Instrument Contamination Research Articles

Risk of bacterial cross infection associated with inspiration through flow-based spirometers

Bacterial contamination of spirometers has been documented in water-sealed devices, mouthpieces, and connection tubes. Little information is available about bacterial contamination of flow-based apparatuses such as turbine-type spirometers and pneumotachographs. Inspiration through contaminated equipment is a potential source of cross infection. To investigate bacteria mobilization (ie, bacteria detachment and aerosolization from the instrument) during routine spirometric testing, 2 types of flow-based spirometers were used. Bacteria mobilization during artificial inspiration through in-line filters or cardboard mouthpieces was evaluated. Nine hundred workers undergoing periodic spirometric testing were enrolled at the occupational physician office in 30sessions of 30 subjects each. The participants were asked to perform a forced vital capacity test in a turbine-type spirometer and in an unheated pneumotachograph fitted with disposable in-line filters or cardboard mouthpieces. To evaluate bacterial mobilization, an artificial inspiration was performed and bacterial growth determined. The bacterial growth analysis was assessed after the first and the thirtieth spirometric tests of each session without disinfecting the instruments between tests. In addition, instrument bacterial contamination was evaluated. No significant bacterial mobilization and instrument contamination were found in spirometric tests executed with in-line filters. Conversely, a significant bacterial mobilization and instrument contamination were observed in tests performed with cardboard mouthpieces. Differences between the 2 spirometers were not significant. In-line filters may effectively reduce the risk of bacterial cross infection. Inspiration through flow-based spirometers fitted with disposable cardboard mouthpieces is completely safe when combined with spirometer disinfection/sterilization between subjects.

Procurement of spore-freeBacillus anthracisfor molecular typing outside of BSL3 environment

To (i) develop a protocol that would eliminate or greatly reduce sporulation within Bacillus anthracis vegetative cells, and (ii) harvest an adequate number of cells and sufficient DNA suitable for molecular methods including Riboprint analysis and pulse field gel electrophoresis (PFGE). Seven strains of B. anthracis (Ames, French B2, Heluky, Kruger, Pasteur, Sterne, and Vollum) were grown at 37, 42 and 45 degrees C under normal air, enhanced CO(2), microaerophilic, and anaerobic conditions on solid media and subcultured in two broths with and without supplements. The bacterial cells were centrifuged and washed. Slides made from the cell pellets were stained with Malachite Green and observed for the presence of spores. Cell preparations were subjected to 80 degrees C for 30 min and processed for and analysed by either Riboprinte or PFGE. Multiple pellets of each strain were processed, stained, placed onto solid culture media, incubated for 7 days and observed for growth. The cell preparations yielded clear and reproducible results with both molecular methods. None of the cell preparations yielded growth on the culture media. This method eliminated viable spores in cell preparations of B. anthracis, yet still allowed the growth of vegetative cells to provide sufficient DNA suitable for analysis by Riboprinter and PFGE. This method will provide safe cell preparations, prevent instrument contamination, and may be useful for other aerobic and anaerobic spore-formers.

The cost-effectiveness of surgical instrument management policies to reduce the risk of vCJD transmission to humans

Current sterilization techniques may not be completely effective at removing prions from surgical instruments, which can then infect patients on whom these instruments are subsequently used. This risk is increased due to the current level of instrument migration. With wide uncertainty in the numbers of patients that are incubating variant Creutzfeldt–Jakob disease (vCJD) and effectiveness of decontamination, the UK is facing a potentially self-sustaining epidemic, which could be averted with the introduction of single-use instruments. This paper focuses on the cost-effectiveness of management strategies concerning the introduction of single-use instruments and measures to prevent migration. We formulated a discrete event simulation model of the dynamics of infection transmission, surgical instrument contamination and migration, to produce results that were pivotal in shaping government policy. Field data about vCJD transmission has then been used to update cost-effectiveness assessments as part of a retrospective analysis, which reinforces the initial decision.

Aerosol quantification with the Aerodyne Aerosol Mass Spectrometer: detection limits and ionizer background effects

Abstract. Systematic laboratory experiments were performed to investigate quantification of various species with two versions of the Aerodyne Aerosol Mass Spectrometer, a Quadrupole Aerosol Mass Spectrometer (Q-AMS) and a compact Time-of-Flight Aerosol Mass Spectrometer (c-ToF-AMS). Here we present a new method to continuously determine the detection limits of the AMS analyzers during regular measurements, yielding detection limit (DL) information under various measurement conditions. Minimum detection limits range from 0.03 μg m−3 (nitrate, sulfate, and chloride) up to 0.5 μg m−3 (organics) for the Q-AMS. Those of the c-ToF-AMS are found between 0.003 μg m−3 (nitrate, sulfate) and 0.03 μg m−3 (ammonium, organics). The DL values found for the c-ToF-AMS were ~10 times lower than those of the Q-AMS, mainly due to differences in ion duty cycle. Effects causing an increase of the detection limits include long-term instrument contamination, measurement of high aerosol mass concentrations and short-term instrument history. The self-cleaning processes which reduce the instrument background after measurement of large aerosol concentrations as well as the influences of increased instrument background on mass concentration measurements are discussed. Finally, improvement of detection limits by extension of averaging time intervals, selected or reduced ion monitoring, and variation of particle-to-background measurement ratio are investigated.

Laboratory instrument contamination with dermatophytes ? a risk for dermatophytosis

Laboratory instrument contamination with dermatophytes ? a risk for dermatophytosis

Study on oral instrument contamination and disinfecting effect

目的 了解临床常用口腔器械污染状况和口腔诊疗器械的消毒效果,以寻找一种安全理想的消毒方法.方法采用细菌培养及酶联免疫吸附法进行细菌和HBsAg的检测,比较0.5%碘伏、2%戊二醛和蒸汽压力灭菌对口腔器械的消毒效果.结果 4种口腔器械使用后细菌检出率最高是口镜510 CFU/件,HBsAg阳性率最高为手机13.33%,器械消毒用0.5%碘伏、2%戊二醛进行,效果均不能保证,只有高压蒸汽压力才能彻底灭菌.结论口腔器械污染严重,蒸汽压力灭菌法是目前理想的灭菌方法。

Design Considerations for High Speed Quantitative Mass Spectrometry with MALDI Ionization

A MALDI ion source on a triple quadrupole mass spectrometer constructed for the purpose of obtaining high speed quantitative measurements on drugs and other low molecular weight compounds is described. Particular attention is given to the ion generation and transport phenomena that affect analysis speed, throughput, and practical instrument robustness. In this regard parameters that affect desorption speed, beam spreading, ion flight times, sensitivity, signal-to-noise, ion fragmentation, sample carry-over, and instrument contamination are examined and experimental results are provided. MALDI and electrospray sensitivity is compared, to provide a practical frame of reference.

Instrument contamination; marking pen sterility; skin preparation for epidural analgesia; implant infection rates

Instrument contamination; marking pen sterility; skin preparation for epidural analgesia; implant infection rates

Rapid method for the sensitive detection of protein contamination on surgical instruments

Hospital sterile service departments (SSDs) currently rely on simple visual confirmation of cleanliness as an assessment of the efficacy of cleaning surgical instruments. The inherent inability to monitor low levels of infectious or proteinaceous contamination on surgical instruments creates the possibility that highly dangerous and robust biological agents may remain infectious and undetected even after standard cleaning and sterilization procedures have been employed. This paper describes the development of a novel microscopy technique, episcopic differential interference contrast microscope, combined with the fluorescent reagent, SYPRO Ruby, to rapidly detect brain tissue protein to below 400 pg/mm(2) on an instrument surface. This technique has displayed a minimum level of detection observed by 50% of volunteers of 85 pg/mm(2) (95% confidence intervals 67-112 pg/mm(2)). Quantitative assessment of instruments supplied from various SSDs enabled the establishment of a 'contamination index' of both proteinaceous and non-proteinaceous deposits on the surface. This new methodology for the assessment of surface contamination is generally applicable and should facilitate future quantitative surveys of instrument contamination in hospitals and other healthcare environments.

American College of Chest Physicians and American Association for Bronchology Consensus Statement: Prevention of Flexible Bronchoscopy-Associated Infection

American College of Chest Physicians and American Association for Bronchology Consensus Statement: Prevention of Flexible Bronchoscopy-Associated Infection

Helicobacter pylori DNA in dental plaques, gastroscopy, and dental devices.

The role of dental plaque in the transmission of Helicobacter pylori (Hp) is unclear due to variability in the detection rates and techniques used. We used nested PCR to estimate the incidence of Hp in dental plaques of 24 dental hygienists. We found an unexpectedly high incidence (50%) of Hp DNA in dental plaques using sterilized dental probes. Additional treatment of sonication and SDS wash prior to sterilization of dental probes reduced the incidence to 13%. We used the treated probes to assess Hp presence in plaque samples of 47 patients visiting the dental clinic for teeth cleaning. Hp DNA was detected in 24% of cases. Since these data may reflect instrument contamination, we tested dental probes, endoscopes, and endoscopy forceps and found that 12.5-37.5% of them were contaminated. Consequently, dental plaques may be a candidate reservoir for Hp, medical equipment may contribute to Hp transmission, and sample collection techniques can bias the true prevalence of Hp in a population.

Effect of Pneumoperitoneal Pressure on Tumor Dissemination and Tumor Recurrence at Port-Site and Midline Incisions

Over the past several years numerous cases of port site tumor recurrence after laparoscopic resection of a cancerous tissue have been reported. Possible mechanisms for tumor seeding include tumor removal, contaminated instruments, pneumoperitoneum, and aerosolization of tumor cells. This experiment examined the relationship among trocar contamination, aerosolization, and tumor recurrence with increasing pneumoperitoneal pressure using a hamster model. Increased pneumoperitoneal pressure significantly increased both instrument contamination and tumor recurrence at midline and port site incisions. Interestingly, increasing pneumoperitoneal pressure had no significant effect on the number of aerosolized tumor cells. The results reaffirm that the use of a reduced pneumoperitoneum or gasless laparoscopy may significantly lower port site tumor recurrence.

DNA contamination of mortuary instruments and work surfaces: a significant problem in forensic practice?

A study of 20 mortuaries was undertaken to assess whether contamination of instruments, tables and cutting areas due to residual material containing human DNA after routine cleaning is an actual or only a theoretical problem. Of the 20 mortuaries studied, 50% were found to have material containing quantifiable human DNA on the instruments and surfaces sampled. This DNA was amplified and found, in some cases, to have been derived from at least three people. Of those that did not yield measurable amounts of DNA, a number of samples were selected at random, amplified and were found to produce partial profiles indicating the presence of low levels of human DNA. The possible sources of human DNA from mortuaries are discussed as well as means to reduce or irradicate the problem of instrument contamination. Finally the implications of these findings for forensic investigations are discussed.

Endoscope washers – a protocol for their use

A protocol for the disinfection of gastroduodenoscopes, retrograde cholangiopancreatography endoscopes and colonoscopes using endoscope washers is described. The process recommends initial manual washing with a disinfectant containing didecyldimethylammonium chloride, surfactants and enzymes, a second washing in the endoscope washer using a detergent associated with a bacteriostatic, fungistatic substance (benzoisothiazolone) and finally the use of a 2% glutaraldehyde product buffered at pH6. After treatment with 2% Steranios added to the washer, less than 1 micro-organism/ml liquid was found in the following units: 83% of the colonoscopes, 83% of the oesophagogastroduodenoscopes, 83% of the main channels of the retrograde cholangiopancreatography endoscopes and 75% of the auxiliary channels of the latter instruments. In 14% of the colonoscopes, 42% of the gastroduodenoscopes, 42% of the main and 50% of auxiliary channels in the retrograde cholangiopancreatography endoscopes there were no signs of microbial growth in the wash liquid. The results obtained indicated that this protocol allowed adequate disinfection of the endoscope channels, structurally the most difficult part of the instrument to disinfect. Emphasis is given to the degree by which instrument contamination can increase during overnight storage, suggesting that endoscopes need to be submitted to further disinfection after overnight storage. Moreover, the water flowing into the washers can also cause instrument recontamination, particularly during the final rinses. Therefore, to better safeguard the health of patients undergoing endoscopy, special care must be taken to maintain the filters and disinfect the washers themselves, no matter how effective the disinfection protocol used may be.

Endoscope washers – a protocol for their use

A protocol for the disinfection of gastroduodenoscopes, retrograde cholangiopancreatography endoscopes and colonoscopes using endoscope washers is described. The process recommends initial manual washing with a disinfectant containing didecyldimethylammonium chloride, surfactants and enzymes, a second washing in the endoscope washer using a detergent associated with a bacteriostatic, fungistatic substance (benzoisothiazolone) and finally the use of a 2% glutaraldehyde product buffered at pH6. After treatment with 2% Steranios added to the washer, less than 1 micro-organism/ml liquid was found in the following units: 83% of the colonoscopes, 83% of the oesophagogastroduodenoscopes, 83% of the main channels of the retrograde cholangiopancreatography endoscopes and 75% of the auxiliary channels of the latter instruments. In 14% of the colonoscopes, 42% of the gastroduodenoscopes, 42% of the main and 50% of auxiliary channels in the retrograde cholangiopancreatography endoscopes there were no signs of microbial growth in the wash liquid. The results obtained indicated that this protocol allowed adequate disinfection of the endoscope channels, structurally the most difficult part of the instrument to disinfect. Emphasis is given to the degree by which instrument contamination can increase during overnight storage, suggesting that endoscopes need to be submitted to further disinfection after overnight storage. Moreover, the water flowing into the washers can also cause instrument recontamination, particularly during the final rinses. Therefore, to better safeguard the health of patients undergoing endoscopy, special care must be taken to maintain the filters and disinfect the washers themselves, no matter how effective the disinfection protocol used may be.

Direct isotope ratio measurement of ultra-trace lead in waters by double focusing inductively coupled plasma mass spectrometry with an ultrasonic nebuliser and a desolvation unit

A double focusing inductively coupled plasma mass spectrometer coupled with an ultrasonic nebuliser and a desolvation unit was used to measure 206 Pb/ 207 Pb, 206 Pb/ 208 Pb and 207 Pb/ 208 Pb isotope ratios in Pb standard SRM981, diluted to total Pb concentrations ranging from 1 to 1000 ng l –1 . The synthetic water standard SRM1654d, diluted by a factor of 100, and the natural riverine water standard SLRS-3 were also analysed for their Pb isotope ratios. It was found that lead isotope data with good accuracy could be obtained down to 10 ng l –1 . At 1 ng l –1 , the blanks became too problematic. The internal precisions found appear to be well correlated with counting statistics, and range from ca. 3 to 0.2% RSD, depending on the Pb concentration and the instrument sensitivity. The long term reproducibility is even better and may reach values down to 0.02% RSD at concentrations above 100 ng l –1 total Pb. Lead isotope values are proposed for the SRM1654d and SLRS-3 water standards. It appears that the reproducibility is affected by matrix effects in the latter, natural water. In future work aimed at lead isotope measurements at the sub-ng l –1 level with this approach, it will be necessary to solve serious instrument contamination and memory effects for Pb.

Quantification of fg-pg amounts by electron capture negative ion mass spectrometry ? Parameter optimisation and practical advices

Electron capture negative ion mass spectrometry (ECNI-MS) is a very suitable and popular technique for the identification and quantification of fg-pg amounts of compounds with a sufficiently high electron affinity. Many users of the ECNI mode have faced a lot of frustrating problems due to instrument contamination and wrong recommendations concerning instrument optimisation. This article summarises 14 years of experience with ECNI-MS using a large number of different instruments. Recommendations are given concerning optimisation procedures of important parameters such as ion source pressure and temperature as well as electron energy. An ion pressure optimisation method is proposed using a gas chromatograph. ECNI-MS is very sensitive against trace amounts of contaminants in the mass spectrometer and requires very clean components in the reagent gas line. Recommendations are given concerning suitable parts. Different other contamination sources are also discussed. The construction of a simple and clean gas inlet system is presented. Furthermore, contamination-free cleaning methods for the ion source are suggested. A test method based on the detection of hexachlorobenzene in the full scan mode (m/z 34–300) is proposed. It allows to evaluate both the background level in the mass spectrometer and the overall system performance. Clean instruments should show a signal-to-noise ratio of the total ion current GC signal of at least 20:1 without applying any mass signal area reject threshold. A linearity test procedure is also suggested. It shows that the linear range of a clean and optimised instrument is at least 3 orders of magnitude in the ECNI mode.

Organic neutralization agents for neutralization-reionization mass spectrometry

Porter has shown that excited neutrals of specified internal energies can be prepared by neutralization of an ion beam with metal vapors of low ionization potential (IP). For specific problems in neutralization-reionization mass spectrometry, a metal with the desired IP value may not be available, or it may present experimental problems such as a high vaporization temperature, instrument contamination, or detector instability. The use of organic neutralization agents such as tetra- p-anisylethylene (IP = 6.0 eV) can minimize these problems (although cross sections for neutralization with these are a factor of 5 lower than those with metals), and can provide a much wider range of IP values. Their utility is demonstrated in the neutralization of C 4H + 4 and C 4H + 8 ions to produce C 4H 4 and C 4H 8 of selected internal energies. However, for CH + 4 neutralization, the CH 4 neutrals formed have a much lower internal energy than predicted, indicating that electron transfer from the neutralization agent predominantly produces its ions in excited states.

A novel quadrupole mass spectrometer operating with no dc voltage component on the rods

A novel quadrupole mass spectrometer has been developed which has certain clearly defined advantages over the standard instrument. The novelty lies in a re-designed collector assembly which allows special filtering at the exit from the quadrupole lens. This lens operates with an a.c. voltage applied to the pairs of rods, the d.c. component always being zero. The new instrument has the important advantage of a mass discrimination which is not critically dependent upon any operating parameter. This can be significant particularly when operating over a wide mass range. It has been verified for example that, certainly up to 300 a.m.u., discrimination will not change even with a significant change in operating parameters and instrument contamination. With every individual instrument in this series of tests the performance was always better in the new as against the conventional operation. That is, if the d.c. level in the conventional mode was adjusted so that both modes gave the same sensitivity, resolution in the new mode was always significantly better.

Stratospheric Water-Vapor Upper Limits Inferred From Upper-Air Observations: Part I. Northern Hemisphere

Observational data from the lower stratosphere are examined to determine to what extent an upper limit can be placed on the water-vapor content of that region of the atmosphere, a quantity which is presently in controversy by half an order of magnitude. Presented herein are the details of a systematic search of 37 winter months (November 1964–December 1971) of Northern Hemispheric 30-mb and 50-mb synoptic maps, as well as a search of over 170,000 individual radiosonde 30-mb temperature soundings for the same period. In addition, the results of a search of all available high-latitude Northern Hemispheric meteorological rocket data and a study of the 30-mb climatology for Jan Mayen Island are presented. The results of these studies are compared with the results of a careful literature search, as well as an inquiry to an airline pilot's volunteer organization, for reports of stratospheric cloud observations. The extreme sparsity of such observations, even with allowance for possible obscuring effects of tropospheric cloud cover, leads to the conclusion that water-vapor saturation is seldom reached in the lower stratosphere of the Northern Hemisphere. This conclusion, coupled with the results of the fairly extensive stratospheric observational data mentioned above, appears to be inconsistent with the concept of an average “moist” (10 ppm or greater) lower stratosphere. From the results of the present investigation, it may be inferred that the average 30-mb and 50-mb water-vapor mixing ratios, for the dates investigated, is almost certainly less than 11 ppm, and probably less than 6–8 ppm. The data appear to constitute reasonable evidence for setting an upper limit on the average 30-mb water-vapor mixing ratio at approximately the 6–8 ppm level for high latitudes in the Northern Hemispheric winter. These 30-mb results fall in between the values quoted by investigators reporting a “dry” (a few ppm mixing ratio) and “moist” (≥ 10 ppm mixing ratio) lower stratosphere, and thus appear to provide a reasonably definitive choice on the question, independent of instrument contamination and calibration problems that have led to discrepancies in stratospheric water-vapor measurements in the past.