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Updated: May 3, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Detection of genes for superantigen toxins in methicillin-resistant Staphylococcus aureus clinical isolates in
Yasmeen Taj1, Izhar Fatima1, Syed Wajid Ali1
1Department of Pathology, Dow Medical College, Dow University of Health Sciences, Karachi.
Objective:
To detect genes for enterotoxins, exfoliative and toxic shock syndrome toxins in Staphylococcus aureus (S. aureus) strains isolated from clinical specimens.
Study Design:
Cross-sectional observational study.
Place And Duration Of Study:
Department of Molecular Genetics, Dr. Ziauddin Hospital, Karachi, from January to December 2010.
Methodology:
Two hundred and ninety eight S. aureus clinical isolates were obtained from various clinical samples received at Dr. Ziauddin Hospital, Karachi. Out of these, 115 were detected as methicillin resistant (MRSA) by cefoxitin disk diffusion test showing a prevalence rate of 38.6%. Detection of individual toxin genes was performed by Polymerase Chain Reaction (PCR) by using only one primer pair for each tube. Uniplex primers were preferred as multiplex primers are longer in base pairs and have the potential for cross reaction due to non-specific binding and increase in optimization time.
Results:
The possession of a single gene or more than a single gene in MRSA isolates was found in 61.73% of clinical samples; the highest number was found in pus swab, followed by sputum, blood, urethral swab, and urine. The prevalence of toxin genes was higher in MRSA as compared to methicillin sensitive (MSSA) isolates (19.12%).
Conclusion:
PCR detects strains possessing toxin genes independent of their expression. The possession of genes for super-antigens seems to be a frequent and habitual trait of S. aureus more so in MRSA.
Insights
Staphylococcus aureus (S. aureus) clinical isolates frequently carry toxin genes, especially in methicillin-resistant strains (MRSA). Polymerase Chain Reaction (PCR) effectively detects these toxin genes, indicating a common trait in MRSA.
Area of Science:
- Molecular Biology
- Clinical Microbiology
- Bacterial Genetics
Background:
- Staphylococcus aureus (S. aureus) is a significant human pathogen.
- Toxin production by S. aureus contributes to its virulence.
- Methicillin-resistant S. aureus (MRSA) poses a growing public health threat.
Purpose of the Study:
- To detect genes encoding enterotoxins, exfoliative toxins, and toxic shock syndrome toxins in S. aureus clinical isolates.
- To compare the prevalence of these toxin genes in methicillin-resistant S. aureus (MRSA) versus methicillin-sensitive S. aureus (MSSA).
Main Methods:
- A cross-sectional observational study was conducted.
- 298 S. aureus clinical isolates were analyzed from samples at Dr. Ziauddin Hospital, Karachi.
- Polymerase Chain Reaction (PCR) with uniplex primers was used to detect specific toxin genes.
Main Results:
- 115 isolates (38.6%) were identified as MRSA.
- Toxin genes were present in 61.73% of MRSA isolates across various sample types (pus, sputum, blood, urine).
- The prevalence of toxin genes was significantly higher in MRSA (61.73%) compared to MSSA (19.12%).
Conclusions:
- Polymerase Chain Reaction (PCR) is a reliable method for detecting toxin genes in S. aureus, irrespective of their expression.
- The presence of super-antigen genes is a common characteristic of S. aureus, particularly prevalent in MRSA strains.
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