稲葉 正人

OBJECTIVES: This study aimed to identify factors deterring secondary household transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from SARS-CoV-2-positive cohabitants. METHODS: A case-control study was conducted with 272 healthcare workers in close contacts with SARS-CoV-2-positive cohabitants. Logistic regression modeling was employed to determine the factors independently associated with secondary household transmission. RESULTS: A SARS-CoV-2 infection within the past 6 months was the most protective factor against secondary household transmission (adjusted odds ratio = 0.07, 95% confidence interval: 0.01-0.61, P < 0.05). Home isolation and older age of primary index case (7-12, ≥18 years) were also associated with a reduced risk. Both monovalent and bivalent messenger ribonucleic acid booster vaccinations exhibited potential protective tendencies, but were not statistically significant. Additionally, bivalent vaccines did not demonstrate a clear advantage over monovalent vaccines. CONCLUSION: A recent history of SARS-CoV-2 infection, home isolation of positive cohabitants, and older age of primary index cases were positively associated with a reduced risk of secondary household transmission. Regarding booster vaccinations, data from a single center with a limited sample size may not capture all statistically significant differences, necessitating broader studies.

Objectives: To establish a point-of-care test for coronavirus disease 2019 (COVID-19), we developed a dry loop-mediated isothermal amplification (LAMP) method to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Methods: We carried out reverse transcription (RT)-LAMP using the Loopamp SARS-CoV-2 Detection kit (Eiken Chemical, Tokyo, Japan). The entire mixture, except for the primers, is dried and immobilized inside the tube lid. Results: To determine the specificity of the kit, 22 viruses associated with respiratory infections, including SARS-CoV-2, were tested. The sensitivity of this assay, determined by either a real-time turbidity assay or colorimetric change of the reaction mixture, as evaluated by the naked eye or under illumination with ultraviolet light, was 10 copies/reaction. No LAMP product was detected in reactions performed with RNA from any pathogens other than SARS-CoV-2. After completing an initial validation analysis, we analyzed 24 nasopharyngeal swab specimens collected from patients suspected to have COVID-19. Of the 24 samples, 19 (79.2%) were determined by real-time RT-PCR analysis as being positive for SARS-CoV-2 RNA. Using the Loopamp SARS-CoV-2 Detection kit, we detected SARS-CoV-2 RNA in 15 (62.5%) of the 24 samples. Thus, the sensitivity, specificity, positive predictive value, and negative predictive values of the Loopamp 2019-CoV-2 detection reagent kit were 78.9%, 100%, 100%, and 55.6%, respectively. Conclusions: The dry LAMP method for detecting SARS-CoV-2 RNA is fast and easy to use, and its reagents can be stored at 4°C, solving the cold chain problem; thus, it represents a promising tool for COVID-19 diagnosis in developing countries.

Carbapenemase-producing Escherichia coli sequence type (ST) 648 strains were isolated from two international visitors without previous medical exposure from Southeast Asian countries in a hospital in Japan. One isolate, FUJ80154, carried bla(NDM-5) in a complex class 1 integron on an IncFIB/FII plasmid; the other isolate, FUJ80155, carried two copies of bla(OXA-48) on the chromosome flanked by IS1R on both sides. The core-genome based-phylogenetic analysis with publicly available genome data of E. coli ST648 carrying bla(NDM-5) or bla(OXA-48-like) demonstrated high genetic similarity between FUJ80154 and NDM-5-prooducing E. coli ST648 strains isolated in South and Southeast Asian countries. On the other hand, no closely related isolates of FUJ80155 were identified. In the absence of prior hospitalization overseas, neither patient had qualified for routine screening of multidrug-resistant organisms, and the isolates were incidentally identified in cultures ordered at the discretion of the treating physician.IMPORTANCE Although patients with history of international hospitalization are often subject to screening for multidrug-resistant organisms, it is unclear whether patients who reside in countries where carbapenemase-producing Enterobacterales (CPE) is endemic but have no history of local hospitalization contribute to the transmission of CPE. In this study, NDM-5-producing and OXA-48-producing Escherichia coli sequence type (ST) 648, a recently recognized high-risk, multidrug-resistant clone, were detected from two overseas visitors without previous medical exposure. The findings of this study suggest that active surveillance culture on admission to hospital may be considered for travelers from countries with endemicity of carbapenem-resistant organisms even without history of local hospitalization and underscore the need to monitor cross-border transmission of high-risk clones, such as carbapenemase-producing E. coli ST648.

Serological tests for detection of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Abs in blood are expected to identify individuals who have acquired immunity against SARS-CoV-2 and indication of seroprevalence of SARS-CoV-2 infection. Many serological tests have been developed to detect Abs against SARS-CoV-2. However, these tests have considerable variations in their specificity and sensitivity, and whether they can predict levels of neutralizing activity is yet to be determined. This study aimed to investigate the kinetics and neutralizing activity of various Ag-specific Ab isotypes against SARS-CoV-2 in serum of coronavirus disease 2019 (COVID-19) patients confirmed via PCR test. We developed IgG, IgM, and IgA measurement assays for each Ag, including receptor-binding domain (RBD) of spike (S) protein, S1 domain, full-length S protein, S trimer, and nucleocapsid (N) domain, based on ELISA. The assays of the S protein for all isotypes showed high specificity, whereas the assays for all isotypes against N protein showed lower specificity. The sensitivity of all Ag-specific Ab isotypes depended on the timing of the serum collection and all of them, except for IgM against N protein, reached more than 90% at 15-21 d postsymptom onset. The best correlation with virus-neutralizing activity was found for IgG against RBD, and levels of IgG against RBD in sera from four patients with severe COVID-19 increased concordantly with neutralizing activity. Our results provide valuable information regarding the selection of serological test for seroprevalence and vaccine evaluation studies.

OBJECTIVE: Reverse transcription loop-mediated isothermal amplification (RT-LAMP) has been validated for diagnosis of several viral infections. However, its diagnostic accuracy in detecting SARS-CoV-2 in real-life clinical settings remains unclear. The aim of this study was to determine the diagnostic sensitivity and specificity of RT-LAMP compared to reverse transcription-quantitative polymerase chain reaction (RT-qPCR) over the disease course of COVID-19. METHODS: A total of 124 nasopharyngeal swab samples obtained from 24 COVID-19 patients were tested by RT-LAMP and RT-qPCR. Sensitivities and specificities of RT-LAMP compared with RT-qPCR were analyzed as a function of time from onset. RESULTS: Up to the 9th day after onset, the RT-LAMP had positivity of 92.8%, and the sensitivity and specificity compared with RT-qPCR was 100%. After the 10th day of onset, however, the positivity of RT-LAMP decreased to less than 25%, and concordance of positivity between the two methods was below 60%. The limit of detection of RT-LAMP was 6.7 copies/reaction. CONCLUSIONS: Until the 9th day after the onset of symptoms, RT-LAMP had the same diagnostic accuracy as RT-qPCR. These finding suggest that RT-LAMP can be used as a diagnostic tool for COVID-19 as an alternative to RT-qPCR in the acute symptomatic phase of COVID-19.

Pediatric cases of the coronavirus disease 2019 (COVID-19) are generally mild or asymptomatic, and are usually detected by virological examination following close contact with COVID-19 patients, often the children's parents. The detailed clinical features and virological data of pediatric patients with COVID-19, particularly young infants, remain unclear. Here, the clinical and virological characteristics of four children with COVID-19 including two young infants were investigated. One- and 4-month-old boys with COVID-19 were both asymptomatic, and seroconversion was demonstrated. These findings suggest that even young infants can mount an immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), despite having weaker immune defenses than adolescents and adults. Three-year-old boy, who was SARS-CoV-2-negative, was admitted to the same room as his SARS-CoV-2-positive father due to the lack of caregivers. Although he was asymptomatic, he had seroconverted to SARS-CoV-2. Eleven-year-old boy, who was sibling of the 3-year-old boy, was also SARS-CoV-2-negative. He was isolated in his own room and did not seroconvert. If young children are SARS-CoV-2 negative, they should be isolated from their SARS-CoV-2-positive parents. This may be difficult in practice, if parents with COVID-19 are the only available caregivers. In such situations, the most appropriate measures should be taken for each patient.

Hypothermia is a significant sign of sepsis, which is associated with poor prognosis, but few mechanisms underlying the regulation of hypothermia are known. Inducible nitric oxide synthase (iNOS) is a key inflammatory mediator of sepsis. However, the therapeutic benefit of iNOS inhibition in sepsis is still controversial, and requires elucidation in an accurate model system. In this study, wild-type (WT) mice showed temperature drops in a biphasic manner at the early and late phase of sepsis, and all mice died within 48 h of sepsis. In contrast, iNOS-knockout (KO) mice never showed the second temperature drop and exhibited improved mortality. Plasma nitric oxide (NO) levels of WT mice increased in the late phase of sepsis and correlated to hypothermia. The results indicate that iNOS-derived NO during the late phase of sepsis caused vasodilation-induced hypothermia and a lethal hypodynamic state. The expression of the iNOS mRNA was high in the lung of WT mice with sepsis, which reflects the pathology of acute respiratory distress syndrome (ARDS). We obtained the results in a modified keyhole-type cecal ligation and puncture model of septic shock induced by minimally invasive surgery. In this accurate and reproducible model system, we transplanted the bone marrow cells of GFP transgenic mice into WT and iNOS-KO mice, and evaluated the role of increased pulmonary iNOS expression in cell migration during the late phase of sepsis. We also investigated the quantity and type of bone marrow-derived cells (BMDCs) in the lung. The number of BMDCs in the lung of iNOS-KO mice was less than that in the lung of WT mice. The major BMDCs populations were CD11b-positive, iNOS-negative cells in WT mice, and Gr-1-positive cells in iNOS-KO mice that expressed iNOS. These results suggest that sustained hypothermia may be a beneficial guide for future iNOS-targeted therapy of sepsis, and that iNOS modulated the migratory efficiency and cell type of BMDCs in septic ARDS.

Prompt法で菌液を調整しMicroScan WalkAway^&reg;で判定する手法（MW prompt）でmethicillin-resistant Staphylococcus aureus（MRSA）に対するvancomycin（VCM）の最小阻止濃度（minimal inhibitory concentration, MIC）を測定した場合，他機種や基準比濁法で測定したMICより高く判定される危険性が指摘されている。そのため，MW promptでVCMのMICが2&mu;g/mlと判定されたMRSA感染症に対するVCMの有効性については不明な部分が多い。今回MRSA肺炎に対しVCMで治療した11例について，MW promptで測定したMIC別の臨床的，細菌学的有効性を検討した。細菌学的有効性を認めた症例は，MIC 1&mu;g/mlの群が3例（50％）であったのに対し，MIC 2&mu;g/mlの群は0例であった。臨床的有効性を認めた症例は，MIC 1&mu;g/mlの群が4例（67％）であったのに対し，MIC 2&mu;g/mlの群は1例（20％）のみであった。今回の検討ではMW promptでMICが2&mu;g/mlと判定された場合，VCMの有効性は過去の報告と同様に，1&mu;g/mlの場合より低い可能性が示唆された。

The host stress hormone norepinephrine (NE), also called noradrenaline, is reported to augment bacterial growth and pathogenicity, but few studies have focused on the effect of NE on the activity of antimicrobials. The aim of this study was to clarify whether NE affects antimicrobial activity against multidrug-resistant Acinetobacter baumannii (MDR-AB). Time-kill studies of tigecycline (TIG) and colistin (COL) against MDR-AB as well as assays for factors contributing to antibiotic resistance were performed using MDR-AB clinical strains both in the presence and absence of 10 µM NE. In addition, expression of three efflux pump genes (adeB, adeJ and adeG) in the presence and absence of NE was analysed by quantitative reverse transcription PCR. Viable bacterial cell counts in TIG-supplemented medium containing NE were significantly increased compared with those in medium without NE. In contrast, NE had little influence on viable bacterial cell counts in the presence of COL. NE-supplemented medium resulted in an ca. 2 log increase in growth and in bacterial cell numbers adhering on polyurethane, silicone and polyvinylchloride surfaces. Amounts of biofilm in the presence of NE were ca. 3-fold higher than without NE. Expression of the adeG gene was upregulated 4-6-fold in the presence of NE. In conclusion, NE augmented factors contributing to antibiotic resistance and markedly reduced the in vitro antibacterial activity of TIG against MDR-AB. These findings suggest that NE treatment may contribute to the failure of TIG therapy in patients with MDR-AB infections.

In the emergency and critical care medicine, infection is easy to merge to various basic conditions and diseases. In the social structure aging in critical care, the immune weakness was revealed as the result of severe infection and septic shock in the reduced function of neutrophils and lymphocytes. In the life-saving emergency care, cardiovascular diseases, diabetes, chronic renal failure and lever dysfunction are often observed, and the underlying diseases have the foundation of biological invasion after a first inflammatory attack of surgery, trauma, burn, and systemic injury. It will be placed into a susceptible situation such as artificial respiratory management. In this review, we discussed severe infection in emergency and critical care. It is necessary to pay attention to the drug resistance bacterias in own critical care setting by trends.