Emerging Challenges in Methicillin Resistance of Coagulase-Negative Staphylococci
<b>Objective:</b> In the present study, we used phenotypic and molecular methods to determine susceptibility to oxacillin in coagulase-negative staphylococci (CoNS) and estimate the prevalence of strains with low-level resistance to oxacillin, <i>mec</i>A-positive oxacillin-s...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-01-01
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| Series: | Antibiotics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2079-6382/14/1/37 |
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| Summary: | <b>Objective:</b> In the present study, we used phenotypic and molecular methods to determine susceptibility to oxacillin in coagulase-negative staphylococci (CoNS) and estimate the prevalence of strains with low-level resistance to oxacillin, <i>mec</i>A-positive oxacillin-susceptible methicillin-resistant (OS-MRCoNS), and borderline oxacillin-resistant (BORCoNS). <b>Methods:</b> One hundred one CoNS strains were screened for oxacillin and cefoxitin susceptibility using phenotypic (disk diffusion, agar dilution, latex agglutination, and chromagar) and molecular (detection of <i>mec</i>A, <i>mec</i>B, and <i>mec</i>C) methods. Staphylococcal cassette chromosome <i>mec</i> (SCC<i>mec</i>) typing was performed. <b>Results</b>: Sixteen (15.8%) CoNS strains were <i>mec</i>A-positive, and 85 (84.2%) were <i>mec</i>-negative. Seven (6.9%) were classified as OS-MRCoNS, accounting for 43.8% of all <i>mec</i>A-positive strains. Twelve (11.9%) <i>mec</i>-negative strains were classified as borderline oxacillin resistant (BORCoNS). Compared with MRCoNS and BORCoNS, OS-MRCoNS strains demonstrated lower resistance to non-beta-lactams. SCC<i>mec</i> type I cassette was predominant. The disc-diffusion method with oxacillin accurately predicted OS-MRCoNS strains but did not provide reliable results for BORCoNS strains. Meanwhile, the latex agglutination test and CHROMagar culture accurately identified BORCoNS but not OS-MRCoNS. <b>Conclusions:</b> Finally, our findings imply that the recognition of methicillin resistance in CoNS requires a meticulous approach and that further research is needed to develop unified laboratory diagnostic algorithms to prevent the misreporting of borderline CoNS. |
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| ISSN: | 2079-6382 |