Diversity in the antimicrobial susceptibility patterns of methicillin-resistant Staphylococcus aureus clones

  • E. Ghaznavi-Rad
  • V. Neela
  • M. Nor Shamsudin
  • H. Ghasemzadeh Moghaddam
  • M. Tavakol
  • A. van Belkum
  • M. R. Etemadi
  • A. F. Andar-Ali


Methicillin-resistant Staphylococcus aureus (MRSA) is well known for its epidemicity, with the emergence of new clones on a daily basis. Diversity in the clonal types of MRSA challenges the success of treatment, as different clones respond to different sets of antibiotics. However, the antibiotic susceptibility among the isolates within the same clones is largely unexplored. In a previous study on MRSA epidemiology in Malaysia, we identified six major clonal complexes (ST-239-CC8, ST-1-CC1, ST-188-CC1, ST-22-CC22, ST-7-CC7 and ST-1283-CC8). In the present study, we investigated the antibiotic susceptibility patterns of isolates of different clones. Three hundred and eighty-nine MRSA isolates were subjected to the disc diffusion test, oxacillin minimum inhibitory concentration (MIC) determination and assessment of the distribution of macrolide, lincosamide and streptogramin B (MLSB) resistance genes. Thirty-six different antibiotic profiles were observed: 30 (83.3 %) among ST-239, 2 (5.6 %) among ST-1283 and 1 (2.8 %) each for ST-1, ST-7, ST-22 and ST-188. All ST-239 (362, 9 %) isolates were multiple drug-resistant (MDR; resistant to more than three classes of antibiotics) and had oxacillin MICs >256 mg/l. Among the 385 clindamycin-resistant isolates, 375 (96.4 %) illustrated inducible resistance (D-zone-positive), while 10 (2.6 %) showed constitutive resistance. The vast majority of the macrolide-resistant isolates carried the ermA gene (95.1 %), followed by ermC (12.9 %). Diversity in the antibiotic susceptibilities of isolates within the clones emphasises the need for continuous surveillance of MDR strains to prescribe the correct antibiotic rather than empirical treatment. This will likely reduce the emergence of new endemic or epidemic resistant MRSA clones.


Minimum Inhibitory Concentration Linezolid Daptomycin Tigecycline Netilmicin 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



This work was supported by the Ministry of Higher Education (MoHE) through the Fundamental Research Grant Scheme (FRGS), grant number 1068 FR.

Competing interest

Nothing to declare.

Conflict of interest

No conflict of interest.


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • E. Ghaznavi-Rad
    • 1
  • V. Neela
    • 2
  • M. Nor Shamsudin
    • 2
    • 3
  • H. Ghasemzadeh Moghaddam
    • 2
  • M. Tavakol
    • 4
  • A. van Belkum
    • 4
    • 5
  • M. R. Etemadi
    • 2
  • A. F. Andar-Ali
    • 2
  1. 1.Department of Microbiology and ImmunologyArak Universiti of Medical SciencesArakIran
  2. 2.Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health SciencesUniversiti Putra MalaysiaSerdangMalaysia
  3. 3.Laboratory of Marine Sciences, Institute of BioscienceUniversiti Putra MalaysiaSerdangMalaysia
  4. 4.Department of Medical Microbiology and Infectious DiseasesErasmus MCRotterdamThe Netherlands
  5. 5.bioMérieuxLa Balme les GrottesFrance

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