Poly-l-lysine-functionalized magnetic beads combined with polymerase chain reaction for the detection of Staphylococcus aureus and Escherichia coli O157:H7 in milk

摘要

Rapid and credible detection of pathogens is essentialto prevent and control outbreaks of foodborne diseases.In this study, a poly-l-lysine-functionalized magneticbeads (PLL-MB) strategy combined with a PCR assaywas established to detect Staphylococcus aureus.We also detected Escherichia coli O157:H7 to furtherverify the strategy for gram-negative bacteria detection.Poly-l-lysine has strong positive charges becauseof its amino groups, which can conjugate with the carboxylof carboxyl magnetic beads. Furthermore, it canbe used to combine with bacteria through electrostaticadsorption. Under optimum conditions, the developedPLL-MB complexes showed 90% capture efficiency inphosphate-buffered saline and 85% capture efficiencyin milk for S. aureus detection. The limit of detectionof the PLL-MB-PCR assay was 10~2 cfu/mL (1.8 ×10~2 cfu/mL for S. aureus and 7 × 10~2 cfu/mL for E.Coli O157:H7) in phosphate-buffered saline and milksamples. The whole assay can be performed within 4 h.The proposed strategy showed a lower limit of detectionwhen compared with the conventional PCR assaywithout enrichment. In addition, this method exhibitedthe advantages of a high-efficient, cost-efficient, andsimple operation, indicating its potential applicationsin foodborne pathogen detection.