Comparison of several Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) screening media for surveillance culture test

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  • CHIBA Mikiko
    Department of Clinical Laboratory, Tohoku University Hospital
  • SATO Takami
    Department of Clinical Laboratory, Tohoku University Hospital
  • MIURA Yuriko
    Department of Clinical Laboratory, Tohoku University Hospital
  • ISHIDOYA Maho
    Department of Clinical Laboratory, Tohoku University Hospital
  • KATSUMI Makoto
    Department of Clinical Laboratory, Tohoku University Hospital
  • ABE Yuko
    Department of Clinical Laboratory, Tohoku University Hospital
  • FUJIMAKI Shin-ichi
    Department of Clinical Laboratory, Tohoku University Hospital
  • FUJIWARA Toru
    Department of Clinical Laboratory, Tohoku University Hospital

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Other Title
  • Methicillin-resistant <i>Staphylococcus aureus</i>（MRSA）監視培養導入のための各種スクリーニング培地の比較検討
  • Methicillin-resistant Staphylococcus aureus (MRSA)監視培養導入のための各種スクリーニング培地の比較検討
  • Methicillin-resistant Staphylococcus aureus (MRSA)カンシ バイヨウ ドウニュウ ノ タメ ノ カクシュ スクリーニングバイチ ノ ヒカク ケントウ

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<p>To introduce the Staphylococcus aureus (MRSA) surveillance culture test in our hospital, we compared the characteristics of different MRSA screening media: Methicillin-resistant MDRS-K agar medium (MDRS-K), X-MRSA agar medium (X-MRSA), Chromagar MRSA screen medium (Kanto Chrom) and CHROMagar MRSA II (MRSA II). In the evaluation using 11 preserved S. aureus strains, small colonies of three variant MRSA strains were detected only in X-MRSA and Kanto Chrom, and a culture time of 48 h was required for these three variant strains to become positive. Aerobic-culture-delayed MRSA was detected only in Kanto Chrom and MRSA II after 48 h of culture. Cefoxitin-sensitive MRSA was negative in all media up to 48 h of culture. In the evaluation using patient samples, the sensitivity/specificity/positive predictive values/negative predictive values (%) of MDRS-K, X-MRSA, Kanto chrom and MRSA II after 48 h of culture were 100.0/80.0/42.9/100.0, 100.0/94.9/75.0/100.0, 100.0/89.7/60.0/100.0 and 93.3/95.9/77.8/98.9, respectively. We detected colonies of contaminating bacteria at 48 h of culture, and some of these contaminants were observed to form MRSA-like colonies at 48 h. On the basis of these results, we propose that the surveillance culture test using these screening media needs to continue for up to 48 h. It is possible to judge the presence of MRSA only by the color of its colonies on the screening medium at 24 h. Our study may lead to the establishment of a low-cost, high-accuracy and quick surveillance culture test.</p>

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