Journal of microorganism control最新文献

Mechanical bead disruption is an efficient DNA extraction method from spore cells for subsequent quantification of the spore population by quantitative polymerase chain reaction（qPCR）. In this study, to validate spore DNA localization and extraction efficiencies, the fractionated DNA included the total DNA（tDNA）extracted from spore cells and intracellular（iDNA）and extracellular DNA（eDNA）extracted from fractionated spores through chemical decoating and alkaline lysis buffers, each followed by bead disruption. Furthermore, alkaline lysis buffer-treated spore cells were intensively washed three and five times after each centrifugation to determine how the amount of DNA is affected by repeated centrifugation. This process was achieved through fractionated spore pellet and suspension treatments with propidium monoazide xx（PMAxx）before mechanical bead disruption. Three fractionated and extracted DNAs were assessed with qPCR. The amount of eDNA was higher than that of iDNA, and closer to tDNA levels in the qPCR assay. These results indicted the following: 1）amount of eDNA was more than iDNA and responsible for majority of amount of tDNA through the combination method involving alkaline lysis buffer and bead disruption, 2）lysis buffer partially eliminated the eDNA fragments through multiple washing steps, but it was not largely independent of the number of times centrifugation was performed.

Cupriavidus metallidurans strain PD11 isolated from laboratory waste drainage can use C1 compounds, such as dichloromethane (DCM) and methanol, as a sole carbon and energy source. However, strain CH34 (a type-strain) cannot grow in the medium supplemented with DCM. In the present study, we aimed to unravel the genetic elements underlying the utilization of C1 compounds by strain PD11. The genome subtraction approach indicated that only strain PD11 had several genes highly homologous to those of Herminiimonas arsenicoxydans strain ULPAs1. Moreover, a series of polymerase chain reaction (PCR) to detect the orthologs of H. arsenicoxydans genes and the comparative study of the genomes of three strains revealed that the 87.9 kb DNA fragment corresponding to HEAR1959 to HEAR2054 might be horizontally transferred to strain PD11. The 87.9 kb DNA fragment identified was found to contain three genes whose products were putatively involved in the metabolism of formaldehyde, a common intermediate of DCM and methanol. In addition, reverse transcription PCR analysis showed that all three genes were significantly expressed when strain PD11 was cultivated in the presence of DCM or methanol. These findings suggest that strain PD11 can effectively utilize the C1 compounds because of transfer of the mobile genetic elements from other bacterial species, for instance, from H. arsenicoxydans.

Campylobacter jejuni causes gastroenteritis in humans and is a major concern in food safety. Commercially prepared chicken meats are frequently contaminated with C. jejuni, which is closely associated with the diffusion of intestinal contents in poultry processing plants. Sodium hypochlorite (NaClO) is commonly used during chicken processing to prevent food poisoning; however, its antimicrobial activity is not effective in the organic-rich solutions. In this study, we investigated the potential of a new photo-disinfection system, UVA-LED, for the disinfection of C. jejuni-contaminated chicken surfaces. The data indicated that UVA irradiation significantly killed C. jejuni and that its killing ability was significantly facilitated in NaClO-treated chickens. Effective inactivation of C. jejuni was achieved using a combination of UVA and NaClO, even in the organic-rich condition. The results of this study show that synergistic disinfection using a combination of UVA and NaClO has potential beneficial effects in chicken processing systems.

Chlorine dioxide (ClO₂) is a powerful disinfectant widely regarded as a safe and effective hygienic agent in pharmaceutical plants and other manufacturing facilities that require sterility. However, the efficacy of low concentrations of ClO₂ gas on sterilizing spore-forming bacteria remains uncertain. In this study, we investigated the optimal conditions for disinfection of spore-forming bacteria with low concentrations of ClO₂ gas using biological indicators. The results showed that 0.05 ppmv (0.13 mg/m³) ClO₂ gas at 37±1℃, 86±2%RH sterilized Bacillus atrophaeus in 14 d and Geobacillus stearothermophilus in 28 d (>6 log₁₀ reductions）. Based on these results, we propose that low concentrations of ClO₂ gas are useful for controlling contamination by spore-forming bacteria in aseptic facilities.

When a hypochlorite solution is ultrasonically fogged in a room, free chlorine, i.e., HOCl and OCl^-, reaches various positions in two forms: fine fog droplets and gaseous hypochlorous acid（HOCl_(g)）. In this study, the cumulative amount of free chlorine reaching various positions on the floor away from the fogger was measured in a 90-m³ room, using a sulfamate-carrying glass-fiber filter indicator. The fine droplets were blown out from the fogger into the spaces at different discharge port angles of 30 - 90°. Free chlorine was successfully trapped by sulfamate, forming monochlorosulfamate, which was stably retained on the indicator. The cumulative amount of free chlorine（ ng/indicator） increased with fogging time at each position and depended on the blow angle and distance from the fogger. Minor differences in the HOCl_(g) concentration near the floor at all positions were observed. The disinfection efficacy of the fogging treatment against Staphylococcus aureus on wet surfaces was relatively higher at positions near the fogger and lower at positions far from the fogger. At each discharge port angle, a strong correlation between the logarithmic reduction in relative viable cells and the cumulative amount of free chlorine reaching S. aureus plates was observed. The slopes of the regression lines of correlation diagrams as a function of the cumulative amount of free chlorine were between -0.0362 and -0.0413 ng^-1. This study demonstrated that the cumulative amount of free chlorine measured using the filter indicator could reflect the sum of the free chlorine of both fine droplets and HOCl_(g), and that the disinfection efficiency depended on the cumulative amount of free chlorine reaching different areas.

During the disinfection of indoor spaces using gaseous hypochlorous acid (HOCl_(g)), inhalation is the most common route of exposure for humans. In this study, an artificial human respiratory tract model was exposed to 12-140 ppb HOCl_(g) at an aspiration flow rate of 800 mL/s for 15 h in a 1 m³ chamber. The respiratory tract model was equipped with 5th order bronchi and all gas-contact parts were made of silicone rubber with no other chlorine-consuming substances. The concentration of HOCl_(g) reaching the lung pseudo-space was approximately 47.4% of the HOCl_(g) concentrations in the chamber and was calculated to be very close to zero when the chamber concentration was less than 20.5 ppb. The disappearance of HOCl_(g) during inhalation is likely due to the adsorption of HOCl_(g) on the gas-contact silicone rubber surfaces. The cytotoxicity of HOCl_(g) on respiratory epithelial cells was also examined using human air-liquid-interface airway tissue models. Human nasal epithelium and bronchiolar epithelium were exposed to 100 ppb and 500 ppb HOCl_(g) for 8 h and 5 d, respectively. No significant effects of HOCl_(g) on cell viability and ciliary activity were observed in any cell type, indicating that low concentrations of HOCl_(g）, less than 500 ppb, had no cytotoxic effect.

The species diversity of xerophilic and halophilic fungi distributed in marine surface water was studied at four local sites located in two geographically distant regions in Japan. At each site, 5-10 samples were collected and isolated using an osmophilic medium. Species identification was conducted based on nucleotide sequence of calmodulin or β -tubulin and morphological characteristics for Aspergillus, Penicillium, and Talaromyces, and on the sequences of rRNA internal transcribed spacer for the other taxa. Overall, 231 strains were isolated from all sites and classified into 85 species belonged to 12 orders and 33 genera. The isolates that showed better mycelial growth than the control（no NaCl added) in the halotolerance test were defined as halophilic fungi, and only 22 species（10 Aspergillus species and 12 Penicillium species) were halophilic. Comparison of the halophilic fungal flora of the two regions revealed that four species common to both regions were isolated for Aspergillus, but no such species were isolated for Penicillium. Given that 15 halophilic species（10 Aspergillus and 5 Penicillium species) are known to be xerophilic species distributed in indoor environments, it can be inferred that indoor xerophilic species are likely to be widely distributed in marine surface water.

This study searched for volatile organic compounds (VOCs）having antibacterial and antiviral efficacy. The antibacterial efficacy of volatilized components was evaluated and (2E,4E）-2,4-hexadienal, α- angelica lactone, 2-cyclohexen-1-one and 2-cyclopenten-1-one were found to inhibit the formation of colonies of Staphylococcus aureus and Escherichia coli. Evaluating the antimicrobial efficacy of the surfaces to which each VOC adhered to, these four compounds were revealed to have antibacterial efficacy (antibacterial activity value (A-value）against S. aureus; ≧2.63, A-value against Klebsiella pneumoniae; >5.07, A-value against E. coli; ≧2.17）. Furthermore, (2E,4E）-2,4-hexadienal and α-angelica lactone were found to have antiviral efficacy against Influenza A virus (H1N1）and Feline calicivirus on the cotton cloths to which it adheres to (antiviral activity value (R-value）against Influenza A virus; >2.94, R-value against Feline calicivirus; ≧2.31）. Using these components, it might be possible to develop antimicrobial products that exhibit antibacterial and antiviral efficacy.

Earlobes, nasal cavities, and fingers of 145 healthcare workers in convalescent and rehabilitation hospital (60 nurses and 85 rehabilitation healthcare workers) were sampled. Of the 3 sites sampled, Staphylococcus aureus was detected in one or more sites in 25 nurses and 27 rehabilitation workers. S. aureus was detected in all 3 sites in 2 (8.0%) nurses and 2 (7.4%) rehabilitation workers, and the S. aureus isolates in each case showed related PFGE pattern. S. aureus was detected in both the fingers and nasal cavities of 5 (18.5%) of the rehabilitation healthcare workers; in all 5 cases, the PFGE patterns of the S. aureus isolates from each site belonged to same cluster based on PFGE. Of the 2 cases in which methicillinresistant S. aureus (MRSA) was recovered from earlobes, fingers, and nasal cavities, in both cases, MRSA isolates from the 3 sites were the same clone according to PFGE analysis and SCCmec type IV. As S. aureus was detected in pierced earlobes of nurses, hand hygiene must be practiced after touching pierced earlobes and before patient contact. The same S. aureus clone in the nasal cavity and earlobes indicates that the route of transmission is through the fingers.