Employment of teicoplanin-coated magnetic particles for quantifying gram-positive bacteria via catalase-catalyzed hydrolysis reaction of H2O2

Based on the specific affinity behavior of teicoplanin towards Gram-positive (G(+)) bacteria, teicoplanin-coated magnetic particles were employed to separate G(+) bacteria. Moreover, intracellular catalase released by catalase-positive bacteria led to catalyzed hydrolysis of H2O2 and inhibition of chemiluminescent signal of luminol-H2O2 system. By combining the separation capability of teicoplanin-coated magnetic particles and the inhibition of luminol chemiluminescence by catalase, a facile method was proposed for quantifying catalase-positive G(+) bacteria. In this proof-of-principle work, Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus were adopted as model bacteria to evaluate its quantification performance. The three bacteria were quantified within the dynamic ranges of 5.0 x 10(2)-5.0 x 10(7) CFU mL(-1), 4.0 x 10(2)-4.0 x 10(7) CFU mL(-1) and 2.0 x 10(2)-2.0 x 10(7) CFU mL(-1), with detection limits of 156 CFU mL(-1), 86 CFU mL(-1) and 44 CFU mL(-1) respectively. Gram-negative bacteria and catalase-negative G(+) bacteria both displayed minor interference. The results for quantifying bacteria in milk, human urine and physiological saline samples demonstrated its reliability for real application. It provided a promising technique tool for food safety, medical diagnosis as well as drug quality control.