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Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Identification of major sequence types among aminoglycoside resistant Staphylococcus aureus and Staphylococcus
Samaneh Bourbour1, Reza Beigverdi1,2, Maryam Beheshti1
1Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Background And Objectives:
Aminoglycosides have been widely used for treating severe staphylococcal infections. Production aminoglycoside modifying enzymes (AMEs) is the main mechanism of resistance to this antibiotic. The aim of this study was to determine the prevalence of AME genes and molecular characterization of aminoglycoside-resistant Staphylococcus aureus and Staphylococcus epidermidis strains isolated from clinical specimens in Iran.
Materials And Methods:
A total of 42 clinical isolates of Gram-positive cocci (20 S. aureus and 22 S. epidermidis) with resistance to gentamicin were tested for antimicrobial resistance and differentiated by multilocus sequence typing (MLST).
Results:
All 42 isolates were resistant to methicillin, kanamycin, and most of them were also resistant to amikacin (98%), tobramycin (98%) and netilmycin (78.5%). Overall, aac(6')-Ie-aph(2")-Ia was the dominant AME gene found in 100% of isolates, followed by aph(3')IIIa found in 90% of isolates. MLST classified S. aureus and S. epidermidis into 5 and 9 distinct sequence types (ST), respectively. The majority of the strains belonged to ST239 (50%) for S. aureus and ST2 (36%) for S. epidermidis.
Conclusion:
The resistance to aminoglycosides was mainly due to the presence of the aac(6')-Ie-aph(2")-Ia and aph(3') IIIa genes as well as the ST239 for S. aureus and ST2 for S. epidermidis have become the predominant clones in the selected university hospital of Tehran, Iran. Thus, it is critical that clinicians and healthcare workers are aware of the population of S. aureus and S. epidermidis present in order to make decisions for appropriate treatment and infection control practices.
Insights
Aminoglycoside resistance in Staphylococcus strains is primarily driven by specific modifying enzyme genes. Predominant clones of S. aureus and S. epidermidis identified in Iran highlight the need for targeted infection control strategies.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Aminoglycosides are crucial for treating severe staphylococcal infections.
- Aminoglycoside-modifying enzymes (AMEs) are a primary mechanism of resistance.
- Understanding resistance patterns is vital for effective treatment.
Purpose of the Study:
- To determine the prevalence of AME genes in resistant Staphylococcus strains.
- To molecularly characterize aminoglycoside-resistant *Staphylococcus aureus* and *Staphylococcus epidermidis* from clinical specimens in Iran.
Main Methods:
- 42 clinical isolates (20 *S. aureus*, 22 *S. epidermidis*) resistant to gentamicin were analyzed.
- Antimicrobial resistance profiling and multilocus sequence typing (MLST) were performed.
Main Results:
- All isolates were resistant to methicillin and kanamycin; high resistance to amikacin and tobramycin was observed.
- The *aac(6 olyl)-Ie-aph(2")-Ia* gene was present in 100% of isolates, followed by *aph(3 olyl)IIIa* in 90%.
- MLST identified 5 *S. aureus* STs (ST239 dominant) and 9 *S. epidermidis* STs (ST2 dominant).
Conclusions:
- The *aac(6 olyl)-Ie-aph(2")-Ia* and *aph(3 olyl)IIIa* genes are key drivers of aminoglycoside resistance.
- ST239 (*S. aureus*) and ST2 (*S. epidermidis*) are the predominant resistant clones in Tehran.
- Awareness of these resistant populations is critical for treatment and infection control.
