1,721,060 research outputs found
Rapid detection of biofilms and adherent pathogens using scanning confocal laser microscopy and episcopic differential interference contrast microscopy
No full textKnowledge of biofilm structure and function has changed significantly in the last few years due to advances in light microscopy. One pertinent example is the use of scanning confocal laser microscopy (SCLM) to visualise corrosion pits caused by the biofilm mosaic footprint on corroding metal surfaces. Nevertheless, SCLM has some limitations as to its widespread use, including cost, inability to observe motile bacteria and eukaryotic grazers within biofilms, and difficulty to scan a curved surface. By contrast, episcopic differential interference contrast (EDIC) microscopy has provided a rapid, real time analysis of biofilms on opaque, curved, natural or man-made surfaces without the need for cover slips and oil. EDIC, coupled with epi-fluorescence (EDIC/EF), microscopy has been used successfully to visualise the 3-D biofilm structure, physiological niches, protozoal grazing and iron biomineralization, and the location of specific pathogens such as Legionella pneumophila, Campylobacter jejuni and Cryptosporidium parvum. These species were identified using gold nanoparticles or fluorophores coupled to monoclonal antibodies or 16S rRNA probes, respectively. Among its many potential uses, the EDIC technique will provide a rapid procedure to facilitate the calibration of the modern generation of biofilm-sensing electrodes
The physico-chemistry of biofilm-mediated pitting corrosion of copper pipe supplying potable water
No full textCopper is a generally robust material that has beneficial properties to reduce biofilm formation and pathogen colonisation of pipes supplying potable water. However, a rare pitting corrosion can occur in soft, poorly buffered waters that can lead to pipe failure. This has been shown to be mediated by a copper-tolerant biofilm whose physical and chemical heterogeneity can establish microenvironments for corrosion potentials, causing micro pits that eventually coalesce into large perforations through the pipe wall. Control of the biofilm, for example through reduced cold water or elevated hot water temperatures, can suppress this corrosion phenomenon
Current limitations about the cleaning of luminal endoscopes
No full textBackground: The presence and potential build up of patient material such as proteins in endoscope lumens can have significant implications, including toxic reactions, device damage, inadequate disinfection/sterilisation, increased risk of biofilm development and potential transmission of pathogens. Aim: We intended to evaluate the potential protein deposition and removal in the channels of flexible luminal endoscopes during a simple contamination/ cleaning cycle. Methods: We evaluated the level of contamination present on disposable endoscopy forceps which come in contact with the lumen of biopsy channels. Following observations in endoscopy units, we evaluated some factors influencing protein adsorption inside luminal endoscope channels and the action of current initial cleaning techniques using a proteinaceous test soil and very sensitive fluorescence epimicroscopy. Findings: Disposable endoscope accessories appeared likely to contribute to the contamination of lumens and were useful indicators of the amount of proteinaceous soil transiting through the channels of luminal endoscopes. Enzymatic cleaning according to the manufacturer’s recommendations and brushing of the channels were ineffective at removing all proteinaceous residues from new endoscope channels after a single contamination. Rinsing applied immediately after contamination only slightly improved decontamination outcome. Conclusion: Limited action of current decontamination procedures and the lack of applicable quality control methods to assess channel cleanliness between each patient contribute to increasing the risk of cross infection of potentially harmful microorganisms and molecules during endoscopy procedures
Hydrodynamic shear stress to remove Listeria monocytogenesbiofilms from stainless steel and polytetrafluoroethylene surfaces
No full textAims: To calculate the shear stress needed to remove sessile Listeria monocytogenes cells from stainless steel (SS) and polytetrafluoroethylene (PTFE) surfaces.Methods and Results: Listeria monocytogenes biofilms were formed on SS and PTFE surfaces. Shear stress was calculated using a radial flow chamber device and cells quantified by staining with 4?,6-diamidino-2-phenylindole. Results showed that shear stress between 24 and 144 N m2 removed up to 98% of cells from SS surfaces. PTFE presents a very hydrophobic surface, and a significant lower removal (P < 0?05) of only 63% was achieved; moreover, on PTFE discs, detachment of L. monocytogenes biofilms was more efficient at alower shear stress (between 8?6 and 34 N m2).Conclusions: Water flow is more effective in removing L. monocytogenes biofilms from SS surfaces than from PTFE materials.Significance and Impact of the Study: This work clearly demonstrates that water flow does not have the same efficiency in removing cells from differentmaterial surfaces and shows the need to optimize cleaning and sampling procedures by considering the conditions in which cells attach to surfaces and the physicochemistry of the surfaces
How clean is clean?
No full textThere are approximately 6.5 million surgical procedures performed within England each year. These procedures are spread across the 182 acute NHS trusts which themselves cover the 249 hospitals with sterile service departments (SSDs) in England (NHS Estates, 2001). Of concern has been the emergence of evidence that highly robust infectious agents such as the Scrapie-form of the prion protein (PrPsc), causing variant or sporadic Creuztfeldt-Jakob disease, may remain viable following standard hospital decontaminating procedures (Taylor, 1999). This led the Department of Health to issue revised guidelines on the decontamination of instruments (Health Service Circulars 1999 178 and 1999 179) in August 1999. However, it is clear that subsequent and ongoing monitoring of cleaning standards must be maintained in order to ensure the highest decontamination standards are reached and maintained, and therefore reduce any possibility of nosocomial infection
Low concentration diffusible molecules affect the formation of biofilms by mixed marine communities
No full textBiofilm formation is a major concern in any venture in the marine environment and often precedes the establishment of fouling by macro-organisms. In this study, the effects of three known cell-to-cell signalling molecules, nitric oxide (NO), cis-2-decenoic acid (CDA) and patulin, on the formation of marine biofilms were investigated. Each of the molecules has been shown to affect biofilms and this is thefirst study to investigate their effect on mixed communities of marine biofilm-forming micro-organisms. Studies of the biomass of those biofilms grown in the presence of the molecules showed that all three reduced biofilm formation by marine communities, with both NO and patulin reducing biofilm formation by more than 90% atthe highest concentrations studied. However, colony counts revealed that the effect of patulin is likely due to toxicity. Analyses of the biofilm communities were also carried out using DGGE to determine whether there was any variation in the effects of each molecule on different bacterial taxa. No effect was seen on the communitiesand the biofilms appeared to form according to a neutral community model. Further investigations are recommended to study biofilms at a functional level
Survival of Cryptosporidium parvum in faecal wastes and salad crops
No full textCryptosporidium parvum is a protozoan parasite of man and a range of animals. An essential stage of the life cycle is the formation in the gastrointestinal tract of oocysts, each containing four infectious sporozoites. Thick wall oocysts are shed in apparently normal or diarrhoetic faeces to contaminate soil and water, providing routes into the food chain. Desiccation and snap freezing are lethal to oocysts. Nevertheless, the robust coat affords significant protection against environmental stressors such as low pH or water activity, temperatures above freezing and a range of sanitising and oxidizing agents such as chlorine. C. parvum may therefore survive in the environment for extending periods of time, posing a threat to animals and man if ingested either directly in contaminated water or in uncooked/ improperly cooked foods which are cropped from contaminated land. This threat has only partially be characterized, due in part to the difficulty in recovering oocysts and other pathogens from complex matrices such as manures and salad leaf surfaces.Accordingly, this study describes improved methods for the recovery of oocysts from faecal waste samples and salad crops, with recovery efficiencies of 40-80%. Using these improved tools, the results of oocyst survival studies in the stored wastes and on salad leaves are presented to show the suitability and drawbacks of current practices to minimize entry and spread of C. parvum in the food chai
Use of copper cast alloys to control Escherichia coli O157 cross-contamination during food processing
No full textThe most notable method of infection from Escherichia coli O157 (E. coli O157) is through contaminated foodproducts, usually ground beef. The objective of this study was to evaluate seven cast copper alloys (61 to 95%Cu) for their ability to reduce the viability of E. coli O157, mixed with or without ground beef juice, and tocompare these results to those for stainless steel. E. coli O157 (NCTC 12900) (2 107 CFU) mixed withextracted beef juice (25%) was inoculated onto coupons of each copper cast alloy or stainless steel andincubated at either 22°C or 4°C for up to 6 h. E. coli O157 viability was determined by plate counts in additionto staining in situ with the respiratory indicator fluorochrome 5-cyano-2,3-ditolyl tetrazolium. Without beefextract, three alloys completely killed the inoculum during the 6-h exposure at 22°C. At 4°C, only thehigh-copper alloys (>85%) significantly reduced the numbers of O157. With beef juice, only one alloy (95% Cu)completely killed the inoculum at 22°C. For stainless steel, no significant reduction in cell numbers occurred.At 4°C, only alloys C83300 (93% Cu) and C87300 (95% Cu) significantly reduced the numbers of E. coli O157,with 1.5 and 5 log kills, respectively. Reducing the inoculum to 103 CFU resulted in a complete kill for all sevencast copper alloys in 20 min or less at 22°C. These results clearly demonstrate the antimicrobial properties ofcast copper alloys with regard to E. coli O157, and consequently these alloys have the potential to aid in foodsafety
Potential use of copper surfaces to reduce survival of epidemic meticillin-resistant Staphylococcus aureus in the healthcare environment
No full textEpidemic meticillin-resistant Staphylococcus aureus (EMRSA) emerged in the early 1980s with EMRSA-15 and -16 being the most prevalent strains within the UK. MRSA transmission between patients is largely via the hands of healthcare workers, and contamination of the hospital environment may occur. The objective of this study was to evaluate the effectiveness of copper and brass to reduce the viability of air-dried deposits of three MRSA strains [MRSA (NCTC 10442), EMRSA-1 (NCTC 11939) and EMRSA-16 (NCTC 13143)] compared with stainless steel. MRSA and EMRSA [107 colony-forming units (CFU)] were inoculated on to coupons (1 cm × 1 cm) of copper, brass or stainless steel and incubated at either 22 °C or 4 °C for various time periods. Viability was determined by resuspending removed CFUs and plating out on tryptone soy agar plates in addition to staining with the respiratory indicator fluorochrome 5-cyano-2,3-ditolyl tetrazolium. On pure copper surfaces, 107 MRSA, EMRSA-1 and EMRSA-16 were completely killed after 45, 60 and 90 min, respectively, at 22 °C. In contrast, viable organisms for all three strains were detected on stainless steel (grade 304) after 72 h at 22 °C. At 4 °C, complete kill was achieved on copper for all three strains within 6 h. The results demonstrate an antimicrobial effect of copper on MRSA, EMRSA-1 and -16 in contrast to stainless steel. Consequently, the contemporary application of stainless steel in hospital environments for work surfaces and door furniture is not recommended
Survival of Listeria monocytogenes Scott a on metal surfaces: Implications for cross-contamination
No full textListeria monocytogenes is an important re-emerging pathogen which is commonly found in the environment. Many outbreaks have been associated with the contamination of food produce, often linked to cross-contamination from surfaces or equipment to prepared foodstuffs. In the present study a number of copper-base metal alloys have been used to assess the survival times of L. monocytogenes on different materials, in comparison with stainless steel. High concentrations (107) of bacteria were placed on metal coupons cut from each alloy. After defined incubation times, coupons were placed in tubes containing phosphate buffered saline and vortexed to remove the cells. Aliquots were then plated onto tryptone blood agar plates and the number of colony forming units counted. The high concentration of bacteria was used to represent a “worst-case” scenario. The results indicate that survival is greatly reduced on a copper-base alloy compared to stainless steel. Viable cells could be detected on stainless steel after 24 h incubation at room temperature. On copper, brass, aluminium bronze and silicon bronze, no viable bacteria could be detected after 60 min incubation, indicating a 5 log reduction (the detection limit of the procedure was 100 bacteria). No cells could be detected from copper nickel and copper nickel zinc alloys, after 90 min incubation. The viability stain, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), confirmed these results, with actively respiring bacteria being clearly labelled on stainless steel after 24 h. The results suggest that careful choice of surface material could reduce the potential risk of cross-contamination in industrial, commercial and domestic environments.<br/
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