Related Experiment Video

Updated: Apr 16, 2026

Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
09:03

Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus

Published on: September 5, 2013

12.4K

The distribution of pathogenic and toxigenic genes among MRSA and MSSA clinical isolates

Abbas Ali Imani Fooladi1, Elnaz Ashrafi2, Shafie Gorbani Tazandareh3

  • 1Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.

Microbial Pathogenesis
|March 18, 2015
PubMed

Insights

This study reveals that methicillin-sensitive Staphylococcus aureus (MSSA) strains can harbor significant virulence factors, similar to methicillin-resistant S. aureus (MRSA). This highlights the need to consider MSSA as a serious threat due to its potential for causing severe infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Molecular Biology

Background:

  • Staphylococcus aureus is a major nosocomial pathogen.
  • Antibiotic resistance contributes to its increasing morbidity and mortality.
  • Limited data exists on the molecular properties of infecting S. aureus strains.

Purpose of the Study:

  • To assess the prevalence of virulence factor genes and staphylococcal cassette chromosome mec (SSCmec) subtypes in clinical S. aureus isolates.
  • To evaluate antibiotic susceptibility patterns and vancomycin resistance.
  • To compare molecular characteristics between methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA).

Main Methods:

  • Polymerase chain reaction (PCR) was used to detect genes for staphylococcal enterotoxins (SEs), toxic shock syndrome toxin (TSST), exfoliative toxins, and SSCmec subtypes.
  • Disk diffusion and micro-dilution methods were employed to determine antibiotic susceptibility and vancomycin minimum inhibitory concentrations (MICs).

Main Results:

  • Out of 192 S. aureus isolates, 88 were MSSA and 104 were MRSA.
  • The mecA gene was detected in 89% of isolates, and various enterotoxin genes (entA, entC, entE) were prevalent.
  • SCCmec type III was associated with higher rates of MRSA and resistance to multiple antibiotics, except penicillin G, kanamycin, and linezolid.
  • A small percentage (2.3%) of strains showed vancomycin MIC > 2 mg/L, notably higher in multi-drug resistant (MDR), MRSA, and SCCmec type III strains.

Conclusions:

  • MSSA isolates can carry significant virulence factor genes, posing a threat comparable to MRSA.
  • SCCmec type III strains exhibit increased antibiotic resistance.
  • Clinical vigilance is necessary for both MSSA and MRSA due to their diverse molecular profiles and resistance patterns.
Keywords:
EntorotoxinMRSAMSSASCCmecStaphylococcus aureusSuperantigen

More Related Videos

Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus10:39

Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus

Published on: March 10, 2017

17.5K
A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues07:10

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues

Published on: February 19, 2019

9.6K

Related Concept Videos

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...
57
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...
143
Modern Molecular Taxonomy01:29

Modern Molecular Taxonomy

Advancements in molecular biology have revolutionized the identification and characterization of bacteria, with multiple methods leveraging DNA sequencing for enhanced precision. As sequencing technologies improve and costs decline, these approaches are increasingly used in clinical, environmental, and evolutionary studies.Multilocus Sequence Typing (MLST) examines several housekeeping genes, essential chromosomal genes encoding cellular functions, to distinguish strains. Approximately...
868
Staphylococcal Skin Infections01:29

Staphylococcal Skin Infections

Staphylococcus aureus is a Gram-positive coccus that resides harmlessly on the skin and mucous membranes of healthy individuals. When the skin barrier is breached, it can shift from a commensal to an opportunistic pathogen. This transition is facilitated by surface adhesins, such as clumping factor B and S. aureus surface protein G (SasG), which bind to structural proteins, including loricrin and cytokeratin, in the damaged epidermis. Protein A, another key factor, binds the Fc region of...
100
Bacterial Gastroenteritis01:18

Bacterial Gastroenteritis

Bacterial gastroenteritis, characterized by diarrhea, abdominal cramps, and vomiting, is often caused by ingestion of contaminated food or water and is frequently associated with pathogenic Escherichia coli strains. These microbes exploit two principal mechanisms to inflict disease.Shiga toxin–producing E. coli, also referred to as STEC—notably O157:H7—release Shiga toxins that target ribosomes, blocking protein synthesis. The B subunit of the toxin binds the host glycolipid...
63
Applications of Molecular Taxonomy01:20

Applications of Molecular Taxonomy

Molecular taxonomy has revolutionized the understanding and classification of bacteria, providing precise insights into their diversity, evolutionary relationships, and ecological roles. By utilizing molecular techniques such as DNA sequencing and fingerprinting, researchers have made significant strides in various fields related to bacterial studies.Resolving Taxonomic AmbiguitiesMolecular taxonomy has been instrumental in distinguishing closely related bacterial species initially thought to...
689