Related Experiment Video

Updated: Aug 16, 2025

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Published on: May 8, 2013

β-Lactamase Suppression as a Strategy to Target Methicillin-Resistant Staphylococcus aureus: Proof of Concept

Payton M Thomas¹, Margaret A Deming¹, Aurijit Sarkar¹

¹Department of Basic Pharmaceutical Sciences, Fred Wilson School of Pharmacy, High Point University, One University Parkway, High Point, North Carolina 27268, United States.

|December 26, 2022

Abstract:

β-Lactamase (penicillinase) renders early, natural β-lactams like penicillin G useless against methicillin-resistant Staphylococcus aureus (MRSA), which also expresses PBP2a, responsible for resistance to semisynthetic, penicillinase-insensitive β-lactams like oxacillin. Antimicrobial discovery is difficult, and resistance exists against most treatment options. Enhancing β-lactams against MRSA would revive its clinical utility. Most research on antimicrobial enhancement against MRSA focuses on oxacillin due to β-lactamase expression. Yet, Moreillon and others have demonstrated that penicillin G is as potent against a β-lactamase gene knockout strain, as vancomycin is against wild-type MRSA. Penicillin G overcame PBP2a because β-lactamase activity was blocked. Additionally, animals treated with a combination of direct β-lactamase inhibitors like sulbactam and clavulanate with penicillin G developed resistant infections, clearly demonstrating that direct inhibition of β-lactamase is not a good strategy. Here, we show that 50 μM pyrimidine-2-amines (P2As) reduce the minimum inhibitory concentration (MIC) of penicillin G against MRSA strains by up to 16-fold by reducing β-lactamase activity but not by direct inhibition of the enzyme. Oxacillin was not enhanced due to PBP2a expression, demonstrating the advantage of penicillin G over penicillinase-insensitive β-lactams. P2As modulate an unknown global regulator but not established antimicrobial-enhancement targets Stk1 and VraS. P2As are a practical implementation of Moreillon's principle of suppressing β-lactamase activity to make penicillin G useful against MRSA, without employing direct enzyme inhibitors.

Insights

Pyrimidine-2-amines (P2As) enhance penicillin G efficacy against MRSA by reducing beta-lactamase activity, not direct inhibition. This approach revives penicillin G

Area of Science:

Microbiology
Infectious Diseases
Drug Discovery

Background:

Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat due to resistance mechanisms like beta-lactamase and PBP2a.
Existing antimicrobial strategies struggle against MRSA, necessitating novel approaches to enhance current therapies.
Direct inhibition of beta-lactamase has proven ineffective and can lead to resistant infections.

Purpose of the Study:

To investigate the potential of pyrimidine-2-amines (P2As) in enhancing the efficacy of penicillin G against MRSA.
To explore the mechanism by which P2As affect beta-lactamase activity and MRSA susceptibility.
To evaluate the advantage of penicillin G enhancement over penicillinase-insensitive beta-lactams like oxacillin.

Main Methods:

Testing the minimum inhibitory concentration (MIC) of penicillin G in combination with P2As against MRSA strains.
Assessing the effect of P2As on beta-lactamase activity without direct enzyme inhibition.
Investigating the impact of P2As on known antimicrobial-enhancement targets (Stk1, VraS) and global regulators.

Main Results:

50 μM P2As reduced the MIC of penicillin G against MRSA by up to 16-fold.
P2As reduced beta-lactamase activity without directly inhibiting the enzyme.
Penicillin G enhancement was observed, while oxacillin showed no improvement due to PBP2a expression.
P2As were found to modulate an unknown global regulator, distinct from Stk1 and VraS.

Conclusions:

Pyrimidine-2-amines offer a novel strategy to restore penicillin G's utility against MRSA by suppressing beta-lactamase activity.
This approach circumvents the limitations of direct beta-lactamase inhibition and offers an advantage over penicillinase-insensitive beta-lactams.
P2As represent a promising avenue for developing new antimicrobial therapies against challenging MRSA infections.

Read full analysis

More Related Videos

Stress-induced Antibiotic Susceptibility Testing on a Chip

Stress-induced Antibiotic Susceptibility Testing on a Chip

Published on: January 8, 2014

Targeting Biofilm Associated Staphylococcus aureus Using Resazurin Based Drug-susceptibility Assay

Targeting Biofilm Associated Staphylococcus aureus Using Resazurin Based Drug-susceptibility Assay

Published on: May 5, 2016

Related Concept Videos

Combined Effects of Drugs: Synergism

Combined Effects of Drugs: Synergism

Synergism is a useful mechanism where combining two or more drugs is more effective than each constituent used alone. Such combinations are also called supra-additive interactions. The drugs collectively enhance the final therapeutic effect by acting on different targets. Another advantage is that the low dose of each constituent drug is sufficient to achieve the desired effect. This helps reduce the duration of therapy and lower the adverse effects of these drugs.
Such synergistic combinations...

Development of Antibiotic Resistance

Development of Antibiotic Resistance

Antibiotic resistance is a major public health concern that arises when bacteria evolve mechanisms to withstand the effects of antibiotic treatments. This resistance can be intrinsic, acquired through genetic mutations, or transferred between bacteria via horizontal gene transfer. The development of antibiotic resistance poses significant challenges in treating bacterial infections and necessitates ongoing research to develop new therapeutic strategies.Intrinsic resistance occurs when bacterial...

Biological Methods for Microbial Control

Biological Methods for Microbial Control

Biological agents offer an effective means of controlling microbial growth by leveraging natural processes like predation, competition, and the secretion of antimicrobial substances.Predatory bacteria such as Bdellovibrio species target and kill pathogens like Salmonella and E. coli. They are widely used in poultry farms to control infections. Myxococcus species help combat plant-pathogenic fungi. These naturally occurring predators serve as eco-friendly alternatives to chemical pesticides and...

Defense Against Bacterial Pathogens

Defense Against Bacterial Pathogens

The human immune system is a complex network of cells, tissues, and organs that work together to defend the body against bacterial infections. It consists of various immune cells, each playing a specific role in the defense mechanism.
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...

Gene Regulation in Microbial Communities: Quorum Sensing

Gene Regulation in Microbial Communities: Quorum Sensing

Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...

Antibiotic Selection

Antibiotic Selection