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Oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA), a hidden resistant mechanism among clinically significant isolates in the Wessex region/UK

Oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA), a hidden resistant mechanism among clinically significant isolates in the Wessex region/UK
Oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA), a hidden resistant mechanism among clinically significant isolates in the Wessex region/UK

Purpose: 

Methicillin-resistant Staphylococcus aureus (MRSA) is defined as S. aureus genetically having the mecA or mecC genes or phenotypically showing minimum inhibitory concentration (MIC) of oxacillin higher than 2 mg/L. However, recently, cefoxitin/oxacillin-susceptible mecA-positive S. aureus (OS-MRSA) has been reported worldwide. Little is known about the prevalence and virulence of these strains among clinically significant isolates in the UK. The aims were to (1) investigate the prevalence of OS-MRSA in seven major hospitals in the Wessex region/UK from a cohort of 500 clinically significant phenotypically identified MSSA isolates, (2) genetically characterise OS-MRSA strains by pulsed-field gel electrophoresis (PFGE) and compare these to common UK epidemic strains; and (3) to determine Panton-Valentine leukocidin (PVL; lukFS) gene carriage rates among these isolates.

Results: 

OS-MRSA was found in six isolates (1.2 %) of phenotypically identified and reported MSSA isolates by conventional methods. PFGE showed OS-MRSA strains to be genetically diverse and distinct from the common UK epidemic strains EMRSA-15 and EMRSA-16. None of these OS-MRSA stains carried the genes encoding PVL; however, overall positivity rate for PVL was 4.4 %, much higher than the nationally reported rates of 2 % in the UK.

Conclusion: 

There are still many unknowns regarding phenotypic and/or genetic characterization of the emerging OS-MRSA isolates in the UK and worldwide. Data regarding their epidemiology and optimal therapy for infection are limited and need further investigation not only in the UK, but also worldwide, as it is likely to have an impact on the empirical treatment of S. aureus infections.

mecA, mecC, Methicillin, MRSA, OS-MRSA, PVL
0300-8126
843-847
Saeed, K.
87cb67e5-71e8-4759-bf23-2ea00ebd8b39
Ahmad, N.
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Dryden, M.
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Cortes, N.
72b7c08e-d1bf-40f9-823f-29bb907aeec8
Marsh, P.
a81b0435-d2b1-4ec6-b9bd-8a15d73a1bc4
Sitjar, A.
e9418799-77e1-421e-97ef-f94b357709f6
Wyllie, S.
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Bourne, S.
b5efbc3f-70be-426f-9d45-9015bb90c8b3
Hemming, J.
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Jeppesen, C.
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Green, S.
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Saeed, K.
87cb67e5-71e8-4759-bf23-2ea00ebd8b39
Ahmad, N.
77321573-fdee-49d5-b12a-a56daa8f3380
Dryden, M.
a6c300f9-5c26-4884-980b-c098b0688ab1
Cortes, N.
72b7c08e-d1bf-40f9-823f-29bb907aeec8
Marsh, P.
a81b0435-d2b1-4ec6-b9bd-8a15d73a1bc4
Sitjar, A.
e9418799-77e1-421e-97ef-f94b357709f6
Wyllie, S.
4a0bd7a0-e6eb-4d93-84f5-4bb2d952fdda
Bourne, S.
b5efbc3f-70be-426f-9d45-9015bb90c8b3
Hemming, J.
c0d0f0b6-e8ac-442c-9303-4a94e54664a5
Jeppesen, C.
2b4e79ae-4487-4668-ab47-72d5b5b67736
Green, S.
1075a760-2a75-443c-96c7-194d0d90ede8

Saeed, K., Ahmad, N., Dryden, M., Cortes, N., Marsh, P., Sitjar, A., Wyllie, S., Bourne, S., Hemming, J., Jeppesen, C. and Green, S. (2014) Oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA), a hidden resistant mechanism among clinically significant isolates in the Wessex region/UK. Infection, 42 (5), 843-847. (doi:10.1007/s15010-014-0641-1).

Record type: Article

Abstract

Purpose: 

Methicillin-resistant Staphylococcus aureus (MRSA) is defined as S. aureus genetically having the mecA or mecC genes or phenotypically showing minimum inhibitory concentration (MIC) of oxacillin higher than 2 mg/L. However, recently, cefoxitin/oxacillin-susceptible mecA-positive S. aureus (OS-MRSA) has been reported worldwide. Little is known about the prevalence and virulence of these strains among clinically significant isolates in the UK. The aims were to (1) investigate the prevalence of OS-MRSA in seven major hospitals in the Wessex region/UK from a cohort of 500 clinically significant phenotypically identified MSSA isolates, (2) genetically characterise OS-MRSA strains by pulsed-field gel electrophoresis (PFGE) and compare these to common UK epidemic strains; and (3) to determine Panton-Valentine leukocidin (PVL; lukFS) gene carriage rates among these isolates.

Results: 

OS-MRSA was found in six isolates (1.2 %) of phenotypically identified and reported MSSA isolates by conventional methods. PFGE showed OS-MRSA strains to be genetically diverse and distinct from the common UK epidemic strains EMRSA-15 and EMRSA-16. None of these OS-MRSA stains carried the genes encoding PVL; however, overall positivity rate for PVL was 4.4 %, much higher than the nationally reported rates of 2 % in the UK.

Conclusion: 

There are still many unknowns regarding phenotypic and/or genetic characterization of the emerging OS-MRSA isolates in the UK and worldwide. Data regarding their epidemiology and optimal therapy for infection are limited and need further investigation not only in the UK, but also worldwide, as it is likely to have an impact on the empirical treatment of S. aureus infections.

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More information

Published date: 12 June 2014
Additional Information: Publisher Copyright: © 2014, Springer-Verlag Berlin Heidelberg. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.
Keywords: mecA, mecC, Methicillin, MRSA, OS-MRSA, PVL

Identifiers

Local EPrints ID: 447553
URI: http://eprints.soton.ac.uk/id/eprint/447553
ISSN: 0300-8126
PURE UUID: e5f69c93-666e-4a69-8ea9-ef613bc150b3
ORCID for K. Saeed: ORCID iD orcid.org/0000-0003-0123-0302
ORCID for S. Green: ORCID iD orcid.org/0000-0003-1760-3679

Catalogue record

Date deposited: 16 Mar 2021 17:30
Last modified: 29 Jul 2022 02:07

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Contributors

Author: K. Saeed ORCID iD
Author: N. Ahmad
Author: M. Dryden
Author: N. Cortes
Author: P. Marsh
Author: A. Sitjar
Author: S. Wyllie
Author: S. Bourne
Author: J. Hemming
Author: C. Jeppesen
Author: S. Green ORCID iD

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