日本感染症学会感染症遺伝子検査委員会では感染症遺伝子検査の現状と要望を把握するために2018 年 10 月から11 月に会員を対象に第2 回のWeb アンケートを実施した．回答者は201 名であり，感染症専門医は50.7% であった．病床数では500 床以上が48.8% と最も多く，微生物検査室が院内にあるのは82.6% であった．感染防止対策加算については，加算1 を取得しているのが81.6% であった．感染症遺伝子検査の意義については，感染症診療と感染制御において重要・必要だと思うという回答がそれぞれ92.5% と89.6% であった．また，感染症遺伝子検査を実施するのに有用な場面については，前回調査と同様に培養困難（長期培養が必要）な病原体の迅速検出が可能という回答が89.1% と最も多かった．前回調査と比較すると，薬剤耐性遺伝子や毒素の検出が可能と回答した割合と網羅的に病原微生物を検出可能と回答した割合が前回調査よりも有意に増加していた．感染症遺伝子検査を自施設で実施しているのは36.3%，外注で実施しているのは33.8% であった．自施設で全自動遺伝子検査システムを使用していたのは17.9% であり，前回調査の7.4% から有意に増加していた．多項目遺伝子関連検査については，導入しているのが7.0%，検討しているのが11.9% であった．多項目遺伝子検査を導入している施設では，全診療科で実施しているのが57.1%，依頼があった場合のみ実施が35.7%，一部の診療科のみで実施が7.1% であった．今回の調査において，感染症遺伝子検査に対するニーズが高いことと全自動遺伝子検査システムの導入が進みつつあることが明らかとなった．多項目遺伝子関連検査については，臨床背景等を含めて総合的な判断が必要であるため，当委員会が公表している実施指針で「検査結果を適正に判断するために感染症専門医もしくは臨床検査専門医は必須」としている．そのため，今後は，感染症遺伝子検査の運用面も含めて実態を把握していくことが重要であると考えられる．

厚生労働省は薬剤耐性（AMR）アクションプランを策定し，抗菌薬の適正使用を求めている．この取組に賛同し抗菌薬処方の現状を省みるため，今回の研究を思い立った．
保険薬局の協力を得て，自施設の抗菌薬処方量についてフィードバックを受けた．応需処方箋から抗菌薬処方量と処方箋枚数を調べ，経年動向を調べ自分の抗菌薬処方の現状を省みた．また，同様の手法で近隣のクリニックの抗菌薬処方動向も調査した．
抗菌薬処方枚数は処方量と正の相関を示した．対受診患者1,000 人の抗菌薬処方枚数は2009 年125，2011 年199.3，2014 年173.3，2016 年171.1，2017 年103.0，2018 年38.6 であった．「抗微生物薬適正使用の手引き」が公表された2017 年下半期から抗菌薬処方枚数が減少し，2011 年と比較し2018 年は処方全体の－80.6％であり，経口セフェム系薬，キノロン系薬，マクロライド系薬に限ると－89.6％でありアクションプランの目標を達成していた．抗菌薬種類別にみると，ペニシリン系薬主体の治療で対応可能であった．第3 世代経口セフェム系薬の微増傾向が判明したが，第1 世代セフェム系薬でも対応可能な皮膚疾患等に第3 世代セフェム系薬の処方を行っていた．近隣耳鼻いんこう科クリニックの抗菌薬処方数を検討したところ，著明な減少を認め，地域における抗菌薬処方の減少を確認できた．
処方枚数から抗菌薬の処方量の動向を推定することは可能であり，自己の抗菌薬処方の傾向を省みることにより抗菌薬不必要，不適切使用の低減に繋がると考えられる．

2009 年から2018 年までの10 年間に当院小児科において有熱性尿路感染症の診断で入院した患者320 名・339 例の尿より分離された腸内細菌科細菌341 株を対象とし抗菌薬感受性を調査した．入院時の年齢は日齢11～14 歳9 カ月（中央値：日齢174），男児195 例，女児144 例であった．菌株はEscherichia coli が297 株（87.1%）で大半を占めた．extended-spectrum β-lactamase（ESBL）産生菌は16 株（4.7%）であり，すべてE. coli であった．CTX 耐性率は2014 年までは2～4% と低値で安定していたが，2015 年以降耐性株が増加し，直近2 年は10% 以上を占めた．LVFX 耐性率も近年上昇傾向をみとめ2018 年は13% を超えた．一方でCMZ は感性率90% 以上を保っていた．TAZ/PIPC の感性率は2010 年以降95% 以上，MEPM の感性率は全期間100% であった．
小児における腸内細菌科細菌の抗菌薬耐性化は現時点では成人と比較すると深刻ではないといえるが，ESBL 産生菌やAmpC 過剰産生菌など多剤耐性菌の増加傾向をみとめており，今後も継続して抗菌薬感受性の推移を監視することが必要と考えられた．

A 17-day-old female infant presenting with fever and diarrhea was admitted to our hospital. We performed a sepsis work-up for neonatal fever. The blood test did not show any increase of inflammatory reaction and urinalysis revealed nothing in particular, either. The cerebrospinal fluid cell count was not raised and bacterial cultures of blood, cerebrospinal fluid and urine were all negative. Human parechovirus was finally detected with a multiplex PCR system (FilmArray Meningitis/Encephalitis Panel) in the cerebrospinal fluid. We diagnosed her as having human parechovirus infection and started maintenance intravenous fluid administration only. Five days later, her temperature became normal and she was discharged another three days later. The differential diagnosis of severe infections such as sepsis, meningitis or encephalitis is essential for neonatal fever. The early diagnosis of the pathogen results is of benefit in both severe central nervous infection cases and relatively mild cases. However, the spread of rapid diagnostic procedures in Japan is limited at present to some pathogens, and a definitive diagnosis is often delayed. The multiplex PCR system that we used in this case may be useful for early diagnosis and for prevention of unnecessary treatment such as antimicrobial agents and antiviral drugs. Convenience and cost are considered as future problems of the multiplex PCR test. The reduction of costs and the continuous review of an appropriate panel are needed. It is also important to select appropriate cases to examine.

A 39-year-old woman was treated for pulmonary hypertension with treprostinil administered via a Hickman catheter. She developed a fever and inflammatory signs at the exit site of the Hickman catheter were observed. On day 2, antimicrobial therapy (ceftriaxone) was started and the Hickman catheter was exchanged. Rhizobium radiobacter was detected from the catheter tip culture. Fever reduction was not observed and her blood culture remained positive despite treatment. We switched antimicrobial therapy from ceftriaxone to tazobactam/piperacillin plus amikacin, but the treatment was not effective. Although enhanced computed tomography scan and transesophageal echocardiography were performed, there were no findings of infectious foci. On day 28, the catheter was exchanged again, but the blood culture on day 29 was still positive. On day 40, we exchanged the catheter again, and this time we exchanged the catheter kit and the injection cap that connected the catheter and drug bag. R. radiobacter was detected from the injection cap. She was afebrile from day 41, and on day 46 her blood culture became negative. Therefore, we diagnosed the problem as catheter related blood stream infection by R. radiobacter, and concluded that the location of infection was the injection cap. Antimicrobial therapy was continued until day 59, and she was subsequently discharged. We experienced a case of catheter related blood stream infection from a Hickman catheter, and it was difficult ―to find the source of infection.

Mycobacterium haemophilum is a non-tuberculous mycobacterium that causes systemic infections involving the skin and soft tissue, pulmonary system, bones and joints, particularly in immunocompromised patients. We report herein on a rare case of cutaneously disseminated M. haemophilum infection accompanying blood stream infection in a patient following renal transplantation. A 41-year-old Japanese woman who had undergone a kidney transplant 5 years previously was referred to us due to prolonged undetermined fever. She was taking prednisolone, tacrolimus, everolimus, and mycophenolate mofetil at the time of hospitalization. In addition to the high fever, the patient suffered from chronic erythema emerging over her body. The results of Gram staining were suggestive of mycobacterium infection, and a genetic analysis based on sequencing of the hsp65 and rpoB genes finally identified this case to be a disseminated M. haemophilum infection. After we initiated combination therapy including clarithromycin, ciprofloxacin, and rifabutin, the patientʼs dermatological condition ameliorated and she was discharged 3 months later in remission.
Diagnosis of non-tuberculous mycobacterial infection is challenging from the aspect of both the clinical and laboratory approaches. In this case, careful observation of Gram staining in laboratory was a clue to the diagnosis of the infection. Among non-tuberculous mycobacteria, M. haemophilum is clinically a rare pathogen. Difficulty in identifying the pathogen may be a reason for its lower prevalence. M. haemophilum prefers a lower temperature (30-32℃) and requires iron or hemin (e.g. a blood agar plate) for proliferation, although we noticed that a chocolate agar plate in 5% CO₂ at 35℃ gave the best culture conditions in this case. In case of refractory and unidentified dermatologic diseases, attention should be paid to the possibility of mycobacterial infection.

An 11-year-old boy, who had undergone repair of a total anomalous pulmonary venous connection (TAPVC) and double outlet right ventricle (DORV) during infancy, presented with a headache. Sinusitis and dental caries were also observed. Computed tomography (CT) scan revealed a mass on the left frontal lobe of his brain. He was diagnosed as having a brain abscess (BA) based on the magnetic resonance imaging (MRI) findings. The BA was drained, and the patient was treated with 300mg/kg cefotaxime and 40mg/kg metronidazole per day intravenously as empirical therapy. The melting temperature mapping method revealed Streptococcus intermedius in the intracranial pus 4.5 h after drainage. The echocardiogram showed no infective endocarditis. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDITOF MS) detected the same organism from the pus 3 days after drainage. The organism was pansusceptible, and treatment was continued because the presence of anaerobic, Gram-negative bacilli was suspected in the sinus cavity and dental plaque. The brain abscess, however, grew to 5cm 3 weeks after the drainage even under continued antibiotic therapy. A craniotomy was performed, and the entire abscess, including the abscess wall, was excised. Antibiotics were continued for 6 weeks, and the patient recovered completely. Rapid detection empirical therapy by administering appropriate antibiotics and total excision of the abscess successfully treated the patient. Thus, the use of rapid diagnostic tests and the melting temperature mapping method had significant impacts on effective antimicrobial stewardship.

Most of prosthetic joint infection (PJI) cases require surgical treatment and appropriate antimicrobial therapy over a long period, so identification of the causative microorganisms is very important to give appropriate antimicrobial therapy for affected patients. However, the utility of joint fluid cultures has been questioned based on relatively high false negative rates because of previous antimicrobial therapy and biofilm formation in PJI. In PJI patients with negative results of joint fluid cultures, PCR testing of the infected joint fluid or tissue is reported to be useful to identify the causative microorganisms.
We report herein on a case of PJI caused by Pseudomonas aeruginosa which was detected with PCR of periprosthetic joint fluid. The patient was treated successfully with intravenous, combined antimicrobial therapy followed by long-term oral antimicrobial therapy, which targeted P. aeruginosa, without surgery. In cases with high clinical suspicion of PJI but negative cultures, PCR tests might be helpful to identify the causative microorganisms.