Biomedical subjects

R Reissbrodt

Publications and source records attributed to R Reissbrodt.

At least 37 records · Page 2Linked to original sources

PubMed1997

Iron uptake and intracellular metal transfer in mycobacteria mediated by xenosiderophores.

Growth promotion was tested using M. smegmatis wild type strain, an exochelin-deficient mutant, and M. fortuitum employing a broad variety of xenosiderophores including hydroxamates, catecholates and alpha-hydroxy carboxylic acids. The experiments revealed that utilization of siderophore-bound iron is substrate specific suggesting high-affinity siderophore receptor and transport systems. Concentration-dependent uptake of a selected xenosiderophore (fericrocin) in M. smegmatis showed saturation kinetics and uptake was inhibited by respiratory poisons. In situ Mössbauer spectroscopy of ferricrocin uptake in M. smegmatis indicated rapid intracellular reductive removal of the metal excluding intracellular ferricrocin accumulation. The ultimate intracellular iron pool is represented by a compound (delta = 0.43 mm s-1, delta EQ = 1.03 mm s-1) which has also been found in many other microorganisms and does not represent a bacterioferritin, cytochrome or iron-sulfur cluster. By contrast, iron uptake via citrate-a compound exhibiting a very low complex stability constant-involves ligand exchange with mycobactin. Mycobactin has merely a transient role. The ultimate storage compound is an E. coli-type bacterioferritin, in which over 90% of cellular iron is located.

Bacterial Outer Membrane Proteins↗

PubMed1997

Iron-regulated excretion of alpha-keto acids by Salmonella typhimurium.

Excretion of alpha-keto acids by clinical isolates and laboratory strains of Salmonella typhimurium was determined by high-performance liquid chromatography analysis of culture supernatants. The levels of excretion increased markedly with increasing iron stress imposed by the presence of alpha,alpha'-dipyridyl or conalbumin in the medium. The major product was pyruvic acid, but significant concentrations of alpha-ketoglutaric acid, alpha-ketoisovaleric acid, and alpha-ketoisocaproic acid were also observed. Maximal excretion occurred at iron stress levels that initially inhibited bacterial growth; the concentration of alpha,alpha'-dipyridyl at which this was observed differed between strains depending on their ability to secrete and utilize siderophores, suggesting that the intracellular iron status was important in determining alpha-keto acid excretion. However, prolonged incubation of the siderophore-deficient S. typhimurium strain enb-7 under conditions of high iron stress resulted in significant delayed bacterial growth, promoted by tonB-dependent uptake of iron complexed with the high accumulated levels of pyruvic acid and other alpha-keto acids. Strain RB181, a fur derivative of enb-7, excreted massive amounts of alpha-keto acids into the culture medium even in the absence of any iron chelators (the concentration of pyruvic acid, for example, was >25 mM). Moreover, RB181 was able to grow and excrete alpha-keto acids in the presence of alpha,alpha'-dipyridyl at concentrations threefold greater than that which inhibited the growth of enb-7.

2,2'-Dipyridyl↗

PubMed1997

Rapid detection of Salmonella enterica with primers specific for iroB.

The iroB gene of Salmonella enterica is absent from the chromosome of the related organism Escherichia coli. We determined the distribution of this gene among 150 bacterial isolates, representing 51 serotypes of different Salmonella species and subspecies and 8 other bacterial species which are frequent contaminants during routine enrichment procedures by Southern hybridization. An iroB-specific DNA probe detected homologous sequences in all strains of S. enterica, including serotypes of S. enterica subsp. enterica (I), salamae (II), diarizonae (IIIb), and houtenae (IV). No hybridization signal was obtained with strains of Salmonella bongori or other bacterial species. In contrast, hybridization with a DNA probe specific for purD, a purine biosynthesis gene, detected homologs in all bacterial species tested. Primers specific for iroB were used to amplify this gene from 197 bacterial isolates by PCR. The iroB gene could be PCR amplified from S. enterica subsp. enterica (I), salamae (II), diarizonae (IIIb), houtenae (IV), arizonae (IIIa), and indica (VI), but not from S. bongori or other bacterial species. Thus, PCR amplification of iroB can be used to distinguish between S. enterica and other bacterial species, including S. bongori. A combination of preenrichment in buffered peptone water supplemented with ferrioxamine E and amplification of iroB by magnetic immuno-PCR allowed detection of S. enterica in albumen within 24 h. In conclusion, PCR amplification of iroB is a new sensitive and selective method which has the potential to rapidly detect S. enterica serotypes.

Bacterial Typing Techniques↗

PubMed1996

TonB-dependent iron supply in Salmonella by alpha-ketoacids and alpha-hydroxyacids.

A range of structurally diverse alpha-ketoacids and alpha-hydroxyacids promoted the growth of isolates of Salmonella serovars S. typhimurium, S. enteritidis, S. agona, S. paratyphi and S. stanleyville in iron restricted conditions in the absence of functional siderophores. Growth stimulation, observed both in cross-feeding tests on solid medium and in liquid cultures, and uptake of 55Fe in the presence of alpha-ketoisocaproic acid, were TonB dependent in S. typhimurium. In this respect the mechanism is distinct from a previously described Serratia marcescens system (sfuABC); the presence of the cloned sfuABC genes mediated tonB-independent uptake by S. typhimurium of iron complexed with alpha-ketoacids.

Bacterial Proteins↗

PubMed1996

Ferrioxamine E-supplemented pre-enrichment and enrichment media improve various isolation methods for Salmonella.

Supplementation of pre-enrichment broth and enrichment broth media with ferrioxamine E (1 microgram/ml) significantly improved the recovery of Salmonella from artificially or naturally contaminated foods. Based on the selectivity of ferrioxamine E, Salmonella enteritidis and S. typhimurium could be isolated also from various mixed cultures (one Salmonella cell in 10(3)-10(4)-fold concentration of cells of competitors) by shaking for 6 h in supplemented buffered peptone water followed by cultivation on XLD- or XLT-4 agars. Isolation of Salmonella from these pre-enrichment cultures by use of Dynabeads-Anti-Salmonella was highly effective. 27 S. typhimurium strains were isolated from 762 naturally infected chicken giblets by use of unsupplemented Tetrathionate broth. However, 33 S. typhimurium isolates were obtained with ferrioxamine E-supplemented Tetrathionate broth from the same samples. Three Salmonella isolates out of 50 evenly divided meat meal samples were obtained by use of ferrioxamine E-supplemented buffered peptone water followed by direct streaking onto XLD- and Rambach agars, no Salmonella isolates could be detected by the conventional method.

Animals↗

PubMed1995

vanA-mediated high-level glycopeptide resistance in Enterococcus faecium from animal husbandry.

Glycopeptide-resistant Enterococcus faecium strains were isolated from a pig farm and a poultry farm both using avoparcin as a food additive. Such organisms were not isolated in a hen's eggs-producing farm not using avoparcin. Glycopeptide-resistant enterococci were also detected in broiler chicken carcasses that were delivered to a hospital's kitchen. The resistance was determined by the vanA gene as indicated by the detection of the inducible 39-kDa cytoplasmic membrane protein and of a vanA-specific DNA sequence amplified by polymerase chain reaction. Genomic DNA fragment patterns of strains from animal sources were different from each other and also from those of strains isolated in hospitals and from sewage treatment plants. This findings suggest the dissemination of the vanA determinant among different enterococcal strains of distinct ecological origin.

Animal Husbandry↗

PubMed1995

Improvement of Salmonella detection on motility enrichment media by ferrioxamine E-supplementation of pre-enrichment culture.

Supplementation of buffered peptone water with ferrioxamine E in concentrations ranging from 0.001 to 1.0 microgram/ml significantly increased the motility of Salmonella on MSRV and DIASSALM semi-solid enrichment media. Zone diameters of swarming S. enteritidis and S. typhimurium increased more than twofold following use of pre-enrichment cultures supplemented with 0.01 microgram ferrioxamine E/ml. The activity of ferrioxamine E is similar at 37 degrees C and 42 degrees C. Pre-enrichment of Salmonella in a variety of foods in supplemented buffered peptone water, with shaking at 37 degrees C for 6 h and motility enrichment at 42 degrees C for 16 h, enabled motile Salmonella to be detected in 1 day.

Culture Media↗

PubMed1995

Iron supply of staphylococci and of micrococci by alpha-ketoacids.

Most of 232 strains of coagulase-negative staphylococci (CNS) belonging to 16 species, and nine strains of micrococci belonging to four species, could be distinguished by their growth on an iron-poor nutrient medium. alpha-Keto-/alpha-hydroxyacids, as primary metabolites, facilitated iron supply to CNS and micrococci under various iron-limited conditions, as detected by different bioassay methods. Twelve selected CNS strains and two micrococcal strains produced significant amounts of alpha-ketoacids in iron-poor liquid nutrient media. In particular, strains of Staphylococcus cohnii, S. xylosus and S. lentus unable to grow on iron-poor media, produced high amounts of pyruvic acid and alpha-ketoglutaric acid. In bioassays, the selected CNS strains being siderophore indicator strains were fed with alpha-ketoacids at different levels of iron limitation. Strains able to grow under iron deprivation appeared to produce additional siderophores such as staphyloferrins under iron stress. alpha-Keto-/alpha-hydroxyacids may be additionally active in the iron supply of CNS and micrococci.

Biological Assay↗

PubMed1995

Iron supplying systems of Salmonella in diagnostics, epidemiology and infection.

Well-known and newly characterised mechanisms, both endogenous and exogenous, for the uptake of iron by Salmonella are outlined, and their possible roles at various stages in infection are discussed. The contributions of a detailed understanding of iron supplying systems to techniques for diagnosis, epidemiology and disease management are described.

Bacterial Outer Membrane Proteins↗

PubMed1994

Iron supply of Pasteurella multocida and Pasteurella haemolytica.

Pasteurella multocida and Pasteurella haemolytica do not produce hydroxamate- or phenolate type siderophores. However, transport- and utilization systems could be detected for the well known siderophores ferrioxamine B, E, G, rhizoferrin and the intermediate 2,3-dihydroxybenzoic acid by means of cross-feeding tests in both Pasteurella species. Enterobactin and ferrichrome did not feed any of the Pasteurella strains tested. Additionally, alpha-ketoacids and alpha-hydroxyacids such as pyruvic acid, alpha-hydroxyisovaleric acid and others acting as primary metabolites enabled growth of P. multocida and P. haemolytica under iron limitation.

Culture Media↗

PubMed1994

Increased occurrence of KCN-resistant Salmonella strains.

104 KCN-resistant Salmonella strains were detected among 1391 strains typed (7.4%) during the first 7 months in 1993. In particular Salmonella enterica strains of subspecies I isolated from humans and foods exhibited this character. Those KCN-resistant Salmonella strains did not belong to a special antigen formula. The second flagellar phase could not be detected in most of these strains. KCN resistance does not seem to be plasmid-encoded.

Drug Resistance↗

PubMed1994

Susceptibility to desferrioxamines and other chelators of coagulase-negative staphylococci.

A total of 233 staphylococci and micrococci belonging to 17 species were tested for their susceptibility to desferrioxamines B, G and E, respectively. Using an agar diffusion method on iron poor media, all of the S. epidermidis, 12 out of 22 S. hominis and 5 out of 22 S. capitis strains were susceptible to desferrioxamines. Among the S. capitis strains tested, two of them were susceptible to desferrioxamine E and resistant to desferrioxamines B and G. All other staphylococci and micrococci tested were resistant to desferrioxamines B, G and E. Different susceptibility to 5 mM ethylenediaminedi-(o-phenylacetic acid) as an artificial chelator demonstrated the existence of additional iron-supplying systems in staphylococci and micrococci.

Chelating Agents↗

PubMed1994

Desferrioxamine-promoted virulence of Yersinia enterocolitica in mice depends on both desferrioxamine type and mouse strain.

The effects of desferrioxamine B (DFOB) and G (DFOG) on growth promotion and virulence of Yersinia enterocolitica as well as on T cell activation and proliferation were investigated. Both desferrioxamines promoted growth of Y. enterocolitica O:8 (WA-314) and O:3 (Y-108). DFOB had a greater immunosuppressive effect on T cells than did DFOG. These results suggest a dual role of DFOB in yersiniosis: growth promotion of the pathogen and immunosuppression of the host. The LD50 of both Yersinia strains for mice was reduced by DFOB but not by DFOG. However, the LD50 of yersiniae was reduced by DFOB to a greater extent in Yersinia-resistant C57BL/6 than in Yersinia-susceptible BALB/c mice. The different impact of DFOB on the LD50 of Y. enterocolitica in C57BL/6 and BALB/c mice might be due to an immunomodulating effect of DFOB.

Animals↗

PubMed1994

Evaluation of Rambach agar for detection of Salmonella subspecies I to VI.

Salmonella strains belonging to subspecies I to VI were investigated for colony color when grown on Rambach agar. Most strains of Salmonella subspecies I, II, IV, and VI behaved as described. All strains of Salmonella subspecies IIIa, IIIb, and V produced beta-D-galactosidase and blue-green colonies which could not be distinguished in color from Escherichia coli and other lactose-fermenting members of the family Enterobacteriaceae.

Agar↗

PubMed1994

[Iron availability in Salmonella in diagnosis, epidemiology, and the infectious process].

Well known and new iron supplying systems were described. Salmonella use siderophores of different chemical structures and uptake-systems for self-produced siderophores and siderophores produced by other microorganisms. Iron supplying systems contribute to new methods in diagnosis, epidemiology, vaccination, and development of new siderophore-beta-lactams. It is hoped to obtain new insights in the pathogenesis of salmonella by using methods of iron supplying systems.

Animals↗

PubMed1993

Selective pre-enrichment of Salmonella from eggs by siderophore supplements.

Salmonella can overcome the iron limitation of iron-limited nutrient media and albumen by utilizing the siderophores ferrioxamine E and G und grow. 14 out of 18 food-poisoning Salmonella strains of different serotypes stored in hen's egg albumen (approx. 2 organisms/ml) could be detected after 6 h of pre-enrichment with buffered peptone water supplemented with ferrioxamine G (1 microgram/ml) on selective nutrient media. In contrast, only 4 of these Salmonella strains could be reisolated without supplementation. E. coli strains cannot be supplied with iron by ferrioxamines E and G. Therefore, Salmonella enteritidis phage type 4/6 could be isolated in great numbers from mixed cultures with E. coli kept in albumen. Buffered peptone water supplemented with ferrioxamine G also permitted a successful reisolation of Salmonella enteritidis from artificially contaminated eggs. Ferrioxamines E and G function as selective growth factors to enhance sensitivity in the isolation of Salmonella in other nutrient media, too.

Culture Media↗

PubMed1993

Alpha-keto acids are novel siderophores in the genera Proteus, Providencia, and Morganella and are produced by amino acid deaminases.

Growth promotion and iron transport studies revealed that certain alpha-keto acids generated by amino acid deaminases, by enterobacteria of the Proteus-Providencia-Morganella group (of the tribe Proteeae), show significant siderophore activity. Their iron-binding properties were confirmed by the chrome azurol S assay and UV spectra. These compounds form ligand-to-metal charge transfer bands in the range of 400 to 500 nm. Additional absorption bands of the enolized ligands at 500 to 700 nm are responsible for color formation. Siderophore activity was most pronounced with alpha-keto acids possessing an aromatic or heteroaromatic side chain, like phenylpyruvic acid and indolylpyruvic acid, resulting from deamination of phenylalanine and tryptophan, respectively. In addition, alpha-keto acids possessing longer nonpolar side chains, like alpha-ketoisocaproic acid or alpha-ketoisovaleric acid and even alpha-ketoadipic acid, also showed siderophore activity which was absent or negligible with smaller alpha-keto acids or those possessing polar functional groups, like pyruvic acid, alpha-ketobutyric acid, or alpha-ketoglutaric acid. The fact that deaminase-negative enterobacteria, like Escherichia coli and Salmonella spp., could not utilize alpha-keto acids supports the view that specific iron-carboxylate transport systems have evolved in members of the tribe Proteeae and are designed to recognize ferric complexes of both alpha-hydroxy acids and alpha-keto acids, of which the latter can easily be generated by L-amino acid deaminases in an amino acid-rich medium. Exogenous siderophores, like ferric hydroxamates (ferrichromes) and ferric polycarboxylates (rhizoferrin and citrate), were also utilized by members of the tribe Proteeae.

Amino Acids↗

PubMed1992

Biochemical and serological patterns of Escherichia coli O2 strains isolated from patients with urinary tract infections.

We examined the results of two biochemical test systems for their ability to discriminate a series of 58 Escherichia coli O2 strains collected from patients with urinary tract infections. The O:K:H serotypes and O antigen factors of the strains were also determined. The strains could be assigned to 13 distinct serological patterns by means of O2 antigen factors as well as K and H antigens. The combination of O:K:H-serotyping with biotyping enabled very fine strain discrimination. These data indicate that the biotyping system of Achtman (BTA) is more precise than the Enterobacteriaceae-code-system described by Reiske (ECR) and that the determination of BTA types supports the identification of bacterial clones.

Bacterial Typing Techniques↗