Detection of acetyltransferase modification of kanamycin, an aminoglycoside antibiotic, in bacteria using ultra-high performance liquid chromatography tandem mass spectrometry

Authors: Perez Jr, Johnny; Chen, Chinyi

Submitted to: Journal of Rapid Communications in Mass Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2018
Publication Date: 8/5/2018
Citation: Perez Jr, J.J., Chen, C. 2018. Detection of acetyltransferase modification of kanamycin, an aminoglycoside antibiotic, in bacteria using ultra-high performance liquid chromatography tandem mass spectrometry. Journal of Rapid Communications in Mass Spectroscopy. 32:1549-1556.

Interpretive Summary: The urgency to stymie the spread of antibiotic resistance has galvanized new analytical methods not typically used to answer microbiology inquiries. Liquid Chromatography Mass Spectrometry (LC-MS) which, first, employs the concept of “likes dissolve likes” to separate molecules based on their interaction with an immobilized nonpolar (waxy) material. These molecules are then weighed in a mass spectrometer. In this paper, we investigate a popular form of antibiotic resistance via the mechanism of enzymatic antimicrobial modification. This is the first in vivo determination of antibiotic resistance of aminoglycosides using mass spectrometry. This analytical technique can provide rapid antibiotic resistance determination presumably for all microorganisms expressing some form of the acetyltransferase enzyme.

Technical Abstract: The emergence of bacterial resistance to antibiotics has become a topical issue globally. International guidelines require rapid detection methods to provide appropriate treatment reducing selective pressures for the proliferation of resistant strains. A common subset of antibiotic resistance involves the chemical modification of the antimicrobial into an inactive form by a bacterium expressed enzyme. Selected reaction monitoring (SRM) has the ability to rapidly determine these characteristic antimicrobial molecular weight shifts. Using a highly sensitive hybrid triple quadrupole/linear ion trap mass spectrometer in full MS and enhanced product ion modes combined with a rugged and versatile UHPLC method, detection of acetyltransferase modification of an aminoglycoside was achieved in less than an hour. Kinetic analysis of production and depletion of the modified and unmodified kanamycin as a function of time was observed. Quantification was achieved for both forms of the antibiotic 50-100 fold lower than the minimum inhibitory concentration (MIC) for the resistant bacteria. High resolution mass spectrometry was employed for confirmation of the novel resistant biomarkers, more specific identification of the modified kanamycin product ions and elucidation of fragmentation pathway for the modified antibiotic.