Characterization of Bacillus pumilus E601 spores after single sublethal gamma irradiation treatments. (41/814)

Eighteen survivor strains of Bacillus pumilus E601 have been isolated after single sublethal irradiation treatments with 60Co. Primary isolation was based on the loss of motility and pellicle formation. However, with subsequent subcultivation, eight isolates reverted back to the standard of exhibiting motility and pellicle formation. Characteristics of the isolates include alterations in space radiation resistance and in the amino acid requirements for spore germination and outgrowth. Other alterations in cultural and physiological characteristics were found. Three of the isolates were asporogenous.  (+info)

Effect of dwell time on carbonyl stress using icodextrin and amino acid peritoneal dialysis fluids. (42/814)

BACKGROUND: Deterioration of the peritoneal membrane limits the technical survival of peritoneal dialysis (PD). Advanced glycation of the membrane has been incriminated in this evolution. Advanced glycation end products (AGEs) develop under the influence of glucose and of its degradation products, mainly reactive carbonyl compounds (RCOs) such as glyoxal (GO), methylglyoxal (MGO), and 3-deoxyglucosone (3-DG). The present study was undertaken to evaluate the impact of recently developed glucose-free PD fluids on AGE generation. METHODS: Recently developed glucose-free PD fluids containing either icodextrin or amino acids were investigated. GO, MGO, and 3-DG [high-performance liquid chromatography (HPLC)] and total RCOs (spectrophotometry) were measured in fresh solutions and in effluents after various dwell duration. The AGE formation potential of PD fluids and effluents was assessed by incubation at 37 degrees C, for one week, with bovine serum albumin and by the eventual measurement of pentosidine (HPLC) and Nepsilon-carboxymethyllysine (CML; gas chromatography/mass spectrometry). RESULTS: GO, MGO, and 3-DG (P < 0. 001) as well as total RCOs levels (P < 0.01) were significantly lower in icodextrin and amino acid PD fluid than in commercial, heat-sterilized, 1.36% glucose PD fluid. Pentosidine and CML generation were also significantly lower (P < 0.001) in icodextrin and amino acid PD fluid than in conventional 1.36% glucose PD fluid. The levels of total RCOs, however, increased in icodextrin and amino acid PD fluid effluents with dwell time. AGE formation potential rose accordingly, as demonstrated by a parallel increase in the generation of pentosidine and CML during incubation of PD effluents. CONCLUSION: The present data demonstrate lower RCO contents and AGE formation potential in fresh icodextrin and amino acid PD fluids than in fresh heat-sterilized glucose PD fluids. However, this difference decreases progressively during dwell time, mainly as a result of the influx of total RCOs.  (+info)

Protozoa as agents responsible for the decline of Xanthomonas campestris in soil. (43/814)

A streptomycin-resistant mutant of Xanthomonas campestris was used to assess the persistence of the plant pathogen in soil and the changes in populations that might be important for its survival. In soil into which large numbers of the organism were introduced, a marked decline in its abundance occurred, but after about 1 week its population density reached a level of about 105 and did not continue to fall during the test period. No such marked decline was evident in sterile soil inoculated with X. campestris. The bacterium did not lose viability if starved for carbon or inorganic nitrogen. Although abundant in soil, the numbers of propagules capable of producing antibiotics or lytic enzymes active against X. campestris did not increase coincident with the pathogen's decline, and no increase in tartrate-extractable toxins was observed. Neither bdellovibrios nor bacteriophages active against the xanthomonad were found in the soil, but a marked increase in the frequency of protozoa paralleled the phase of rapid diminution in the X. campestris population. In actidione-treated soil, in which protozoan activity was severly limited, the high cell density of the pathogen was maintained. On the basis of these data, it is concluded that predation by protozoa is responsible for the abrupt fall in frequency of the bacterium in natural soil.  (+info)

Sterilization of Mycobacterium tuberculosis Erdman samples by antimicrobial fixation in a biosafety level 3 laboratory. (44/814)

Incomplete sterilization of Mycobacterium tuberculosis Erdman cultures followed 1 h of incubation in low concentrations of glutaraldehyde (0.5 and 1.0%) or azide. In contrast, 2.5% glutaraldehyde, paraformaldehyde (2 or 4%), Vesphine IIse or 5% formalin sterilized these samples after 1 h. These results suggest caution in removing fixed M. tuberculosis samples from biosafety level 3.  (+info)

Risk of infection by reprocessed and resterilized virus-contaminated catheters; an in-vitro study. (45/814)

AIMS: In spite of increasing reuse of disposable catheters, there are few scientific data on potential viral transmission and infection after reuse. To determine the theoretical risk of virus transmission during reuse of catheters an in vitro study was performed using an RNA virus (echovirus-11) and a DNA virus (adenovirus-2). METHODS AND RESULTS: After deliberate contamination of the catheters, reprocessing and reuse of the cleaned and glutaraldehyde sterilized catheters was simulated. The presence of residual virus was determined by cell culture and by polymerase chain reaction (PCR). After the sterilization step, infectious enterovirus was detectable in one (10%) of the samples, whereas two (20%) contained detectable enterovirus RNA. After simulated reuse, enterovirus was cultured from one (10%) of the catheters, but no less than six (60%) of the samples were enterovirus PCR positive and one (10%) contained detectable adenovirus DNA. After sonification of the catheter tips no infectious virus could be detected, but enterovirus RNA was detected in two (20%) and adenovirus DNA in three (30%) of the samples. CONCLUSIONS: It has been clearly demonstrated in this in vitro study that, even after rigorous cleaning and sterilization, virus was still present in the catheter. Reuse of catheters, labelled for single-use only, is dangerous and should be prevented.  (+info)

Reclassification of bioindicator strains Bacillus subtilis DSM 675 and Bacillus subtilis DSM 2277 as Bacillus atrophaeus. (46/814)

On the basis of high DNA-DNA reassociation values and confirmatory automated RiboPrint analysis, two aerobic spore-forming strains hitherto allocated to Bacillus subtilis and used as bioindicators (DSM 675, hot-air sterilization control; DSM 2277, ethylene oxide sterilization control) are reclassified as Bacillus atrophaeus.  (+info)

Biological significance of reducing glucose degradation products in peritoneal dialysis fluids. (47/814)

Carbohydrates are not stable when exposed to energy; they degrade into new molecules. In peritoneal dialysis (PD) fluids, degradation of glucose occurs during the heat sterilization procedure. The biological consequences of this degradation are side effects such as impaired proliferation and impaired host defense mechanisms, demonstrated in vitro for a great variety of cells. Several highly toxic compounds--such as formaldehyde and 3-deoxyglucosone--have been identified in PD fluids. Carbonyl compounds, apart from being cytotoxic, are also well-known promoters of irreversible advanced glycation end-products (AGEs), which might participate in the long-term remodeling of the peritoneal membrane. Various approaches can be used to reduce the formation of glucose degradation products (GDPs) during heat sterilization. Some examples are shortening the sterilization time, lowering the pH, removing catalyzing substances, and increasing glucose concentration. The latter three factors are employed in the multi-compartment bag with a separate chamber containing pure glucose at high concentration and low pH. Gambrosol trio, a PD fluid produced in this way, shows reduced cytotoxicity, normalized host defense reactions, less AGE formation, and reduced concentrations of formaldehyde and 3-deoxyglucosone. Moreover, in the clinical situation, the fluid turns out to be more biocompatible for the patient, causing less mesothelial cell damage, which in the long term could lead to a more intact peritoneal membrane. CONCLUSION: Glucose degradation products in heat-sterilized fluids for peritoneal dialysis are cytotoxic, promote AGE formation, and cause negative side effects for the patient. Using improved and well-controlled manufacturing processes, it is possible to produce sterile PD fluids with glucose as the osmotic agent but without the negative side effects related to GDPs.  (+info)

First in vitro and in vivo experiences with Stay-Safe Balance, a pH-neutral solution in a dual-chambered bag. (48/814)

In addition to low pH and high osmolarity, glucose degradation products (GDPs) are considered to play a major role in the bioincompatibility of peritoneal dialysis fluids (PDFs). The formation of GDPs can be reduced by separating the glucose component of the solution (kept at very low pH) from the lactate component of the solution (kept at alkaline pH) during sterilization and storage. This development has been achieved by the use of a dual-chambered bag. Immediately before infusion, the seam between the two chambers is opened, and the contents are mixed. The result is a fluid with a more physiologic pH in the range 6.8 - 7.4. Concentrations of 3-deoxyglucosone (3-DG), methylglyoxal (MG), acetaldehyde (AA), and formaldehyde (FA) in Stay-Safe Balance (Fresenius Medical Care, Bad Homburg, Germany) were remarkably reduced when compared to conventional PD solution [conventional PDF (1.5% glucose): 172 micromol/L, 6 microLmol/L, 152 micromol/L, and 7 micromol/L respectively; Stay-Safe Balance (1.5% glucose): 42 micromolL, < 1 micromol/L, < 2 micromol/L, and < 3 micromol/L respectively; conventional PDF (4.25% glucose): 324 micromol/L, 10 micromol/L, 182 micromol/L, and 13 micromol/L respectively; Stay-Safe Balance (4.25% glucose): 60 micromol/L, < 1 micromol/L, < 2 micromol/L, and < 3 micromol/L respectively). Human peritoneal mesothelial cells (HPMCs) were exposed to a control solution, a conventional PDF [CAPD 2, 1.5% glucose (Fresenius Medical Care, Bad Homburg, Germany)], and Stay-Safe Balance, either in a co-incubation model (24-hour PDF exposure) or in a pre-incubation model (30-min PDF exposure), followed by 24-hour recovery in culture medium. Interleukin-1beta (IL-1beta)-stimulated (1 ng/mL) IL-6 secretion from HPMCs was assessed by ELISA. Exposure of HPMCs to conventional PDF resulted in a significant reduction in IL-6 release, which was fully restored following exposure to Stay-Safe Balance. In addition to the short-term investigations, long-term in vitro studies were also carried out. All fluids had near-neutral pH and were changed every second day. After 1, 3, 5, 7, 10, and 13 days of exposure, cell viability was assessed. Whereas exposure to conventional PDF resulted in a significant reduction in HPMC viability after just 3 - 5 days, no significant toxicity of filter-sterilized or dual-chambered fluid was observed for up to 13 days. An observational study with 9 patients suggested that the efficacy of Stay-Safe Balance is equivalent to that of conventional solution. However, even short-term treatment (8+/-1 weeks) with this more biocompatible solution seems to improve mesothelial cell mass as indicated by a rise in cancer antigen 125 (CA125) from a baseline of 47+/-37 U/min to 172+/-90 U/min. Our data indicate that Stay-Safe Balance may help to better preserve peritoneal membrane cell function. An ongoing European multicenter study is expected to confirm these results.  (+info)