Journal of microorganism control最新文献

In this study, the malodor detection method was constructed in our laboratory using bacteria isolated from washed fabrics and some effective disinfection techniques for suppressing malodor emitted by the isolates were evaluated. Bacterial isolates from a previous study (Okuda et al. 2025) were incubated on cotton fabric in basal salt medium containing glucose, casamino acids and squalene (BSM+C) . The intensity of malodor from the incubated fabric was evaluated by a sensory method on a six-point odor intensity scale. Fabric cultivated with each isolate emitted noticeable malodor. Sulfur compounds, short-chain alcohols and short-chain ketones were detected in cultivated fabrics using GC/MS analysis. Pretreatment before cultivation with heat or benzalkonium chloride reduced odor intensities, whereas those using ultrasonication or didecyl dimethyl ammonium chloride sustained high odor intensities. These results indicate that not only bacterial cell death but also enzyme denaturation or inactivation derived from them may be important to suppress malodor emission.

This study aimed to compare and assess residual microorganisms and organic materials on selected dental instruments after practicing two infection control methods, including the standard protocol. Scaler tips (ST) , 3-way syringe tips（3ST) , Bristle brushes（BB) , and Rubber cups（RC) were collected and grouped into Standard (Group S) and Non-standard (Group N) for processing. In ST and 3ST, Group S was cleaned and autoclaved, while Group N was disinfected. For BBs and RCs, Group N was cleaned and autoclaved, and new instruments were used as Group S. To confirm the presence of residual microorganisms, instruments from each group were incubated in liquid and solid medium. The generated colonies on solid medium were identified at the species level by polymerase chain reaction (PCR) . To confirm the presence of residual organisms, each instrument was stained with Phloxine B and observed using a stereomicroscope. Only ST（8.0%) and 3ST (28.0%) samples from Group N were detected with residual microorganisms. The identified colonies included Staphylococcus, Cupriavidus, and Streptococcus spp. Residual organics were observed in all samples from Group S and N. These findings highlight the limitations of cleaning followed by autoclaving and especially disinfection in completely eradicating all microorganisms and organics.

Copper is known as an antibacterial material. Reactive oxygen species (ROS) with antibacterial effectiveness are generated on copper surfaces mainly by the Fenton-type reaction. The antibacterial effectiveness is higher in Cu₂O than in CuO. In this study we discussed the effects of the difference in the amount of generated ROS on the difference in the antibacterial effectiveness between Cu₂O and CuO. Both Cu₂O and CuO produced hydrogen peroxide (H₂O₂）, hydroxyl radical(･OH）, and singlet oxygen (¹O₂）, but not superoxide radical (･O₂^-）. The concentration of H₂O₂ produced was higher in Cu₂O than in CuO. When catalase, a scavenger of H₂O₂, was added, the antibacterial activities of both Cu₂O and CuO reduced to almost the same value. These experimental results indicate that Cu₂O is higher in antibacterial effectiveness than CuO because Cu₂O produced more H₂O₂ than CuO. As ･OH was detected even when H₂O₂ was scavenged by catalase before it reacted with Cu ion, a part of ･OH was generated by chemical reactions different from the Fenton-type reaction when copper oxides were in contact with water.

The copper (II) ion is valuable as an antimicrobial reagent and is highly safe for humans, animals, plants, and the environment. In this study, the effect of sodium sophoroselipid (SL-Na) on the bactericidal activity of CuSO₄ was investigated. SL-Na enhanced the bactericidal activity of CuSO₄ when incubated with it for 10 min or more at 20℃. Its bactericidal activity is significant against gram-negative bacterial cells. CuSO₄ at a concertation of 100 µM, when mixed with 100 µM SL-Na, effectively killed Escherichia coli cells at a rate of more than one order of magnitude higher than that observed without SL-Na after 30 minutes at 20℃. The structural differences between SL-Na, CuSO₄ and their mixture were confirmed by ultraviolet visible absorption spectrum analyses, resulting in the absorption of ca. 800 nm derived from copper (II) ions shifting to ca. 680 nm in the mixture. This shift suggests that the acid-form sophoroselipids and copper (II) ions bind weakly to form a complex (SL-Cu complex）. The purified SL-Cu complex also revealed a unique absorption at approximately 1,600 cm^-1 using a Fourier transform infrared analysis and demonstrated a higher bactericidal activity than CuSO₄. Our results indicate that SL-Cu complex formation enhanced the bactericidal activity of copper (II) ions.

Coptis chinensis is a traditional Chinese herb and the alkaloids in aqueous extract of C. chinensis are natural fungicides. The present study reports the inhibitory effect of aqueous extracts from five medicinal herbs on Nigrospora sphaerica. The aqueous extract of C. chinensis shows highest activity against N. sphaerica among these five herbs. The active alkaloids in aqueous extract of C. chinensis were identified and quantified. The results show that freeze-dried powder of aqueous extract of C. chinensis contains 46.62% berberine, 11.76% epiberberine, 15.88% coptisine, 13.26% palmatine and 3.86% jatrorrhizine. The additive effect among these alkaloids were also determined where the four-compound combination (epiberberine/coptisine/palmatine/berberine) exhibitsexhibits the best inhibitory effect. These findings highlight alkaloids from C. chinensis as promising eco-friendly alternatives to traditional fungicides for integrated pest management.

We evaluated the efficacy of peracetic acid (PAA) products in disinfecting Methylobacterium radiotolerans biofilms within hemodialysis systems, using a Centers for Disease Control and Prevention (CDC) biofilm reactor. Twelve PAA products were tested with an appropriate neutralization. All products completely eradicated planktonic bacteria within 10 minutes. In contrast, the effectiveness against biofilms varied, with log reduction values (LRVs) ranging from 2.47 to 9.40, depending on PAA concentration. Products with higher hydrogen peroxide concentrations achieved greater LRVs at the same PAA concentrations, although its effect was secondary. Similar to sodium hypochlorite, extended reaction times further improved LRVs, even at higher dilutions. These findings suggest that PAA products are promising alternatives for the routine biofilm control in dialysis systems.

Recently, perioperative oral function management, focusing on oral care, has been considered important from the perspective of preventing infections caused by oral microorganisms. One of the infectious diseases that should be prevented is oral candidiasis. The purpose of this study was to clarify the oral local factors related to Candida colonization in perioperative patients. The analyses of the relationship between oral local factors and Candida colonization revealed that three factors - a reduction in the number of remaining teeth, wearing dentures, and increased dry mouth - were related to Candida colonization. The oral local factors related to Candida colonization identified in this study may be useful indicators for easily and quickly determining whether or not Candida colonization is present. It is difficult to perform bacteriological tests on all perioperative patients, who are subject to various constraints, including physical, mental, and time constraints, so we hope that oral examinations focusing on these oral local factors would provide a foothold in preventing the onset of oral candidiasis in perioperative patients.

The high permeability of silicone rubber is beneficial for use in membranes for pervaporation. In this study, pervaporation of hypochlorous acid (HOCl) was studied using a separation module containing a 6,000 silicone rubber (SR) hollow fiber membrane. Pervaporation experiments were conducted in a 1 m³ chamber. The membrane module was operated without using a vacuum pump, and the permeation of HOCl proceeded according to the solution-diffusion process. When weakly acidic (pH 5.0) hypochlorite solutions with concentrations of 100-1,000 mg/L were fed through the lumen of the SR hollow fiber membrane, the permeation of HOCl proceeded spontaneously under atmospheric pressure. During the operation of the membrane module, the concentration of gaseous hypochlorous acid (HOCl_(g)) in the chamber gradually increased and reached a steady state. The steady-state HOCl_(g) concentration increased as the concentration of undissociated hypochlorous acids (HOCl_(aq)) in the feed hypochlorite solutions increased. An exponential dependence of the steady-state HOCl_(g) concentration on the steady-state HOCl_(aq) concentration was observed. Operation of the SR hollow fiber membrane fed with weakly acidic hypochlorite solutions (i.e., 500 mg/L) in a 75 m³ room resulted in a uniform distribution of 7-10 ppb HOCl_(g), thereby exerting a moderate bactericidal effect against Staphylococcus aureus cells.

An air washer-type humidifier has two useful functions: humidification, and air purification, and it applies to large indoor spaces. In this study, the efficacy of an air washer-type humidifier fed with 24 L of weakly acidic electrolyzed water（WAEW) at pH 5.0 and 30 mg/L in disinfecting attached bacteria and airborne microorganisms was studied in a 480 ^m3 indoor space. The humidifier was operated at a shower volume of 9.0 L/min of WAEW and at an air flow rate of 29 ^m3/min. Volatilization of gaseous hypochlorous acid（HOCl_(g)) proceeded according to first-order kinetics during the 60 min of operation. Fresh WAEW was supplied to the humidifier every 60 min, and the HOCl_(g) concentration in the indoor space was maintained within the range of 25-52 ppb for at least 180 min of operation. The number of viable bacterial cells on wet agar plates placed on the floor at a distance of 5-20 m away from the humidifier decreased by 2.0-3.0 log after 30 min of operation, and no viable cells were detected after 60 min of operation. A logarithmic reduction of more than 2.7 was achieved within 15 min against bacteria-attached plates placed at a 1.5 m-height position where the outlet airflow from the humidifier was directly exposed. This indicates that the disinfection efficacy of HOCl_(g) volatilized from the humidifier depends on the rate of outlet airflow reaching the bacteria-attached plates. The number of viable airborne microorganisms decreased by approximately 54% after 180 min of operation. This study demonstrated that an air-washer-type humidifier can spread HOCl_(g) evenly throughout a large indoor space and is effective in disinfecting attached bacteria and airborne microorganisms.

The growth of acid-fast bacteria often hinders the detection of Legionella in water samples on agar plates by the plate culture method. We studied whether anti-tubercular agents inhibit acid-fast bacteria growth on agar plates. First, the antimicrobial activities of isoniazid, ethionamide, and ethambutol were evaluated against Mycobacterium and Legionella. We found that ethambutol at ≥ 100 μg/mL completely inhibited Mycobacterium growth, but ethambutol at 1,000 μg/mL did not inhibit Legionella growth. Next, the effect of ethambutol dissolved in acid buffer was examined. Cell suspensions of L. pneumophila and Mycobacterium spp. were mixed, and ethambutol-acid buffer was added. After 5 min, mixtures were inoculated on GVPC agar plates and incubated at 36℃ for 6 d. We found that ethambutol inhibited Mycobacterium growth on agar plates, but the Legionella colonies recovered. The effect of ethambutol was also significant in the evaluation using bathwaters. Comparing 1,302 bathwaters, the addition of ethambutol reduced the detection rate of acid-fast bacteria from 30.6% to 0% and increased the detection rate of Legionella from 7.1% to 7.5%. Ethambutol, which selectively inhibited acid-fast bacteria growth, enhanced the detection of Legionella on agar plates and will contribute to improving the accuracy of Legionella testing by the plate culture method.