[Paper Review] Susceptibility of Methicillin Resistant Staphylococcus aureus to Vancomycin using Liposomal Drug Delivery System

Kiran Vishwasrao, Arjumanara Surti+1 more|arXiv (Cornell University)|Jan 15, 2018

Antimicrobial Resistance in Staphylococcus20 references3 citations

TL;DR

This study investigates liposomal encapsulation of vancomycin to enhance its efficacy against Methicillin-Resistant Staphylococcus aureus (MRSA). The liposomal delivery system significantly reduced the minimum inhibitory concentration (MIC) of vancomycin by approximately 50% compared to free vancomycin, demonstrating improved antibacterial activity and enhanced phagocytic clearance, thereby offering a promising strategy to overcome vancomycin resistance in MRSA.

ABSTRACT

Staphylococcus aureus responsible for nosocomial infections is a significant threat to the public health. The increasing resistance of S.aureus to various antibiotics has drawn it to a prime focus for research on designing an appropriate drug delivery system. Emergence of Methicillin Resistant Staphylococcus aureus (MRSA) in 1961, necessitated the use of vancomycin "the drug of last resort" to treat these infections. Unfortunately, S.aureus has already started gaining resistances to vancomycin. Liposome encapsulation of drugs have been earlier shown to provide an efficient method of microbial inhibition in many cases. We have studied the effect of liposome encapsulated vancomycin on MRSA and evaluated the antibacterial activity of the liposome-entrapped drug in comparison to that of the free drug based on the minimum inhibitory concentration (MIC) of the drug. The MIC for liposomal vancomycin was found to be about half of that of free vancomycin. The growth response of MRSA showed that the liposomal vancomycin induced the culture to go into bacteriostatic state and phagocytic killing was enhanced. Administration of the antibiotic encapsulated in liposome thus was shown to greatly improve the drug delivery as well as the drug resistance caused by MRSA.

Motivation & Objective

• To address the growing challenge of vancomycin resistance in MRSA, a leading cause of nosocomial infections.
• To evaluate whether liposomal drug delivery can improve the efficacy of vancomycin against MRSA.
• To compare the minimum inhibitory concentration (MIC) of liposomal-encapsulated vancomycin versus free vancomycin.
• To assess the impact of liposomal vancomycin on bacterial growth dynamics and phagocytic killing.
• To develop a targeted delivery system that enhances drug delivery and overcomes resistance mechanisms in MRSA.

Proposed method

• Liposomes were formulated using standard thin-film hydration and extrusion techniques to encapsulate vancomycin.
• The antibacterial activity of liposomal vancomycin was evaluated using broth microdilution assays to determine the minimum inhibitory concentration (MIC).
• Growth kinetics of MRSA cultures were monitored in the presence of free versus liposomal vancomycin to assess bacteriostatic effects.
• Phagocytic killing assays were performed to compare the susceptibility of MRSA to macrophage-mediated clearance when exposed to liposomal versus free vancomycin.
• The liposomal system was designed to improve drug stability, target delivery, and intracellular penetration in bacterial cells.
• Data were analyzed to compare MIC values, growth inhibition, and phagocytic clearance rates between the two formulations.

Experimental results

Research questions

• RQ1 Does liposomal encapsulation of vancomycin reduce the minimum inhibitory concentration (MIC) against MRSA compared to free vancomycin?
• RQ2 How does liposomal vancomycin affect the growth phase and viability of MRSA cultures?
• RQ3 To what extent does liposomal vancomycin enhance phagocytic clearance of MRSA by immune cells?
• RQ4 Can liposomal delivery improve the therapeutic index of vancomycin in resistant S. aureus strains?
• RQ5 What is the mechanism by which liposomal vancomycin enhances antibacterial efficacy beyond free drug delivery?

Key findings

• The minimum inhibitory concentration (MIC) of liposomal vancomycin against MRSA was approximately 50% lower than that of free vancomycin.
• Liposomal vancomycin induced a bacteriostatic state in MRSA cultures, indicating effective growth inhibition.
• Phagocytic killing of MRSA was significantly enhanced when the bacteria were exposed to liposomal vancomycin compared to free vancomycin.
• The liposomal delivery system improved drug delivery efficiency, resulting in greater antibacterial activity at lower concentrations.
• Liposome-encapsulated vancomycin demonstrated superior efficacy in overcoming resistance mechanisms in MRSA.
• The study confirms that liposomal formulation can potentiate the activity of vancomycin against multidrug-resistant S. aureus.