology has a promising potential for a hand-held device for POC through the integration of micropotentiostat.

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