わが国では，Yersinia enterocolitica による食中毒は非常に少ない．しかし2012 年～2013 年にかけて全国で 4 事例の集団感染が報告された．東京都ではこのうち2 事例について検査を実施したのでその概要を報告する．事例1：2012 年8 月，合宿先の食事を喫食した高校生等39 名が腹痛，下痢，発熱等を呈したため検査を実施した．その結果，患者便28 検体中18 検体（64.3％）からY. enterocolitica 血清群O8 が検出された．合宿先の食事や環境材料からY. enterocolitica は検出されず，感染源は不明であった．事例2：2013年4月に寮の食事を喫食した学生52 名が下痢，発熱等を呈した．検査の結果，患者便および調理従事者糞便の合計24 検体からY. enterocolitica 血清群O8 が検出された．原因食品を特定するため，保存してあった食品の検査を行った．各食品にリン酸緩衝生理食塩水（PBS）を加え，4℃，21 日間増菌培養後，培養液を対象にail 遺伝子を対象としたリアルタイムPCR 法でスクリーニング試験を行った．その結果，1 検体（野菜サラダ）が陽性となったため，菌の分離を試みた．培養液中にはY. enterocolitica 以外の菌も非常に多く，培養液を直接CIN 寒天に塗抹した方法では分離が困難であった．そこで培養液のアルカリ処理（10 秒間）や免疫磁気ビーズ法により集菌する方法を検討した結果，効率的にY. enterocolitica を分離することが可能となった．事例2 は「野菜サラダ」を原因食品とした食中毒であると断定された．

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A 66-year-old Japanese male with a history of a rectal ulcer and rectovesical fistula following brachytherapy and radiotherapy for prostate cancer, who had undergone colostomy and vesicotomy presented with a painful peristomal ulcer of approximately 5×2.5cm adjacent to the direction of 6 oʼclock of the stoma in his left lower abdomen. Although he was admitted to be treated with intravenous antibiotics and topical debridement, the ulcer was rapidly increasing. In the laboratory findings, WBC was 12,400/μL, CRP was 16.9 mg/dL, ESR was 105mm in the first hour. Contrast enhanced CT images showed a wide high density area of skin and subcutaneous tissue around the stoma and dillitation of the transverse and descending colon. Colonoscopy showed furred profound ulcers in the rectum. A biopsy from the ulcer floor submitted to histopathology showed necrotic tissue with a mixed inflammatory infiltrates mainly composed of neutrophils and lymphocytes in the dermis. We suspected pyoderma gangrenosum with an inflammatory bowel disease in the beginning. Although he was started on oral prednisolone 60mg daily, the ulcer did not respond to treatment. Additional methylprednisolone pulse therapy, intravenous cyclosporine and granulocytapheresis were also ineffective. A biopsy specimen from the skin ulcer margin showed erythrophagocytosis by trophozoites of amebae which were identified on PAS stained slides. The PCR method and stool examination showed positive for Entamoeba histolytica (E. histolytica), but serum antibodies were negative. Within two weeks of treatment with oral metronidazole 2,250mg/day and topical metronidazole ointment, resolution of the ulcer was observed, then the prednisolone dosage was tapered. A split-thickness skin graft was used to cover the ulcer with a successful result. Even though we originally misdiagnosed this case, we finally reached a diagnosis of amebiasis. It is important to take account of amebiasis in the differential diagnosis of intractable ulcers which can be contaminated by feces.

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A 79-year-old man experienced severe chronic obstructive pulmonary disease (COPD) and was receiving treatment for ischemic heart disease. Starting from dizziness and chilliness, he lost consciousness after few days. He was taken to our emergency department. On initial evaluation, he complained of dyspnea and was afebrile with a pulse rate, blood pressure, and respiratory rate of 105 beats/min, 112/98 mmHg, and 28 breath/min, respectively. His respiratory sounds were clear and chest radiography did not show any abnormal shadows, but his arterial blood gas examination showed type II respiratory failure. Because the nasopharyngeal seasonal influenza A virus (IAV) test was positive, the patient was admitted with the diagnosis of acute exacerbation of COPD due to IAV. We administered peramivir, a specific anti-influenza drug, and started mechanical ventilation. Over time, he started to show signs of disseminated intravascular coagulation, such as multiple organ failure and thrombocytopenia. Subsequently, blood tests showed elevation of ferritin and soluble interleukin 2 receptor (sIL2R)；microscopic examination of the peripheral blood revealed hemophagocytosis. Secondary hemophagocytic lymphohistiocytosis (HLH) due to IAV was diagnosed and together with corticosteroid therapy, intravenous gamma globulin was administered from the 3^rd clinical day. The patint was saved with our early diagnosis and treatment of HLH and was discharged on the 92^nd clinical day. Viral-induced HLH, formerly known as virus-associated hemophagocytic syndrome (VAHS), leads to multiple organ failure due to a cytokine storm scattered by viral-infected pathogenic inflammatory cells. It is well known that pandemic swine flu causes secondary HLH leading to poor outcomes. Currently, not much is known about HLH due to seasonal flu；particularly, IAV (H3N2)-related HLH cases are rare and reported cases showed poor outcomes as well. With an early diagnosis and minimum immunotherapy, we report herein on a case of IAV (H3N2)-related HLH which was treated successfully.

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We report herein on the case of a 33-year-old Japanese man in whom an abnormal shadow was detected on chest radiography during a medical checkup after a 1-year-stay in Mexico. Chest computed tomography showed a nodule in the left lower lobe adjacent to the visceral pleura. Histopathologic examination of a thoracoscopic partial pulmonary resection specimen showed coagulation necrosis with a number of yeast-like forms on Grocott staining. In addition, serum anti-Histoplasma antibody positivity was detected with an enzyme-linked immunosorbent assay, and Histoplasma-specific nested real-time polymerase chain reaction results were positive in the pulmonary region. Finally, pulmonary histoplasmosis was diagnosed, and treatment with itraconazole was initiated. The patientʼs wife who had accompanied him to Mexico was asymptomatic and was not found to have histoplasmosis based on diagnostic imaging and serological findings. Although rare in Japan, histoplasmosis should be considered in the differential diagnosis of pulmonary lesions in patients who have returned from travel to endemic areas.

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