Journal of microorganism control最新文献

Considering the lack of detailed research on the antibacterial mechanism of polyoxometalates, we examined the synergistic effect of novel bulky mixed Ti/W hetero-polyoxometalates (K_9.5H_2.5 ［α-Ge₂Ti₄W₂₀O₇₈］・ 29H₂O; αTi4, K₉H₅ ［α-Ge₂Ti₆W₁₈O₇₇］・16H₂O; αTi6, K₂₃H₅［α-Ge₄Ti₁₂W₃₆O₁₅₄］・39H₂O; αTi12, K₉H₅ ［β-Ge₂Ti₆W₁₈O₇₇］・ 45H₂O; βTi6) with the antibiotic oxacillin against vancomycin intermediate-resistant Staphylococcus aureus (VISA) using fractional inhibitory concentration (FIC) index and growth curve in this study. All polyoxometalates used in this study showed remarkable synergistic effects with oxacillin. Its synergistic antibacterial mechanism was examined using reverse transcription PCR (RT-PCR) and penicillin binding protein-2' (PBP2') latex agglutination test. The results suggested that these polyoxometalates did not inhibit mecA gene transcription but resulted in PBP2' protein malfunction. From these results, we concluded that the substances producing resistance in VISA were affected by polyoxometalates depending on their molecular size, facilitating a synergistic antibacterial effect with oxacillin.

Respiratory infectious diseases have potential of aerosol transmission such as COVID-19. The development of new technologies for infection control against airborne viruses are further required. It is necessary for effective development to evaluate properly the effect and role of these technologies in indoor environment. Here, the author provided essential knowledge for infection control of viral aerosols, i.e., basic concept of infection control, features of COVID-19 and Influenza including the entry receptor in body of each virus, behavior of the viral aerosols released from patient bodies, and Wells-Riley model as a traditional quantitative assessment of the infection risk by aerosol transmission. Previous evaluation studies on airborne viruses were categorized into three types of experiments, namely, in vitro, in vivo, and in humans and real indoor environments. Some prospects were described, including standard evaluation methods for air cleaners, the research group to formulate guidelines for evaluating the hygienic effects of chemical substances on microbes in real indoor space, and personal opinions on evaluation concept linked to three types of experiments. This minireview may help to correctly evaluate the hygienic effects of control technologies against airborne viruses in indoor environment and to contribute development of technologies with required performance according to infection risk.

Bacterial stresses can occur from the production to the distribution environments of produce, and these stresses can lead to nonlethal bacterial damage that is an injured state called sublethally injured bacteria. The damage is mainly due to the disruption of the surface structure and cytoplasmic membrane of the cells. Sublethally sanitizer-injured indicator coliform bacteria injured by chlorine, ethanol, and/or fungicide stress could exhibit on vegetables during production and harvest. Chlorine stress and cold stress could induce sublethally injured indicator and pathogenic coliform bacteria on fresh-cut vegetables during processing and subsequent storage. Enterobacter kobei and Pantoea ananatis injurd by chlorine stress, E. amnigenus, E. asburiae, and E. kobei injured by ethanol stress, and Rahnella aquatilis, Yersinia mollaretii, and Escherichia coli injured by fungicide stress could be amongst the injured cells in the coliforms detected in the produce environments. To ensure the microbiological quality and safety of fresh-cut vegetables, it is necessary to adjust the concentration of sanitizer to a level that kills bacteria and does not produce sanitizer- injured cells when sanitizer is applied to the produce, and also to consider the storage temperature to inhibit the recovery of injured bacteria due to cold injury during the chilling storage period.

Ultraviolet (UV) -C is widely used to kill bacteria as it damages chromosomal DNA. We analyzed the denaturation of the protein function of Bacillus subtilis spores after UV-C irradiation. Almost all of the B. subtilis spores germinated in Luria-Bertani (LB) liquid medium, but the colony-forming unit (CFU) of the spores on LB agar plates decreased to approximately 1/10³ by 100 mJ/cm² of UV-C irradiation. Some of the spores germinated in LB liquid medium under phase-contrast microscopy, but almost no colonies formed on the LB agar plates after 1 J/cm² of UV-C irradiation. The fluorescence of the green fluorescent protein (GFP) -fused spore proteins, YeeK-GFP, YeeK is a coat protein, decreased following UV-C irradiation of over 1 J/cm², while that of SspA-GFP, SspA is a core protein, decreased following UV-C irradiation of over 2 J/ cm², respectively. These results revealed that UV-C affected on coat proteins more than core proteins. We conclude that 25 to 100 mJ/cm² of UV-C irradiation can cause DNA damage, and more than 1 J/cm² of UV-C irradiation can cause the denaturation of spore proteins involved in germination. Our study would contribute to improve the technology to detect the bacterial spores, especially after UV sterilization.

Clavibacter michiganensis, a gram-positive actinomycete, is a major seed-borne tomato pathogen. We investigated the inactivation efficacy of low-pressure plasma treatment against C. michiganensis inoculated on tomato seeds by placing them on a mesh sheet above the bottom dielectric glass plate. The 2- and 5-minute plasma treatment reduced C. michiganensis populations on the tomato seeds by 0.8 and 1.8 log cfu/seed, respectively. The reduction rates were similar to those of C. michiganensis on shirona (cruciferous) seeds, which have different shapes and surface structures. In contrast, the inactivation of C. michiganensis cells using plasma was more difficult than that of X. campestris cells. Additionally, it was found that placing seeds on a mesh sheet laid on the dielectric glass plate was remarkably effective in inactivating the pathogens on tomato seeds. Since the tomato seeds were susceptible to damage from plasma treatment, methods to reduce its damage need to be investigated.

Norovirus (NoV）is a major causative virus of viral gastroenteritis and requires a general disinfection method because it is resistant to common disinfectants such as ethanol and chlorhexidine. This study aimed to find natural extracts as candidates for versatile disinfectant ingredients. The antiviral effect of natural extracts against NoV can be evaluated using the feline calicivirus (FCV）-inactivation test and NoV virus-like particle (NoV-VLP）-binding inhibition test. In this study, screening of natural extracts with anti- NoV effects was performed using these two methods. Of the 63 natural extracts examined, 14 were found to have high FCV-inactivation and NoV-VLP-binding inhibitory effects. In addition, we evaluated the NoV-VLPbinding inhibitory effect of grape seed extract（GSE）containing proanthocyanidins under multiple concentration conditions and treatment times and determined that the binding inhibitory effect of GSE was concentration- and time-dependent. Electron microscopy showed that GSE-treated NoV-VLPs aggregated, distorted, and swelled, suggesting that GSE directly interacts with NoV particles. The results suggest that some natural extracts containing GSE can be used as components of disinfectants against NoV.

Various sterilization and disinfection processes are used to control harmful microorganisms in food, medicine, and the environment. During killing, microorganisms often remain between life and death, being called injured microorganisms. The degree of injury of the injured microorganisms depends on the load of the disinfection treatment, and the treatment conditions and varies not only quantitatively but also qualitatively. Knowing how they are injured by sublethal and lethal stresses of disinfection, how they repair themselves, what makes the difference between life and death, and their physiological characteristics, will lead to appropriate microbial testing and optimization of disinfection conditions for practical viability and growth potential, and will deepen our understanding of the effectiveness of the treatment. Focusing on mainly heat injury and using Escherichia coli as a model microorganism, in this review, I will discuss the classification of injury modes in injured microorganisms caused by disinfection treatment, including "λ injury" (delayed resumption of growth）," μ injury" (reduced growth rate injury）," β injury" (secondary injury）, and other derivatives.