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PubMed2006

Biodegradation of p-nitrophenol by aerobic granules in a sequencing batch reactor.

In this study, aerobic granules to treat wastewater containing p-nitrophenol (PNP) were successfully developed in a sequencing batch reactor (SBR) using activated sludge as inoculum. A key step was the conditioning of the activated sludge seed to enrich for biomass with improved settleability and higher PNP degradation activity by implementing progressive decreases in settling time and stepwise increases in PNP concentration. The aerobic granules were cultivated at a PNP loading rate of 0.6 kg/ m3 x day, with glucose to boost the growth of PNP-degrading biomass. The granules had a clearly defined shape and appearance, settled significantly faster than activated sludge, and were capable of nearly complete PNP removal. The granules had specific PNP degradation rates that increased with PNP concentration from 0 to 40.1 mg of PNP/L, peaked at 19.3 mg of PNP/(g of VSS) x h (VSS = volatile suspended solids), and declined with further increases in PNP concentration as substrate inhibition effects became significant. Batch incubation experiments show that the PNP-degrading granules could also degrade other phenolic compounds, such as hydroquinone, p-nitrocatechol, phenol, 2,4-dichlorophenol, and 2,6-dichlorophenol. The PNP-degrading granules contained diverse microbial morphotypes, and PNP-degrading bacteria accounted for 49% of the total culturable heterotrophic bacteria. Denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments showed a gradual temporal shift in microbial community succession as the granules developed from the activated sludge seed. Specific oxygen utilization rates at 100 mg/L PNP were found to increase with the evolution of smaller granules to large granules, suggesting that the granulation process can enhance metabolic efficiency toward biodegradation of PNP. The results in this study demonstrate that it is possible to use aerobic granules for PNP biodegradation and broadens the benefits of using the SBR to target treatment of toxic and recalcitrant organic compounds.

Aerobiosis↗

PubMed1998

Microbiological profile and potential hazards associated with imported and local brands of tomato paste in Nigeria.

Cans of three tomato paste brands (two of which are imported and one produced locally) showing defective or normal appearance were purchased from various retail outlets and analysed for microbial composition and pH values. Substantially higher total viable counts were observed in samples from defective cans but the lowest population was found in the local brand. Ratio of mesophilic to thermophilic micro-organisms increased in samples obtained from cans showing visible defects. Anaerobic spore counts were higher than the aerobic population in both normal and defective cans, but the counts varied with the brands. Four dominant bacterial genera (Bacillus, Clostridium, Lactobacillus and Leuconostoc) were isolated from the samples with the greater proportion being spore-formers. Percentage occurrence of Clostridium thermosaccharolyticum was appreciably higher in samples from defective cans while a preponderance of Lactobacillus occurred in samples from normal cans. Of the moulds isolated, Absidia and Aspergillus fumigatus showed a higher percentage in defective cans. pH values higher than the critical safe level of 4.6 were found in cans with visible defects and greater microbial diversity with higher microbial load was more often associated with these samples. Imported brands showed more undesirable microbial quality and pH values, making them potentially hazardous.

Bacteria, Aerobic↗

PubMedDate not supplied

Nitrification and denitrification rates of Everglades wetland soils along a phosphorus-impacted gradient.

Little information is available on the effect of phosphorus (P) enrichment on nitrogen (N) biogeochemical cycling in wetland soil. Of particular importance are the coupled nitrification-denitrification reactions that regulate the microbially mediated loss of N from wetland systems. Soils from the northern Florida Everglades have been affected by P loading from surface waters over the past 40 years. Elevated P levels have been show to have an effect on the size and activity of the microbial pool and a decrease in the N to P ratio of the microbial biomass. The objective of the study was to determine if P enrichment in soils affected microbial activities related to nitrification and denitrification in these flooded, peat soils. Potential nitrification rates of soil and detritus were determined using constantly stirred reactors under aerobic conditions while denitrification rates were determined from anaerobic incubations of slurry. Nitrification rates showed two distinct linear phases, a slower initial rate, signifying activity of nitrifiers present, followed by a sharp increase in the NH4+ conversion rate indicative of maximum potential rates. Initial rates of nitrification were highest in the surficial detrital layer decreasing with soil depth and did not correlate to soil total P. The potential rates of nitrification were 13 times greater than the initial rates. Potential denitrification rates were highest in the detritus and 0- to 10-cm soil interval with significantly lower values in the 10- to 30-cm soil interval, significantly correlated to total P of the soil. A significant (P < 0.01) relationship was seen between potential denitrification rates and soil total P suggesting an increased rate of N removal from P-enriched regions of the northern Everglades.

Conservation of Natural Resources↗

PubMed2006

Bedding and within-pen location effects on feedlot pen runoff quality using a rainfall simulator.

Soluble salts, nutrients, and pathogenic bacteria in feedlot-pen runoff have the potential to cause pollution of the environment. A 2-yr study (1998-1999) was conducted at a beef cattle (Bos taurus) feedlot in southern Alberta, Canada, to determine the effect of bedding material [barley (Hordeum vulgare L.) straw versus wood chips] and within-pen location on the chemical and bacterial properties of pen-floor runoff. Runoff was generated with a portable rainfall simulator and analyzed for chemical content (nitrogen [N], phosphorus [P], soluble salts, electrical conductivity [EC], sodium adsorption ratio [SAR], dissolved oxygen [DO], and pH) and populations of three groups of bacteria (Escherichia coli, total coliforms, total aerobic heterotrophs at 27 degrees C) in 1998 and 1999. Bedding had a significant (P < or = 0.05) effect on NH4-N concentration and load in 1999, SO4 load in 1998, SO4 concentration and load in 1999, and total coliforms in both years; where these three variables were higher in wood than straw pens. Location had a significant effect on EC and concentrations of total Kjeldahl nitrogen (TKN), Na, K, SO4, and Cl in 1998, and total coliforms in both years. These seven variables were higher at the bedding pack than pen floor location, indicating that bedding packs were major reservoirs of TKN, soluble salts, and total coliforms. Significantly higher dissolved reactive phosphorus (DRP), total P, and NH4-N concentrations and loads at the bedding pack location in wood pens in 1998, and a similar trend for TKN concentration in 1999, indicated that this bedding-location treatment was a greater source of nutrients to runoff than the other three bedding-location treatments. Bedding, location, and their interaction may therefore be a potential tool to manage nutrients, soluble salts, and bacteria in feedlot runoff.

Alberta↗

PubMed2006

Influence of free-stall flooring on comfort and hygiene of dairy cows during warm climatic conditions.

An evaluation of behavioral and hygienic conditions was carried out with 4 materials used as free-stall flooring for dairy cows: polyethylene vinyl acetate (EVA) and polypropylene vinyl acetate (PVA) mats, wood shavings, and solid manure. The free-stall type selected by cows was evaluated in response to changes in environmental temperature and humidity. Two tests were used: 1) a preference test, in which 8 cows were housed in a pen with 32 free stalls and 4 types of flooring; and 2) an aversion test, in which 32 cows were placed in 4 pens, each with 8 free stalls. The free stalls in each pen had a single type of bedding material. These tests showed that the comfort of dairy cows was predominantly influenced by environmental conditions. The preference test for lying showed that cows preferred free-stall floors with EVA mats over those with PVA mats, wood shavings, and solid manure (332.4 +/- 24.0 vs. 130.8 +/- 6.2, 160.9 +/- 23.7, and 102.6 +/- 23.2 min/d, respectively), but under conditions of heat stress, with a temperature-humidity index > 80, they chose wood shavings and solid manure lying areas. These results were confirmed by the aversion test. In all experimental and environmental conditions, the PVA mats were the least suitable. The mats contaminated with organic manure and the free stalls bedded with wood shavings and organic solids did not differ in either the coliform load on the lying surfaces (EVA mats: 290 +/- 25; PVA mats: 306 +/- 33; wood shavings: 290 +/- 39; and solid manure: 305 +/- 23 log(10) cfu/mL) or the total bacterial count in the raw milk (EVA mats: 232 +/- 22; PVA mats: 233 + 24; wood shavings: 221 +/- 24; and solid manure: 220 +/- 25 log(10) cfu/mL). These results demonstrate that the comfort of dairy cows housed in barns with free stalls as resting areas does not depend only on the material used, but also on the value of the material in microenvironmental conditions.

Animals↗

PubMed2004

[Nanoparticulate silver. A new antimicrobial substance for bone cement].

BACKGROUND: Multiresistant bacteria have become an important problem in prosthetic joint infections. Their frequent resistance against gentamicin, which is commonly used in antibiotic-loaded bone cements, makes a new prophylaxis necessary. METHODS: PMMA-cement was loaded with 1% nanoparticulate silver and its antibacterial activity tested in vitro against gentamicin-resistant MRSE and MRSA strains as well as being compared to the activity of plain and gentamicin-loaded bone cements. A quantitative elution testing was also done to study the potentially cytotoxic effects of NanoSilver cement. RESULTS: Unloaded and PMMA-cement loaded with 2% gentamicin did not exhibit any antibacterial activity against MRSE and MRSA. At 1%, NanoSilver cement completely inhibited the proliferation of MRSA and MRSE. NanoSilver bone cement did not show any significant differences compared to the non-toxic control group. CONCLUSIONS: If these promising in vitro results can be confirmed in vivo, NanoSilver bone cement may be of considerable value in total joint arthroplasty.

Animals↗

PubMed2005

Preventive measures to reduce bioaerosol exposure during refuse collection: results of field studies in the real-life situation.

The aim of the present research project was to investigate and evaluate technical and organisational measures targeted at bioaerosol reduction during the refuse collection and to determine the exposure of refuse collectors to dust, fungi and endotoxins in an on-the-job situation with different vehicle technologies and states of hygiene. The following technical factors were found to influence the bioaerosol concentration at the refuse collector's workplace: compaction method, lifting device control, rave rail height, hopper depth, design of intake area and dust interception. For instance, notably higher total fungal counts were recorded with rotating drum compaction than with packer plate compaction. A hinged lid closure at the lifting device in conjunction with a suction unit induced a positive effect. In addition, the automatic lifting system had a positive influence on rear-end loaders, as did loading operation control from the closed driver's cab on side loaders. Regular internal and external high-pressure cleaning of the lifting device at intervals of not more than 14 days is recommended as a basic rule for vehicle hygiene.

Aerosols↗

PubMed1987

Collagen and collagenase in ulcer tissue--2. Restraint and water immersion induced gastric lesions and effects of cimetidine and misoprostol.

Collagenase activity was considered to play an important role in the process of ulcer formation, as one of the aggressive factors. We measured the collagen metabolism using the restraint and water immersion stress ulcer model with time and studied the effects of cimetidine and misoprostol (PGE1 derivative) on the collagen metabolism. The active forms and total collagenases in the gastric mucosal connective tissues were elevated as early as at two hours after loading by restraint and water immersion stress, and a decrease in the amount of collagen (as hydroxyproline) was observed. Increase in the collagenase activity was inhibited in groups to which cimetidine or misoprostol was given before restraint and water immersion. From these results it is believed that an elevation of collagenase activity related directly to tissue destruction might be involved, as well as a decrease in the gastric mucosal blood flow, in the etiology of ulcers due to restraint and water immersion stress.

Alprostadil↗

PubMed2003

Quantification of incidental needle and suture contamination during strabismus surgery.

PURPOSE: To quantify the level of bacterial contamination of needles and sutures immediately after use in strabismus surgery. METHODS: Strabismus surgery was performed on 56 eyes from 31 pediatric strabismus surgical cases. Preoperative site preparation included instillation of 5% povidone-iodine in the conjunctival fornices in all cases. A total of 124 needles and 127 sutures were cultured immediately after final scleral passage. RESULTS: Seventeen of the 31 cases (54.8%) produced at least one positive specimen. Nineteen per cent of the needles and 25.2% of the sutures were culture positive. The bulk of positive specimens (96.7% of needles, 91.3% of sutures) produced 3 or less colony forming units, corresponding to 7 or less total viable organisms per needle or sutures in accordance with the dilution scheme. Coagulase-negative staphylococci overwhelmingly predominated. CONCLUSIONS: Needles and sutures used in strabismus surgery can become contaminated during surgery despite preoperative povidone-iodine preparation. The number of viable bacterial contaminants is usually below the level known to consistently produce experimental endophthalmitis. However, a few needles and sutures carried a high contaminant load, suggesting the possibility that contaminated needles and sutures could potentially cause postoperative intraocular infection.

Adolescent↗

PubMed1995

Semiquantitative study of tinea capitis and the asymptomatic carrier state in inner-city school children.

OBJECTIVE: To quantify and characterize the asymptomatic carrier state of tinea capitis in school children from the inner city. METHODS: All students attending a parochial school (kindergarten through seventh grade) in the city of Philadelphia were cultured for tinea capitis periodically over 16 months (1404 hemi-scalp cultures from 224 children). RESULTS: Our initial prevalence study of this all-black population (ages 5 to 13 years) found a 3% rate of index cases (symptomatic) and a 14% rate of asymptomatic carriers (without black-dot lesions, obvious hair loss, scaling, crusts, pustules, or erythema). Trichophyton tonsurans was the predominant dermatophyte (96% of 125 positive cultures; Microsporum canis was the only other isolate). Fifty percent of all positive cultures came from children in kindergarten and first grade; first grade had the highest rate of index cases. The overall prevalence of asymptomatic carriers was not higher in the classes containing index cases. Fifty-nine percent of asymptomatic carriers had a 1+ spore load (1 to 10 colonies isolated per scalp), while 74% of index cases had a 4+ spore load (> 150 total colonies). Forty-five untreated asymptomatic carriers were followed for 2 to 5 months: 19 (42%) became culture-negative; of these, 17 (90%) had a 1+ spore load. CONCLUSIONS: We found that inner-city black school children who are asymptomatic carriers of T tonsurans had lower spore loads than index cases. Index cases did not appear to be the primary mode of transmission within a classroom. More than half of untreated asymptomatic carriers remained culture-positive after 2 months and probably play a role in the transmission of tinea capitis within this population.

Adolescent↗

PubMed2002

Bacteriological characteristics of dressed young pigeon (squabs) Columba livia domesticus.

A total of 50 frozen squabs carcasses were collected from different retail markets in Cairo and Giza governorates. The collected samples were examined bacteriologically. The aerobic plate count, the enterobacteriaceae and the Staphylococcus count were 6.6 x 10(5), 6.3 x 10(2) and 1.4 x 10(3) cfu./gram, respectively. The results revealed no positive samples for Salmonella Yersinia entercolitica, Listeria monocytogenes and Campylobacter jejuni. Staphylococcus aureus was isolated from 2% of samples. The sources of contamination of processed squabs carcasses and measures to minimize the bacterial load and safe guard the consumer are mentioned.

Animals↗

PubMed2004

A chimeric peptide composed of a dermaseptin derivative and an RNA III-inhibiting peptide prevents graft-associated infections by antibiotic-resistant staphylococci.

Staphylococcal bacteria are a prevalent cause of infections associated with foreign bodies and indwelling medical devices. Bacteria are capable of escaping antibiotic treatment through encapsulation into biofilms. RNA III-inhibiting peptide (RIP) is a heptapeptide that inhibits staphylococcal biofilm formation by obstructing quorum-sensing mechanisms. K(4)-S4(1-13)(a) is a 13-residue dermaseptin derivative (DD(13)) believed to kill bacteria via membrane disruption. We tested each of these peptides as well as a hybrid construct, DD(13)-RIP, for their ability to inhibit bacterial proliferation and suppress quorum sensing in vitro and for their efficacy in preventing staphylococcal infection in a rat graft infection model with methicillin-resistant Staphylococcus aureus (MRSA) or S. epidermidis (MRSE). In vitro, proliferation assays demonstrated that RIP had no inhibitory effect, while DD(13)-RIP and DD(13) were equally effective, and that the chimeric peptide but not DD(13) was slightly more effective than RIP in inhibiting RNA III synthesis, a regulatory RNA molecule important for staphylococcal pathogenesis. In vivo, the three peptides reduced graft-associated bacterial load in a dose-dependent manner, but the hybrid peptide was most potent in totally preventing staphylococcal infections at the lowest dose. In addition, each of the peptides acted synergistically with antibiotics. The data indicate that RIP and DD(13) act in synergy by attacking bacteria simultaneously by two different mechanisms. Such a chimeric peptide may be useful for coating medical devices to prevent drug-resistant staphylococcal infections.

Amphibian Proteins↗

PubMed1986

Effect of an elevated level of carbon dioxide containing atmosphere on the growth of spoilage and pathogenic bacteria at 2, 7, and 13 C.

The effect of 80% CO2 (balance air) on the survival and growth of microorganisms most often associated with spoilage and foodborne disease in poultry carcasses was compared to air at 2, 7, and 13 C. The CO2 atmosphere substantially retarded the growth of the total bacterial load in uninoculated ground chicken meat and parts at all temperatures when compared to air; however, temperature had a larger overall effect than atmosphere. Ground chicken meat and synthetic broth were inoculated (greater than 10(4) cells/ml or g) with Pseudomonas fragi, Salmonella typhimurium, Staphylococcus aureus, or Clostridium sporogenes and the influence of 80% CO2 and incubation temperature studied. With the exception of Cl. sporogenes, 80% CO2 was inhibitory when compared to air at any given temperature. In most cases, CO2 was more inhibitory at 2 C than at 7 or 13 C. The Cl. sporogenes inoculum failed to grow above initial inoculum levels in any combination of temperature and atmosphere, but samples packed in 80% CO2 had higher numbers of colony forming units than air-packaged samples. This study does not indicate that modified atmosphere packaging of refrigerated poultry in elevated CO2 atmospheres increases the microbial hazards when compared to air at the same temperature.

Animals↗

PubMed2002

Transmembrane TNF induces an efficient cell-mediated immunity and resistance to Mycobacterium bovis bacillus Calmette-Guérin infection in the absence of secreted TNF and lymphotoxin-alpha.

The contribution of a transmembrane (Tm) form of TNF to protective immunity against Mycobacterium bovis bacillus Calmette-Guérin (BCG) was studied in transgenic (tg) mice expressing a noncleavable Tm TNF but lacking the TNF/lymphotoxin-alpha (LT-alpha) locus (Tm TNF tg mice). These mice were as resistant to BCG infection as wild-type mice, whereas TNF/LT-alpha(-/-), TNF(-/-), and LT-alpha(-/-) mice succumbed. Tm TNF tg mice developed granulomas of smaller size but at 2- to 4-fold increased frequencies compared with wild-type mice. Granulomas were mainly formed by monocytes and activated macrophages expressing Tm TNF mRNA and accumulating acid phosphatase. NO synthase 2 activation as a key macrophage bactericidal mechanism was low during the acute phase of infection in Tm TNF tg mice but was still sufficient to limit bacterial growth and increased in late infection. While infection with virulent Mycobacterium tuberculosis resulted in very rapid death of TNF/LT-alpha(-/-) mice, it also resulted in survival of Tm TNF tg mice which presented an increase in the number of CFU in spleen (5-fold) and lungs (10-fold) as compared with bacterial load of wild-type mice. In conclusion, the Tm form of TNF induces an efficient cell-mediated immunity and total resistance against BCG even in the absence of LT-alpha and secreted TNF. However, Tm TNF-mediated protection against virulent M. tuberculosis infection can also be efficient but not as strong as in BCG infection, in which cognate cellular interactions may play a more predominant role in providing long-term surveillance and containment of BCG-infected macrophages.

Animals↗

PubMed2003

Use of a similarity index based on microbial fatty acid (MFA) analysis to monitor biological wastewater treatment systems.

Estimating the stability of microbial community structures may be useful in advanced biological wastewater treatment system design and operation. In this research, a monitoring method using fatty acid profiles was evaluated for detecting changes in microbial community structures. For the evaluation, the operating parameters such as pH, organic loading, and chlorine addition were varied in two identical laboratory scale conventional activated sludge systems. A similarity index based on microbial fatty acid analysis was used to express the stability of microbial community structures in the systems. Experiments using a model microbial community showed that microbial compositions changed daily even under constant operating conditions and that the rate of change increased under dynamic operating conditions. Substrate changes brought about a relatively large change in a microbial community structure, eventually resulting in a very different microbial community. After only 7 days following a substrate change in a lab-scale bioreactor, the biomass exhibited only 45% similarity to the original structure. The analysis of microbial fatty acids conveys additional information, in that it could be used for the calculation of biomass concentrations in a wastewater treatment system if microbial fatty acid analyses are executed on a routine basis as a monitoring tool for biological wastewater treatment systems. The total fatty acid concentrations were about 0.61% of the biomass concentration as mixed liquor volatile suspended solid concentrations in this research.

Bacteria↗

PubMed2006

Sensitization to Alternaria and Cladosporium in patients with respiratory allergy and outdoor counts of mold spores in Ankara atmosphere, Turkey.

Sensitization to Alternaria and Cladosporium has been reported to be 3% to 30% in European countries. However, in Turkey, there is limited data about the prevalence of sensitization to these molds and the intensity of the two mold spores in Ankara atmosphere. This study was designed to evaluate the sensitization to Alternaria and Cladosporium in patients with respiratory allergy in Ankara and also the concentration of the two molds in Ankara atmosphere. Allergic rhinitis and asthma patients living in Ankara were included in the study. Demographic and diagnostic data of the patients were recorded. A skin prick test with extracts supplied by three different laboratories was used to evaluate the sensitization to Alternaria and Cladosporium. Mold spores were measured using a Burkard 7-day recording volumetric spore trap in Ankara atmosphere during a year. Overall sensitization to the two molds was found to be 14.8%, and isolated Alternaria or Cladosporiumsensitization was 3%. Considering the positive reaction to at least one of the three suppliers, the sensitization rate was 11.9% and 8.1% for Alternaria and Cladosporium, respectively. Cochran's Q homogenization test demonstrated that the positive and negative reaction were not homogeneous among three laboratories. The total number of mold spores in Ankara atmosphere was 429,264 spores/m3 of which 75.5% and 6% were constituted by Cladosporium and Alternaria, respectively. The prevalence of Cladosporium and Alternaria sensitization in respiratory allergy patients is quite similar to European countries; however, our data indicate that commercial mold extracts should be standardized to establish the real sensitization rates. Additionally, considering the great numbers of these mold spores in Ankara atmosphere, long-term follow-up studies are needed to evaluate the relationship between the mold load and sensitization patterns.

Adolescent↗

PubMed2026

Microbiome and resistome successions in pig carcasses and fresh pork meat throughout slaughtering, processing and shelf-life.

BACKGROUND: Slaughterhouses and meat cutting plants represent potential hotspots for the spread and transfer of spoilage and pathogenic, including antimicrobial resistant, bacteria to meat and meat products. Here, we characterise the progression of the microbiome and resistome of two pork cuts (loin and sirloin) at different stages of processing, from the slaughter line to the end of shelf-life. To this end, we analysed samples from facility surfaces, carcasses, and meat cuts using whole metagenome sequencing. RESULTS: The taxonomic and antimicrobial resistance gene (ARG) profiles of carcasses and meat cuts were significantly influenced by the point of sampling and the processing room. The facility surfaces were found to be the main source of some abundant genera, such as Anoxybacillus, Acinetobacter, Pseudomonas, and Brochothrix, in carcasses and meat cuts. A total of 1,291 metagenome-assembled genomes were reconstructed, corresponding to the most prevalent species identified in the taxonomic analysis at the read level. A reduction in bacterial and ARGs richness and diversity was observed for carcasses and meat cuts along the production chain, which suggests that processing procedures are effective in reducing bacterial and ARGs loads. Nonetheless, an increase in the ARGs load was observed at two sampling points: the carcass after evisceration and the sirloin at the end of its shelf-life (in this case linked to the increase of a single gene, tet(L)). The ARGs most frequently detected were those associated with resistance to tetracyclines, aminoglycosides, and lincosamides. Acinetobacter (in processing environments and carcass/meat samples) and Staphylococcus (in carcasses and meat) were identified as the main genera associated with the ARGs found. CONCLUSIONS: Overall, our results provide the most detailed metagenomics-based perspective on the microbial successions of pig carcasses and fresh meat cuts during slaughtering, processing, and commercialisation. The observations made suggest that selection pressures imposed by processing steps and contact with facility surfaces contribute to shaping the microbiome and resistome of the two pork products throughout their production line and shelf-life. Video Abstract.

Animals↗

PubMed2005

Suitability of the German test method for cleaning efficacy in washer-disinfectors for flexible endoscopes according to prEN ISO 15883.

In Europe, the evaluation of processing flexible endoscopes in washer-disinfectors (WDs) is performed in compliance with prEN ISO 15883-1 which includes determination of the efficacy of the cleaning process. Recent data suggest that cleaning processes show large differences when the prEN ISO 15883-1 German test model is applied. Hence, we analysed a total of 72 experiments in order to evaluate the test method. Transparent test tubes as test pieces (length 2 m, lumen 2 mm) were contaminated with a mixture of blood and Enterococcus faecium. Three set-ups were used: WD 425 with soft water, WD 425 with hard water and WD 440 with demineralized water. WDs were set to perform the cleaning stage of the programme alone. Seven cleaning agents were used according to the manufacturers' instructions (21 cleaning processes); in addition, three cleaning processes were carried out without a cleaning agent (i.e. with water alone). Each cleaning process was assessed by means of three experiments. Suspensions of test organism had 9.2x10(10) colony-forming units (cfu)/mL E. faecium (mean of 24 processes). Controls (recovery) contained 1.0x10(6) cfu/mL E. faecium (mean of 71 experiments). Mean log(10) reduction factors (RFs) for each process, i.e. the difference in microbial loads on the control and the processed tubes, were calculated. Cleaning processes led to RFs of 0-4.1, but no process led to residual bacterial loads below the limit of detection (1.8l gcfu/mL). Standard deviations for a cleaning process were small (< or =0.6 in 79% of the processes) indicating adequate reproducibility. The test model led to reproducible results and revealed large differences between the individual processes. If a cleaning process is intended to result in a bioburden reduction (i.e. RF> or =4), the control must carry a minimum bioburden of 6.5x10(5) cfu/mL. This was achieved in 58% of the processes. However, controls with a bioburden <6.5x10(5) cfu/mL never yielded a residual bacterial load below the limit of detection. We found that the prEN ISO 15883-1 German test method is suitable to determine the cleaning efficacy in WDs and leads to reproducible and valid results.

Decontamination↗