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Published on: July 9, 2012
[About microbiological methods for detection of oxacillin resistance in coagulase-negative staphylococci]
Objective:
Coagulase-negative staphylococci (CoNS) take part of the human skin and mucous membranes, but they are also involving in infections with the increasing use of prosthetic, indwelling devices or intravascular catheter-related bacteraemia. They are more resistance than Staphylococcus aureus against a wide range of antimicrobial agents, and it have been observed an increase in morbidity and mortality of patients with incorrect treatment.
Methods:
To analyze the results obtained by different commercial techniques: two automatic microdilution systems (MicroScan and Vitek2 Compact), PBP2a agglutiation test, with and without 1 μg oxacillin disk induction, and detection of mecA gene by nucleic acids amplification techniques, for the diagnosis of methicillin resistance staphylococci in 170 strains of CoNS isolated from blood cultures.
Results:
One hundred and seventy methicillin resistance staphylococci were detected by MicroScan, 167 strains by Vitek 2 Compact, 115 strains were PBP2a positive without oxacillin induction and 168 after oxacillin induction. Finally, 167 strains were mecA gene positive detected by nucleic acids amplification techniques.
Conclusions:
It is necessary to do oxacillin induction before PBP2a test to avoid false negatives. There are a great variability in the phenotypic expression of methicillin resistance in CoNS.
Insights
Accurate detection of methicillin resistance in Coagulase-negative staphylococci (CoNS) is crucial. Oxacillin induction before the PBP2a test is necessary to prevent false negatives in CoNS infections.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Coagulase-negative staphylococci (CoNS) are opportunistic pathogens frequently associated with device-related infections.
- CoNS exhibit increasing resistance to antimicrobial agents, complicating treatment and leading to higher morbidity and mortality.
- Accurate and timely diagnosis of methicillin resistance in CoNS is essential for effective patient management.
Purpose of the Study:
- To evaluate the performance of various commercial methods for detecting methicillin resistance in CoNS.
- To compare automated systems (MicroScan, Vitek2 Compact), PBP2a agglutination tests (with and without oxacillin induction), and molecular detection (mecA gene).
- To identify optimal diagnostic strategies for methicillin-resistant CoNS.
Main Methods:
- Analysis of 170 CoNS strains isolated from blood cultures.
- Utilized MicroScan and Vitek2 Compact automated microdilution systems.
- Employed PBP2a agglutination test with and without oxacillin induction.
- Performed mecA gene detection via nucleic acid amplification techniques.
Main Results:
- MicroScan detected 170 methicillin-resistant strains; Vitek2 Compact identified 167.
- PBP2a test yielded 115 positive results without induction and 168 with induction.
- Nucleic acid amplification confirmed 167 mecA gene-positive strains.
Conclusions:
- Oxacillin induction is critical before PBP2a testing to avoid false-negative results.
- Significant variability exists in the phenotypic expression of methicillin resistance among CoNS strains.
- Accurate diagnostic methods are vital for managing CoNS infections effectively.
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