適正な抗生剤使用にもかかわらず疣腫の増大・増加が認められた感染性心内膜炎の1例

A Case of Infective Endocarditis in whom Increased Size and Amount of Vegetation was Observed Despite Appropriate Antimicrobial Therapy

要旨　患者は33歳，男性．心室中隔欠損症と診断されるも放置．今回，大動脈弁疣腫と血液培養でのStreptococcus viridans検出にて，感染性心内膜炎と診断された．高感受性であるPCG2,400万単位＋GM120mgを，有効血中濃度であることを確認したうえで投与した．投与開始1週間後から一度低下した炎症反応が再上昇し，肺膿瘍が発症した．また，大動脈弁の疣腫径が増大し，僧帽弁前尖後面に新たな疣腫が出現した．しかし，抗生剤使用の適正性が再確認されたため，PCG＋GMの継続投与を経て，弁・欠損孔修復術を施行した．術後は炎症反応の上昇もなく順調に経過した．

　感染性心内膜炎では，適正な抗生剤使用下でもその開始期には疣腫径の増大や炎症反応の高値遅延など適正性を疑問視する現象が生じうる．臨床所見の推移を注視するとともに，抗生剤の適正使用に関わる薬剤感受性・血中濃度の確認を怠らぬ必要がある．

　A 33-year-old male was admitted because of a ventricular septal defect(VSD) complicated with infective endocarditis, diagnosed by the findings of vegetation on the aortic valve and the detection of Streptococcus viridans in blood cultures. Despite the administration of antibiotic agents including PCG and GM confirmed as the appropriate manner of use by the investigation with antimicrobial sensitivity and pharmacokinesis, the inflammatory response in blood increased concomitant with increased size and amount of vegetation and embolic pulmonary abscesses. However, dare to continued the same antibiotic regimen because of the adequacy of these drug use reconfirmed, and thereafter the inflammatory response decreased again. After we undertook surgical repair with aortic valve replacement and patch closure of VSD, the patient improved without any　additional complications.

　Some clinical phenomena by which to doubt the adequacy of antibiotic use, such as increased amount of vegetation or persistent increase in the inflammatory response can occur during the course of infective endocarditis. We should always confirm the adequacy of antibiotic use through antimicrobial sensitivity and pharmacokinesis not to misinterpret such seemingly refractory cases with infective endocarditis.