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Updated: Feb 26, 2026
Development and Assessment of Intracellular Infection Models for Staphylococcus aureus
Published on: January 17, 2025
Analysis of virulence genes and accessory gene regulator (agr) types among methicillin-resistant Staphylococcus
Sara Cheraghi1, Leyla Pourgholi1, Maryam Shafaati1
1Department of Molecular Pathology, Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran.
Objectives:
Methicillin-resistant Staphylococcus aureus (MRSA) strains are a major cause of hospital-acquired infections and are considered a serious public health concern. MRSA isolates have abundant virulence factors that are the basis for their pathogenicity. The accessory gene regulator (agr) locus co-ordinates the expression of these genes. The aim of this study was to determine the presence and frequency of various virulence genes encoding enterotoxins and adhesins as well as to identify agr specificity groups in MRSA isolates.
Methods:
This descriptive study included a total of 296 MRSA strains isolated from clinical samples collected in Tehran Heart Center (Tehran, Iran) between October 2004 and March 2013. Following DNA extraction, PCR-based assays were used to evaluate the presence of various virulence genes. IBM SPSS Statistics for Windows v.21.0 was used for statistical analysis.
Results:
The results indicated that the most frequent toxin genes were see (120/296; 40.5%), followed by sea (79/296; 26.7%); the other genes were encoded less frequently. The presence of seb and seh was not found in any of the isolates. Furthermore, the most frequent adhesin genes were clfA, spa, cna, map/eap and bbp, found in 281 (94.9%), 275 (92.9%), 267 (90.2%), 265 (89.5%) and 264 (89.2%) isolates, respectively. The majority of isolates belonged to agr group I (53.0%), followed by agr group III (1.4%). None of the isolates belonged to agr group II.
Conclusions:
The relatively high frequency of various virulence genes suggests the emergence and pathogenic potential of MRSA isolates containing these genes in the study area.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) strains carry many virulence genes, with
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of hospital-acquired infections.
- MRSA pathogenicity is linked to numerous virulence factors.
- The accessory gene regulator (agr) locus controls the expression of these virulence genes.
Purpose of the Study:
- To determine the prevalence and frequency of enterotoxin and adhesin virulence genes in MRSA.
- To identify the accessory gene regulator (agr) specificity groups among MRSA isolates.
Main Methods:
- A descriptive study of 296 MRSA strains from clinical samples (Tehran Heart Center, 2004-2013).
- DNA extraction followed by Polymerase Chain Reaction (PCR)-based assays for virulence gene detection.
- Statistical analysis using IBM SPSS Statistics.
Main Results:
- The most common toxin genes detected were `see` (40.5%) and `sea` (26.7%).
- High frequencies of adhesin genes `clfA` (94.9%), `spa` (92.9%), and `cna` (90.2%) were observed.
- The majority of isolates belonged to `agr` group I (53.0%), with `agr` group III (1.4%) also present; `agr` group II was absent.
Conclusions:
- The high prevalence of specific virulence genes indicates the potential for MRSA emergence and pathogenicity.
- Findings highlight the genetic makeup of MRSA strains in the study region, informing infection control strategies.
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