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Biomedical subjects

R Helmuth

Publications and source records attributed to R Helmuth.

45 records · Page 3Linked to original sources
PubMed1978

Cell-cell interactions in conjugating Escherichia coli: purification of F pili with biological activity.

A mutant of the F sex factor has been isolated that produces more F pili per cell than does the wild-type F factor. F pili have been purified in milligram amounts from cells carrying either the mutant or the wild-type sex factor. The technique described yields F pili of up to 99% purity that can specifically bind to Escherichia coli cells and that bind to and reversibly inactivate male-specific bacteriophages. The F pilin subunit has a molecular weight of 10,750 and purified F pili have a buoyant density of 1,200 g/cm3.

Bacterial Proteins↗
PubMed1978

Assignment of tra cistrons to EcoRI fragments of F sex factor DNA.

We describe here the cloning of single EcoRI fragments from the tra region of F DNA using ColE1::Tn3 as vector. These plasmids, as well as the series of Skurray et al. (Proc. Natl. Acad. Sci. U.S.A. 73:64-68, 1976), have been used to refine the map positions of tra cistrons on the F factor as well as to define a new DNA transfer cistron, traM. The current map of the tra cistrons is presented. None of the known tra cistrons, with the exception of traG, straddles an EcoRI site. The EcoRI site at 82 kilobases splits the traG cistron into two portions, an operator-proximal portion necessary for F pilus synthesis and an operator distal portion involved in conjugation itself. The operon structure of the tra cistrons was reevaluated, and we found that traI is at least partially independent of transcription of the traA to traD operon.

Conjugation, Genetic↗
PubMedDate not supplied

Evaluation of molecular typing methods for Salmonella enterica serovar Typhimurium DT104 isolated in Germany from healthy pigs.

The discriminatory power of four different DNA based typing methods was tested for the molecular subtyping of Salmonella Typhimurium phage type DT104 isolates. German DT104 strains (n = 133) originating from slaughter pigs were analysed by plasmid profiling, and 32 of them by pulsed-field gel electrophoresis (PFGE) using the restriction enzymes XbaI, SpeI or BlnI, random amplification of polymorphic DNA (RAPD) using 13 different primers and IS200 typing. A resulting subtyping scheme was obtained which is based on the most discriminatory power of the individual methods i.e. plasmid profiling and PFGE with all three enzymes. The index of discrimination obtained by the subtyping scheme was 0.909 closely approaching the maximum value of one. Although minor differences occurred in the molecular DNA pattern of single DT104 strains, a dominating subtyping pattern was observed confirming other studies which showed, that S. Typhimurium DT104 isolates are highly clonal.

Animals↗
PubMedDate not supplied

Epidemiology of resistance to quinolones in Salmonella.

Fluoroquinolones account for about 11% of antimicrobial prescriptions in human medicine worldwide and represent the drug of choice for the treatment of a wide range of human infectious diseases. They were introduced into veterinary medicine in Europe in the late 1980s and early 1990s and in the USA in 1995. Following their introduction, resistant strains of bacteria, including Salmonella, started to emerge. Resistance to quinolones depends on chromosomal mutations and the subsequent spread of resistant clones. While the selective pressure caused by the use of quinolones facilitates their epidemic transmission, the resistant mutants may spread independently of quinolone use. In view of the key role of this group of antimicrobials in human medicine and the position of Salmonella as the leading cause of food-borne infections in many countries, the public health hazard posed by quinolone-resistant zoonotic Salmonella serovars has been a subject of concern. The fluoroquinolones are on the WHO list of drugs that should be reserved for human use. Considering the mounting evidence that quinolone-resistant zoonotic Salmonella are the cause of severe, sometimes fatal, infections in humans, the use of fluoroquinolones in food animals should be discontinued or severely restricted. Such an intervention should be accompanied by prudent use measures involving all other groups of antimicrobials to reduce the need for fluoroquinolones in veterinary medicine.

Animals↗
PubMedDate not supplied

Towards the rational use of antibiotics: results of the first International Symposium on the Risk Analysis of Antibiotic Resistance.

The results of four expert working groups on the risk analysis process on anti-microbial resistance are described. They focus on the procedure recommended by the FAO/WHO CODEX Alimentarius Commission in 1999 including hazard identification, hazard characterization, exposure assessment and risk characterization. In all four areas, the current scientific knowledge was evaluated and recommendations for risk management options were given. They will form the basis for mitigating the health risk caused by resistant micro-organisms.

Animals↗
PubMedDate not supplied

Resistance of Salmonella isolates in Germany.

During 2000-2002 the National Veterinary Reference Laboratory for Salmonella (NRL-Salm) in Germany typed 11,911 isolates from animals, food, feed and the environment. All of them were tested for their susceptibility to 17 anti-microbial agents. Sixty-three per cent of all isolates were resistant and 40% were multiresistant (resistant against more than one anti-microbial). This general resistance level was strongly influenced by those specific serotypes which dominate the Salmonella epidemiology in Germany. Salmonella Typhimurium DT104 isolates from pig and cattle, and their resulting food products, were multiresistant in 98 and 94% of the cases respectively. During the period 2000-2003 an increasing quinolone resistance especially in Salmonella isolates from poultry and poultry meat (to 26%) and in S. Paratyphi B D-tartrate positive isolates (to 64%) could be observed. This increase was accompanied by a shift towards higher minimal inhibitory concentrations for ciprofloxacin.

Animals↗
PubMedDate not supplied

[Increasing number of Salmonella paratyphi B isolates from slaughtered poultry sent in to the national Salmonella reference laboratory].

In the last years the number of isolations of Salmonella enterica subspecies enterica serovar paratyphi B (S. paratyphi B) sent to the national salmonella reference laboratory of Germany has increased steadily. Most of the isolates originated from fowl or poultry products. The bacteriological, serological and biochemical properties of the isolates were investigated. Special emphasis was given to the utilization of d-tartrate which subgroups the serovar. All of them belonged to the d-tartrate positive variant, which is generally considered less virulent for humans and was formerly called S. java. The performance of various tests is compared and in addition the possibility of the spread within the production line is discussed.

Animals↗
PubMedDate not supplied

Nursing staff educational preparation and patient inflicted injuries in a 160 bed psychiatric hospital.

This is a retrospective study of the incidence and severity of patient inflicted injuries upon nursing staff in a 160 bed psychiatric hospital over a period of two years. The investigation explored possible relationships between the basic educational preparation of the injured staff members, the severity of their injuries, and whether they used the behavior management techniques learned in the Mandt System classes. (The Mandt System has been used at Alaska Psychiatric Institute since 1979 to train nursing staff in how to safely deal with assaultive people.)

Absenteeism↗