Acinetobacter baumannii biofilm biomass mediates tolerance to cold plasma.

Acinetobacter baumannii is an intrinsically multidrug-resistant pathogen that, when existing as a biofilm, confers increased environmental tolerance to desiccation, nutrient starvation as well as increased tolerance to antimicrobials. Outbreaks of A. baumannii infections within the clinical setting are often associated with the biofilm phenotype. This study investigates the role of biofilm biomass in A. baumannii susceptibility to exposure to a kilohertz-driven, in-house-designed, cold plasma jet, through the examination of cold plasma treatment efficacy in A. baumannii biofilms grown over various times for up to 72 h. For biofilms grown for 24, 48 and 72 h, D values were 19·32 ± 2·71, 29·18 ± 3·15 and 24·70 ± 3·07 s respectively. Monitoring A. baumannii biofilm biomass over these time periods revealed that the greatest biomass was observed at 48 h with the lowest biofilm biomass at 24 h growth. Enumeration of viable biofilm colony counts at each time point was comparable. Scanning electron microscopy images of plasma-treated biofilms revealed extensive surface damage of A. baumannii cells. These results describe the role of biomass in mediating A. baumannii biofilm susceptibility to cold plasma treatment, implicating the biofilm matrix as a protective barrier to the antimicrobial effects of cold plasma. SIGNIFICANCE AND IMPACT OF THE STUDY: Acinetobacter baumannii biofilm formation results in increased environmental and antimicrobial tolerance and resistance compared to the planktonic phenotype. Cold plasma technology is increasingly investigated as a new tool for decontamination of biofilm-contaminated surfaces, especially those found in the clinical setting. This new technology presents a promising approach to the remediation of surfaces contaminated by biofilms. This study identifies the role played by A. baumannii biofilm biomass in mediating tolerance and susceptibility to cold plasma treatment. This work demonstrates that increased biofilm biomass reduces the efficacy of antimicrobial species generated by cold plasma, resulting in greater tolerance to plasma exposure.

Synthesis of surfactant-free electrostatically stabilized gold nanoparticles by plasma-induced liquid chemistry.

Plasma-induced non-equilibrium liquid chemistry is used to synthesize gold nanoparticles (AuNPs) without using any reducing or capping agents. The morphology and optical properties of the synthesized AuNPs are characterized by transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy. Plasma processing parameters affect the particle shape and size and the rate of the AuNP synthesis process. Particles of different shapes (e.g. spherical, triangular, hexagonal, pentagonal, etc) are synthesized in aqueous solutions. In particular, the size of the AuNPs can be tuned from 5 nm to several hundred nanometres by varying the initial gold precursor (HAuCl4) concentration from 2.5 µM to 1 mM. In order to reveal details of the basic plasma-liquid interactions that lead to AuNP synthesis, we have measured the solution pH, conductivity and hydrogen peroxide (H2O2) concentration of the liquid after plasma processing, and conclude that H2O2 plays the role of the reducing agent which converts Au(+3) ions to Au(0) atoms, leading to nucleation growth of the AuNPs.

Atmospheric pressure, nonthermal plasma inactivation of MS2 bacteriophage: effect of oxygen concentration on virucidal activity.

AIMS: The main aim of this study was to determine the virucidal inactivation efficacy of an in-house-designed atmospheric pressure, nonthermal plasma jet operated at varying helium/oxygen feed gas concentrations against MS2 bacteriophage, widely employed as a convenient surrogate for human norovirus. METHODS AND RESULTS: The effect of variation of percentage oxygen concentration in the helium (He) carrier gas was studied and found to positively correlate with MS2 inactivation rate, indicating a role for reactive oxygen species (ROS) in viral inactivation. The inactivation rate constant increased with increasing oxygen concentrations up to 0·75% O2 . 3 log10 (99·9%) reductions in MS2 viability were achieved after 3 min of exposure to the plasma source operated in a helium/oxygen (99·25% : 0·75%) gas mixture, with >7 log10 reduction after 9 min exposure. CONCLUSIONS: Atmospheric pressure, nonthermal plasmas may have utility in the rapid disinfection of virally contaminated surfaces for infection control applications. SIGNIFICANCE AND IMPACT OF STUDY: The atmospheric pressure, nonthermal plasma jet employed in this study exhibits rapid virucidal activity against a norovirus surrogate virus, the MS2 bacteriophage, which is superior to previously published inactivation rates for chemical disinfectants.

Slam haplotypes modulate the response to lipopolysaccharide in vivo through control of NKT cell number and function.

CD1d-restricted NKT cells make up an innate-like T cell subset that plays a role in amplifying the response of innate immune leukocytes to TLR ligands. The Slam locus contains genes that have been implicated in innate and adaptive immune responses. In this study, we demonstrate that divergent Slam locus haplotypes modulate the response of macrophages to the TLR4 ligand LPS through their control of NKT cell number and function. In response to LPS challenge in vivo, macrophage TNF production in Slam haplotype-2(+) 129S1/SvImJ and 129X1/SvJ mice was significantly impaired in comparison with macrophage TNF production in Slam haplotype-1(+) C57BL/6J mice. Although no cell-intrinsic differences in macrophage responses to LPS were observed between strains, 129 mice were found to be deficient in liver NKT cell number, in NKT cell cytokine production in response to the CD1d ligand alpha-galactosylceramide, and in NKT cell IFN-gamma production after LPS challenge in vivo. Using B6.129c1 congenic mice and adoptive transfer, we found that divergent Slam haplotypes controlled the response to LPS in vivo, as well as the diminished NKT cell number and function, and that these phenotypes were associated with differential expression of signaling lymphocytic activation molecule family receptors on NKT cells. These data suggest that the polymorphisms that distinguish two Slam haplotypes significantly modulate the innate immune response in vivo through their effect on NKT cells.

Longitudinal pulmonary function losses in Vermont granite workers. A reevaluation.

Previous studies have suggested that excessive losses of FVC and FEV1 were occurring in Vermont granite workers despite the fact that mean quartz levels existing in the industry were below the current OSHA standard of 100 micrograms/m3. We reexamined these losses in granite workers over an 8-year period, testing the workforce biennially from 1979 to 1987. All workers, including stone shed, quarry, and office, were offered forced spirometry using a 10-L water-sealed spirometer (Collins). In the peak year of participation (1983), 887 workers out of a total of approximately 1,400 were tested. Estimates of longitudinal loss were based on 711 workers who participated in at least three of the surveys. The mean age of this group was 42.9 years, and the mean years employed was 19.3 years; 21.4 percent were non-smokers (NS), 34.2 percent were ex-smokers (ES), and 44.4 percent were current smokers (CS). Average annual losses of FVC were 0.018 (SD = 0.056) L (CS, 0.025 L; NS, 0.006 L: and ES, 0.016 L). Average annual losses of FEV1 were 0.030 (SD = 0.041) L (CS, 0.038 L; NS, 0.020 L; and ES, 0.027 L). Analysis of covariance indicated that losses were related to the initial values for FVC or FEV1, height, age, and smoking status. After adjusting for these variables, the losses of both FVC and FEV1 were not correlated with years employed in the granite industry. No significant differences existed in the loss of FVC or FEV1 in categories of workers exposed to different levels of granite dust, eg, office, quarry, and stone shed workers. The annual losses of pulmonary function were significantly smaller than those estimated previously, which were 0.070 to .080 L in FVC, and 0.050-0.070 L in FEV1. We conclude that dust levels in the Vermont granite industry, which have been in conformance with OSHA permissible exposure limits, do not accelerate pulmonary function loss.

Radiographic abnormalities in Vermont granite workers exposed to low levels of granite dust.

The issue of whether low levels of granite dust exposure lead to radiographic abnormalities after a lifetime of exposure has not been settled. In 1983, we carried out a radiographic survey of the Vermont granite industry, consisting of quarry and stone shed workers who had been exposed to the low dust levels prevailing in the industry since 1938 to 1940. Films were read by three "B" readers, using the ILO classification system, which requires the identification of both rounded and irregular opacities, as well as combinations of both. X-ray films were taken of 972 workers, out of a total work force of approximately 1,400. Of these films, 28 (3 percent) were interpreted by either two or three of the three readers as showing abnormalities consistent with pneumoconiosis. Only seven films (or 0.7 percent of the entire cohort) showed nodular or rounded opacities of the type typically seen in uncomplicated silicosis. The remainder of the abnormal x-ray films showed irregular opacities, largely in the lower lung zones, which are of uncertain significance, but may be related to heavy cigarette smoking and aging, and possibly dust inhalation. In addition, total gravimetric dust concentrations in the workplace were measured; 417 respirable-size mass samples showed concentrations of 601 micrograms/cu m +/- 368 micrograms/cu m. Using previously published estimates of 10 percent quartz in granite dust, the average quartz concentration was 60 micrograms/cu m. Twelve percent of the samples exceeded 100 micrograms/cu m, the current OSHA standard for quartz. We conclude that control of quartz exposure in the Vermont granite industry to levels which are on average less than the current OSHA standard has essentially eliminated definite radiographic changes of silicosis. The significance of the irregular opacities in the lower lung zones seen on a majority of the 28 x-ray films judged to be abnormal is not clear.

Pulmonary arteriovenous fistula. Preoperative evaluation with a Swan-Ganz catheter.

A balloon-tipped catheter was used in the preoperative assessment of a patient with a solitary pulmonary arteriovenous fistula and coexistent chronic obstructive pulmonary disease and ischemic heart disease. Studies before and two months following surgical excision of the fistula showed that the increase in arterial oxygenation (49 mm Hg vs 77 mm Hg) and the reduction in the fraction of the shunted cardiac output (37% vs 6%) closely approximated the predicted preoperative estimates.

Silicosis.

Silicosis is an ancient disease, but with modern understanding of safe levels of exposure, it should be a vanishing disease. Emphasis will be placed on newer concepts in the pathogenesis of the disease and the health effects of low levels of quartz dust in relation to current exposure standards. The ongoing controversy regarding the carcinogenicity of quartz is discussed.

Vermont granite mortality study: an update with an emphasis on lung cancer.

This mortality study extends the period of observation of an article published in 1988 of 5414 workers in Vermont granite sheds and quarries to assess whether previously reported reductions in silicosis and tuberculosis mortality were maintained. The relationship between lung cancer and quartz exposure is also examined by comparing mortality in workers hired before and after 1940, when dust controls were introduced and exposures were reduced by 80% to 90%. Before 1940, general stone shed air contained 20 million particles/cubic foot (mppcf) (approximately equivalent to 0.2 mg/m of quartz), and pneumatic chisel workers were exposed on average to 60 mppcf (approximately equivalent to 0.6 mg/m of quartz). Other workers had variable exposures. After 1940, a period of decline occurred in dust levels and then stabilized in approximately 1955, when average dust levels were 5 to 6 mppcf (equivalent to 0.05-.06 mg/m of quartz). Dust exposures in the Vermont industry is considered to be free of confounding occupational substances such as arsenic, although cigarette smoking was common. By the end of 1996, 2539 workers, or 46.9% of the cohort, had died. There were no silicosis deaths in workers hired after 1940 who were exposed only in the Vermont granite industry, illustrating the effect of lowering quartz exposures. Tuberculosis caused 2 deaths in those hired after 1940 (standardized mortality ratio [SMR] = 0.52; not significant). Overall lung cancer mortality was elevated in shed workers who had been exposed both to high levels of quartz before 1940 and to the lower levels prevailing after 1940 (SMR = 1.32; P < 0.01). Quarry workers did not show an excess of lung cancer (SMR = 0.73; not significant). When shed workers with high and low exposure histories (before and after 1940) but with comparable latency and tenure were contrasted, lung cancer mortality was similar. Differing levels of quartz exposure, which resulted in large differences in the mortality experience from silicosis, did not result in differences in lung cancer mortality. The results do not support the hypothesis that granite dust exposure has a causal association with lung cancer.

Radiographic abnormalities in long-tenure Vermont granite workers and the permissible exposure limit for crystalline silica.

This study was undertaken to assess the prevalence of radiographic abnormalities consistent with silicosis in a group of 600 retired granite workers who were receiving pensions. Files of regional clinics and hospitals were searched for chest radiographs taken on these men, and 470 x-ray films suitable for interpretation were located. After exclusions (women, and men who had worked in the granite industry elsewhere), 408 x-ray films were independently read by three experienced readers using the 1980 International Labour Office scheme. Dust exposures were estimated for workers hired after 1940, when the dust-control standard of 10 million particles per cubic foot (mppcf) (equivalent to 0.1 mg/m3) was put in place and monitored by the Vermont Division of Industrial Hygiene. Dust levels were initially high but were gradually reduced from 1940 to 1954, after which average quartz exposures stabilized to a mean of approximately 0.05 to 0.06 mg/m3; however, about 10% to 15% of samples after 1954 exceeded 0.1 mg/m3. Of the 408 x-ray films, 58 were taken on workers hired before dust controls were instituted in 1940, and 25.9% showed abnormalities (a profusion score of 1/0 or greater). A total of 350 x-ray films were taken on workers hired in 1940 or after, and the prevalence in this group was 5.7%. The radiographic changes in workers hired after 1940 are likely due to excessive exposures during the first 15 years of dust control. We conclude that if the exposure standard of 0.1 mg/m3 is rigorously observed in the workplace, radiographic abnormalities caused by quartz dust in long-term workers will be rare.

Electrical breakdown in water vapor.

In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm (~0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.

Vermont granite workers' mortality study.

A cohort mortality study was carried out in Vermont granite workers who had been employed between the years 1950 and 1982. The cohort included men who had been exposed to high levels of granite dust prior to 1938-1940 (average cutters to 40 million parts/cubic foot), and those employed at dust levels after 1940, which on average were less than 10 million parts/cubic foot. Deaths were coded by a qualified nosologist and standardized mortality ratios were calculated. The results confirm previous studies that show that death rates from silicosis and tuberculosis, the major health threats in the years before 1940, were essentially eliminated after dust controls. However, we found excessive mortality rates from lung cancer in stone shed workers who had been employed prior to 1930, and hence had been exposed to high levels of granite dust. When information was available, 100% of those dying from lung cancer had been smokers.

Short-term adaptation to moderate altitude. Patients with chronic obstructive pulmonary disease.

Eight patients with mild-to-moderate chronic obstructive pulmonary disease (COPD) and average resting Pao2 of 66 mm Hg were studied clinically and physiologically at sea level and after ascent to 1,920 m. At sea level the patients were symptomatic but not disabled. After ascent the patients had only mild symptoms of fatigue and insomnia, and one had severe headache during exercise on the first day. Funduscopic changes were not observed, nor did cardiac or pulmonary findings change. Resting sea level Pao2 dropped to 51.5 mm Hg within three hours of ascent, and the Paco2 fell from 37.8 to 33.9 mm Hg. Over the next three days, the Pao2 increased to 54.5 mm Hg as hyperventilation continued. At exercise, sea level Pao2 dropped from a mean value of 63 to 46.8 mm Hg at altitude. Pulse rates at rest or exercise did not change. Normal values for 2,3-diphosphoglycerate (2,3-DPG) did not change after ascent at 16 and 42 hours. We believe aircraft flight or travel to moderate altitudes for this type of COPD patient is safe. Preexisting hypoxemia resulting from disease may facilitate the adaptation of patients to severe hypoxia and may prevent symptoms similar to acute mountain sickness.

Efficacy of chest physiotherapy and intermittent positive-pressure breathing in the resolution of pneumonia.

We undertook a randomized clinical trial to evaluate the efficacy of chest physiotherapy and intermittent positive-pressure breathing in the treatment of pneumonia. The diagnosis of pneumonia required a compatible clinical history and x-ray confirmation. A total of 54 patients were assigned to treatment and control groups and were similar in age, smoking history, underlying lung disease and prior antibiotic treatment. Antibiotic therapy, guided by Gram stain and sputum and blood cultures, was similar in both groups. Chest physiotherapy, consisting of postural drainage, percussion and vibration, was given concurrently with intermittent positive-pressure breathing with use of racemic epinephrine every four hours. There was no statistically significant difference in duration of fever, extent of radiographic clearing, duration of hospital stay and mortality between the control and treated groups. Chest physiotherapy and intermittent positive-pressure breathing do not hasten the resolution of pneumonia.

Pulmonary function loss in Vermont granite workers. A long-term follow-up and critical reappraisal.

Previous studies of Vermont granite workers averred that pulmonary function loss was occurring at 2 to 3 times the normal rate. The excess loss was attributed to the current, relatively low concentrations of dust prevailing in the stone sheds. Because the Vermont State Health Department had traditionally provided surveillance of granite workers to detect evidence of occupationally related illness, we offered pulmonary function screening to any currently employed worker. Spirometric data from the first 150 workers, compared with data from the previous studies, showed a large increase in the FVC and a smaller increase in the FEV1. We therefore undertook a survey of the entire stone shed work force, as well as of retired workers tested previously. The results in 487 current workers indicated an overall increase in FVC from 1974 to 1979 of 0.540 L, and an increase in FEV1 of 0.030 L: predicted losses based on the previous studies were 0.350 to 0.400 L in FVC and 0.250 to 0.350 L in the FEV1. Analysis of data in various subgroups, such as retired workers or those with more than 20 yr of work experience, also showed increases in FVC, and either slight gains or minimal losses in FEV1. The possible reasons for apparent improvement in pulmonary function are discussed. We concluded that technical deficiencies in the previous studies led to exaggerated and erroneous estimates of loss. At this time, the actual decrement in pulmonary function values for exposed granite workers is not known and requires further investigation. Because the newly proposed, stricter standard, for silica was importantly influenced by the previous studies, we believe that adoption of this standard would be premature.

Mineral dust and cell recovery from the bronchoalveolar lavage of healthy Vermont granite workers.

We characterized the bronchoalveolar lavage (BAL) from healthy Vermont granite workers to investigate the pulmonary response to a chronic exposure to an injurious agent. Nine granite workers with 4 to 36 yr of employment in the industry and 27 unexposed volunteers were normal by history, physical examination, electrocardiogram, blood count, spirometry, and chest radiograph. Lavage cell recovery and percent neutrophils were not different. Lymphocyte recovery in BAL was increased in the granite-exposed population. Granite dust was present within the majority of alveolar macrophages from granite workers compared with those from control subjects, as determined by polarizing light microscopy and confirmed by scanning electron microscopy with X-ray energy spectrometry. There were no differences in phagocytic function or viability of macrophages from granite workers compared with those from unexposed volunteers. We conclude that in exposed populations, granite dust can be detected and semiquantitated in lavage specimens within the alveolar macrophages, macrophage function is preserved, and the response to this exposure involves an influx of lymphocytes.