Jiancheng Qi

Decontamination of Bacillus subtilis var. niger spores on selected surfaces by chlorine dioxide gas.

ObjectiveChlorine dioxide (CD) gas has been used as a fumigant in the disinfection of biosafety laboratories. In this study, some experiments were conducted to assess the inactivation of spores inoculated on six materials [stainless steel (SS), painted steel (PS), polyvinyl chlorid (PVC), polyurethane (PU), glass (GS), and cotton cloth (CC)] by CD gas. The main aims of the study were to determine the sporicidal efficacy of CD gas and the effect of prehumidification before decontamination on sporicidal efficacy.MethodsMaterial coupons (1.2 cm diameter of SS, PS, and PU; 1.0 cm×1.0 cm for PVC, GS, and CC) were contaminated with 10 μl of Bacillus subtilis var. niger (ATCC 9372) spore suspension in mixed organic burden and then dried in a biosafety cabinet for 12 h. The spores were recovered by soaking the coupons in 5 ml of extraction liquid for 1 h and then vortexing the liquid for 1 min.ResultsThe log reductions in spore numbers on inoculated test materials exposed to CD gas [0.080% (volume ratio, v/v) for 3 h] were in the range of from 1.80 to 6.64. Statistically significant differences were found in decontamination efficacies on test material coupons of SS, PS, PU, and CC between with and without a 1-h prehumidification treatment. With the extraction method, there were no statistically significant differences in the recovery ratios between the porous and non-porous materials.ConclusionsThe results reported from this study could provide information for developing decontamination technology based on CD gas for targeting surface microbial contamination.

Facile preparation and antibacterial properties of cationic polymers derived from 2-(dimethylamino)ethyl methacrylate

One kind of polymeric quaternary ammonium salts derived from dimethylaminoethyl methacrylate are synthesised and their antibacterial efficacy is evaluated, indicating that the antibacterial efficacy is greatly enhanced after polymerisation and the mechanism of this effect is clarified by zeta potential tests, SEM and protein leakage measurements.

Kinetics of Inactivation of Bacillus subtilis subsp. niger Spores and Staphylococcus albus on Paper by Chlorine Dioxide Gas in an Enclosed Space

ABSTRACT Bacillus subtilis subsp. niger spore and Staphylococcus albus are typical biological indicators for the inactivation of airborne pathogens. The present study characterized and compared the behaviors of B. subtilis subsp. niger spores and S. albus in regard to inactivation by chlorine dioxide (ClO2) gas under different gas concentrations and relative humidity (RH) conditions. The inactivation kinetics under different ClO2 gas concentrations (1 to 5 mg/liter) were determined by first-order and Weibull models. A new model (the Weibull-H model) was established to reveal the inactivation tendency and kinetics for ClO2 gas under different RH conditions (30 to 90%). The results showed that both the gas concentration and RH were significantly (P < 0.05) and positively correlated with the inactivation of the two chosen indicators. There was a rapid improvement in the inactivation efficiency under high RH (>70%). Compared with the first-order model, the Weibull and Weibull-H models demonstrated a better fit for the experimental data, indicating nonlinear inactivation behaviors of the vegetative bacteria and spores following exposure to ClO2 gas. The times to achieve a six-log reduction of B. subtilis subsp. niger spore and S. albus were calculated based on the established models. Clarifying the kinetics of inactivation of B. subtilis subsp. niger spores and S. albus by ClO2 gas will allow the development of ClO2 gas treatments that provide an effective disinfection method. IMPORTANCE Chlorine dioxide (ClO2) gas is a novel and effective fumigation agent with strong oxidization ability and a broad biocidal spectrum. The antimicrobial efficacy of ClO2 gas has been evaluated in many previous studies. However, there are presently no published models that can be used to describe the kinetics of inactivation of airborne pathogens by ClO2 gas under different gas concentrations and RH conditions. The first-order and Weibull (Weibull-H) models established in this study can characterize and compare the behaviors of Bacillus subtilis subsp. niger spores and Staphylococcus albus in regard to inactivation by ClO2 gas, determine the kinetics of inactivation of two chosen strains under different conditions of gas concentration and RH, and provide the calculated time to achieve a six-log reduction. These results will be useful to determine effective conditions for ClO2 gas to inactivate airborne pathogens in contaminated air and other environments and thus prevent outbreaks of airborne illness.

Immobilized antibacterial peptides on polyethylene terephthalate non-woven fabrics and antibacterial activity evaluation

Two novel antibacterial materials were prepared by immobilizing antibacterial peptides protamine sulfate and polymyxin sulfate on polyethylene terephthalate (PET) non-woven fabrics in this study. The fabrics were surface modified by a chemical procedure to create carboxyl groups followed by grafting coupling agent and immobilization of peptide. Scanning electron microscopy images showed that there were no changes on the surface of the fabrics after treatment. X-ray photoelectron spectroscopy confirmed that protamine and polymyxin were successfully grafted on the surface of the PET fabrics. Antibacterial testing using the liquid droplet method showed that fabrics treated with both peptides had excellent antibacterial activity against Escherichia coli and Staphylococcus aureus.

One-pot fabrication and antimicrobial properties of novel PET nonwoven fabrics.

Recently, with the ever-growing demand for healthy living, more and more research is focused on materials capable of killing harmful microorganisms around the world. It is believed that designing such protective materials for hygienic and biomedical applications can benefit people in professional areas and daily life. Thus, in this paper, one novel kind of antibacterial poly(ethylene terephthalate) (PET) nonwoven fabrics was conveniently one-pot prepared, with the combined immobilization of two biological antimicrobial agents, i.e. ε-polylysine and natamycin, by using the soft methacrylate nonwoven fabrics adhesives. Then, the antimicrobial activities of the functional fabrics were investigated by using the standard shaking-flask method, showing excellent antibacterial efficiency (AE) against both Escherichia coli (8099) and Staphylococcus aureus (ATCC 6538) (AE > 99.99%) compared with untreated PET nonwoven fabrics. The anti-bioaerosol tests also showed similar trends. Meantime, scanning electron microscopy analysis indicated that the bacteria on the antibacterial PET appeared to be partly bacteriolyzed and showed much less viability than those on the pristine ones. Moreover, the long residual biocidal action of such modified PET fabrics was also evaluated, and the antibacterial activity of antibacterial fibers was unaffected by the 3 month artificially accelerated aging.

A pilot study on using chlorine dioxide gas for disinfection of gastrointestinal endoscopes

ObjectivesThis pilot study of employing chlorine dioxide (CD) gas to disinfect gastrointestinal endoscopes was conducted to meet the expectations of many endoscopy units in China for a high-efficiency and low-cost disinfectant.MethodsAn experimental prototype with an active circulation mode was designed to use CD gas to disinfect gastrointestinal endoscopes. One type of testing device composed of polytetrafluoroethylene (PTFE) tubes (2 m long, inner diameter 1 mm) and bacterial carrier containers was used to simulate the channel of the endoscope. PTFE bacterial carriers inoculated with Bacillus atrophaeus with or without organic burden were used to evaluate the sporicidal activity of CD gas. Factors including exposure dosage, relative humidity (RH), and flow rate (FR) influencing the disinfection effect of CD gas were investigated. Moreover, an autoptic disinfecting test on eight real gastrointestinal endoscopes after clinical use was performed using the experimental prototype.ResultsRH, exposure dosage, organic burden, and the FR through the channel significantly (P<0.05) affected the disinfection efficacy of CD gas for a long and narrow lumen. The log reduction increased as FR decreased. Treatment with 4 mg/L CD gas for 30 min at 0.8 L/min FR and 75% RH, resulted in complete inactivation of spores. Furthermore, all eight endoscopes with a maximum colony-forming unit of 915 were completely disinfected. The cost was only 3 CNY (0.46 USD) for each endoscope.ConclusionsThe methods and results reported in this study could provide a basis for further studies on using CD gas for the disinfection of endoscopes.中文概要目 的以大型消化内镜中心控制消化内镜消毒成本的需求为牵引,评价二氧化氯气体应用于消化内镜消毒的可行性。创新点首次研究了二氧化氯气体对细长管腔内部的消毒效果及其影响因素,并以此为基础研究了采用主动灌流方法的二氧化氯气体消毒消化内镜的原型机。方 法设计了一种聚四氟乙烯(PTFE)细长管腔实验装置(长2 m,内径1 mm),在其进气端、中部和出气端分别设置PTFE 菌片容器。将含有PTFE 菌片和细长管腔和置于平皿内的PTFE 菌片装载于一种消毒实验原型机中,通过主动灌流使二氧化氯气体流过细长管腔,平皿内的PTFE菌片直接曝露于二氧化氯气体中,分别评价二氧化氯气体对PTFE 细长管腔内壁和外壁的消毒效果。以萎缩芽孢杆菌为指示微生物,评价二氧化氯剂量(浓度与时间的乘积)、相对湿度、流过细长管腔的流量及有机干扰物对消毒效果的影响。同时使用实验原型机对8 条消化内镜进行了实效验证实验。结 论实验结果表明,除了相对湿度、二氧化氯剂量和有机干扰物都显著影响二氧化氯气体的消毒效果外(图3、5 和6),随着经过细长管腔流量的增大,二氧化氯气体对细长管腔内部的芽孢杀灭对数值有减小的趋势(图4)。按照本文设计的流程,应用实验原型机对8 条消化内镜消毒后,未检出存活的微生物。应用二氧化氯气体消毒消化内镜时,其每条内镜的消毒剂成本小于3 元人民币。

Response surface modeling for the inactivation of Bacillus subtilis subsp. niger spores by chlorine dioxide gas in an enclosed space.

ABSTRACT Bacillus subtilis subsp. niger spores are a commonly used biological indicator to evaluate the disinfection of an enclosed space. In the present study, chlorine dioxide (ClO2) gas was applied to inactivate B. subtilis subsp. niger spores in an enclosed space. The effects of the ClO2 gas concentration (1-3 mg/l), relative humidity (RH, 30-70%) and exposure time (30-90 min) were investigated using a response surface methodology (RSM). A three-factor Box-Behnken experimental design was used. The obtained data were adequately fitted to a second-order polynomial model with an R2adj of 0.992. The ClO2 gas concentration, RH and exposure time all significantly (P<0.05) and positively correlated with the inactivation of B. subtilis subsp. niger spores. The interaction between the ClO2 gas concentration and RH as well as that between the exposure time and RH indicated significant and synergistic effects (P<0.05). The predictive model was validated by additional eight experiments and proven to be with good accuracy. Overall, this model established by the RSM could show the trend of the inactivation of spores, indicate the interactions between important factors, and provide a reference to determine effective conditions for the disinfection in different enclosed spaces by ClO2 gas. Implications: The inactivation of indoor biological contaminants plays an important role in preventing the transmission of pathogens and ensuring human safety. The predictive model using response surface methodology indicates the influence and interaction of the main factors on the inactivation of Bacillus subtilis subsp. niger spores by ClO2 gas, and can predict a ClO2 gas treatment condition to achieve an effective sterilization of enclosed spaces. The results in this paper will provide a reference for the application of ClO2 gas treatments for indoor disinfection.

A blunt sampling probe developed for an in situ leak test of HEPA filters in high-level biosafety laboratory

High-efficiency air filtration is an important means of preventing harmful aerosol overflow in biosafety laboratories. For convenience in the in situ scanning leak test of a high-efficiency particulate air (HEPA) filter to ensure the filters intactness, a cylindrical blunt sampling probe is developed. The sampling inlet is of the slot type and the inlets length equal the width of the HEPA filter. Thus, the entire downstream face of the HEPA filter may be scanned. To evaluate the blunt sampling probes ability to detect leaks, the scanning leak test performed on a HEPA filter unit was compared with a test using the thin-walled rectangular sampling probe that is recommended by relevant standards. Based on the comparison, the leak penetration determined using the blunt sampling probe was slightly lower than that determined using the reference sampling probe. Additionally, differences were observed according to the location that was tested. However, the blunt sampling probe could detect leaks through the comprehensive analysis of the local penetration of most-penetrating particle size (MPPS) and non-MPPS particles.