細菌性赤痢の細菌学的，疫学的特徴を把握するため，2000年～2017年に東京都で分離・収集された赤痢菌を対象に，その菌種，血清型，薬剤耐性菌出現状況について比較検討した．

輸入事例由来584株と国内事例由来215株における菌種別検出頻度は，両由来株ともShigella sonnei，次いでShigella flexneriが高かった．また，新血清型として提案されている赤痢菌が25株分離された．

10種薬剤について実施した薬剤感受性試験では，94.5％がいずれか1薬剤以上に耐性であった．その耐性パターンは全体で57種類認められたが，両由来株ともテトラサイクリン（TC），ストレプトマイシン（SM），スルファメトキサゾール・トリメトプリム合剤（ST）の3剤耐性が最も高頻度であった．調査した18年間でフルオロキノロン系薬剤への耐性頻度の上昇が確認され，また，基質特異性拡張型β-ラクタマーゼ（ESBL）産生株も認められた．国内事例由来株のうち，特定の耐性パターンの集積がみられた株について分子疫学的解析を実施したところ，男性間性的接触者（MSM）関連の広域散発事例であることが判明した．患者情報と組み合わせた菌株の細菌学的・分子疫学的解析結果は，細菌性赤痢の実態把握に有用であった．今後も赤痢菌株の解析を継続して行い，情報を発信していくことが必要であると考えられた．

A 67-year-old Japanese woman with a history of contact with a COVID-19 patient presented with a one-day history of fever, malaise, and dyspnea, and was hospitalized with a positive nasopharyngeal swab test for SARS-CoV-2 LAMP. Chest CT revealed bilateral patchy infiltrates. The patient was treated with remdesivir and dexamethasone and supplemental oxygen supplied via a nasal cannula. The supplemental oxygen therapy was continued for 6 days, and the drug administration was completed on the 10th day of hospitalization. The patient was then scheduled to be discharged, when she developed severe hyponatremia with a serum Na level of 110 mEq/L, but no consciousness disorder.

The patient was diagnosed as having SIADH after several examinations suggesting higher levels of secretion of antidiuretic hormone, with a higher specific gravity of the urine than that of the serum, in addition to evidence of normal functioning of the thyroid, adrenal, and pituitary glands, and of the liver and kidneys. Whole-body CT showed no evidence of any tumors. The hospitalization was extended for correcting the serum sodium levels by restriction of water intake. It was assumed that the SIADH was caused by COVID-19, presumably by the elevated serum IL-6 levels inducing secretion of ADH, similar to the phenomenon reported in other inflammatory diseases associated with elevated serum IL-6 levels.

COVID-19 could lead to SIADH due of unresolved systemic inflammation even in the absence of worsening of the findings of chest imaging after the completion of antiviral treatments. Further studies are required to evaluate the correlation between the inflammatory state (e.g., serum concentration of IL-6) and serum ADH level causing hyponatremia during the clinical course of COVID-19.

The patient was a 2-year 1-month-old boy who had undergone hypospadias repair 2 months earlier. He was brought to us with a 2-day history of fever and pain while urinating. A neighborhood doctor noted increased levels of inflammatory markers and the patient was referred to our hospital. He was admitted to our hospital and at admission, laboratory examination revealed elevated values of the peripheral blood leukocyte count (21,900/μL; neutrophils 82.5%) and serum C-reactive protein (CRP) level (13.0mg/dL). Urinalysis revealed pyuria, with a white blood cell count of 100 or more/high power field (HPF). Microscopic examination of the urine revealed phagocytozed Gram-positive rods in the white cells. The patient was diagnosed as having urinary tract infection and initiated on treatment with vancomycin. On the third day of hospitalization, the fever resolved, the inflammatory reaction decreased, and the pyuria improved. Vancomycin was administered for 10 days, and the patient was discharged on the 12th day of admission. Actinotignum schaalii was isolated and identified by culture of a urine specimen collected via a catheter at the time of admission. In recent years, there have been some reports in Japan of urinary tract infection caused by A. schaalii in children. When urinary tract infection is suspected, microscopic examination of Gram-stained specimens of the urine is important. If Gram-positive rods are observed under the microscope, it is necessary to consider the possibility of anaerobic bacteria and immediately carry out anaerobic culture. In addition, background diseases of the urinary system, such as urinary tract malformations, appear to predispose to urinary tract infections caused by A. schaalii, and further examination is needed.

Moraxella catarrhalis is a common causative bacterium of otitis media and respiratory tract infection in children. Childhood-onset M. catarrhalis bacteremia is more common in children with underlying conditions, such as immunodeficiency, or those using a nasal device. In children without underlying conditions, the onset is usually at younger than 2 years of age.

We encountered a case of M. catarrhalis bacteremia in a previously healthy 3-year-old boy. The patient was hospitalized with a 5-day history of fever. Physical examination on admission showed redness and swelling of the ear drums bilaterally. Blood culture and upper nasopharyngeal swab culture both grew M. catarrhalis, which led to the diagnosis of bacteremia and otitis media caused by this organism. The patient was treated with intravenous cefotaxime for 3 days and sulbactam/ampicillin for the subsequent 3 days, followed by oral clavulanate/amoxicillin for 8 days, with good response. Absence of abnormalities in immunological screening tests and absence of any significant past medical history suggested that the patient was not immunocompromised.

During the COVID-19 pandemic, nosocomial infections in healthcare facilities were frequent. A COVID-19 cluster was identified at a long-term care facility, but due to the disastrous collapse of the healthcare system, patients could not be transported and had to be treated locally. In this case, from the day of identification of the cluster, the infection control team took the lead in providing support in cooperation with the infectious disease treatment and disaster medicine teams. In addition to on-site support, remote support was provided using electronic medical records connected via a virtual private network. By the ninth day after the outbreak, 14 patients and 6 healthcare professionals were confirmed as having COVID-19. However, the outbreak was contained without any fatality.

Vaccines are considered as one of the effective tools for tackling the COVID-19 pandemic. At the same time, however, information regarding the adverse effects of the vaccines must be collected and analyzed carefully. We encountered the case of an 87-year-old woman who was suspected as having drug-induced lung injury as a side effect of the BNT162b2 COVID-19 vaccine (Pfizer/BioNTech). Four days after the second vaccination, the patient developed fever, dyspnea, and cough. Computed tomography showed ground-glass opacities in both lung fields, and the pneumonia improved rapidly with steroid treatment. Since there was no other potential cause than the vaccine, the condition was strongly suspected as drug-induced lung injury caused by the vaccine. The results of a drug-induced lymphocyte stimulation test also supported this diagnosis. While the COVID-19 vaccine is reported to exert high efficacy, the frequency of lung injury caused by the vaccine remains unknown. Therefore, it is necessary to pay attention to the physical condition of persons after COVID-19 vaccination.