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Determination of antimicrobial susceptibility patterns and inducible clindamycin resistance in Staphylococcus aureus
Fahriye Eksi1, Efgan Dogan Gayyurhan, Aysen Bayram
1Department of Clinical Microbiology, School of Medicine, Gaziantep University, Gaziantep, Turkey. eksi@gantep.edu.tr
Background:
In this study, we determined the susceptibility patterns of Staphylococcus aureus strains to various antimicrobials and prevalence of inducible clindamycin resistance (ICR) in these isolates.
Methods:
Two hundred and one S aureus strains, isolated from various clinical samples, were included in the study. Antibiotic susceptibilities were studied by disc diffusion method on the basis of the guidelines by the Clinical and Laboratory Standards Institute. The disc diffusion induction test (D test) was applied to determine ICR resistance among erythromycin-resistant S aureus isolates.
Results:
Of the 201 S aureus strains, 101 (50.2%) were resistant to methicillin. All strains were susceptible to vancomycin, teicoplanin, quinupristin/dalfopristin, and linezolid. It was found that 54 (53.4%) methicillin-resistant S aureus (MRSA) strains were erythromycin resistant, and 40 (39.6%) of them showed constitutive clindamycin resistance. ICR was detected in seven (6.9%) MRSA strains. It was found that 13 (13.0%) methicillin-susceptible S aureus (MSSA) strains were erythromycin resistant. Constitutive clindamycin resistance was seen in one (1.0%) MSSA strain, and ICR was detected in 10 (10.0%) cases.
Conclusion:
There was a high rate of methicillin resistance among S aureus strains in our hospital. However, no statistically significant difference of ICR was observed between MRSA and MSSA strains (p=0.434) or between inpatients and outpatients (p=0.804). It was concluded that ICR should be routinely evaluated in each S aureus case to avoid therapy failure among patients.
Insights
This study found high rates of methicillin resistance in Staphylococcus aureus. Inducible clindamycin resistance (ICR) was present in both MRSA and MSSA strains, highlighting the need for routine ICR testing to prevent treatment failures.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Staphylococcus aureus is a significant human pathogen.
- Antimicrobial susceptibility patterns and resistance mechanisms, such as inducible clindamycin resistance (ICR), are crucial for effective treatment.
- High rates of methicillin resistance are a growing concern.
Purpose of the Study:
- To determine the antimicrobial susceptibility patterns of Staphylococcus aureus isolates.
- To investigate the prevalence of inducible clindamycin resistance (ICR) in Staphylococcus aureus.
- To compare ICR prevalence between methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains.
Main Methods:
- Analysis of 201 Staphylococcus aureus strains from clinical samples.
- Antimicrobial susceptibility testing using the disc diffusion method.
- Detection of inducible clindamycin resistance (ICR) via the D test in erythromycin-resistant isolates.
Main Results:
- 50.2% of S. aureus strains were methicillin-resistant (MRSA).
- High rates of erythromycin resistance were observed in both MRSA (53.4%) and MSSA (13.0%) strains.
- Inducible clindamycin resistance (ICR) was detected in 6.9% of MRSA and 10.0% of MSSA isolates.
Conclusions:
- A high prevalence of methicillin resistance was found in S. aureus.
- No significant difference in ICR prevalence was noted between MRSA and MSSA.
- Routine evaluation of ICR in S. aureus infections is recommended to guide therapy and prevent treatment failure.
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