The antibiotic vancomycin induces complexation and aggregation of gastrointestinal and submaxillary mucins

Abstract

Vancomycin, a branched tricyclic glycosylated peptide antibiotic, is a last-line defence against serious infections caused by staphylococci, enterococci and other Gram-positive bacteria. Orally-administered vancomycin is the drug of choice to treat pseudomembranous enterocolitis in the gastrointestinal tract. However, the risk of vancomycin-resistant enterococcal infection or colonization is significantly associated with oral vancomycin. Using the powerful matrix-free assay of co-sedimentation analytical ultracentrifugation, reinforced by dynamic light scattering and environmental scanning electron microscopy, and with porcine mucin as the model mucin system, this is the first study to demonstrate strong interactions between vancomycin and gastric and intestinal mucins, resulting in very large aggregates and depletion of macromolecular mucin and occurring at concentrations relevant to oral dosing. In the case of another mucin which has a much lower degree of glycosylation (~60%)-bovine submaxillary mucin-a weaker but still demonstrable interaction is observed. Our demonstration-for the first time-of complexation/depletion interactions for model mucin systems with vancomycin provides the basis for further study on the implications of complexation on glycopeptide transit in humans, antibiotic bioavailability for target inhibition, in situ generation of resistance and future development strategies for absorption of the antibiotic across the mucus barrier. Vancomycin is a branched tricyclic glycosylated peptide antibiotic. In the clinic, it represents a last-line defence against infections caused by Gram-positive pathogenic bacteria. Isolated in 1956 and introduced into clinical practice in 1958, it acts by inhibiting cell wall synthesis in sensitive bacteria 1. The largely hydrophilic molecule (see Fig. 1a) is able to form hydrogen bond interactions with the terminal d-alanyl-d-alanine moieties of the muramyl pentapeptide of the peptidoglycan. Under normal environments, the binding of vancomycin to d-Ala-d-Ala inhibits transglycosylase and transpeptidase activities during peptidoglycan growth, preventing the incorporation of new peptidoglycan into the expanding matrix, thereby leading to osmotic shock and cell lysis 2,3. Vancomycin was recently the subject of a detailed study using molecular hydrodynamics 4. It was shown to form dimers (in common with other studies) and the reversibility and strength of the dimerization process in four different aqueous solvents (including a medically-used formulation) were studied using short-column sedimentation equilibrium in the analytical ultracentrifuge and model-independent SEDFIT-MSTAR analysis across a range of loading concentrations. The change in the weight average molar mass M w with loading concentration was consistent with a monomer-dimer equilibrium. Overlap of data sets of point weight average molar masses M w (r) versus local concentration c(r) for different loading concentrations demonstrated a completely

Population Pharmacokinetics Modeling of Vancomycin Among Chinese Infants With Normal and Augmented Renal Function

“…The model for the normal renal function group included SCR as a covariate, but the model for the ARC group did not. Since vancomycin is hydrophilic with a large molecular volume and many non-ionic groups ( 22 ), the tissue distribution speed of vancomycin is expected to be limited by the lipid membrane. Moreover, Du et al, by using an established physiologically based pharmacokinetics (PBPK) model, found out that the concentration of vancomycin in renal tubules was about 40–50 times higher than that in plasma.…”

A Pandemic Early Warning System Decision Analysis Concept Utilizing a Distributed Network of Air Samplers via Electrostatic Air Precipitation

“…Most human or animal airborne pathogens will be contained in aerosol droplets consisting of principally aqueous fluid, glycoproteins, and mucins. Mucin has been shown to dissolve in phosphate buffered saline solution or PBS [27]. However, phosphate buffers used in electrospray can accumulate on the spray tip owing to their nonvolatility and clog over time.…”

Analytical Ultracentrifugation as a Matrix-Free Probe for the Study of Kinase Related Cellular and Bacterial Membrane Proteins and Glycans

“…The antibiotic vancomycin is normally administered intravenously but can also be administered orally to treat bacterial based gasterointestinal diseases such as pseudomembranous enterocolitis. One of the issues however that are peculiar to oral administration is the possible complications through potential interactions with gasterointestinal mucus and in particular the mucin glycoprotein component: A study involving analytical ultracentrifugation reinforced by quasi-elastic or “dynamic” light scattering (DLS) and environmental scanning electron microscopy (ESEM) was therefore undertaken to explore for the presence of interactions which could help explain the poor absorption of the antibiotic from the intestine and the glycopeptide impacts on the intestinal microbiota and its connection with antimicrobial resistance [ 25 ]. A somewhat different AUC approach to probe these large supramolecular aggregation reactions rather than the study of the well-defined dimerisation (vancomycin by itself) or dimerisation/tetramerisation (band 3) described above, was taken.…”

“…We will also consider some of the studies done so far on the enterococcal kinase VanS system under aqueous only conditions together with the interactions involving the ligand vancomycin. Relevant to oral-based formulations we will also consider how the analytical ultracentrifuge has revealed strong interactions between vancomycin and mucin [ 25 ]. To avoid the review becoming opaque to the non-specialist without a background in hydrodynamics, a minimum of methodological detail is given, but key follow-up references are provided instead.…”