1,530 research outputs found
Horizontal transfer of antibiotic resistance genes on abiotic touch surfaces: implications for public health
No full textHorizontal gene transfer (HGT) is largely responsible for increasing incidence of antibiotic-resistant infections worldwide. Whilst studies have focussed on HGT in vivo, this work investigates whether the ability of pathogens to persist in the environment, particularly on touch surfaces, may also play an important role. Escherichia coli, virulent clone ST131, and Klebsiella pneumoniae encoding extended-spectrum ?-lactamase (ESBL) bla CTX-M-15 and metallo-?-lactamase bla NDM-1, respectively, exhibited prolonged survival on stainless steel with approximately 104 viable cells remaining from an inoculum of 107cfu per cm2 after one month at 21oC. HGT of bla to an antibiotic-sensitive but azide-resistant recipient E. coli occurred on stainless steel dry touch surfaces and in suspension, but not on dry copper. Conjugation frequency was approximately 10-50 times greater, occurred immediately and resulting transconjugants were more stable with ESBL E. coli as donor cell compared to K. pneumoniae but bla NDM-1 transfer increased with time. Transconjugants also exhibited the same resistance profile as donor suggesting multiple gene transfer. Rapid death, inhibition of respiration and destruction of genomic and plasmid DNA of both pathogens occurred on copper alloys accompanied by a reduction in bla copy number. Naked E. coli DNA degraded on copper at 21oC and 37oC but slowly at 4oC suggesting a direct role for the metal. Persistence of viable pathogenic bacteria on touch surfaces may not only increase risk of infection transmission but also contribute to spread of antibiotic resistance by HGT. The use of copper alloys as antimicrobial touch surfaces may help reduce infection and HGT
Inactivation of murine norovirus on a range of copper alloy surfaces is accompanied by loss of capsid integrity
No full textNorovirus is one of the most common causes of acute viral gastroenteritis. The virus is spread via the fecal-oral route, most commonly from infected food and water, but several outbreaks have originated from contamination of surfaces with infectious virus. In this study, a close surrogate of human norovirus causing gastrointestinal disease in mice, murine norovirus type 1 (MNV-1), retained infectivity for more than 2 weeks following contact with a range of surface materials, including Teflon (polytetrafluoroethylene [PTFE]), polyvinyl chloride (PVC), ceramic tiles, glass, silicone rubber, and stainless steel. Persistence was slightly prolonged on ceramic surfaces. A previous study in our laboratory observed that dry copper and copper alloy surfaces rapidly inactivated MNV-1 and destroyed the viral genome. In this new study, we have observed that a relatively small change in the percentage of copper, between 70 and 80% in copper nickels and 60 and 70% in brasses, had a significant influence on the ability of the alloy to inactivate norovirus. Nickel alone did not affect virus, but zinc did have some antiviral effect, which was synergistic with copper and resulted in an increased efficacy of brasses with lower percentages of copper. Electron microscopy of purified MNV-1 that had been exposed to copper and stainless steel surfaces suggested that a massive breakdown of the viral capsid had occurred on copper. In addition, MNV-1 that had been exposed to copper and treated with RNase demonstrated a reduction in viral gene copy number. This suggests that capsid integrity is compromised upon contact with copper, allowing copper ion access to the viral genome
Uncovering microbial populations in the lumen of neonatal enteral feeding tubes utilising 16s rRNA sequencing
No full textGastrointestinal microbiome is increasingly implicated in the morbidity associated with being born preterm. Enteral tubes (ET) are essential for the nutritional care of preterm infants. Limited culture-based studies have suggested they are colonised by high densities of microorganisms. Microbial DNA was extracted from 60 ETs retrieved from infants in a tertiary neonatal unit and analysed by16s rRNA sequencing of the V4 variable region. Relative abundance analysis on dominant microorganisms demonstrated that compared to breast milk, formula significantly increased abundance of Streptococcus spp and significantly decreased Enterococcus spp and Enterobacteriaceae Vaginal birth was also associated with significantly increased relative abundance of Streptococcus . This study more accurately demonstrates the extent of microbial diversity in neonatal ETs, with feeding regime significantly influencing colonisation patterns. Colonisation with unwanted organisms, as a result of specific care regimes, could result in disruption of the fragile infant gut microbiome, with implications for long-term morbidity
Influence of flow on the structure of bacterial biofilms.
No full textBacteria attached to surfaces in biofilms are responsible for the contamination of industrial processes and many types of microbial infections and disease. Once established, biofilms are notoriously difficult to eradicate. A more complete understanding of how biofilms form and behave is crucial if we are to predict, and ultimately control, biofilm processes. A major breakthrough in biofilm research came in the early 1990’s when confocal scanning laser microscopy (CSLM) showed that biofilms formed complex structures which could facilitate nutrient exchange. We have recently found that biofilms growing in turbulent flow can also be temporally complex. Structures such as cell clusters and ripples can migrate downstream along solid surfaces. Further, biofilm viscoelasticity allows the biofilm to structurally deform when exposed to varying shear stresses
Cw ion lasers pumped by electron beams
No full textWe have obtained cw laser radiation from singly ionized Hg, I, Cd, Se, and As by exciting He metal-vapor mixtures with a dc electron beam. The beam is generated by glow discharge electron guns located apart from the active medium. This is the first time that cw ion laser action has been obtained using electron beam excitation
CW laser action in atomic fluorine
No full textWe have obtained CW laser action on four transitions in the doublet system of atomic fluorine for the first time. All previously reported laser action was on a pulsed basis only. CW laser radiation was obtained when F2 or AgF was used as a fluorine donor in an electron beam pumped helium plasma. A multiline output power of 200 mW was obtained
Development of a sensitive cell culture system to assess prion infectivity and the efficacy of prion decontamination technologies
No full textCreutzfeldt-Jakob disease (CJD) can be iatrogenically transmitted during transplants, grafts and transfusions from CJD infected donors and also contaminated surgical instruments. A variety of methods to amplify and detect the presence of infectious prions as disease markers are available. However, these techniques do not measure the infectivity potentially associated with these markers. Currently, animal-bioassays are used to detect infectivity; however, they have limitations in detectable prion strains, cost, ethical considerations and assay length. Novel cell-based infectivity assays offer the potential to overcome these limitations, lower the requirements for animal use and the application of different cell lines could detect a wider range of prion strains. This project utilised murine neuroblastoma, N2a #58 cells infected with 22L-murine scrapie to develop a highly sensitive assay for the in situ detection of amyloid-rich prion (PrPSc) accumulation as an indication of prion infectivity. The autofluorescence quenching properties of Sudan black (SB) were incorporated into a novel Thioflavin T (ThT) based protocol for amyloid staining with improved specificity and sensitivity. Cell passages were incorporated into the assay to increase incubation time, improve cell viability and subsequently improve assay sensitivity; thus, demonstrating the detection of infectivity from a final 10-10 dilution of 22L-infected brain homogenate. Introduction of 22L-inoculated, surgical grade stainless steel wires to the N2a #58 cells demonstrated the SB/ThT detection of prion infectivity pre and post decontamination, which was comparable to animal bioassay data. Furthermore, preliminary work on the incorporation of the SB/ThT detection of prion infectivity within neural stem cells (NSC’s), for prion propagation within a cell line that did not require genetic manipulation for increased prion susceptibility, highlighted problems with unspecific fluorescence of dead cells during NSC differentiation. Improvements in culture conditions of the NSC’s regarding atmospheric conditions and trophic support were addressed in preparation for their use in future prion infectivity assays
Advantages of peptide nucleic acid oligonucleotides for sensitive site directed 16S rRNA fluorescence in situ hybridization (FISH) detection of Campylobacter jejuni, Campylobacter coli and Campylobacter lari
No full textTraditionally fluorescence in situ hybridization (FISH) has been performed with labeled DNA oligonucleotide probes. Here we present for the first time a high affinity peptide nucleic acid (PNA) oligonucleotide sequence for detecting thermotolerant Campylobacter spp. using FISH. Thermotolerant Campylobacter spp, including the species Campylobacter coli, Campylobacter jejuni and Campylobacter lari, are important food and water borne pathogens. The designed PNA probe (CJE195) bound with higher affinity to a previously reported low affinity site on the 16S rRNA than the corresponding DNA probe. PNA also overcame the problem of the lack of affinity due to the location of the binding site and the variation of the target sequence within species. The PNA probe specificity was tested with several bacterial species, including other Campylobacter spp. and their close relatives. All tested C. coli, C. jejuni and C. lari strains were hybridized successfully. Aging of the Campylobacter cultures caused the formation of coccoid forms, which did not hybridize as well as bacteria in the active growth phase, indicating that the probe could be used to assess the physiological status of targeted cells. The PNA FISH methodology detected C. coli by membrane filtration method from C. coli spiked drinking water samples
Acquisition of proteinaceous contamination through the handling of surgical instruments by hospital staff in sterile service departments
No full textUsing Episcopic Differential Interference Contrast (EDIC) microscopy, this study has investigated the potential reapplication of proteinaceous contamination onto surgical instruments following a washer-disinfector cycle through the handling of staff within the clean room. The deposition of 0.51 ng/mm2 of protein onto surgical grade stainless steel by one finger print alone has been demonstrated. Moreover, using a previously described contamination index, a 5 to 10-fold increase in protein present on surgical instruments was noted following handling by clean-room staff under current departmental practices, relative to instruments handled by staff wearing gloves. While unlikely to pose a direct risk to patient health, subsequent sterilisation will fix protein to an instrument surface thereby decreasing the effectiveness of further decontamination cycles. Current guidelines make no recommendations surrounding the use of gloves by staff working within the clean room. However it is clear that this matter must be reviewed to limit the unnecessary transference of protein to surgical instruments
CW silver ion laser with electron beam excitation
No full textA CW laser power of 140 mW was obtained in the 840.39 nm transition of Ag II by electron beam excitation. This electron beam excited metal vapor ion laser is capable of operating using metals with high vaporization temperatures and is of interest for generation of CW coherent radiation in the 220-260 nm spectral region
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