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Updated: Jun 28, 2025
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Antibiotic Susceptibility of Staphylococcus Aureus with VanA and MecA Genes
Lata Ghimire1, Megha Raj Banjara2, Abdelkodose Mh Abdulla1
1Department of Medical Microbiology, University of Cyberjaya, Malaysia.
Background:
Staphylococcus aureus (S.aureus) is an emerging antibiotic resistant bacterium responsible for various infections in human. Resistance to methicillin and vancomycin are of prime concern in S. aureus. The study aims to determine the minimum inhibitory concentration (MIC) of Vancomycin and evaluate the existence of mecA and vanA genes, associated with antibiotic resistance.
Methods:
Clinical specimens from three Kathmandu hospitals were processed and S. aureus was identified using conventional microbiological procedures. MRSA was phenotypically identified with cefoxitin (30µg) disc diffusion, while vancomycin susceptibility was assessed using the Ezy MICTM stripes. The mecA and vanA genes were detected by polymerase chain reaction (PCR).
Results:
Out of 266 S. aureus samples from various clinical specimen subjected for analysis, 77 (28.9%) were found methicillin-resistant (MRSA) and 10 (3.8%) were observed vancomycin-resistant (VRSA). Vancomycin resistant isolates showed a significant correlation between resistance to ampicillin, chloramphenicol, and cefoxitin. The mecA gene was found in 39 of the MRSA isolates, having 50.64% of MRSA cases, while the vanA gene was detected in 4 of the VRSA cases, constituting 40% of VRSA occurrences.
Conclusions:
The strains with higher vancomycin minimum inhibitory concentration values (≥ 1.5 μg/ml) displayed increased resistance rates to various antibiotics compared to strains with lower minimum inhibitory concentration values (< 1.5 μg/ml). The presence of vanA genes was strongly associated (100%) with vancomycin resistance, while the 10.3% mecA gene was identified from MRSA having resistance towards vancomycin also.
Insights
Antibiotic resistance in Staphylococcus aureus is a growing concern. This study found that vancomycin resistance in S. aureus correlates with resistance to other antibiotics and is linked to the vanA gene.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Staphylococcus aureus is a significant cause of human infections, with increasing antibiotic resistance.
- Methicillin and vancomycin resistance in S. aureus are critical public health concerns.
- Understanding resistance mechanisms is vital for effective treatment strategies.
Purpose of the Study:
- To determine the minimum inhibitory concentration (MIC) of vancomycin for S. aureus isolates.
- To investigate the prevalence of mecA and vanA genes associated with antibiotic resistance.
- To correlate genotypic resistance with phenotypic antibiotic susceptibility patterns.
Main Methods:
- Conventional microbiological techniques for S. aureus identification.
- Phenotypic detection of methicillin-resistant S. aureus (MRSA) using cefoxitin disc diffusion.
- Assessment of vancomycin susceptibility using Ezy MICTM stripes and PCR for mecA and vanA gene detection.
Main Results:
- Out of 266 S. aureus isolates, 77 (28.9%) were MRSA and 10 (3.8%) were vancomycin-resistant S. aureus (VRSA).
- Vancomycin resistance showed significant correlation with resistance to ampicillin, chloramphenicol, and cefoxitin.
- The mecA gene was detected in 50.64% of MRSA cases, and the vanA gene in 40% of VRSA cases.
Conclusions:
- Higher vancomycin MIC values (≥ 1.5 μg/ml) correlated with increased resistance to multiple antibiotics.
- The vanA gene was 100% associated with vancomycin resistance.
- The mecA gene was found in 10.3% of MRSA isolates that also exhibited vancomycin resistance.
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