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R Stephan

Publications and source records attributed to R Stephan.

18 recordsLinked to original sources
PubMed1992

Restriction fragment length polymorphisms associated with alpha-hemolysin determinants are correlating with the expression of alpha-hemolysin in strains of Escherichia coli.

Three different phenotypes of hemolysis on blood-agar were detected when 58 isolates of Escherichia coli were investigated for alpha-hemolysin synthesis. In strains with chromosomally encoded alpha-hly genes, phenotype I (large and clear hemolysis zones) corresponded with high hemolytic activity and with a 17.2 kb size BamHI restriction fragment hybridizing with an alpha-hly-specific gene probe. Phenotype II (small and turbid hemolysis zones) was associated with low hemolytic activity and generally with a 12.8 kb size hybridizing BamHI restriction fragment. An intermediate phenotype (type I/II) was found in a few strains with moderate hemolytic activity. This correlation between hemolytic phenotype and activity was not found in E. coli carrying alpha-hly plasmids. Type I strains differed from all others in the promotor region of their 17.2 kb size BamHI fragment associated chromosomal alpha-hly determinant. The relation between hemolytic phenotype and DNA hybridization pattern was found in unrelated E. coli isolates of human and animal origin. An association of alpha-hemolysin with other virulence factors was found in most strains of all three phenotypes.

Animals↗
PubMed1991

Characteristics of alpha-hemolytic strains of Escherichia coli isolated from dogs with gastroenteritis.

Twenty-four hemolysin producing (Hly+) strains of Escherichia coli isolated from dogs with gastroenteritis were investigated for their virulence markers and their phenotypic properties. The strains were distributed over eleven known E. coli O-serogroups and most of them were heterogeneous for their phenotypes. All strains were found to produce alpha-hemolysin which was detected by Southern hybridization and colony immunoblotting using a specific gene probe and a monoclonal antibody. Eight strains were carrying plasmids encoding alpha-hemolysin sequences (hly-plasmids) and 16 strains carried chromosomal hly-determinants. Twelve of the strains showed enterotoxic activities which were tested for in different assays. Among these, three O42:H37 and two O70:H-strains carrying hly-plasmids were found to harbour other plasmids encoding the heat-stable enterotoxin STA1. The other seven strains showing enterotoxicity in the ileal loop or the suckling mouse assay were negative for STA1, STA2, or LT. None of the 24 strains were positive for invasiveness or for production of Vero (Shiga-like) toxins. The production of alpha-hemolysin was closely associated with the production of cytotoxic necrotizing factor (CNF), which was detected in 17 of 24 strains. Of these, 16 elaborated CNF1 and one strain produced an unknown CNF type. Surprisingly, all strains carrying ST-plasmids and six of eight strains carrying hly-plasmids were negative for CNF. Thus, in canine E. coli strains CNF production seems to be closely associated with production of chromosomally encoded alpha-hemolysin whereas hly-plasmids are more often associated with ST-producing, CNF negative isolates.

Animals↗
PubMed1990

Clonal diversity and virulence factors in strains of Escherichia coli of the classic enteropathogenic serogroup O114.

Eighty-eight Escherichia coli strains of the enteropathogenic (EPEC) group O114 that were isolated from humans and animals in geographically different places and over more than 30 years were examined for virulence markers, O:H serotypes, and for electrophoretic types by multilocus enzyme electrophoresis. Four major genetically tightly related clusters of strains showed close correlation between electrophoretic types and other phenotypic characters. Cluster I contained 35 EPEC class II strains of serotypes O114:H9 and O114:H- and 5 enterotoxigenic E. coli belonging to O114:H21 and O114:H49. Clusters II and III comprised 36 O114:H4, O114:H32, and O114:H- strains; most were of doubtful pathogenicity except one Verotoxin-positive O114:H4 strain isolated from a human with diarrhea. Cluster IV contained 9 classic EPEC strains of serogroup O114:H2 that were characterized by localized adherence to HEp-2 cells and by the EPEC adherence factor.

Alleles↗
PubMed1990

Enterohemolysin production is associated with a temperate bacteriophage in Escherichia coli serogroup O26 strains.

A temperate bacteriophage that determines the expression of enterohemolysin was isolated from Escherichia coli O26 strain C3888. The genetic determinant associated with enterohemolysin production (E-Hly determinant) was cloned from EcoRI-digested bacteriophage DNA in vector plasmid pUC8. pUC8 recombinant plasmid pEO19 carries a 3.7-kb EcoRI insert of phage DNA, and enterohemolysin was expressed in E. coli K-12 after transformation. Hemolysin-negative derivatives of pEO19 were generated by transposon mutagenesis with Tn1725. By subcloning, the phage E-Hly determinant was assigned to a 2,150-bp piece of DNA which is flanked by EcoRI and AccI restriction sites. The enterohemolysin-producing recombinant strains and wild-type strain C3888 express a 60-kDa protein which was detected in the bacterial outer membrane by Western immunoblotting. Biologically active enterohemolysin was detected only in bacteria grown to the stationary phase, and the hemolysin was not released into the culture medium. Lysis of erythrocytes was inhibited by 30 mM dextran 4, which functions as an osmotic protectant without destroying the enterohemolysin itself.

Bacteriophages↗
PubMed1989

Close association of verotoxin (Shiga-like toxin) production with enterohemolysin production in strains of Escherichia coli.

Sixty-four verotoxin-producing (VT+) Escherichia coli strains were analyzed for VT1- and VT2-specific DNA sequences and for production of hemolysin. Strains of human origin were of the following serotypes: O157:H7 or H-, O111:H8 or H-, O26:H11, O114:H4, and rough:H7. Strains of serotypes O157:H7, O113:H21, O116:H21, and rough:H- were from cattle, while those of serotype O139:K12:H1 were from pigs. All 64 isolates carried either VT1 or VT2 or both genes. Sixty of the strains (93.8%) were hemolytic (Hly+). The three O139:K12:H1 strains examined produced alpha-hemolysin, as shown by their reaction with the alpha-hemolysin-specific monoclonal antibody h2A and by DNA hybridization with an alpha-hly gene probe. The remaining 57 Hly+ strains (95%) produced a different type of hemolysin (enterohemolysin), which is genetically and serologically unrelated to alpha-hemolysin. The two types of hemolysin are further distinguished by the appearance of the lysis zone on blood agar and by the time interval for the detection of hemolysis. In contrast to alpha-hemolysin, enterohemolysin can be detected only on blood plates containing washed erythrocytes. The frequent association of enterohemolysin with verotoxin production (89%) makes it useful as an epidemiological marker for rapid and simple detection of potential VT+ E. coli.

Animals↗
PubMed1977

[The development of antibiotics resistance among Salmonella bacteria of animal origin in the Federal Republic of Germany and Berlin (West). 5th communication: 1974 Annual report (author's transl)].

2713 salmonella strains having been isolated by veterinary laboratories in the Federal Republic of Germany including West Berlin in 1974 were tested for resistance to tetracyclines, ampicillin, chloramphenicol, kanamycin, gentamycin, furazolidone, nitrofurazone, and trimethoprim. 21.7% of the strains tested were resistant to one or several of the antibacterially effective substances examined. The proportion of the resistant strains amounted to 52% for S. typhimurium and 4.7% for S. typhimurium var. copenhagen, 16.8% for S. enteritidis, and 22.1% for S. panama, 85.1% of all resistant strains belonged to these types. Out of 589 resistant strains found, resistance determinants were present in 93.7% to tetracyclines, 34.6% to ampicillin, 32.4% to chloramphenicol, 25.3% to kanamycin, 3.4% to furazolidone, and 0.5% to nitrofurazone. 1 strain of S. typhimurium var. copenhagen had a transmissible determinant of resistance to trimethoprim. No strain was resistant to gentamycin. 93.4% of the strains transmitted resistance determinants to E. coli K-12. A transmission of resisance to furazolidone and nitrofurazone could not be demonstrated. The serotypes were exhibiting clear-cut differences in their resistances patterns.

Animals↗
PubMed1977

[The development of antibiotics resistance among Salmonella bacteria of animal origin in the Federal Republic of Germany and Berlin (West). 6th communication: 1975 Annual report (author's transl)].

2563 salmonella strains having been isolated by veterinary laboratories in the Federal Republic of Germany including West Berlin in 1975 were tested for resistance to tetracyclines, ampicillin, chloramphenicol, kanamycin, gentamycin, furazolidone, nitrofurazone, and trimethoprim. 11.4% of the strains tested were resistant to one or several of the above mentioned substances. The proportion of the resistant strains amounted to 36.0% for S. typhimurium, and 4.3% for S. typhimurium var. copenhagen, as well as 70% for S. dublin. 79.4% of all resistant strains belonged to these types. For S. panama, the proportion of resistant strains decreased to 6.7%. Out of 291 resistant strains found, resistance determinants were present in 89.0% to tetracyclines, 47.0% to chloramphenicol, 28.5% to ampicillin, 24.1% to kanamycin, and 4.1% to furazolidone. Resistance determinants to gentamycin, nitro-furazone, and trimethoprim did not occur, 81.1% of the strains transmitted resistance determinants to E. coli K-12. A transmission of resistance to furazolidone could not be demonstrated. The different serotypes exhibited clear-cut differences in their resistance patterns.

Animals↗
PubMed1976

Biosynthesis of chondroitin sulfate side chains and hyaluronate. Time-course studies with cartilage slices of calf ribs under different conditions.

The time course of double labeling with 35SO24- and [3H]glucosamine was followed in a semi-in vitro system of cartilage slices from calf ribs whose chondroitin sulfate peptide pool consists of (A) less than 1% of very short under sulfated side chains of less than 10 disaccharide units length, (B) 3--5% of short under sulfated longer side chains (16 to 25 disaccharide units), (C) 3--5% of short, slightly oversulfated side chains (16--23 dissacharide units, very probably containing some dermatan sulfate), (D) the bulk material (74--82% of total uronate) of longest, slightly undersulfated or equally sulfated side chains (22--42 disaccharide units). After 10 min incubation rapid chain elongation with [3H]glucosamine and prelabeling with 35SO24- of endogenous acceptors are apparent. Chains of type A exhibit highest specific radioactivities. During 30--60 min incubation it is mainly chains of type B that show highest specific radioactivities, after 90 min chains of type C. On the after hand, chains of type D always incorporated the highest total amount of both precursors. Preincubation of slices for 40 min at 37 degres C strongly enhances labeling rates of all types A and B. After 10 min preincubation followed by 35SO24- labeling for 60 min, a decrease of radioactivity of type A and a distinct increase with type B are observed during the post incubation period. After pulse chase experiments type B exhibits highest specific radioactivities. The data make it evident that undersulfated short chondroitin sulfate side chains form very rapidly in a well organised manner and grow, by elongation and proceeding sulfation processes, to longer higher sulfated chains. The labeling of the hyaluronate pool is about half of that of the chondroitin sulfate pool after a lag phase of 10 min. The latter increases linearly after 35--45 min incubation time. However, after preincubation and chase experiments the hyaluronate pool is more highly labeled. The data indicate different precursor pools of both biosynthesis mechanisms, probably located in different cell compartments and/or different cartilage cells.

Animals↗
PubMed1976

[The development of antibiotics resistance among Salmonella bacteria of animal origin in the Federal Republic of Germany and Berlin (West). 3rd Communication: 1972 Annual Report (author's transl)].

2273 Salmonella strains received from veterinary laboratories in the Federal Republic of Germany including Berlin (West) in 1972 were examined for their resistance against tetracyclines, ampicillin, chloramphenicol, kanamycin, nitrofurazone, and furazolidone. 13.3% of the strains studied were found to be resistant to one or more of these antibacterial substances. The proportion of resistant strains was 37.5% for S. typhimurium (excluding var. copenhagen), 3.1% for S. typhimurium var. copenhagen and 57% for S. panama. 79.8% of resistant strains were found to belong to these types. From 303 resistant strains found, resistance determinants were present in 87.4% to tetracyclines, in 37.2% to ampicillin, in 15.8% to chloramphenicol, in 4.6% to kanamycin, in 0.9% to furazolidone, and in 1.3% to nitrofurazone. 16 combinations of resistance determinants were found to occur 95.0% of strains transmitted resistance to E. coli K-12. A transmission of resistance determinants to furazolidone and nitrofurazone could not be demonstrated. Resistance patterns differed considerably from one serotype to another.

Ampicillin↗
PubMed1976

[The development of antibiotics resistance among slamonella bacteria of animal origin in the Federal Republic of Germany and Berlin (West). 4th Communication: 1973 Annual Report (author's transl)].

2894 salmonella strains received from veterinary laboratories in the Federal Republic of Germany including Berlin (West) in 1973 were examined for their resistance against tetracyclines, ampicillin, chloramphenicol, kanamycin, nitrofurazone, and furazolidone. 24.4% of the strains studied were found to be resistant to one or more of these antibacterial substances. The proportion of resistant strains was 63.9% for S. typhimurium (excluding var. copenhagen), 6.5% for S. typhimurium var. copenhagen and 51% for S. panama. 81.3% of resistant strains were found to belong to these types. From 708 resistant strains found, resistance determinants were present in 92.9% to tetracyclines in 27.9% to ampicillin, in 22.0% to chloramphenicol, in 13.6% to kanamycin, in 1.4% to furazolidone, and in 1.7% to nitrofurazone. 20 combinations of resistance determinants were found to occur 90.9% of strains transmitted resistance to E. coli K-12. A transmission of resistance determinants to furazolidone and nitrofurazone could not be demonstrated. As in the preceding years, there was a clear difference of resistance patterns from one serotype to another.

Ampicillin↗
PubMed1975

Plasma renin activity and renal sodium and water excretion following infusion of arachidonic acid in rats.

Plasma renin activity (PRA) and urinary sodium and water excretion were measured following infusion of the prostaglandin (PG) precursor arachidonic acid (C20:4) in normal hydrated rats (saline i.v.:0.5 ml/hr/100 g body weight) and in rats with moderate volume expansion (saline i.v.:1.5 ml/hr/100 g body weight). Nonhypotensive doses of C20:4(40-70 mu/min/100 g b.w.) increased PRA in both normal and volume-expanded rats (p less than 0.05, and p less than 0.025, respectively). In volume-expanded rats, C20:4 was followed by reduced lrine volume (p less than 0.01) and sodium excretion (p less than 0.001) in comparison to volume-expanded control rats, whereas in normal hydrated rats these parameters remained unchanged after C20:4. The present results indicate that the C20:4-stimulated PG-synthetase system can increase PRA independently of the extracellular fluid volume. Furthermore, these results suggest a complex interrelationship between PG-synthetase action, activation of the renal renin-angiotensin system and urinary water and sodium excretion.

Animals↗
PubMedDate not supplied

Thermal lability of membrane proteins of age separated erythrocytes as studied by electron spin resonance spin label technique.

Thermal lability of bovine erythrocyte membrane proteins was studied by electron spin resonance using maleimide spin label. The temperature of the sample during measurements could be varied for the first time between 0 and 60 degrees C with an accuracy of +/- 0.1 degrees C. Our results show that "old" erythrocyte membrane proteins are less stable against thermal denaturation then "young" cells.

Animals↗
PubMedDate not supplied

[Vitamin E].

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Anemia, Hemolytic↗