Mass spectrometric measurement of β-lactamase resistances

A method for the determination of a β-lactam resistance of microbes based on the production of β-lactamases by the microbes, the method comprising:

• obtaining the microbes from a colony cultivated on a nutrient medium or from a blood culture;
• combining the microbes with a β-lactam antibiotic covalently bonded to a 6-His tag in a solution, wherein β-lactamases of the microbes may cause hydrolytic breakdown of the β-lactam antibiotic;
• extracting remaining-lactam antibiotic and/or its breakdown product from the solution via a reversible bond of the 6-His tag to an extracting partner;
• partly applying the extracted remaining β-lactam antibiotic and/or breakdown product to a mass spectrometric support;
• and
• measuring the enzymatic breakdown of the β-lactam antibiotic by the β-lactamases of the microbes mass spectrometrically by acquiring a mass spectrum of the extracted remaining β-lactam antibiotic and/or breakdown product using ionization by matrix-assisted laser desorption, wherein a matrix used is α-cyano-4-hydroxycinnamic acid.

A method for the determination of a β-lactam resistance of microbes based on the production of β-lactamases by the microbes, the method comprising:

• obtaining the microbes from a colony cultivated on a nutrient medium or from a blood culture;
• combining the microbes with a substrate in a solution, said substrate comprising a β-lactam ring;
• partly applying the solution to a mass spectrometric support;
• and
• measuring an enzymatic breakdown of the substrate by the β-lactamases of the microbes mass spectrometrically by acquiring a mass spectrum of remaining substrate and breakdown product, which are embedded in crystals of a matrix substance, using a time of flight mass spectrometer with ionization by matrix-assisted laser desorption, wherein the breakdown product comprises a mass which is 18 atomic mass units heavier than the substrate and wherein the matrix used is α-cyano-4-hydroxycinnamic acid.