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Antimicrobial synergism against different lineages of methicillin-resistant Staphylococcus aureus carrying SCCmec IV

Authors

  • P.D.M. de Matos,

    1. Department of Medical Microbiology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Nova Friburgo, Rio de Janeiro, Brazil
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  • S. Sedaca,

    1. Department of Medical Microbiology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Nova Friburgo, Rio de Janeiro, Brazil
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  • D.C. Ferreira,

    1. Department of Medical Microbiology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Nova Friburgo, Rio de Janeiro, Brazil
    2. Department of Oral Medicine, School of Dentistry, Veiga de Almeida University, Rio de Janeiro, Brazil
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  • N.L. Iorio,

    1. Basic Science Department, Fluminense Federal University, Nova Friburgo, Rio de Janeiro, Brazil
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  • V.C.S. Toledo,

    1. Department of Medical Microbiology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Nova Friburgo, Rio de Janeiro, Brazil
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  • A.I.C. Freitas,

    1. Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Braga, Portugal
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  • F.L. Coelho,

    1. Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Braga, Portugal
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  • C. Sousa,

    1. Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Braga, Portugal
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  • K.R.N. dos Santos,

    Corresponding author
    1. Department of Medical Microbiology, Institute of Microbiology Paulo de Góes, Federal University of Rio de Janeiro, Nova Friburgo, Rio de Janeiro, Brazil
    • Correspondence

      Kátia Regina N. dos Santos, Laboratório de Infecções Hospitalares, Departamento de Microbiologia Médica, Instituto de Microbiologia Prof. Paulo de Góes, CCS, Bloco I, UFRJ, Cidade Universitária, Rio de Janeiro, CEP: 21941-590, RJ, Brazil.

      E-mail: santoskrn@micro.ufrj.br

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  • M.O. Pereira

    1. Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Braga, Portugal
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Abstract

Aim

To evaluate the synergistic activity of antimicrobial drugs against lineages of methicillin-resistant Staphylococcus aureus (MRSA) carrying SCCmec IV. The biofilm production and related genes were also detected.

Methods and Results

Forty two MRSA isolates were tested for biofilm production and related genes. Biofilm/biomass susceptibility to gentamicin (G), linezolid (L), rifampicin (R) and vancomycin (V) was determined for six isolates from three lineages prevalent in Rio de Janeiro hospitals in concentrations ranging from 0·25 to 64 μg ml−1. Biomass was evaluated by microtitre plate test and number of viable cells (CFU cm−2) and inspected by epifluorescence microscopy. All isolates presented the icaA and sasG genes, but only 38% were biofilm producers. There were 50 and 45% biomass reductions when concentrations ≥4 μg ml−1 of R or L and ≥16 μg ml−1 of G or V, respectively, were used. Synergism tests produced a 55% biomass reduction with inline image + inline image, inline image + inline image, inline image  + inline image, and inline image + inline image. Number of viable cells was reduced from 2 to 3 logs with inline image + inline image and inline image + inline image.

Conclusions

Synergisms involving R plus L and R plus V caused important reductions in biofilm/biomass and the number of viable cells. Drug combinations should be considered in the chemotherapies of MRSA-SCCmec IV infections.

Significance and Impact of the Study

Biofilms in MRSA infections restrict the clinical choice of antimicrobials. Thus, knowledge of the best options for monotherapy and drug synergisms could improve clinical results.

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