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Updated: Jun 15, 2026
A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection
Published on: February 28, 2019
Modified methicillin-resistant Staphylococcus aureus detected in neonatal intensive care patients
Melissa R Gitman1, Bremy Alburquerque2,3, Marilyn Chung2
1Department of Pathology and Laboratory Medicine, Icahn School of Medicine at Mount Sinai, New York City, NY, USA.
Objectives:
As part of an active MRSA surveillance programme in our neonatal ICU, we identified nares surveillance cultures from two infants that displayed heterogeneity in methicillin resistance between isolated subclones that lacked mecA and mecC.
Methods:
The underlying mechanism for the modified Staphylococcus aureus (MODSA) methicillin-resistance phenotype was investigated by WGS.
Results:
Comparison of finished-quality genomes of four MODSA and four MSSA subclones demonstrated that the resistance changes were associated with unique truncating mutations in the gene encoding the cyclic diadenosine monophosphate phosphodiesterase enzyme GdpP or a non-synonymous substitution in the gene encoding PBP2.
Conclusions:
These two cases highlight the difficulty in identifying non-mecA, non-mecC-mediated MRSA isolates in the clinical microbiology laboratory, which leads to difficulties in implementing appropriate therapy and infection control measures.
Insights
Novel methicillin-resistant Staphylococcus aureus (MRSA) mechanisms were found in infants, involving mutations in GdpP or PBP2 genes, not the usual mecA/mecC. This complicates detection and treatment in neonatal intensive care units.
Area of Science:
- Microbiology
- Genomics
- Infectious Diseases
Background:
- Methicillin resistance in Staphylococcus aureus (MRSA) is typically mediated by the mecA or mecC genes.
- Surveillance programs are crucial for monitoring MRSA prevalence, especially in vulnerable populations like neonates.
Purpose of the Study:
- To investigate the genetic mechanisms underlying heterogeneous methicillin resistance in Staphylococcus aureus (MRSA) isolates from neonatal surveillance cultures.
- To identify novel resistance pathways in MRSA beyond the canonical mecA and mecC genes.
Main Methods:
- Whole-genome sequencing (WGS) was employed to analyze MRSA and methicillin-susceptible Staphylococcus aureus (MSSA) subclones.
- Comparative genomic analysis was performed on finished-quality genomes.
Main Results:
- Two infant MRSA isolates exhibited heterogeneous methicillin resistance in subclones lacking mecA and mecC.
- Genomic analysis revealed resistance was linked to truncating mutations in the GdpP gene or a substitution in the PBP2 gene.
- These findings identified non-mecA/mecC mediated resistance mechanisms in Staphylococcus aureus.
Conclusions:
- The study highlights challenges in identifying non-mecA/mecC mediated MRSA in clinical microbiology labs.
- Difficulties in accurate MRSA identification can impede appropriate therapeutic interventions and infection control strategies.
- Novel resistance mechanisms necessitate advanced diagnostic approaches for effective MRSA management.
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