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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Decrease in vancomycin MICs and prevalence of hGISA in MRSA and MSSA isolates from a German pediatric tertiary care
Katharina Haas1, Melanie Meyer-Buehn1, Ulrich von Both1,2
1Division of Pediatric Infectious Diseases, Dr. Von Hauner Children's Hospital, Ludwig-Maximilians-University Munich, Munich, Germany.
Purpose:
Resistance of Staphylococcus aureus to vancomycin includes a general increase of minimal inhibitory concentrations (MIC) within the susceptible range over time (Vancomycin MIC Creep) and the presence of a subset of the bacterial population that expresses resistance (heterogeneous glycopeptide-intermediate S. aureus; hGISA). Increased MICs have been associated with adverse clinical outcomes. However, the vancomycin MIC creep is not a uniform trend suggesting the importance of regional surveys.
Methods:
We performed a retrospective analysis at a German pediatric tertiary care hospital. Isolates from 2002 to 2017 were selected which were newly identified methicillin-resistant S. aureus (MRSA) or samples from invasive methicillin-susceptible S. aureus (MSSA) or MRSA infections. Vancomycin and oxacillin MICs as well as GISA/hGISA were measured using MIC test strips and resistance was evaluated over time.
Results:
A total of 540 samples were tested, 200 from the early (2002-2009) and 340 from the later period (2010-2017). All samples were vancomycin susceptible, but the MIC was higher for the earlier samples as compared to the later ones (1.11 vs 0.99; p < 0.001). 14% of the samples were hGISA, GISA strains were not detected. Again, vancomycin resistance decreased over time with 28 vs. 6% hGISA (p < 0.001). There was no significant difference between MRSA and MSSA samples with respect to vancomycin MIC and hGISA prevalence.
Conclusion:
This study shows a decreasing trend for both MIC values and presence of hGISA strains highlighting the importance of monitoring local susceptibilities. Vancomycin remains a first-line treatment option for suspected severe infection with Gram-positive cocci and proven infection with MRSA.
Insights
Vancomycin resistance in Staphylococcus aureus, including MIC creep and hGISA, showed a decreasing trend in a German hospital. This highlights the need for local susceptibility monitoring.
Area of Science:
- Infectious Diseases
- Microbiology
- Clinical Pharmacy
Background:
- Vancomycin resistance in Staphylococcus aureus presents as MIC creep and heterogeneous GISA (hGISA).
- Increased vancomycin MICs are linked to poorer clinical outcomes.
- Regional variations in vancomycin resistance necessitate local surveillance.
Purpose of the Study:
- To analyze trends in vancomycin resistance, including MIC creep and hGISA prevalence.
- To evaluate vancomycin susceptibility over time in a German pediatric tertiary care hospital.
Main Methods:
- Retrospective analysis of Staphylococcus aureus isolates from 2002-2017.
- Measurement of vancomycin and oxacillin MICs using MIC test strips.
- Evaluation of GISA/hGISA prevalence and resistance trends over time.
Main Results:
- Vancomycin MICs decreased significantly from 1.11 in 2002-2009 to 0.99 in 2010-2017 (p < 0.001).
- hGISA prevalence decreased from 28% to 6% over the study period (p < 0.001).
- No significant difference in vancomycin MIC or hGISA prevalence was observed between MRSA and MSSA isolates.
Conclusions:
- A decreasing trend in vancomycin MIC values and hGISA prevalence was observed.
- Local monitoring of Staphylococcus aureus susceptibilities is crucial.
- Vancomycin remains a primary treatment for severe Gram-positive infections and MRSA.
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