Related Experiment Video
Updated: Sep 26, 2026

Development and Assessment of Intracellular Infection Models for Staphylococcus aureus
Published on: January 17, 2025
Staphylococcus aureus accessory gene regulator (agr) group II: is there a relationship to the development of
George Sakoulas1, George M Eliopoulos, Robert C Moellering
1Department of Medicine, Division of Laboratory and Transfusion Medicine and Harvard Medical School, Boston, Massachussetts, USA. gsakoulas@crystalrunhealthcare.com
Abstract:
We previously determined that all 6 Staphylococcus aureus strains with confirmed intermediate-level resistance to glycopeptides (glycopeptide intermediate S. aureus [GISA]) from the United States that we tested belonged to accessory gene regulator (agr) group II. In the present study, we found that 56% of surveyed bloodstream methicillin-resistant S. aureus isolates (n = 148) at our hospital were agr group II, whereas only 24% of methicillin-susceptible S. aureus isolates (n = 33) were agr group II (P = .001). Population analysis of genetically engineered agr-null and parent wild-type strains of groups I, II, and IV revealed that, when agr function is lost, the agr group II knockout S. aureus was most likely to develop glycopeptide heteroresistance after growth in 1 microg/mL but not 16 microg/mL vancomycin. This strain was unique in showing decreased autolysis after growth in these conditions. This study suggests that some S. aureus strains have an intrinsic survival advantage under a glycopeptide selective pressure, which is possibly related to reduced autolysis after exposure to subinhibitory concentrations of glycopeptide.
Related Concept Videos
Mechanism of Antibiotic Resistance in MRSA
Clinical Significance of Antibiotic Resistance
Staphylococcal Skin Infections
Development of Antibiotic Resistance
Gene Regulation in Microbial Communities: Quorum Sensing
Antibiotic Selection
