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PubMedDate not supplied

Evaluation of arthrocentesis site bacterial flora before and after 4 methods of preparation in horses with and without evidence of skin contamination.

OBJECTIVE: To evaluate the effectiveness of four methods of povidone-iodine preparation on skin bacterial flora of arthrocentesis sites, in horses, with and without evidence of skin contamination. STUDY DESIGN: Prospective randomized study. ANIMALS: Twenty-four adult horses. METHODS: Horses were assigned to either the clean or contaminated group based on housing environment and visual evidence of contamination. Using a moist sterile swab, microbial culture samples were obtained from the skin over the distal interphalangeal joints immediately before and after preparation. Each site was aseptically prepared with 1 of 4 povidone-iodine techniques: 10-minutes scrub, 5-minutes scrub, three 30-second scrubs, or commercial one-step iodophor surgical solution. Colony forming units (CFUs) were determined for each sample, 24 hours after inoculation, on blood agar plates. RESULTS: Mean (+/-SD) pre-scrub CFUs/mL was significantly higher in the contaminated group (9588.33+/-1223.65) compared with the clean group (4489.00+/-3842.03) (P<.01). After preparation of the arthrocentesis sites, there were no significant differences in post-scrub CFUs/mL among the 10 minutes (mean clean, 46.00+/-64.36; mean contaminated, 28.67+/-18.04), 5 minutes (mean clean, 84.17+/-109.80; mean contaminated, 40.33+/-44.52), three 30 seconds povidone-iodine scrubs (mean clean, 95.50+/-172.29; mean contaminated, 46.67+/-56.94), or application of a commercial one-step iodophor surgical solution (mean clean, 102.17+/-161.78; mean contaminated 117.67+/-143.78); or between the clean (81.96+/-131.69) and contaminated groups (58.33+/-85.90) (P<.01). CONCLUSIONS: Preparation of the distal interphalangeal joint arthrocentesis site with each of these techniques significantly reduces the bacterial flora to a similar level for arthrocentesis in horses with and without evidence of skin contamination. Clinical Relevance- Aseptic preparation of the skin over the distal interphalangeal joint may be accomplished with any of these techniques.

Administration, Cutaneous↗

PubMed1997

Use of rRNA gene restriction patterns to evaluate lactic acid bacterium contamination of vacuum-packaged sliced cooked whole-meat product in a meat processing plant.

Molecular typing was applied to an in-plant lactic acid bacterium (LAB) contamination analysis of a vacuum-packaged sliced cooked whole-meat product. A total of 982 LAB isolates from the raw mass, product, and the environment at different production stages were screened by restriction endonuclease (EcoRI and HindIII) analysis. rRNA gene restriction patterns were further determined for different strains obtained from each source. These patterns were used for recognizing the spoilage-causing LAB strains from the product on the sell-by day and tracing the sources and sites of spoilage LAB contamination during the manufacture. LAB typing resulted in 71 different ribotypes, of which 27 were associated with contamination routes. Raw material was distinguished as the source of the major spoilage strains. Contamination of the product surfaces after cooking was shown to be airborne. The removal of the product from the cooking forms was localized as a major site of airborne LAB contamination. Food handlers and some surfaces in contact with the product during the manufacture were also contaminated with the spoilage strains. Some LAB strains were also able to resist cooking in the core of the product bar. These strains may have an effect on the product shelf life by contaminating the slicing machine. The air in the slicing department and adjacent cold room contained very few LAB. Surface-mediated contamination was detected during the slicing and packaging stages. Food handlers also carried strains later found in the packaged product. Molecular typing provided useful information revealing the LAB contamination sources and sites of this product. The production line will be reorganized in accordance with these results to reduce spoilage LAB contamination.

Bacteria↗

PubMed1985

A multi-route exposure assessment of chemically contaminated drinking water.

This report provides an example of how a single source of contamination could potentially contribute to all routes of exposure. A modeling approach was used to estimate multiple exposure routes in an attempt to assess the health significance of gasoline-contaminated drinking water supplies. This model consisted of a two-compartment, indoor air quality equation that calculates the contribution made by ambient and indoor air contaminated by a pollutant volatilized from drinking water to that pollutant's inhalation burden. In addition, the model uses the traditional equations for assessing a pollutant's oral and dermal burdens. Benzene, toluene and xylene were used as surrogates for gasoline contamination to determine the contribution of contaminated water to adult and child body burdens from indoor air, oral (drinking water and food) and dermal exposure routes. The contribution thus calculated for each chemical was compared to the EPA's Office of Drinking Water Health Advisories. In terms of acute exposure, the use of chemically contaminated water for showering purposes may generate vapor in the confined area of the bathroom at levels sufficient to cause or contribute to mucous tissue irritation, as commonly reported in affected homes. High temperatures and humidity may also contribute to these effects, especially in the bathroom. In terms of chronic exposure, the use of chemically contaminated water at EPA-recommended guideline amounts in an affected home may result in inhalation, oral and dermal exposures leading to cumulative doses exceeding adult and child total daily body burdens based on EPA's Health Advisories. Thus, this model indicates that the traditional standard/guidelines derivation processes should be reevaluated to consider the pollutant contribution from multiple routes of exposure. The New Jersey Departments of Health and Environmental Protection conducted a study in which concentrations of several pollutants including benzene in the breathing zone were measured during a 15-minute shower in homes with contaminated water. The findings suggest that the air quality model used in the present study may satisfactorily predict the airborne concentrations of pollutants in, at least, the bathroom after showering with contaminated water (Pearson rank correlation coefficient of 0.773 with p = 0.0012 for n = 14). The findings of the present study support the use of an adjustment factor for all exposure durations to account for exposures to other sources of the contaminant, i.e., urban, occupational, and food. A value of 20% seems appropriate based on the study's findings.(ABSTRACT TRUNCATED AT 400 WORDS)

Aerosols↗

PubMedDate not supplied

The influence of blood contamination on bond strengths between dentin and an adhesive resin cement.

The objective of this study was to determine in which step of adherent surface treatments blood contamination affects the bond strength between an adhesive resin and dentin. The coronal part of bovine incisors was polished flat to expose the dentin. The specimens were randomly divided into three groups and specific surface treatments were applied to each group: (1) a self-etching primer application (SP group); (2) 38% phosphoric acid etching followed by primer (non-HC group); (3) acid etching followed by 10% sodium hypochlorite solution application and primer (HC group). The dentin surface was contaminated by human blood before or after either step of the surface treatments. The contaminated surfaces were washed with water after 30-second exposure and air-dried. A stainless-steel rod was adhered on the dentin surface with Panavia 21 after completing the surface treatment(s), and the tensile bond strength was measured. Fifteen subgroups including control groups were tested. If blood contamination occurred before collagen fibers were exposed by either phosphoric acid etching or self-etching primer application, the contamination presented almost no influence on bond strength. Blood contamination of the dentin surface where collagen fibers had been exposed decreased the bond strength. However, when the contaminated collagen fibers were dissolved or when the contamination occurred after the exposed collagen fibers were dissolved, the bond strength was maintained. The bond strength was markedly decreased when the contamination occurred after the primer application (Scheffé's Comparison, SP group: p = 0.0003, non-HC group: p < 0.0001), but was restored by reapplication of the self-etching primer. This study revealed that the effects of blood contamination on the bond strength of adhesive resin to dentin vary greatly depending on the adherent surface conditions.

Acid Etching, Dental↗

PubMed2003

Interference of contaminating DNA in the quantification of a toluene-induced tod gene in Pseudomonas putida.

To determine the extent of interference of co-extracted DNA contamination in the quantification of the tod gene transcript, two different concentrations of RNA (high, 500 ng/microl; low, 250 ng/microl) from a toluene-induced culture of Pseudomonas putida were treated with different amounts of DNase (2, 4, 6 and 8 U) and incubated for 30 and 60 min. The highly sensitive and reproducible TaqMan system was used to quantify the transcript of the tod gene, the tod gene in contaminating DNA and the 16S rRNA gene in DNase-treated RNA samples. For the high RNA concentration, the shorter incubation time (30 min) lowered the level of contaminating DNA as evidenced by the presence of 2.5 x 10(6) copies of the tod gene before treatment to 1.4 x 10(5) copies/microl (8 U), whereas, irrespective of the DNase units used, the longer incubation time (60 min) considerably lowered the level of DNA contamination (2.5 x 10(6) to 6.5 x 10(2) copies of the tod gene/microl). However, for the low RNA concentration, DNase treatment was found to be equally effective in lowering the level of contaminating DNA (10(6) to 10(2) copies of the tod gene/mu), irrespective of the incubation time and the amount of DNase used. Although the results of gel electrophoresis of conventional PCR amplification of the low RNA concentration revealed the absence of the target gene in contaminating DNA, the results of the TaqMan PCR indicated that a very low amount of contaminating DNA (less than 10(3) copies of the tod gene/mul) was still present in RNA samples, even after the DNase treatment. The number of copies of the tod gene transcript in RNA samples did not show any marked variation because of the DNase treatment. However, the proportion of contaminating DNA in RNA samples considerably decreased due to the treatment (0.01 to 0.000001). Furthermore, these results suggested that the extent of the removal of contaminating DNA from RNA samples depends on the concentration of RNA, the amount of DNase used and the incubation time. It is also suggested that the copies of the catabolic genes in contaminating DNA have to be quantified along with the target genes in RNA samples to have a more accurate quantification of the target genes for better understanding of their roles in many microbial processes.

Journal Article↗

PubMed1998

Salivary contamination during bonding procedures with a one-bottle adhesive system.

OBJECTIVE: The effect of salivary contamination of enamel and dentin on bonding efficacy of an experimental one-bottle resin adhesive was investigated. METHOD AND MATERIALS: The adhesive was a light-curing urethane dimethacrylate/hydroxyethyl methacrylate/4-methacryloxyethyl trimellitate anhydride mixture dissolved in acetone. Evaluation parameters were shear bond strength and marginal gap width in a dental cavity. Apart from a control group without contamination (group 1), etched enamel and dentin were (2) contaminated with saliva and air dried; (3) contaminated, rinsed, and blot dried; (4) coated with adhesive, contaminated, rinsed, and blot dried; (5) coated with adhesive, light cured, contaminated, rinsed, and air dried; or (6) treated as in group 5, with additional adhesive application after air drying. RESULTS: There was no negative effect in groups 3 and 4, compared with control. Air drying after salivary contamination (group 2) resulted in low shear bond strengths and wide marginal gaps. Contamination of the cured adhesive layer (groups 5 and 6) had no adverse effect on enamel shear bond strengths, but resulted in 50% reduced dentin shear bond strengths and wide marginal gaps. CONCLUSION: The one-bottle adhesive system is relatively insensitive to salivary contamination, provided that the contamination occurs prior to light curing of the adhesive and is carefully rinsed and blot dried. Salivary contact after adhesive curing must be avoided.

Adhesives↗

PubMed1989

Contamination of commercially available quisqualic acid by glutamate-like and aspartate-like substances.

Six different batches of the glutamic acid analogue quisqualic acid were analyzed with high-pressure liquid chromatography (HPLC). All batches examined showed contaminant peaks. Different batches had different contaminant peaks and differing amounts of each contaminant. Every batch of quisqualic acid tested demonstrated a contaminant peak which co-eluted with exogenously added glutamic acid. Certain batches possessed a contaminant which co-eluted with aspartic acid. The levels of glutamate-like contamination ranged from 0.08 to 0.60%, and the levels of aspartate-like contamination ranged from undetectable amounts to 0.80%. The amount of combined glutamate- and aspartate-like contamination of each batch of quisqualate correlated very highly with the ability of that batch to interact with non-quisqualate receptors in an autoradiographic binding assay. These non-quisqualate receptors are likely N-methyl-D-aspartate (NMDA) receptors. Thus, when high concentrations of quisqualate are used experimentally, contamination is likely to produce spurious effects at non-quisqualate glutamate receptors. Quisqualate itself may be a more specific agonist than assumed previously.

Aspartic Acid↗

PubMed2004

Effects of cleaning and disinfection in reducing the spread of Norovirus contamination via environmental surfaces.

A reverse transcriptase polymerase chain reaction assay was used to study the transfer of Norovirus (NV) from contaminated faecal material via fingers and cloths to other hand-contact surfaces. The results showed that, where fingers come into contact with virus-contaminated material, NV is consistently transferred via the fingers to melamine surfaces and from there to other typical hand-contact surfaces, such as taps, door handles and telephone receivers. It was found that contaminated fingers could sequentially transfer virus to up to seven clean surfaces. The effectiveness of detergent- and disinfectant-based cleaning regimes typical of those that might be used to decontaminate faecally contaminated surfaces and reduce spread of NV was also compared. It was found that detergent-based cleaning with a cloth to produce a visibly clean surface consistently failed to eliminate NV contamination. Where there was faecal soiling, although a combined hypochlorite/detergent formulation at 5000 ppm of available chlorine produced a significant risk reduction, NV contamination could still be detected on up to 28% of surfaces. In order consistently to achieve good hygiene, it was necessary to wipe the surface clean using a cloth soaked in detergent before applying the combined hypochlorite/detergent. When detergent cleaning alone or combined hypochlorite/detergent treatment failed to eliminate NV contamination from the surface and the cleaning cloth was then used to wipe another surface, the virus was transferred to that surface and to the hands of the person handling the cloth. In contrast, were surfaces where contaminated with NV-infected faecal suspension diluted to 1 in 10 and 1 in 80, intended to simulate surfaces that have become contaminated after secondary transfer, treatment with a combined bleach/detergent formulation, without prior cleaning, was sufficient to decontaminate surfaces and prevent transfer.

Caliciviridae Infections↗

PubMedDate not supplied

Increase of the PCDD/F-contamination of milk, butter and meat samples by use of contaminated citrus pulp.

In Germany from 1993 to 1997, the polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) contamination of food decreased slowly but constantly. However, for milk and butter, this trend was gradually reversed beginning in September 1997: From summer 1997 to February 1998 the average PCDD/F contamination of dairy products increased from a low level of about 0.6 pg I-TEQ/g fat in summer 1997. The dioxin content, of a limited number of randomly collected samples, rose on average to 1.41 pg I-TEQ/g fat (median 1.06 pg I-TEQ/g fat) in different regions of Germany in February 1998. A butter sample from the Netherlands with 1.96 pg I-TEQ/g fat hinted at the same source. The congener pattern in all contaminated milk and butter samples had elevated amounts of 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD. Also, meat samples (beef, cow's meat and veal) with the same dioxin pattern were found to contain between 1.72 and 4.26 pg I-TEQ/g fat (background contamination of 0.53 pg I-TEQ/g fat). Large number of samples were analyzed to find a key for the cause. With a farmer producing milk with about 4.9 pg I-TEQ/g fat, a new source of PCDD/F for food contamination was discovered: the use of PCDD/F contaminated citrus pulp from Brazil as feed material for ruminants on a very large scale. Containing about 5-10 ng I-TEQ/kg, this component was about 20-100 times more highly contaminated than average feed with background contamination. Very complex pieces of circumstantial evidence were gathered to prove the correlation between this component of feed and the increase of dioxin contamination in milk. With respect to the huge trade of this feed ingredient on the global market, many other countries were involved. As an immediate response on these findings, the European Community fixed a preliminary maximum permitted level of 500 pg I-TEQ/kg citrus pulp, valid since August 1998.

Animal Feed↗

PubMed1996

Microbial contamination of antiseptics and disinfectants.

BACKGROUND: There have been a number of reports on microbial contamination of antiseptics and disinfectants. At present, however, the necessity of measures to prevent contamination do not seem to be fully appreciated. We investigated microbial contamination of antiseptics and disinfectants that are used in our hospital. METHODS: Fifty-one samples of benzalkonium chloride and chlorhexidine gluconate that were being used in the hospital were examined. Viability of the contaminants detected in these samples was also tested in the agents. Then we examined measures to prevent contamination of these agents. RESULTS: Microbial contamination was detected at 10(2) to 10(7) CFU/ml in the following samples: 6 of 23 samples of cotton balls soaked in 0.02% benzalkonium chloride kept in a canister for antisepsis and disinfection (26.1%); 7 of 13 samples of 0.02%, benzalkonium chloride or 0.02% chlorhexidine gluconate in an irrigation apparatus kept at 37 degrees C for vaginal douching (53.8%); and 9 of 15 samples of 0.02% benzalkonium chloride or 0.05% chlorhexidine gluconate for storage of suction catheters in a plastic bottle (60%). The major contaminants were Burkholderia cepacia, Pseudomonas aeruginosa, Xanthomonas maltophilia, and Pseudomonas fluorescens. The first two organisms examined grew in the agents. After improvements in the handling of the antiseptics and disinfectants, no microbial contamination was observed. CONCLUSIONS: It is necessary to check microbial contamination of diluted benzalkonium chloride and diluted chlorhexidine gluconate that are in use. Such products are not recommended as antiseptics.

Anti-Infective Agents, Local↗

PubMed2006

Influence of harvest bacterial contamination on autologous peripheral blood progenitor cells post-transplant.

Microbiological contamination of manipulated blood products, including hematopoietic progenitors obtained from peripheral blood, is an infrequent but persistent problem in transplant units. The relevance of such contamination in causing patient infection has been reported as insignificant, but the effect on the post-transplant course has not been well documented. We studied the incidence of bacterial contamination in autologous peripheral blood progenitor cell transplants in two of the bench processing steps, as well as the repercussions in the post-transplant course affecting incidence of infections, transfusion requirements and time to engraftment. A total of 365 aphereses performed on 152 patients were cryopreserved in 617 bags. In 31 of these bags (5.0%), bacterial cultures were positive for Coagulase-negative Staphylococcus (31.1%), S. epidermidis (21.9%), Corynebacterium sp. (6.3%), S. warneri (6.3%), Stenotrophomonas maltophilia (6.3%), Streptococcus sp. (9.4%), Viridans group Streptococcus (3.1%) and more than one bacteria (Coagulase-negative Staphylococcus plus Corynebacterium) (15.6%). Half of the bags were contaminated at the time of freezing and the others at the time of thawing. The 31 contaminated bags were infused into 17 patients. In five of these the same contaminating bacteria was found. No difference between the two groups of patients (contaminated and non-contaminated) was found on the day the fever started, length of fever, blood transfusion requirements and engraftment, but length of hospitalization was significantly greater in patients receiving contaminated transplants.

Bacteria↗

PubMed1993

Strategies for the avoidance of bacterial contamination of blood components.

Gram staining and bacterial culturing methods were used to determine the incidence of bacterial contamination of cellular blood components at the time of transfusion reactions. Over a 5-year period, 2208 (4.3%) of 51,278 transfusions were complicated by reactions. Overall bacterial contamination occurred in 5 (0.03%) of 17,928 transfusions of single-donor apheresis platelets, 1 (0.14%) of 712 transfusions of pooled random-donor platelet concentrates, 1 (0.003%) of 31,385 transfusions of red cells, and 0 of 1253 transfusions of fresh-frozen plasma. Gram staining done at the time of positive cultures was positive in three of six cases. Although six of seven recipients of contaminated components suffered no clinical sequelae, contaminated transfusions may have been a contributing cause of death in one case. Attempts were made to avoid the transfusion of contaminated cellular blood components by performing routine bacterial cultures: 0 of 341 quality control cultures were positive. To avoid the transfusion of contaminated platelets by identifying bacteria, Gram staining was performed in all single-donor apheresis platelet units collected on open systems and daily in platelets stored > 48 hours: 8 (0.15%) of 5334 smears done on 3829 platelet units were interpreted as positive, and those units were not transfused, but only two of eight units were culture positive. These studies suggest that bacterial contamination can result in adverse clinical sequelae in transfusion recipients and that both culturing and Gram staining are poor methods of screening for contaminated units. More sensitive and specific methods of generalized screening for bacterial contamination are needed.

Adolescent↗

PubMed2001

The response of cattle and sheep to feed contaminated with rodent faeces.

On farms where rats and mice are present, unprotected livestock feed may become contaminated with rodent faeces, thereby creating a possible source of infection for cattle and sheep. Livestock unable to avoid contaminated feed may choose to eat it entirely, reject it completely or attempt to reject faeces selectively while consuming some of the feed. Two experiments were conducted to investigate which of these three responses were demonstrated by livestock. Ten cattle and ten sheep were presented individually with three repeats of ten feed treatments. Treatments were based on two feed types (meal and pelleted compound), with three levels of contamination (none, 'low' and 'high'), from one of two rodent species (rat and mouse). Avoidance behaviour was greater for feed contaminated with rat faeces compared to feed contaminated with mouse faeces. At low levels of rat contamination there was evidence that livestock actively rejected faeces whilst consuming feed. At higher levels of contamination animals rejected faeces and feed. Livestock could not actively discriminate against mouse faeces and thus rejection of feed was used to avoid faeces ingestion. Despite rejection of contaminated feed and some discrimination against faeces, significant numbers of rodent faeces were ingested illustrating that livestock feeding behaviour cannot prevent ingestion of rodent faeces. Feed contaminated with rodent faeces therefore poses a significant risk of disease infection to livestock.

Animal Feed↗

PubMed2003

Soil contamination and plant uptake of heavy metals at polluted sites in China.

We investigated heavy metal contamination in soils and plants at polluted sites in China including some with heavy industries, metal mining, smelting and untreated wastewater irrigation areas. We report our main findings in this paper. The concentrations of heavy metals, including Cd and Zn, in the soils at the investigated sites were above the background levels, and generally exceeded the Government guidelines for metals in soil. The concentrations of metals in plants served to indicate the metal contamination status of the site, and also revealed the abilities of various plant species to take up and accumulate the metals from the soil. Substantial differences in the accumulation of heavy metals were observed among the plant species investigated. Polygonum hydropiper growing on contaminated soils in a sewage pond had accumulated 1061 mg kg(-1) of Zn in its shoots. Rumex acetosa L. growing near a smelter had accumulated more than 900 mg kg(-1) of Zn both in its shoots and roots. Therefore these species have potential for phytoremediation of metal-contaminated sites. Our results indicate the need to elucidate the dynamics of soil metal contamination of plants and the onward movement of metal contaminants into the food chain. Also our results indicate that the consumption of rice grown in paddy soils contaminated with Cd, Cr or Zn may pose a serious risk to human health, because from 24 to 22% of the total metal content in the rice biomass was concentrated in the rice grain. Platanus acerifolia growing on heavily contaminated soil accumulated only very low levels of heavy metals, and this mechanism for excluding metal uptake may have value in crop improvement. Sources of metal entering the environmental matrices studied included untreated wastewater, tailings or slurries and dust depositions from metal ore mining, and sewage sludge. Pb, Zn or Cd concentrations declined with the distance from metal smelter in accordance with a good exponential correlation (R2>0.9), and this shows that metal dust deposition is an important contributor to metal contamination of soils.

Biodegradation, Environmental↗

PubMed2004

Persistence of Salmonella enterica serovar typhimurium on lettuce and parsley and in soils on which they were grown in fields treated with contaminated manure composts or irrigation water.

There are many sources of pathogen contamination of vegetable crops in the field that include manure used as fertilizer and irrigation water. An avirulent strain of Salmonella enterica serovar Typhimurium was added to three different types of composts-PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline stabilized dairy manure compost)-and irrigation water at 10(7) colony forming units (cfu)/g and 10(5) cfu/mL, respectively, to determine under field conditions the persistence of salmonellae in soils treated with these composts or irrigation water, and also on leaf lettuce and parsley grown on such treated soil. Contaminated compost was applied to soil in the field as a strip at a rate of 4.5 metric tons/hectare on the day before lettuce and parsley seedlings were transplanted. Contaminated irrigation water was applied only once on the plants at the rate of 2 liters per plot on the same day after the seedlings were transplanted. Twenty-five plots, each measuring 1.8 x 4.6 meters, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but applied with contaminated water) and five replication plots for each treatment. Salmonella persisted for 161 and up to 231 days in soils amended with contaminated composts on which lettuce and parsley, respectively, were grown, and was detected for up to 63 days and 231 days on lettuce and parsley, respectively. The type of contaminated compost had minimal effect on the persistence of S. Typhimurium in soil. Occurrence of Salmonella on vegetables and survival in soil on which these vegetables were grown, irrespective of source of contamination through irrigation water or compost, were similar, suggesting both contaminated manure compost and irrigation water can play important roles in contaminating soil and vegetables with Salmonella for an extended period of time.

Colony Count, Microbial↗

PubMed2005

Internal contamination of gloves: routes and consequences.

The effect of internal glove contamination was investigated using N-methyl pyrrolidone (NMP) as a biological marker to assess systemic absorption when wearing internally contaminated gloves, and when not wearing gloves but subjected to the same challenge contaminant. The routes by which the insides of gloves become contaminated were also investigated. The area of dermal contamination was quantified using a fluorescent tracer dye and a surface monitoring fluorimeter. The main routes of internal glove contamination were found to be self-contamination, cuff entry and failed gloves. Wearing internally contaminated gloves led to higher systemic absorption than was gained from the equivalent skin contamination when not wearing gloves. Repeat wetting of fingers with aqueous NMP, when gloves were not worn, gave higher systemic absorption than the equivalent continuous exposure, probably due to the low volatility of NMP leading to increased concentration and longer residence time on the skin.

Environmental Monitoring↗

PubMed2004

Contamination affects the performance of insecticidal baits against German cockroaches (Dictyoptera: Blattellidae).

The effects of contamination of insecticidal bait formulations, by using mint oil and silica aerogel, were evaluated in a series of laboratory experiments against the German cockroach, Blattella germanica (L.). Bait consumption at 3 d for uncontaminated baits ranged from 0.01 g for Avert dust to 0.399 g for Combat dry bait with hydramethylnon presented in a station. LT50 values for uncontaminated gel bait deposits ranged from 0.4 d for PreEmpt containing imidacloprid to 4.1 d for Maxforce containing hydramethylnon. As a group, significantly more gel bait was consumed than solid formulations even when both formulations had similar concentrations of the same active ingredient. As a result, gel baits were significantly more toxic than solid formulations. Application of mint oil directly to bait deposits significantly decreased bait consumption and increased overall LT50 values. When bait formulation types were examined individually, there was no difference in consumption or toxicity between contaminated and uncontaminated gel formulations. Contaminated solid baits, however, had significantly greater LT50 values and less consumption than uncontaminated solid baits. Gel formulations probably absorbed the contaminants and removed them from the surface of the bait deposits resulting in normal bait consumption and toxicity. Gel and solid bait deposits, inside plastic exposure stations or alone with no station and placed onto mint oil-contaminated substrates, had significantly lower bait consumption and greater LT50 values than baits placed on uncontaminated substrates. Contamination of a baited area is more likely than contamination of just the bait deposit and therefore a more realistic test of the effects of contamination on bait performance. The importance of contamination to the performance of cockroach baits is discussed.

Animals↗

PubMed2006

Stochastic, compartmental, and dynamic modeling of cross-contamination during mechanical smearing of cheeses.

Cheese smearing is a complex process and the potential for cross-contamination with pathogenic or undesirable microorganisms is critical. During ripening, cheeses are salted and washed with brine to develop flavor and remove molds that could develop on the surfaces. Considering the potential for cross-contamination of this process in quantitative risk assessments could contribute to a better understanding of this phenomenon and, eventually, improve its control. The purpose of this article is to model the cross-contamination of smear-ripened cheeses due to the smearing operation under industrial conditions. A compartmental, dynamic, and stochastic model is proposed for mechanical brush smearing. This model has been developed to describe the exchange of microorganisms between compartments. Based on the analytical solution of the model equations and on experimental data collected with an industrial smearing machine, we assessed the values of the transfer parameters of the model. Monte Carlo simulations, using the distributions of transfer parameters, provide the final number of contaminated products in a batch and their final level of contamination for a given scenario taking into account the initial number of contaminated cheeses of the batch and their contaminant load. Based on analytical results, the model provides indicators for smearing efficiency and propensity of the process for cross-contamination. Unlike traditional approaches in mechanistic models, our approach captures the variability and uncertainty inherent in the process and the experimental data. More generally, this model could represent a generic base to use in modeling similar processes prone to cross-contamination.

Algorithms↗