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M J Muszynski

Publications and source records attributed to M J Muszynski.

12 recordsLinked to original sources
PubMed1999

Direct ultrastructural imaging of macrophages using a novel x-ray contact microscopy.

A compact, high-resolution, laser-plasma, x-ray contact microscopy method using a table-top Nd:glass laser system has been developed. This x-ray microscopy system was applied for the observation of macrophage ultrastructures. These images were produced using proximity imaging in which a 5-ns pulse of soft x-rays with wavelengths near and inside the water windows (23A-44A) produced by the laser-plasma were absorbed by the specimen and then registered on a photo resist. The x-ray images imprinted on the photo resist were then developed and analyzed with an atomic force microscope (AFM). Mouse thioglycollate-elicited peritoneal macrophages in suspension were examined by this new x-ray microscope. The x-ray images of the macrophages were compared with those observed by conventional transmission electron microscopy (TEM). The x-ray images showed no obvious organelles, including the nucleus and endoplasmic reticulum, as can be seen with TEM, but high- and low-contrast structures caused by mass distribution of carbon were observed. Thus, using the x-ray microscopy we visualized the first x-ray images of macrophage ultrastructures. The successful x-ray imaging of macrophage ultrastructure indicates that proximity x-ray microscopy may be of value in studying physiology linked to the dynamics of a cell.

Animals↗
PubMed1998

Sensitization of Burkholderia cepacia to antibiotics by cationic drugs.

Chlorpromazine and prochlorperazine have previously been shown to enhance the susceptibility of Burkholderia cepacia to aminoglycosides. To screen other non-antibiotic drugs containing similar amine (-N-CH3) groups, we examined a range of such agents that are in current clinical use for the treatment of non-infectious diseases, in combination with antibiotics that are ineffective against B. cepacia. At a concentration of 0.2 mM, theobromine, theophylline, trifluoperazine, fluophenazine and coumarin-152 significantly reduced (by four-fold) the MICs of gentamicin and ceftazidime. Theobromine and theophylline also reduced the MICs of amikacin and azithromycin.

Amikacin↗
PubMed1998

Application of X-ray micrography and imaging to study the effect of gentamicin on Pseudomonas aeruginosa.

Aminoglycosides disrupt the outer membrane of Pseudomonas aeruginosa to facilitate access to their intracellular target. High-resolution X-ray micrography of live specimens is a relatively new technique. We used laser (nanosecond) plasma to image live cells of P. aeruginosa ATCC 27853. After exposure to 25 mg/L gentamicin for 15 min. we observed perturbation of the cell surface, membrane blebbings (370 nm and 273 nm diameter) away from the cell, formation of distinct channels (241 nm long) resulting from indentation and induction of cell elongation from 3-3.6 microm (control) to 4.6-5.26 microm (gentamicin-treated cells). These data illustrate the potential of high-resolution X-ray micrography for studying effects of drugs on live microbiological specimens.

Anti-Bacterial Agents↗
PubMed1997

X-ray micrography and imaging of Escherichia coli cell shape using laser plasma pulsed point x-ray sources.

High-resolution x-ray microscopy is a relatively new technique and is performed mostly at a few large synchrotron x-ray sources that use exposure times of seconds. We utilized a bench-top source of single-shot laser (ns) plasma to generate x-rays similar to synchrotron facilities. A 5 microlitres suspension of Escherichia coli ATCC 25922 in 0.9% phosphate buffered saline was placed on polymethylmethyacrylate coated photoresist, covered with a thin (100 nm) SiN window and positioned in a vacuum chamber close to the x-ray source. The emission spectrum was tuned for optimal absorption by carbon-rich material. Atomic force microscope scans provided a surface and topographical image of differential x-ray absorption corresponding to specimen properties. By using this technique we observed a distinct layer around whole cells, possibly representing the Gram-negative envelope, darker stained areas inside the cell corresponding to chromosomal DNA as seen by thin section electron microscopy, and dent(s) midway through one cell, and 1/3- and 2/3-lengths in another cell, possibly representing one or more division septa. This quick and high resolution with depth-of-field microscopy technique is unmatched to image live hydrated ultrastructure, and has much potential for application in the study of fragile biological specimens.

Escherichia coli↗
PubMed1997

X-ray microscopy and imaging of Escherichia coli, LPS and DNA.

Ultrastructural examination by transmission and scanning electron microscopy involves a series of specialized preparation steps which may introduce artefacts in the micrographs. X-ray microscopy can take instant images of specimens but is mostly restricted to a few synchrotron X-ray sources. We have utilized a bench-top nanosecond laser-plasma to produce a single-shot source of nanosecond X-rays tuned for maximum contrast with carbon-rich material. To examine the ultrastructure by absorption profiles, we utilized a laser-produced plasma generated by a single-shot laser (1.06 microns wavelength, 5 x 10(12) W cm-2 intensity) focused on to a silicon target as an X-ray source for high-resolution X-ray microscopy. This approach eliminates the specimen preparation steps. Whole hydrated cells of Escherichia coli and purified preparations of lipopolysaccharide (LPS) and chromosomal DNA (cDNA) were streaked onto poly(methyl methacrylate) (PMMA)-coated grids (resist). This resist was exposed to X-rays under vacuum at a distance of 2.5 cm from the target disc. The silicon plasma produced by a 10-ns burst of laser energy (at 20J) radiates strong emission lines in the region of 300 eV. The X-rays penetrate the sample and their absorption profile is transferred on to the resist where PMMA acts as a negative to generate an image. By atomic force microscopy imaging of this photoresist we have visualized layers around cells of E.coli, darker areas inside the cell probably corresponding to cDNA, and preliminary images of LPS and DNA molecules. This technique has resolution at the 100 A level, produces images similar to the space-filling models of macromolecules and may be of great value in the study of the ultrastructure of hydrated live biological specimens.

DNA, Bacterial↗
PubMed1997

Enhancement of Burkholderia cepacia antimicrobial susceptibility by cationic compounds.

Infections in cystic fibrosis (CF) due to Burkholderia cepacia are challenging due to their resistance to antibiotics. We explored a new strategy for increasing the permeability of B. cepacia using cationic agents, including amino compounds, to reduce the MICs of standard antibiotics. Twenty-eight B. cepacia isolates from four CF centres in North America and four non-CF B. cepacia were examined by standard microtitre broth dilution methods for susceptibility to a variety of antibiotics in the presence of non-inhibitory concentrations of diaminoacetone (DAA), methylglyoxal bis-guanylhydrazone (MGBH), chlorpromazine (CPZ) and prochlorperazine (PCPZ). The proportion of isolates with greater than four-fold reductions in MIC in the presence of 0.3 mM CPZ or 0.4 mM PCPZ were 90% and 94% for gentamicin, 80% and 83% for tobramycin, 45% and 17% for ceftazidime, and 35% and 17% for amifloxacin. CPZ showed the same degree of reduction in the MIC of azithromycin in 79% strains (MIC50 reduced to 16 from > or = 256 mg/L). Non-CF B. cepacia showed a greater than four-fold reduction in MIC with CPZ for gentamicin, tobramycin and azithromycin and two-fold reduction for ceftazidime. Little or no reduction in MIC was seen with DAA or MGBH for any antibiotic. Addition of magnesium ions to the medium competitively inhibited any MIC reduction effect seen with the cationic agents. CPZ and PCPZ appeared to enhance the permeability of B. cepacia to antibiotics based upon ionic charge characteristics of the antibiotic. No significant differences were seen in outer membrane protein and lipopolysaccharide profiles between the culture treated with CPZ and the respective control culture of strain B. cepacia ATCC 13945. The fluorescent probe 1N-phenylnaphthylamine had no increased access across the outer membrane in the presence of CPZ for B. cepacia ATCC 13945. However, thin-section electron microscopy revealed separation between the outer membrane and the rest of the cytoplasm accompanied by a widening of the periplasmic space. These data provide a rationale for investigating amino compounds as potential permeability-increasing agents against B. cepacia.

1-Naphthylamine↗
PubMed1997

Association of resistance to trimethoprim/sulphamethoxazole, chloramphenicol and quinolones with changes in major outer membrane proteins and lipopolysaccharide in Burkholderia cepacia.

Antibiotic treatment options for Burkholderia cepacia infection are limited because of high intrinsic resistance. The problem is complicated by development of cross-resistance between antibiotics of different classes. We isolated antibiotic-resistant mutants by stepwise exposure to chloramphenicol (Chlor) and to trimethoprim/sulphamethoxazole (T/S) for four B. cepacia strains: ATCC13945, Per (clinical isolate), Cas and D4 (environmental isolates). Chlor(r) mutants did not produce chloramphenicol acetyl-transferase. Cross-resistance, defined as greater than four-fold increase in MIC by microtitre dilution method, was consistently seen in both types of mutants. For chloramphenicol-resistant (Chlor[r]) and trimethoprim/sulphamethoxazole-resistant (Tr/Sr) mutants of B. cepacia ATCC13945 and Cas, no MIC change was seen for piperacillin, ceftazidime, rifampicin, gentamicin, tobramycin, polymyxin B or azithromycin. B. cepacia-Per and -D4 mutants showed cross-resistance to ceftazidime and to piperacillin. Comparison of outer membrane protein (OMP) profiles of B. cepacia and their mutants by SDS-PAGE revealed Tr/Sr) mutants to be deficient in a major OMP (molecular weight 39-47 kDa). Tr/Sr mutants also expressed additional OMPs not found in wild type strains at 75-77 kDa for B. cepacia-ATCC13945 and -Cas, and 20-21 kDa in B. cepacia-D4 and -Per. No OMP changes occurred in Chlor(r) mutants. Lipopolysaccharide (LPS) profiles of each type of mutant showed new high and low molecular weight LPS bands. Cross-resistance seems to be mediated by alterations in porin and LPS for Tr/Sr mutants, but only by LPS in Chlor(r) mutants.

Anti-Bacterial Agents↗
PubMed1991

Early meningitis.

Explore the source record for details and available documents.

Child, Preschool↗
PubMed1989

Recovery of Pseudomonas gladioli from respiratory tract specimens of patients with cystic fibrosis.

Pseudomonas gladioli was isolated from 11 patients with cystic fibrosis. It resembled Pseudomonas cepacia on the selective and differential medium OFPBL, producing yellow colonies after 48 to 72 h of incubation. Isolates were characterized biochemically, by DNA hybridization, and by cellular fatty acid analysis. A review of the clinical status of selected patients colonized by P. gladioli did not reveal any apparent association of this organism with infectious complications of cystic fibrosis. Thus, the clinical implications may differ depending on which of these two closely related species is reported by laboratories. Determination of the fatty acid profile of isolates by gas chromatography may be a useful adjunct to biochemical characterization as a means of identification. In contrast to P. cepacia, most isolates of P. gladioli contained 3-OH C10:0 fatty acid under the growth conditions used.

Adolescent↗
PubMed1987

Prevalence of thymidine-dependent Staphylococcus aureus in patients with cystic fibrosis.

During a 1-year period, the prevalence of thymidine-dependent (TD) Staphylococcus aureus in patients at two geographically distinct cystic fibrosis (CF) centers was determined. Of 200 CF patients who had their respiratory secretions cultured, 95 harbored S. aureus, and 20 (21%) had TD S. aureus as their predominant staphylococcal isolate. All 20 TD S. aureus-positive patients had received trimethoprim-sulfamethoxazole for an average of 30.9 months. It was also observed that TD S. aureus exhibited aberrant colony morphologies or did not grow on media commonly used in CF centers for S. aureus isolation, suggesting that this organism could be missed by routine culture methods. In contrast, all 20 isolates had typical staphylococcal morphology on mannitol salt agar after 48 h of incubation. Mannitol salt agar is recommended for primary isolation of TD S. aureus.

Culture Media↗
PubMed1987

Selective and differential medium for recovery of Pseudomonas cepacia from the respiratory tracts of patients with cystic fibrosis.

A selective and differential medium, OFPBL (oxidation-fermentation base supplemented with agar, lactose, and two antimicrobial agents), for the isolation of Pseudomonas cepacia from respiratory specimens of patients with cystic fibrosis was developed and tested. Among 725 specimens submitted from seven centers over a 4- to 6-month period, 58 (8%) yielded P. cepacia on OFPBL; only 19 of these were recovered on MacConkey or sheep blood agar (P less than 0.001). No isolate was recovered on MacConkey or sheep blood agar alone. Ranges of recovery rates among centers were 0 to 15% on OFPBL and 0 to 10% on MacConkey or sheep blood agar. Ninety percent of P. cepacia isolates were detected on OFPBL in less than or equal to 3 days. Other nonfermenters and yeasts isolated on OFPBL were distinguished from P. cepacia by failure to acidify the medium. The new medium was clearly superior to MacConkey and sheep blood agars for the isolation of P. cepacia from the respiratory secretions of patients with cystic fibrosis.

Culture Media↗