An optimized method for the detection and spatial distribution of aminoglycoside and vancomycin antibiotics in tissue sections by mass spectrometry imaging

Abstract

Suboptimal antibiotic dosing has been identified as one of the key drivers in the development of multidrug‐resistant (MDR) bacteria that have become a global health concern. Aminoglycosides and vancomycin are broad‐spectrum antibiotics used to treat critically ill patients infected by a variety of MDR bacterial species. Resistance to these antibiotics is becoming more prevalent. In order to design proper antibiotic regimens that maximize efficacy and minimize the development of resistance, it is pivotal to obtain the in situ pharmacokinetic–pharmacodynamic profiles at the sites of infection. Mass spectrometry imaging (MSI) is the ideal technique to achieve this. Aminoglycosides, due to their structure, suffer from poor ionization efficiency. Additionally, ion suppression effects by endogenous molecules greatly inhibit the detection of aminoglycosides and vancomycin at therapeutic levels. In the current study, an optimized method was developed that enabled the detection of these antibiotics by MSI. Tissue spotting experiments demonstrated a 5‐, 15‐, 35‐, and 54‐fold increase in detection sensitivity in the washed samples for kanamycin, amikacin, streptomycin, and vancomycin, respectively. Tissue mimetic models were utilized to optimize the washing time and matrix additive concentration. These studies determined the improved limit of detection was 40 to 5 μg/g of tissue for vancomycin and streptomycin, and 40 to 10 μg/g of tissue for kanamycin and amikacin. The optimized protocol was applied to lung sections from mice dosed with therapeutic levels of kanamycin and vancomycin. The washing protocol enabled the first drug distribution investigations of aminoglycosides and vancomycin by MSI, paving the way for site‐of‐disease antibiotic penetration studies.

Lesion Penetration and Activity Limit the Utility of Second-Line Injectable Agents in Pulmonary Tuberculosis

“…Mass spectrometry imaging experiments were carried out on 10 µm sections taken adjacent to those used for histological registration of the LCM sections, as described above. Tissue washing was carried out prior to matrix deposition by submerging the slides in chloroform for 15 s at -20°C as previously published (72). The slides were then allowed to air-dry for 10 min prior to matrix deposition.…”

The Transporter-Mediated Cellular Uptake and Efflux of Pharmaceutical Drugs and Biotechnology Products: How and Why Phospholipid Bilayer Transport Is Negligible in Real Biomembranes

“…If trans-bilayer permeability were significant in real biomembranes, the free concentrations of drugs inside cells and organelles (modulo pH and potential gradients) would be more or less homogeneous. Of course, they are not, as is well-known (and as can easily be determined by chemical imaging methods, e.g., [ 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 , 147 , 148 , 149 , 150 , 151 , 152 , 153 , 154 , 155 , 156 , 157 , 158 , 159 ]). A particularly well-established case is that of the blood–brain barrier, where, despite the lipids not being noticeably different from those in other cells, the permeability is negligible if specific transporters are not involved [ 160 , 161 , 162 , 163 , 164 ].…”