Reduction Of Spores Research Articles

Effect of Humidity on Sporicidal Activity of Iodine Vapor on Bacillus thuringiensis.

The emergence of Bacillus anthracis as a potential bioterrorism and biological warfare agent points to the need for safe, effective, and economical sporicides for infection prevention and control. This work examined the efficacy of iodine vapor decontamination technologies to inactivate a surrogate for B. anthracis, Bacillus thuringiensis spores on glass materials. 106-107 colony-forming units of spores inoculated onto circular glass cover slips were treated with different concentrations of iodine vapor under various temperature and relative humidity. Only minimal spore killing activity was observed at low humidity. Higher humidity levels, as well as pre-hydration or post-hydration of the spores, increased the rate of inactivation as long as the contact between spores and iodine was maintained in a hydrated environment. Significant sporicidal activity of 3-log and 6-log spore reduction has been observed with 2.1mgL-1 iodine vapor concentration at 90% relative humidity and 22°C, with 1 and 24h of exposure, respectively. The results showed that the relative humidity of the environment is of major importance in regulating the rate at which the spores are inactivated by iodine. The results of this study may provide insight into the parameters of effective decontamination procedures for Bacillus spores using gaseous iodine.

Sensitizing Clostridium difficile Spores with Germinants on Skin and Environmental Surfaces Represents a New Strategy for Reducing Spores via Ambient Mechanisms.

Background:Clostridium difficile is a leading cause of healthcare-associated infections worldwide. Prevention of C. difficile transmission is challenging because spores are not killed by alcohol-based hand sanitizers or many commonly used disinfectants. One strategy to control spores is to induce germination, thereby rendering the spores more susceptible to benign disinfection measures and ambient stressors.Methods/Results:C. difficile spores germinated on skin after a single application of cholic acid-class bile salts and co-germinants; for 4 C. difficile strains, recovery of viable spores from skin was reduced by ~0.3 log10CFU to 2 log10CFU after 2 hours and ~1 log10CFU to > 2.5 log10CFU after 24 hours. The addition of taurocholic acid to 70% and 30% ethanol significantly enhanced reduction of viable spores on skin and on surfaces. Desiccation, and to a lesser extent the presence of oxygen, were identified as the stressors responsible for reductions of germinated spores on skin and surfaces. Additionally, germinated spores became susceptible to killing by pH 1.5 hydrochloric acid, suggesting that germinated spores that remain viable on skin and surfaces might be killed by gastric acid after ingestion. Antibiotic-treated mice did not become colonized after exposure to germinated spores, whereas 100% of mice became colonized after exposure to the same quantity of dormant spores.Conclusions:Germination could provide a new approach to reduce C. difficile spores on skin and in the environment and to render surviving spores less capable of causing infection. Our findings suggest that it may be feasible to develop alcohol-based hand sanitizers containing germinants that reduce spores on hands.

Effects of processing parameters on the inactivation of Bacillus cereus spores on red pepper (Capsicum annum L.) flakes by microwave-combined cold plasma treatment

The efficacy of microwave-combined cold plasma treatment (MCPT) for inactivating Bacillus cereus spores contaminating red pepper (Capsicum annum L.) flakes was investigated. The effects of red pepper drying method, particle size, and water activity (aw) were also evaluated at two levels of microwave power (1700 and 2500W/cm2). The inactivation effect of MCPT was higher at higher microwave power. Spore reduction was more effective with vacuum-dried red pepper than far-infrared-dried flakes. A significantly higher level of spore reduction was observed with the red pepper sample with a smaller surface to volume ratio when one surface (exterior surface) was inoculated (p<0.05). Spore reduction by MCPT at high microwave power increased from 1.7 to 2.6logspores/cm2 when the aw of flake increased from 0.4 to 0.9 (p<0.05). MCPT did not change the color of red pepper flakes. MCPT demonstrated potential as a microbial decontaminating technology for red pepper flakes.

Benchmarking the minimum Electron Beam (eBeam) dose required for the sterilization of space foods

As manned space missions extend in length, the safety, nutrition, acceptability, and shelf life of space foods are of paramount importance to NASA. Since food and mealtimes play a key role in reducing stress and boredom of prolonged missions, the quality of food in terms of appearance, flavor, texture, and aroma can have significant psychological ramifications on astronaut performance. The FDA, which oversees space foods, currently requires a minimum dose of 44kGy for irradiated space foods. The underlying hypothesis was that commercial sterility of space foods could be achieved at a significantly lower dose, and this lowered dose would positively affect the shelf life of the product. Electron beam processed beef fajitas were used as an example NASA space food to benchmark the minimum eBeam dose required for sterility. A 15kGy dose was able to achieve an approximately 10log reduction in Shiga-toxin-producing Escherichia coli bacteria, and a 5log reduction in Clostridium sporogenes spores. Furthermore, accelerated shelf life testing (ASLT) to determine sensory and quality characteristics under various conditions was conducted. Using Multidimensional gas-chromatography–olfactometry–mass spectrometry (MDGC-O-MS), numerous volatiles were shown to be dependent on the dose applied to the product. Furthermore, concentrations of off –flavor aroma compounds such as dimethyl sulfide were decreased at the reduced 15kGy dose. The results suggest that the combination of conventional cooking combined with eBeam processing (15kGy) can achieve the safety and shelf-life objectives needed for long duration space-foods.

Investigation of the use of ultrasonication followed by heat for spore inactivation

Conventional thermal sterilization is the most commonly used technique to inactivate microbial spores in low acidic liquid food products. In recent years, food researchers have investigated ultrasonication in combination with heat as an alternate technology for the reduction of microbial spores. However, the competitive advantage of this process over conventional thermal sterilization has not been properly assessed. In this study, energy delivered by ultrasound was used to provide the heating needed, which fulfils 55% of the thermal energy requirement in addition to the effect caused by cavitation. The effect of pre-treatment with ultrasonication (20kHz, 750W) on decimal reduction time (D values) of Bacillus subtilis ​(B. subtilis) spores ATCC 6633 was evaluated in three different suspending media (water, whole milk and rice porridge) and were compared with thermal treatment. Among these, pre-treatment with ultrasonication (114μm, 1.1W/ml, 5min) of whole milk resulted in 35% reduction in D-value compared to thermal only treatment at 100°C whereas under the same treatment conditions, water and rice porridge gave only 18% and 4% reduction respectively. These reduction in D values through the use of combined technology is minimal unless excessive ultrasonication is used, which is commercially not viable.

Role of aqueous chlorine dioxide in controlling the growth of Fusarium graminearum and its application on contaminated wheat

Fusarium graminearum is the main worldwide causal agent of Fusarium head blight grain disease. The production of mycotoxin caused by Fusarium head blight epidemics of wheat affects the flour and malt products, which results in heavy economic losses to farmers. In this paper, an inactivation procedure for F. graminearum F7875 spores was tested and found to follow a first-order kinetic model. We characterized the inactivation of F7875 by aqueous chlorine dioxide (ClO2) under different concentrations (5–15 mg L−1). The results suggest that aqueous ClO2 significantly enhanced inactivation of F7875 at high concentration (15 mg L−1) compared to lower concentration of 5 and 10 mg L−1. The time required for a five-log reduction of F7875 spores was calculated based on the established models. Observed by scanning electron microscope, the ClO2 destroys the structure of the outer coats of F7875, the surface of F7875's hyphal appeared smooth prior to treatment, but after treatment with 30 mg L−1 aqueous ClO2, it appeared rugged and wrinkled. In conclusion, our study shows that treatment with aqueous ClO2 is an effective, fast, and safe method to control F. graminearum in grain production.

Supercritical Fluid CO2 Technique for Destruction of Pathogenic Fungal Spores in Solid Clinical Wastes

The present study deals with the inactivation of fungal spores in clinical waste using the advanced supercritical carbon‐dioxide (SC‐CO2) treatment technique. The process of inactivation was investigated under different conditions of pressure, temperature, and processing time. The efficiency of SC‐CO2 was determined in terms of log reduction and inactivation rate of fungal spores. Almost 100% inactivation of initial fungal spores was obtained. Predicted and experimental log reduction of fungal spores was found to be 5.93 and 6.00, respectively, under optimal conditions (35 MPa, 75°C in 90 min). SC‐CO2 treated Aspergillus niger and Penicillium simplicissimum spores were examined using scanning electron microscopy which showed spore damage in the form of rupture, tear, and shape distortion. These damages confirmed complete spore inactivation when no renewed fungal growth occurred after the treated samples were cultured onto fresh media. The inactivation of fungal spores using SC‐CO2 and autoclave inhibits the production of lipase, cellulase, amylase, and protease enzymes. Thus, without addition of any chemicals, the SC‐CO2 sterilization method can be potentially used for the inactivation of microorganisms in clinical waste as well as in food and pharmaceutical products.

0707 Efficient removal of spores from skim milk using microfiltration: Spore size and surface property considerations

Presence of spores in milk can cause numerous quality and shelf-life issues for dairy products. Microfiltration (MF) using a 1.4-μm pore size can effectively remove vegetative bacterial cells from milk and is used in commercial applications. However, this pore size may be not be equally effective in spore removal. The objective of this study was to determine the effectiveness of MF using 1.4- and 1.2-μm pore sizes for removing spores of Bacillus licheniformis (BL) and Geobacillus spp. (GEO) from skim milk. Cell size of both spores and vegetative cells was evaluated by scanning electron microscopy, surface charge by zeta potential analysis, and surface hydrophobicity by contact angle measurements, in triplicate. Commercially pasteurized skim milk was inoculated in a sterilized feed tank with a spore suspension, at about 106 spores/mL, and then treated by MF (in triplicate) using ceramic Isoflux membranes at 6°C, cross-flow velocity of 4.1 m/s, and transmembrane pressure between 69 and 74 kPa. Total aerobic plate count and spore count of the permeate were conducted. An unpaired t test was used to determine significant differences between samples at a P < 0.05 significance level. Vegetative cell length ranged between 2.40 and 3.82 μm and the width ranged between 0.39 and 0.64 μm. Spores were shorter and wider, averaging 1.39 to 1.58 μm in length and 0.63 to 0.88 μm in width, therefore having a higher probability to pass through a 1.4-μm membrane. Indeed, for BL (1.39-μm length × 0.63-μm width) an average spore reduction of only 2.17 log was achieved by 1.4-μm pore size. For the 1.2-μm membrane, a 4.57 log reduction was achieved. For GEO spores, their larger spore size (1.58-μm length by 0.81-μm width) allowed a practically complete removal using both pore sizes (spore counts in permeate below the detection limit). The surface properties of BL and GEO indicated that they may interact differently with the membrane. Both spore species and the ceramic membrane had negative surface charge at the milk pH, indicating slight electrostatic repulsion between them. Geobacillus spp. spores were hydrophilic, whereas BL spores were slightly hydrophobic; the ceramic membrane surface changes from hydrophilic (in unfouled state) to hydrophobic after adsorption of caseins during MF. Consequently, BL spores may experience slight attractive force to the membrane through hydrophobic interactions, which will facilitate their passage through the membrane. A good understanding of all factors that affect the removal of spores using MF can lead to the production of milk with lower spore count, higher quality, and increased shelf life.

Application of response surface methodology for modeling and optimization of Bacillus subtilis spores inactivation by the UV/persulfate process

Stronger disinfection techniques are required to inactivate Bacillus subtilis spores as surrogate microorganisms for Cryptosporidium parvum oocysts. In this study, the effects of UV and persulfate separately and also in combination were investigated on B. subtilis spore inactivation. Central composite design and response surface methodology were used to optimize target microorganism reduction. Contact time, initial pH, and persulfate dosage were considered as input experimental variables. Based on the design of the experiments, first and second order response surface models have been developed to correspond to the output response of B. subtilis spore reduction. It can be concluded that microbial reduction by UV alone was more effective than persulfate, while the combined UV/persulfate process demonstrated the highest log reduction (4.1) under the following optimal conditions: 60 min contact time, pH = 7.8, and persulfate dosage of 30 mM. On the other hand, the optimal condition for UV treatment was a contact time of 60 min at a pH of 5.0, which led to a 3.19 log spore inactivation. Consequently, the UV/persulfate system can be introduced as an alternative disinfectant for the inactivation of B. subtilis spores.

Application of high pressure processing for controlling Clostridium tyrobutyricum and late blowing defect on semi-hard cheese

In this study we evaluated the application of different high pressure (HP) treatments (200–500 MPa at 14 °C for 10 min) to industrial sized semi-hard cheeses on day 7, with the aim of controlling two Clostridium tyrobutyricum strains causing butyric acid fermentation and cheese late blowing defect (LBD). Clostridium metabolism and LBD appearance in cheeses were monitored by sensory (cheese swelling, cracks/splits, off-odours) and instrumental analyses (organic acids by HPLC and volatile compounds by SPME/GC–MS) after 60 days. Cheeses with clostridial spores HP-untreated and HP-treated at 200 MPa showed visible LBD symptoms, lower concentrations of lactic, citric and acetic acids, and higher levels of pyruvic, propionic and butyric acids and of 1-butanol, ethyl and methyl butanoate, and ethyl pentanoate than cheeses without spores. However, cheeses with clostridial spores and HP-treated at ≥ 300 MPa did not show LBD symptoms and their organic acids and volatile compounds profiles were comparable to those of their respective HP-treated control cheeses, despite HP treatments caused a low spore reduction. A decrease in C. tyrobutyricum spore counts was observed after curd pressing, which seems to indicate an early spore germination, suggesting that HP treatments ≥300 MPa were able to inactivate the emerged C. tyrobutyricum vegetative cells and, thereby, prevent LBD.

Influence of thermosonication on Geobacillus stearothermophilus inactivation in skim milk

The influence of high intensity ultrasound coupled with thermoprocessing on the inactivation of Geobacillus stearothermophilus vegetative cells and spores in skim milk powder was explored using response surface methodology and two polynomial models were developed. Optimization of cell reduction (4.8 log) was found to be at 19.75% total solids (TS), 45 °C, and 30 s, while optimization of spore reduction (0.45 log) was found to be at 31.5% TS, 67.5 °C, and 17.5 s. Model verification experiments were performed using common milk powder processing conditions. Results showed the inactivation of cells and spores to be most effective before (9.2% TS, 75 °C, and 10 s) and after (50% TS, 60 °C, and 10 s) the evaporator during milk powder processing and may produce an additive effect in microbial reduction when the two locations are combined, resulting in a 5.8 log reduction for vegetative cells and 0.51 log reduction for spores.

Reproducible elimination of Clostridium difficile spores using a clinical area washer disinfector in 3 different health care sites

Following a Clostridium difficile infection outbreak, the Infection Prevention and Control team at our institution queried the risk of transmission via bedpans reprocessed in washer disinfectors (WDs). This study's objective was to determine the effectiveness of the mechanical action, detergent, and temperature on the eradication of C difficile spores in 1 type of WD model. Three types of reusable bedpans/pots were inoculated with sterile human feces that contained 1 × 10(7) CFU/mL C difficile spores. The 0.3 mL fecal-spore suspension was inoculated in sealed cryovials. These items were reprocessed using the longest wash cycle of WDs in 9 clinical units, and then tested for residual C difficile spores. The number of colonies on each replicate organism detection and counting plate was recorded after anaerobic incubation at 35°C for 48 hours, and the log reduction was calculated. All 9 WDs met the manufacturer's operational specifications. Forty-three (96%) of 45 bedpans had no viable spores (>5.9 log10C difficile spore reduction). Two bedpans had 1 to 2 spores remaining. Viable C difficile spores were isolated from all 9 cryovials. Results demonstrated that when operating the WD as stipulated, C difficile spores were satisfactorily eliminated from bedpan surfaces. Temperature alone was insufficient to kill C difficile spores. It also suggested the importance of staff training, machine maintenance, and WD purchase specifications.

Effectiveness of the SYSTEM 1E Liquid Chemical Sterilant Processing System for reprocessing duodenoscopes

A troubling number of health care-acquired infection outbreaks and transmission events, some involving highly resistant microbial pathogens and resulting in serious patient outcomes, have been traced to reusable, high-level disinfected duodenoscopes in the United States. The Food and Drug Administration (FDA) requested a study be conducted to verify liquid chemical sterilization efficacy of SYSTEM 1E(®) Liquid Chemical Sterilant Processing System (STERIS Corporation, Mentor, OH) with varied duodenoscope designs under especially arduous conditions. Here, we describe the system's performance under worst case SYSTEM 1E(®) processing conditions. The test protocol challenged the system's performance by running a fractional cycle to evaluate reduction of recoverable test spores from heavily contaminated endoscopes, including all channels and each distal tip, under worst case SYSTEM 1E(®) processing conditions. All devices were successfully liquid chemically sterilized, showing greater than a 6 log10 reduction of Geobacillus stearothermophilus spores at every inoculation site of each duodenoscope tested, in less than half the exposure time of the standard cycle. The successful outcome of the additional efficacy testing reported here indicates that the SYSTEM 1E(®) is an effective low-temperature liquid chemical sterilization method for duodenoscopes and other critical and semicritical devices. It offers a fast, safe, convenient processing alternative while providing the assurance of a system expressly tested and cleared to achieve liquid chemical sterilization of specific validated duodenoscope models.

Thermal and Pressure-Assisted Thermal Destruction Kinetics for Spores of Type A Clostridium botulinum and Clostridium sporogenes PA3679

The purpose of this study was to determine the inactivation kinetics of the spores of the most resistant proteolytic Clostridium botulinum strains (Giorgio-A and 69-A, as determined from an earlier screening study) and of Clostridium sporogenes PA3679 and to compare the thermal and pressure-assisted thermal resistance of these spores. Spores of these strains were prepared using a biphasic medium method. C. sporogenes PA3679 spores were heat treated before spore preparation. Using laboratory-scale and pilot-scale pressure test systems, spores of Giorgio-A, 69-A, and PA3679 suspended in ACES [N-(2-acetamido)-2-aminoethanesulfonic acid] buffer (pH 7.0) were exposed to various combinations of temperature (93 to 121°C) and pressure (0.1 to 750 MPa) to determine their resistance. More than a 5-log reduction occurred after 3 min at 113°C for spores of Giorgio-A and 69-A and after 5 min at 117°C for spores of PA3679. A combination of high temperatures (93 to 121°C) and pressures yielded greater log reductions of spores of Giorgio-A, 69-A, and PA3679 compared with reduction obtained with high temperatures alone. No survivors from initial levels (>5.0 log CFU) of Giorgio-A and 69-A were detected when processed at a combination of high temperature (117 and 121°C) and high pressure (600 and 750 MPa) for <1 min in a pilot-scale pressure test system. Increasing pressure from 600 to 750 MPa at 117°C decreased the time from 2.7 to 1 min for a >4.5-log reduction of PA3679 spores. Thermal D-values of Giorgio-A, 69-A, and PA3679 spores decreased (i.e., 29.1 to 0.33 min for Giorgio-A, 40.5 to 0.27 min for 69-A, and 335.2 to 2.16 min for PA3679) as the temperature increased from 97 to 117°C. Pressure-assisted thermal D-values of Giorgio-A, 69-A, and PA3679 also decreased as temperature increased from 97 to 121°C at both pressures (600 and 750 MPa) (i.e., 17.19 to 0.15 min for Giorgio-A, 9.58 to 0.15 min for 69-A, and 12.93 to 0.33 min for PA3679 at 600 MPa). At higher temperatures (117 or 121°C), increasing pressure from 600 to 750 MPa had an effect on pressure-assisted thermal D-values of PA3679 (i.e., at 117°C, pressure-assisted thermal D-value decreased from 0.55 to 0.28 min as pressure increased from 600 to 750 MPa), but pressure had no effect on pressure-assisted thermal D-values of Giorgio-A and 69-A. When compared with Giorgio-A and 69-A, PA3679 had higher thermal and pressure-assisted thermal D-values. C. sporogenes PA3679 spores were generally more resistant to combinations of high pressure and high temperature than were the spores of the C. botulinum strains tested in this study.

Assessment of Clostridium difficile Burden in Patients Over Time With First Episode Infection Following Fidaxomicin or Vancomycin.

In patients with first episode Clostridium difficile infection treated with vancomycin or fidaxomicin, more patients receiving fidaxomicin achieved at least 2 log10 colony-forming units/g reduction in spores at the follow-up visit (P=.02). Similar to published literature, a higher proportion of patients receiving fidaxomicin demonstrated sustained clinical response.

Biocontrol of tomato plant diseases caused by Fusarium solani using a new isolated Aspergillus tubingensis CTM 507 glucose oxidase

The present study focuses on the potential of glucose oxidase (GOD) as a promising biocontrol agent for fungal plant pathogens. In fact, a new GOD producing fungus was isolated and identified as an Aspergillus tubingensis. GOD (125 AU) has been found to inhibit Fusarium solani growth and spore production. Indeed, GOD caused the reduction of spores, the formation of chlamydospores, the induction of mycelial cords and the vacuolization of mycelium. In vivo assays, GOD acted as a curative treatment capable of protecting the tomato plants against F. solani diseases. In fact, the incidence was null in the curative treatment with GOD and it is around 45% for the preventive treatment. The optimization of media composition and culture conditions led to a 2.6-fold enhancement in enzyme activity, reaching 81.48U/mL. This study has demonstrated that GOD is a potent antifungal agent that could be used as a new biofungicide to protect plants from diseases.

Control of Alicyclobacillus spp. vegetative cells and spores in apple juice with rosemary extracts

In this study, we initially investigated the antimicrobial activities of two commercial rosemary extracts (V20, V40) against Alicyclobacillus strains, with the ultimate purpose to determine whether these can be used in apple juice for the control of growth of alicyclobacilli. Minimum inhibitory concentrations (MICs) were first determined, and put through sensory analysis. Addition of the rosemary extracts to apple juice at their MICs did not change the colour, odour, taste or opacity of the apple juice. Growth kinetics studies with these rosemary extracts indicated a reduction in vegetative cells for Alicyclobacillus acidoterrestris, Alicyclobacillus hesperidum and Alicyclobacillus cycloheptanicus in Bacillus acidoterrestris broth and in apple juice. Further studies with A. acidoterrestris spores showed that the MICs of these rosemary extracts had relatively low effects on spore numbers in B. acidoterrestris broth, but had a spore number inhibition index >15% in apple juice. A four-fold increase in the rosemary extract concentrations showed the opposite effects: greater reduction in spores in B. acidoterrestris broth (inhibition index, >60%) than in apple juice (inhibition index, <10%). These data indicate that at their MICs, the V20 and V40 rosemary extracts allow outgrowth of spores but reduce vegetative cells, acting together with the low pH or other particular constituents of the apple juice. Rosemary extracts applied at their MICs thus represent an alternative method for the control of A. acidoterrestris in apple juice.

Ultra high pressure homogenization (UHPH) inactivation of Bacillus amyloliquefaciens spores in phosphate buffered saline (PBS) and milk.

Ultra high pressure homogenization (UHPH) opens up new areas for dynamic high pressure assisted thermal sterilization of liquids. Bacillus amyloliquefaciens spores are resistant to high isostatic pressure and temperature and were suggested as potential surrogate for high pressure thermal sterilization validation. B. amyloliquefaciens spores suspended in PBS buffer (0.01 M, pH 7.0), low fat milk (1.5%, pH 6.7), and whole milk (3.5%, pH 6.7) at initial concentration of ~106 CFU/mL were subjected to UHPH treatments at 200, 300, and 350 MPa with an inlet temperature at ~80°C. Thermal inactivation kinetics of B. amyloliquefaciens spores in PBS and milk were assessed with thin wall glass capillaries and modeled using first-order and Weibull models. The residence time during UHPH treatments was estimated to determine the contribution of temperature to spore inactivation by UHPH. No sublethal injury was detected after UHPH treatments using sodium chloride as selective component in the nutrient agar medium. The inactivation profiles of spores in PBS buffer and milk were compared and fat provided no clear protective effect for spores against treatments. Treatment at 200 MPa with valve temperatures lower than 125°C caused no reduction of spores. A reduction of 3.5 log10CFU/mL of B. amyloliquefaciens spores was achieved by treatment at 350 MPa with a valve temperature higher than 150°C. The modeled thermal inactivation and observed inactivation during UHPH treatments suggest that temperature could be the main lethal effect driving inactivation.

Induced sporicidal activity of chlorhexidine against Clostridium difficile spores under altered physical and chemical conditions.

BackgroundChlorhexidine is a broad-spectrum antimicrobial commonly used to disinfect the skin of patients to reduce the risk of healthcare-associated infections. Because chlorhexidine is not sporicidal, it is not anticipated that it would have an impact on skin contamination with Clostridium difficile, the most important cause of healthcare-associated diarrhea. However, although chlorhexidine is not sporicidal as it is used in healthcare settings, it has been reported to kill spores of Bacillus species under altered physical and chemical conditions that disrupt the spore’s protective barriers (e.g., heat, ultrasonication, alcohol, or elevated pH). Here, we tested the hypothesis that similarly altered physical and chemical conditions result in enhanced sporicidal activity of chlorhexidine against C. difficile spores.Principal Findings C. difficile spores became susceptible to heat killing at 80°C within 15 minutes in the presence of chlorhexidine, as opposed to spores suspended in water which remained viable. The extent to which the spores were reduced was directly proportional to the concentration of chlorhexidine in solution, with no viable spores recovered after 15 minutes of incubation in 0.04%–0.0004% w/v chlorhexidine solutions at 80°C. Reduction of spores exposed to 4% w/v chlorhexidine solutions at moderate temperatures (37°C and 55°C) was enhanced by the presence of 70% ethanol. However, complete elimination of spores was not achieved until 3 hours of incubation at 55°C. Elevating the pH to ≥9.5 significantly enhanced the killing of spores in either aqueous or alcoholic chlorhexidine solutions.ConclusionsPhysical and chemical conditions that alter the protective barriers of C. difficile spores convey sporicidal activity to chlorhexidine. Further studies are necessary to identify additional agents that may allow chlorhexidine to reach its target within the spore.

Field evaluation of the effectiveness of mesh crop covers for the protection of potatoes from tomato potato psyllid

Tomato potato psyllid (TPP; Bactericera cockerelli) is a serious pest of solanaceous crops in New Zealand. Control of TPP is currently dominated by synthetic biocides, although this method is curative and does not always prevent transmission of TPP-vectored plant diseases. This study evaluated mesh crop covers as non-chemical alternatives for controlling TPP in potato crops. Over two growing seasons in Canterbury, New Zealand, potatoes growing under mesh covers were found to have reduced numbers of TPP nymphs and adults, increased tuber size, increased overall yield and enhanced storage potential compared with uncovered plots. There was also a slight reduction in potato blight spores under mesh, and the actual occurrence of blight was slightly reduced in one trial. The results of this study indicate that mesh crop covers could provide a viable option for potato growers who wish to protect their crops from TPP without using chemical insecticides.