当院より分離されたarbekacin耐性メチシリン耐性黄色ブドウ球菌 (MRSA) 株の疫学的検討 Epidemiological Study of Arbekacin-Resistant, Methicillin Resistant <I>Staphylococcus aureus</I> in Saitama Medical School Hospital
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埼玉医科大学附属病院では, arbekacin (ABK) 耐性メチシリン耐性黄色ブドウ球菌 (MRSA) の分離頻度が一定の時期に増加したが, 病棟の担当者に交差感染の防止を指導することなどにより, その後はABK耐性MRSAの検出率は減少した. 多数検出された時期に由来するABK耐性MRSA 22株について, 薬剤感受性を含む生物学的表現型および<I>Sma I</I>を使用したパルスフィールドゲル電気泳動法 (PFGE) を組み合わせて疫学的検討を行った.<BR>ABK耐性MRSA株はA～Jの異なる10病棟に由来し, 外科系のA病棟由来が8株と最も多く, 以下B病棟3株, C, D, E病棟は各々2株, F, G, H, I, J病棟は各々1株であった. A病棟由来の8株では, 6株がPFGEで同一パターンを示した. PFGEにて同一パターンをとった6株は, 同様の薬剤感受性および生物学的性状パターンをとった. B病棟由来の3株のうち2株, F病棟由来の1株およびI病棟由来の1株も, PFGEは同じパターンをとり, 薬剤感受性や生物学的性状もA病棟由来の6株と同様であった.さらに, C, DおよびG病棟で分離された5株は, 各々類似したPFGEパターンをとっていた.<BR>MRSA感染症における治療薬剤を維持するためにも, 各医療施設においてABK耐性MRSAの動向を監視し, 施設内感染防止に努めることが必要と考える.
Arbekacin-resistant, methicillin-resistant <I>Staphylococcus aureus</I> was frequently isolated in Saitama Medical School Hospital during 1996 and 1998. The minimum inhibitory concentration for ABK was 8μg/ml in 14 strains, 16μg/ml in 6 strains, and 32μg/ml in 2 strains. The maximum isolation rate of these resistant strains in one month was 8%. Use of ABK in the hospital did not increase during the same period. The infection control team (ICT) of the hospital recognized the increase of resistant strains and started intervention for the hospital staff. The ICT instructed the staff of each ward to follow standard precautions for the prevention of nosocomial infections and the risk of ABKresistant MRSA was explained repeatedly. Thereafter, the isolation rate decreased to 3%.<BR>An epidemiological study was done using 22 strains of ABK-resistant MRSA that were isolated in this period. The strains originated from different patients and from 10 different wards, which were designated as wards A to J. Eight strains were isolated from surgical ward A, followed by the other wards (ward B: 3, C: 2, D: 2, E: 2, F: 1, G: 1, H: 1, I: 1, J: 1). The specimens from which ABKresistant MRSA were isolated were as follows, : sputum: 4, wound: 4, decubitus ulcer: 4, urine: 2, pus: 2, blood: 1, central venous catheter: 1, drainage tube: 1, tracheal aspirate: 1, skin: 1, stool: 1. Several investigations were done using these strains. Sensitivity tests for ABK, VCM, MINO, LVFX, FOM, IPM were performed by the standard method of the Japan Society for Chemotherapy. Coagulase types were determined. Production of toxic shock syndrome toxin-1 (TSST-1), enterotoxin, and β-lactamase was assayed. Pulse-field gel electrophoresis (PFGE) using <I>Sma I</I> was also done and differences were compared.<BR>Seven of the 8 strains from ward A showed the same drug sensitivity profile and biological phenotype. Two of the 3 strains from ward B and 2 strains from ward C were also identical by these methods. Six of the 8 strains from ward A were also identical by PFGE. These 6 isolates showed the same drug sensitivity pattern, same coagulase type, and same production of TSST-1 and enterotoxin. Two other strains from ward B, one strain from ward F, and one from ward I also showed the same PFGE pattern, drug sensitivity profile, and toxin profile as the 6 strains from ward A.<BR>Our data show that the same strains were transmitted around the hospital during the study period, although serious nosocomial infections due to ABK-resistant MRSA were avoided. Thus, intervention by the ICT in each ward was effective. ABK-resistant MRSA should be recognized as an important hospital pathogen and should be surveyed consistently.
- Kansenshogaku Zasshi
Kansenshogaku Zasshi 78(4), 305-311, 2004
The Japanese Association for Infectious Diseases