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Open Access Research article

Fusidic acid resistance among clinical isolates of methicillin-resistant Staphylococcus aureus in a Taiwanese hospital

Chih-Ming Chen1, Mei Huang2, Huei-Fen Chen3, Se-Chin Ke4, Chia-Ru Li5, Jen-Hsien Wang67 and Lii-Tzu Wu3*

Author affiliations

1 Division of Infectious Disease, Department of Internal Medicine, Tungs' Taichung MetroHarbor Hospital, Taiwan

2 Division of Infectious Disease, Show Chwan Memorial Hospital, Taiwan

3 The Institute of Medical Science and Department of Microbiology, China Medical University and Hospitals, Taichung, Taiwan

4 Infection Control Office, Tungs' Taichung MetroHarbor Hospital, Taiwan

5 Department of Medical Research, Tungs' Taichung MetroHarbor Hospital, Taiwan

6 Department of Internal Medicine and Section of Clinical Microbiology, China Medical College-Hospital, Taichung, Taiwan

7 Department of Laboratory Medicine, China Medical College-Hospital, Taichung, Taiwan

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Citation and License

BMC Microbiology 2011, 11:98  doi:10.1186/1471-2180-11-98

Published: 12 May 2011

Abstract

Background

The prevalence of resistance to fusidic acid of methicillin-resistant Staphylococcus aureus (MRSA) was increased each year in a Taiwan hospital. Thirty-four MRSA clinical isolates collected in 2007 and 2008 with reduced susceptibility to FA were selected for further evaluation the presence of resistance determinants.

Results

The most common resistance determinant was fusC, found in 25 of the 34 MRSA isolates. One of the 25 fusidic acid-resistant MRSA harboured both fusB and fusC, which is the first time this has been identified. Mutations in fusA were found in 10 strains, a total of 3 amino-acid substitutions in EF-G (fusA gene) were detected. Two substitutions with G556S and R659L were identified for the first time. Low-level resistance to fusidic acid (MICs, ≤ 32 μg/ml) was found in most our collection. All collected isolates carried type III SCCmec elements. MLST showed the isolates were MRSA ST239. PFGE revealed nine different pulsotypes in one cluster.

Conclusions

Our results indicate that the increase in the number of fusidic acid resistant among the MRSA isolates in this hospital is due mainly to the distribution of fusC determinants. Moreover, more than one fusidic acid-resistance mechanism was first detected in a same stain in our collection.

Keywords:
fusidic acid; MRSA; fusA; fusB; fusC