Related Experiment Video

Updated: May 25, 2026

Visualization of Bacterial Resistance using Fluorescent Antibiotic Probes
08:23

Visualization of Bacterial Resistance using Fluorescent Antibiotic Probes

Published on: March 2, 2020

MurAA is required for intrinsic cephalosporin resistance of Enterococcus faecalis

Dušanka Vesić1, Christopher J Kristich

  • 1Department of Microbiology and Molecular Genetics, Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.

Antimicrobial Agents and Chemotherapy
|February 1, 2012
PubMed

Insights

Enterococcus faecalis intrinsic cephalosporin resistance involves MurAA, an enzyme in peptidoglycan synthesis. Disrupting murAA increases susceptibility to cephalosporins like ceftriaxone.

Area of Science:

  • Microbiology
  • Bacterial cell wall biosynthesis
  • Antibiotic resistance mechanisms

Background:

  • Enterococcus faecalis exhibits intrinsic resistance to cephalosporins, crucial antibiotics targeting bacterial cell wall synthesis.
  • The precise molecular mechanisms underlying this intrinsic resistance remain incompletely understood.

Purpose of the Study:

  • To identify genetic factors contributing to Enterococcus faecalis's intrinsic cephalosporin resistance.
  • To elucidate the specific role of MurAA in cephalosporin resistance.

Main Methods:

  • Screening of a transposon mutant library in E. faecalis for increased susceptibility to ceftriaxone.
  • In-frame deletion mutagenesis of murAA and its homolog murAB.
  • Assessing cephalosporin resistance in wild-type and mutant strains, including those lacking the IreK kinase.

Main Results:

  • A transposon mutant with disruption in murAA displayed heightened susceptibility to ceftriaxone.
  • Deletion of murAA, but not murAB, significantly increased cephalosporin susceptibility.
  • Overexpression of MurAA enhanced cephalosporin resistance in an IreK-deficient mutant, indicating MurAA's catalytic activity is necessary but not sufficient.

Conclusions:

  • MurAA and MurAB play distinct roles in E. faecalis physiology.
  • MurAA possesses a unique function that contributes to the intrinsic resistance of E. faecalis to cephalosporins.

More Related Videos

Quadruple-Checkerboard: A Modification of the Three-Dimensional Checkerboard for Studying Drug Combinations11:15

Quadruple-Checkerboard: A Modification of the Three-Dimensional Checkerboard for Studying Drug Combinations

Published on: July 24, 2021

Related Concept Videos

Mechanism of Antibiotic Resistance in MRSA01:25

Mechanism of Antibiotic Resistance in MRSA

Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
Clinical Significance of Antibiotic Resistance01:25

Clinical Significance of Antibiotic Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) presents a critical public health threat, arising from its capacity to resist β-lactam antibiotics due to acquisition of the mecA gene within the staphylococcal cassette chromosome mec (SCCmec). This gene encodes penicillin-binding protein 2a (PBP2a), which impairs binding efficacy of methicillin and other β-lactams. MRSA has evolved into distinct clonal lineages impacting humans and animals alike, reinforcing its significance within the One...
Development of Antibiotic Resistance01:30

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...
Bacterial Cell Wall01:22

Bacterial Cell Wall

The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and protecting against osmotic stress. This rigid yet flexible structure primarily comprises peptidoglycan, a polymer that forms a mesh-like matrix conferring mechanical strength and flexibility.Peptidoglycan Composition and StructurePeptidoglycan, the core of the bacterial cell wall, comprises alternating units of N-acetylglucosamine (NAG) and...
Inhibitors of Gram-positive Cell Wall Synthesis01:23

Inhibitors of Gram-positive Cell Wall Synthesis

Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...
Surface Membrane Barriers01:18

Surface Membrane Barriers

The skin and mucous membranes serve as the primary line of defense against pathogens by providing both physical and chemical protection. These barriers are essential in preventing the entry and establishment of microbes, thereby maintaining the integrity of the host.
The outer layer of the skin, the epidermis, is a robust barrier comprising layers of closely packed keratinized cells. This dense arrangement prevents microbes from penetrating the body. The periodic shedding of epidermal cells...