A total of 799 Shigella strains, consisting of 584 imported and 215 domestic strains isolated in Tokyo between 2000 and 2017, were analyzed. To reveal the current state of the bacteriological and epidemiological characteristics of bacterial dysentery, the isolated species, their serovar distribution, and their resistance profiles to antibiotics were examined.

Shigella sonnei was found to be the most prevalent species among both imported and domestic strains, followed by Shigella flexneri. In addition, 25 strains with provisional new serovars of Shigella were isolated.

Antimicrobial susceptibility testing using 10 drugs showed that 94.5% of the strains were resistant to at least one of the drugs examined. The antibiotic resistance profiles of the resistant strains varied among the 57 serovars. A triple antibiotic resistance type resistant to tetracycline (TC)/streptomycin (SM)/trimethoprim-sulfamethoxazole (ST) was the most frequent resistance type in both groups. An increase in the frequency of resistance to fluoroquinolones was observed over the 18-year study period. Furthermore, 3.3% of the tested strains were found to be extended-spectrum β-lactamase (ESBL) producers. Among the resistant strains isolated from domestic cases, 16.3% showed a pattern of two-drug resistance to TC and SM. These were presumed to be related to an outbreak among men having sex with men (MSM).

In order to understand the actual current epidemiology of outbreaks of bacterial dysentery, we found it useful to analyze the serovars of the isolated strains, their antibiotic resistance patterns, their pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem-repeat analysis (MLVA) patterns, etc., together with the patient information.

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.