Journal of microorganism control最新文献

CAT agar plates, which contain cycloheximide, amphotericin B and thiabendazole as antifungal agents and vancomycin and polymyxin B as antibiotics, are selective agars with enhanced selectivity for Legionella detection, but preparation of these plates is not easy. We have therefore developed a CAT additive that produces CAT agars by simply spreading the additive on GVPC agars. GVPC agars that had been spread with the CAT additive performed as well as or better than CAT agars in detecting Legionella in concentrated stock samples of environmental water. The CAT additive would be effective for Legionella testing such as in cooling tower water samples, which are often contaminated with non-target microorganisms, and for retesting when Legionella cannot be detected due to the effects of contamination by non-target microorganisms.

In this report, microbial cells on washed fabrics and in washing water in home laundry were analyzed, in order to suppress malodors and construct a highly sanitary home laundry system. Many bacterial cells (10⁹-10¹⁰ cells/g dry fabric) were detected from washed fabrics emitting relative strong malodors even after washing. Detergents with or without antimicrobial agents partially removed the microorganism cells and more than 20% of cells survived even after washing and drying in almost all households. Bacterial flora analyses of washed fabrics revealed the presence of several typical genera: Enhydrobacter sp., Paracoccus sp., Sphingomonas sp., Roseomonas sp. and Kocuria sp. These results indicated that it is difficult to remove or eliminate microbial cells adhering to clothes and fabrics in home laundry. This report also indicated certain typical bacteria (adhesive type) seem to adhere or attach to fabrics, while bacteria (transient type) found in washing water have low adhesivity to fabrics. Therefore, understanding the adhesive properties of bacteria on fabrics may permit more efficient removal of microorganisms and reduction of malodors in home laundry.

Otitis externa is an ear disease that is present in 10-20% of dogs. Bacterial organisms are a common cause, and infection may cause severe and chronic inflammation. Thus, there is a need for early detection and identification of bacteria in ear discharge samples. In this study, 31 such samples were analyzed to identify microorganisms using MALDI-TOF MS with pretreatment using a membrane filtration protocol and a rapid BACpro II kit, compared to pretreatment with a rapid BACpro II kit alone. Reliable scores for E. coli and E. faecalis were obtained after inoculation of samples with 1.0×10⁴ CFU/ml using the membrane filter with the rapid BACpro II kit, with approximately 10-fold higher sensitivity compared to rapid BACpro pretreatment alone. Among 31 bacteria-positive colonies in the samples, MALDI-TOF MS and membrane filtration (0.80 µm) with a rapid BACpro II kit was significantly more accurate compared to use of the kit alone (29 (82.9%) vs. 17 (48.6%) isolates identified, p<0.001). These results show that MALDI-TOF MS with a membrane filter and a rapid BACpro II kit is a quick and reliable method for bacterial identification in ear discharge samples.

This study aimed to investigate the bactericidal effect of ethanol-soluble lignin (ESL) from rice straw under ultraviolet-A (UV-A) irradiation. Following steam explosion pretreatment of rice straw, ethanol extraction was used to separate the lignin. The total phenolic content (TPC) in the ESL was 258 mg/g (gallic acid equivalent). Under UV-A irradiation, ESL exhibited bactericidal activity against Gram-positive and -negative bacteria at ≤10 mg TPC/L. Fluorescence experiments demonstrated significant adsorption of ESL to the cell surface of Staphylococcus aureus. Scanning electron microscopy revealed membrane deformation, producing many vesicles on the cell surface, when the ESL was activated by UV-A irradiation. These morphological changes were associated with an increase in membrane permeability, which elevated cell counts stained with propidium iodide to 51% and resulted in a 57% decrease in the intracellular ATP level. ESL exposed to UV-A light generated hydrogen peroxide. Addition of a scavenger of reactive oxygen species (ROS) or replacement of dissolved oxygen with argon gas in a bacterial suspension significantly suppressed the synergistic bactericidal activity of ESL and UV-A radiation, indicating that ROS are involved in the bactericidal mechanism. Organosolv lignin pretreated using steam explosion can be developed for antimicrobial application in combination with UV-A irradiation.

We compared the results of Legionella pneumophila detection in cooling tower water samples using Legiolert and the conventional plate culture method. Both 1 mL and 10 mL volumes of cooling tower water samples were analyzed using Legiolert. The concordance rate of the Legiolert-1 mL test and the plate culture method was 86.7%. The Legiolert-10 mL test and the plate culture method showed 85.0% concordance. Legiolert would be effective for hygiene control in cooling towers because it can easily detect viable L. pneumophila in cooling tower water and produces results comparable to the conventional plate culture method.

When microbial cells exposed to γ-rays and UV light are cultured in a liquid medium, reproductive death is observed. These cells can divide for one to several generations but cannot form visible colonies on an agar medium and are therefore eventually recognized as dead. We call this specific type of lethal injury "ρ injury" and the apparent growth observed "phantom growth". To estimate such a lethal cell population, we propose in this study the use of a double subculture method that combines a derivative of the previously reported growth delay analysis (GDA) method and the conventional colony count method. Furthermore, a novel theoretical model is developed for this purpose.

Consumer products such as detergents, fabric softeners, and cosmetics are typically used in various environments. Manufacturers must ensure the quality of products and ensure their safety through their lifecycle, from manufacturing to usage. Preservation efficacy testing (PET) is typically conducted to determine the preservative of a product prior to use. However, PET is time-consuming and laborious due to its long-term storage and culture-based detection methods. In this study, we focused on the metabolic activities of microorganisms and developed a rapid alternative to PET. We observed that 72 h of preservation was sufficient to predict preservation efficacy using the metabolic activity method. Finally, the accuracy of the metabolic activity method was compared to that of PET using a variety of products such as detergents and cosmetics. The accuracy of this alternative method exceeds 85% for highly fluid and easy-to-handle samples. These results suggest that the developed metabolic activity method possesses the potential to determine the preservative efficacy of products in only four days（72 h of preservation and 24 h of detection）. Thus, this method possesses the potential to provide a rapid and simple alternative to PET.

Bacterial diseases are among the primary constraints to marine fish aquaculture, which negatively impacting the health and economic viability of fish. Vaccines and paraprobiotics are being formulated as efficacious and sustainable alternatives to antibiotics in disease prevention and health management. Efficient inactivation of the bacterial pathogens without compromising their structural and immunogenic integrity is paramount to the formulation of such biological remedies. In this review, recent advances in methods of bacterial inactivation, including chemical treatments, ultrashort pulse lasers (USPL) , high hydrostatic pressure (HHP) , photodynamic inactivation (PDI) , and gamma irradiation, are addressed. Each method has its own advantages and limitations, indicating that a clear understanding of their mechanisms and uses is essential. Together, these novel methods have excellent potential for the improvement of bacterial control strategies in aquaculture systems. Future research needs to prioritize the optimization of these techniques for scale, safety, and regulatory compliance to enable broader application in marine fish farming. The incorporation of such technologies may lead to a resilient, more productive, and sustainable aquaculture industry.

This study investigated the pervaporation of hypochlorous acid (HOCl) using a vacuum-driven process with a separation module containing 6,000 silicone rubber (SR) hollow fibers. Gaseous hypochlorous acid (HOCl_(g)) discharged from the membrane module was accumulated in a 1 m³ chamber. Weakly acidic (pH 5.0) hypochlorite solutions with free available chlorine (FAC) concentrations of 100-1,000 mg/L were fed through the lumen of the SR hollow fibers. Both the HOCl permeation rate and the steady-state HOCl_(g) concentration increased with the feed FAC concentration. When a 1,000 mg/L hypochlorite solution was used, the HOCl_(g) concentration in the chamber reached 5,500 ppb within 40 min. This accumulated HOCl_(g), when applied to microorganisms on wet agar plates at a concentration of approximately 320 ppb, achieved a >3-log reduction in viable bacterial cells within 10 min and fungal spores within 20 min. These results demonstrate that high-rate pervaporation of HOCl can be achieved using an SR hollow fiber membrane in a vacuum-driven process, and the resulting HOCl_(g) is effective for rapid disinfection.

The commercial products of calcium hypochlorite (Ca（OCl) ₂) , a solid hypochlorite salt, are hygroscopic because of the presence of calcium chloride as an impurity. In this study, we investigated the volatilization of gaseous hypochlorous acid (HOCl _(g) ) from Ca (OCl) ₂ tablets and its disinfection efficacy against Staphylococcus aureus on wet agar plates were studied in a 75 m³ room. HOCl _(g) volatilization occurred spontaneously and continuously, even in ambient air. Under airflow conditions, the absorption of water vapor from the air into the Ca (OCl) ₂ tablet was accelerated, and numerous droplets were formed on the tablet surface. The deliquescent property of calcium chloride indices these phenomena. When a glass Petri dish containing 10 Ca (OCl) ₂ tablets was placed in the room under airflow conditions, HOCl _(g) volatilization of was enhanced, and the HOCl _(g) concentration in the room was maintained within the range of 60‒80 ppb for at least 24 h of volatilization. Viable S. aureus count on wet agar plates placed on the floor 1‒5 m away from the tablets decreased by 3.1-log after 1.5 h of exposure. This study indicates that sufficient concentrations of HOCl _(g) can be volatilized from Ca (OCl) ₂ tablets without the use of water, contributing to the disinfection of attached bacteria.