Virucidal efficacy of hypochlorous acid water for aqueous phase and atomization against SARS-CoV-2.

Coronavirus disease 2019 (COVID-19) is an infectious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that emerged at the end of 2019. SARS-CoV-2 can be transmitted through droplets, aerosols, and fomites. Disinfectants such as alcohol, quaternary ammonium salts, and chlorine-releasing agents, including hypochlorous acid, are used to prevent the spread of SARS-CoV-2 infection. In the present study, we investigated the efficacy of ionless hypochlorous acid water (HOCl) in suspension and by spraying to inactivate SARS-CoV-2. The virucidal efficacy of HOCl solution in tests against SARS-CoV-2 was evaluated as 50% tissue culture infectious dose. Although the presence of organic compounds influenced the virucidal efficacy, HOCl treatment for 20 s was significantly effective to inactivate Wuhan and Delta strains in the suspension test. HOCl atomization for several hours significantly reduced the SARS-CoV-2 attached to plastic plates. These results indicate that HOCl solution with elimination containing NaCl and other ions may have high virucidal efficacy against SARS-CoV-2. This study provides important information about the virucidal efficacy and use of HOCl solution.

Single nucleotide polymorphism leads to daptomycin resistance causing amino acid substitution-T345I in MprF of clinically isolated MRSA strains.

Daptomycin (DAP) is one of the most potent antibiotics used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. Due to an increase in its administration for combating MRSA infections, DAP non-susceptible (DAP-NS) MRSA strains have recently been reported in clinical settings. The presence of single nucleotide polymorphisms (SNPs) in the multiple peptide resistance factor (mprF) gene is the most frequently reported cause for the evolution of DAP-NS MRSA strains; however, there are some variations of SNPs that could lead to DAP-NS. In this study, we used two clinical MRSA strains, including DAP susceptible (DAP-S) and DAP-NS, isolated from the same patient at different time points. We introduced T345I SNP to mprF of the DAP-S MRSA strain using the gene exchange method with pIMAY vector. Further, we investigated the phenotype of the mutant strain, including drug susceptibility, cell surface positive charge, and growth speed. The mutant strain exhibited (i) resistance to DAP, (ii) up-regulation of positive surface charge, (iii) slower growth speed, and (iv) thickened cell walls. Hence, the SNP in mprF may have caused an up-regulation in MprF function, with a subsequent increase in positive surface charge. Cumulatively, these results demonstrated that the T345I amino acid substitution in mprF represents one of the primary causes of DAP-NS in MRSA strains.

Complete genome sequencing and comparative plasmid analysis of KPC-2-producing Klebsiella pneumoniae isolated from hospital sewage water in Japan.

OBJECTIVES: The Klebsiella pneumoniae carbapenemase (blaKPC) gene is one of the most widespread carbapenemase genes in the world. However, there are few reports on KPC-producing bacteria in Japan. The aim of this study was therefore to investigate KPC-producing K. pneumoniae in Japan. METHODS: A KPC-2-producingK. pneumoniae strain (KAM260) was isolated from hospital sewage water in Japan in 2018. The complete genome was determined by whole-genome sequencing. Subsequent comparative sequence analysis of the blaKPC-2-carrying plasmid was performed. RESULTS: Klebsiella pneumoniae KAM260, belonging to sequence type 3026 (ST3026), harboured the blaKPC-2 gene in 114.6-kbp plasmid pKAM260_2 with IncFIB(pQIL) and IncFII(K) replicons. pKAM260_2 was highly identical to pKpQIL-like plasmids, which carry blaKPC genes and have spread worldwide. pKAM260_2 had functional conjugation-associated genes and was transferable to Escherichia coli. CONCLUSION: pKAM260_2, the self-transmissible plasmid carrying theblaKPC-2 gene, was detected from hospital sewage water in Japan and was characterised as a pKpQIL-like plasmid. This plasmid needs to be monitored in Japan in the future owing to its high diffusivity.

Trends and molecular characteristics of carbapenemase-producing Enterobacteriaceae in Japanese hospital from 2006 to 2015.

BACKGROUND: The increasing number of carbapenemase-producing Enterobacteriaceae (CPE) has become a global problem. Most carbapenemases detected in Japan are imipenemase, which is an imipenem-degrading enzyme with low ability; thus, CPE could have been overlooked. Therefore, this study aimed to detect and analyze CPE, without overlooking CPE showing the low minimum inhibitory concentration phenotype. METHODS: CPE screening was conducted on 531 ceftazidime-resistant Enterobacteriaceae isolated from Kitasato University Hospital during 2006-2015. We confirmed the presence of the carbapenemase genes (blaIMP, blaVIM, blaKPC, blaNDM, and blaOXA-48) by multiplex polymerase chain reaction. The detected CPE strains were analyzed by antimicrobial susceptibility testing, multilocus sequence typing, conjugal experiments, replicon typing, and plasmid profiling by restriction enzyme treatment. RESULTS: The CPE detection rate in Kitasato University Hospital within the past 10 years was 0.0003% (nine CPE strains). These nine CPE strains were identified to harbor 8 blaIMP-1 or 1 blaNDM-5. The CPE strains consisted of five species including Klebsiella pneumoniae and Citrobacter freundii. Six of eight blaIMP-1 were coded by IncHI2 plasmid, and the other two were coded by IncA/C plasmid. Plasmid profiling revealed that K. pneumoniae and C. freundii isolated from the same patient harbored the same plasmid. CONCLUSION: The CPE detection rate in this study was significantly lower than those previously reported in Japan. In one case, IncA/C plasmid transmission through different bacterial species within the body was speculated. Although the number of CPE detected was low, these results indicated that the resistance plasmid could spread to other bacterial species.

Characterization of the IncFII-IncFIB(pB171) Plasmid Carrying bla NDM-5 in Escherichia coli ST405 Clinical Isolate in Japan.

PURPOSE: New Delhi metallo-ß-lactamase 5 (NDM-5) shows stronger resistance to carbapenems and broad-spectrum cephalosporins than NDM-1 because NDM-5 differs from NDM-1 by two amino acid substitutions. In this study, our aim was to characterize a NDM-5-producing Escherichia coli isolate KY1497 from a patient with urinary tract infection in Japan, who had no recent history of overseas travel. PATIENTS AND METHODS: NDM-5-producing E. coli isolate KY1497 was detected in the urine sample of a patient hospitalized in a tertiary hospital in Japan. The complete genome sequence of isolate KY1497 was determined by short- and long-read sequencing with hybrid assembly, followed by multilocus sequence typing (MLST), core-genome phylogeny analysis, plasmid analysis, and transconjugation experiments. RESULTS: KY1497 was classified as ST405 by MLST, and core-genome phylogeny exhibited the closest lineage to the clinical isolates in Nepal (IOMTU605) and Canada (FDAARGOS_448). KY1497 harbors bla NDM-5 in the IncFII-IncFIB(pB171) replicon plasmid (pKY1497_1, 123,767 base pairs). Plasmid analysis suggested that the cognate plasmids of pKY1497_1 have a minor plasmid background, rather than the globally disseminated IncX3 plasmid carrying bla NDM-5. Transconjugation analysis revealed that pKY1497_1 is transmissible to the recipient E. coli J53 strain. CONCLUSION: We characterized a novel Inc replicon plasmid (IncFII-IncFIB[pB171]) carrying bla NDM-5 and its host E. coli strain. NDMs are associated with a high risk of infection worldwide because of their antibiotic resistance and untreatable and hard-to-treat infections. Other patients in the hospital showed negative results for carbapenem-resistant Enterobacteriaceae. As NDM-producing strains are only sporadically detected in Japan, attention should be provided to the community prevalence of NDM-producing E. coli strains to prevent nosocomial infections.