Objective   To develop a new type of piezoelectric quartz crystal microbalance DNA sensor based on lambda exonuclease to detect Staphylococcus aureus (S. aureus) and optimize the main detection conditions.    Methods   After the DNA was extracted from the stain of S. aureus and the target fragment was amplified with self-designed universal primers

the PCR products were treated with Lambda exonuclease and visualized by agarose gel electrophoresis with ethidium bromide followed by a gel documentation system analysis. Then the products with or without exonuclease digestion were added into our piezoelectric quartz crystal microbalance DNA sensor for hybridization. The tempe

rature and time of hybridization were optimized respectively. The specificity and sensitivity of our detection system were evaluated.    Results   The optimal temperature for hybridization was 35℃ and the optimal time was 60 min. The sensitivity of the lambda exonuclease based DNA sensor was better than that of common DNA sensor. The lowest detection limit of this new type quartz crystal microbalance system was 1.0×10

4

CFU/ml.    Conclusion   The lambda exonuclease based quartz crystal microbalance system we designed has the advantages of high efficiency in hybridization

easy to operate

and good response performance. Thus it can be applied to detect S. aureus infections.