Biocontrol science最新文献

The current pandemic of novel coronavirus disease (COVID-19) has highlighted the importance of disinfectants. As a raw material for next-generation disinfectants, scallop shell-derived calcium oxide (CaO) has been revealed to exhibit significant virucidal and microbicidal activities and is compatible with living tissues and the environment. This minireview summarizes recent progress in the development of disinfectants from scallop shell-CaO, focusing especially on studies of clinical and daily use applications. We describe the preparation, basic characteristics, and virucidal and microbicidal activities of scallop shell-CaO disinfectants. Furthermore, their applications in the disinfection of contaminated masks and the treatment of infected wounds are briefly introduced.

We isolated a fungus from a 20% (= 200,000 µg/mL) aqueous solution of polyhexamethylene biguanide hydrochloride (PHMB), a widely used antimicrobial and examined its morphology and drug resistance profile. Based on the sequence of the internal transcribed spacer region of ribosomal DNA, the fungus was identified as Purpureocillium lilacinum. Although the P. lilacinum type and resistant strains showed similar morphology, the latter had extremely low PHMB susceptibility and was able to grow in 20% aqueous solution of PHMB, which eliminated the type strain. The minimum inhibitory concentration (MIC) of PHMB for the resistant strain was significantly higher than that of the type strain and other pathogenic filamentous fungi and yeasts. The susceptibility to antimicrobial agents and antifungal agents other than PHMB was similar to that of the type strain, therefore the drug resistance of the isolate was specific to PHMB. Furthermore, we sequenced the genome of the isolate to predict PHMB resistance-related genes. Despite its high resistance to PHMB, no well-known genes homologous to fungal PHMB-resistant genes were detected in the genome of the resistant strain. In summary, P. lilacinum was found to be significantly more resistant to PHMB than previously reported, via an unidentified mechanism of drug resistance.

A large volume of historical archives was extensively damaged by flood water, following Typhoon Hagibis in Fukushima, Japan, in October 2019. They were rescued from the stricken area within a week, however, the prolonged exposure of paper documents to water caused severe biodegradation by fungal growth. To disinfect fungi, the paper documents were exposed to gamma radiations emitted by a source of Cobalt 60 by the industrial irradiation service. The wet paper documents were mainly contaminated with hydrophilic and cellulolytic fungi, including Trichoderma, Stachybotrys, and Fusarium; no fungi grew after irradiation. These results indicated that the average absorbed dosage from 13.1 kGy to 16.1 kGy were sufficient to disinfect paper documents heavily contaminated with fungi. In the present study, we demonstrated the successful practical use of irradiation in fungi-damaged paper documents using a commercial gamma-irradiation facility.

Sodium percarbonate (SP) is a relatively low-cost and stable solid oxidizer with a small environmental burden. It is often included in cleansers for sanitizing circulating water pipes and as bleaching reagents in laundry, although the bactericidal effect of SP is lower than that of chlorine-based agents. 2-[Bis(carboxymethyl)amino] propanoic acid-chelated copper (MGDA-Cu) was added to increase the effect of SP. The addition of 12 µM MGDA-Cu increased the bactericidal effect of 0.5 wt% SP against Staphylococcus aureus even in the presence of 0.3 wt% BSA, which is an experimental model of organic stain to protect bacteria from SP. MGDA-Cu was effective against Escherichia coli only in the absence of BSA and showed little effect against Bacillus subtilis. It enhanced the effect of SP to decrease the viscosity of sodium alginate, which is one of the major components of biofilms. The effect of MGDA-Cu on sanitization was also evaluated by 16S rRNA amplicon sequencing of the bacterial flora of the biofilm on an experimental model of a circulating water pipe. The structure of the bacterial flora was more influenced by a cleanser containing both MGDA-Cu and SP than a cleanser with only SP, suggesting that MGDA-Cu increases the sanitization effect.

Household air conditioners are known to be contaminated with dematiaceous fungi such as genus Toxicocladosporium and genus Cladosporium. We frequently encounter cases in which a large amount of fungi, which are presumed to belong to the family Cordycipitaceae, are isolated from the blowout air of the household air conditioners. Therefore, the Cordycipitaceae isolated in the survey of four cases of the air conditioners were identified by genetic analyses. As a result, all of them were found to be Simplicillium sympodiophorum. The concentration of airborne fungi, S. sympodiophorum in the blowout air was high (> 10⁴ cfu/m³) as exceeding the upper limit of quantification in three of four cases, and 5,000 cfu/m³ in one case. This study revealed that S. sympodiophorum contaminated multiple air conditioners. Genus Toxicocladosporium was also isolated from the two air conditioners, and it was found to be Toxicocladosporium irritans by the genetic analysis.

The preservative efficacy test is an important method for assessing the antimicrobial effect of cosmetic products. In this study, the optimum conditions for the efficient microbial enumeration of Aspergillus brasiliensis were investigated. Cosmetic products, inoculated with A. brasiliensis spore suspensions, were cultivated at 22.5°C, 32.5°C, or 40°C and the detection rate and the number of colonies were determined using the pour culture method. There was no difference in the viable counts of visible colonies among different temperature conditions. However, the viable counts after 3 days of culture were significantly greater for the cultures maintained at 32.5°C or 40°C compared with those maintained at 22.5°C. This effect was attenuated in products containing fatty acids, which could inhibit fungal growth. Overall, these results demonstrate that cultivating A. brasiliensis at 32.5°C reduces the time required for enumeration in the preservative efficacy test. Thus, the results of this study are expected to help improve and expedite microbiological quality control in the cosmetic industry.

In these days, all agar media used for both pharmaceutical and industrial territories were required to meet performance criteria. There were recovery rates of assigned microorganisms as performance criteria in both pharmacopeia and ISO standards. However, in spreading plate method, there is no concrete spreading time even though it is shown only "as quickly as possible" in ISO standards. In this study, we verified the impact of spreading time in spreading plate method for the quality control of SCD (Soybean Casein Digest) agar plate. When 30s, 60s, and 120s of spreading time were compared using Bacillus subtilis ATCC 6633, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 6538, Candida albicans ATCC 10231, and Aspergillus brasiliensis ATCC 16404, respectively, there is no significant difference in recovery rates of all strains tested between 30s and 60s. However, recovery rates of E. coli and P. aeruginosa were decreased in 120s of spreading time. Our results demonstrated that spreading using plastic rod would be better to complete within 60s in spreading plate method since long spreading time had the impact to recovery rate of certain bacteria.

The microcolony formation at 30℃ on an enriched minimal salts agar plates by individual Escherichia coli cells heated at 50℃ was monitored with a time-lapse shadow image analysis system, MicroBio μ3D^TM AutoScanner. While the time course of microcolony count detected every half an hour for the unheated cells seemingly demonstrated a normal distribution, that for the heated cell population demonstrated totally the growth delay probably resulting from cell injury and also interestingly distributed in its rather deformed pattern with a tailing. Those patterns of the cumulative counts of appearing microcolonies during the post-heating cultivation period were expressed in three different mathematical models. This approach may be proposed as a rapid cultivation method predictable for enumeration of viable and repairable injured cells in practical use.

There is a worldwide attempt to develop prevention strategies against SARS-CoV-2 transmission. Here we examined the effectiveness of tungsten trioxide (WO₃)-based visible light-responsive photocatalyst on the inactivation of SARS-CoV-2 under different temperatures and exposure durations. The viral titer on the photocatalyst-coated glass slides decreased from 5.93 ± 0.38 logTCID₅₀ /mL to 3.05 ±. 25 logTCID₅₀/mL after exposure to 3,000 lux of the visible light irradiation for 6h at 20℃. On the other hand, lighting without the photocatalyst, or the photocatalyst-coat without lighting retained viral stability. Immunoblotting and electron microscopic analyses showed the reduced amounts of spike protein on the viral surface after the photocatalyst treatment. Our data suggest a possible implication of the photocatalyst on the decontamination of SARS-CoV-2 in indoor environments, thereby preventing indirect viral spread.

Benzo［a］pyrene (BaP) is one of the strongest carcinogenic compounds among polycyclicaromatic hydrocarbons (PAHs) .We previously identified the ITB9 strain of Olleya species, which shows BaP-degrading activity; our report was the first about BaP degradation by the genus Olleya. In this study, BaP-degradation efficiency by ITB9 was about 50% when the strain was suspended in 20 ml of L9 liquid medium with 100 μg/ml BaP and 0.2 M NaCl, with pH 8.0, and incubated at 25℃ for 5 days. Under the same conditions, all four type strains (O. marilimosa CIP108537, O. aquimaris KCTC22661, O. namhaensis KCTC23673, and O. algicola KCTC22024) also showed BaP-degrading activities, at efficiencies ranging from 49% to 63%. Olleya sp. ITB9 and O. aquimaris KCTC22661 were found to be in the same clade in the phylogenetic tree of the genus Olleya, given that the homology of 16S rRNA gene sequences between ITB9 and KCTC22661 was 99.77%.