Probing scattering phase shifts by attosecond streaking

Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal (i.e. phase) information on the energy domain. We show that on the single-particle level attosecond streaking time shifts contain spectral phase information associated with the Eisenbud-Wigner-Smith (EWS) time delay, provided the influence of the streaking infrared field is properly accounted for. While the streaking phase shifts for short-ranged potentials agree with the associated EWS delays, Coulomb potentials require special care. We show that the interaction between the outgoing electron and the combined Coulomb and IR laser fields lead to a streaking phase shift that can be described classically

Prevalence of Salmonella enterica in pigs before the start of the Danish Salmonella Control Program (1993/94) and four years later (1998)

The Danish Salmonella Control Program (I) was started in 1995 with the main objective to reduce the occurrence of Salmonella enterica in swineherds and pork. The total cost of the program is about 14.3 mill $US annually. About 2,6 mill$US is paid by the state and the farmers or their organization pay the remaining costs (11.7 $US). Therefore, both to ensure the objective is met and for economical reason, it is important to evaluate if the prevalence of Salmonella decreases

Dose dependent establishment of subclinical S. typhimurium infection in pigs and protection against homologous re-challenge

The fact that the majority of Salmonella infected pig herds are subclinically infected is accepted worldwide. In subclinically infected herds shedding of salmonella from infected pigs and the contamination of the environment is markedly below the level known from herds having experienced a clinical outbreak (Baggesen et al., 1996)

Subclinical salmonella infection in Danish finishing herds - prevalence of S. enterica measured by bacteriological and serological examination

Subclinically salmonella infected herds may represent a contamination risk for pork products although no clinical signs are present. In the nation-wide Salmonella enterica surveillance and control programme in Danish slaughter pig herds (Mousing et al. 1997) the salmonella prevalence in Danish pig herds is being monitored. The monitoring is based on serological examination of meat juice (Nielsen et al. 1997). Serological examination of blood samples and bacteriological examination of pen samples is used as follow-up

Characterisation of Salmonella enterica isolated from swine herds in a cross-sectional study of the Danish swine production

In a cross-sectional study including a total of 2633 Danish swine herds, Salmonella enterica was isolated from at least one of 10 samples in 43 (12%) breeding- and multiplying herds, in 51 (17%) farrow-to-grower herds and in 223 (II%) slaughterpig herds. Isolates were characterised by serotyping and isolates of S. Typhimurium were phage typed. Isolates from 305 herds were tested for susceptibility to 12 antimicrobial agents. The most frequently isolated serotype was S. Typhimurium, and the most frequently isolated phage type was DTI2. Multiresistant S. Typhimurium DTI 04 was isolated from one slaughterpig herd. The majority of isolates were susceptible to the antimicrobial agents tested, but resistance was identified in 58 (17%) of the infected herds, and multiresistance (resistance to 4 or more types of antibiotics) was identified in S. Typhimurium of different phage types as well as in other serotypes. Compared to a previous study of 1363 Danish slaughterpig herds performed in 1993-94 no major changes in type distribution had occurred

PathOrganic – Risks and Recommendations Regarding Human Pathogens in Organic Vegetable Production Chains

PathOrganic assesses risks associated with the consumption of fresh and minimally processed vegetables due to the prevalence of bacterial human pathogens in plant produce. The project evaluates whether organic production poses a risk on food safety, taking into consideration sources of pathogen transmission (e.g. animal manure). The project also explores whether organic versus conventional production practices may reduce the risk of pathogen manifestation. In Europe, vegetable-linked outbreaks are not well investigated. A conceptual model together with novel sampling strategies and specifically adjusted methods provides the basis for large-scale surveys of organically grown plant produce in five European countries. Critical control points are determined and evaluated and factors contributing to a food safety problem are analyzed in greenhouse and field experiments. The project aims at developing a quantitative risk assessment model and at formulating recommendations for improving food safety in organic vegetable production

Subclinical salmonella infection in Danish finishing herds - association between serological and bacteriological testing

As part of the salmonella surveillance programme in Danish slaughter pig herds (Mousing et a!. 1997), the occurrence of subclinical salmonella infection in pigs is monitored serologically at slaughter by examination of meat juice samples, using a mix-ELISA (Nielsen eta!. 1997). Subsequently blood samples and pen (faecal) samples are used as diagnostic tests in infected herds. The association between the serological and the bacteriological testing therefore needs assessment. The objective of the present study was to assess the association between serological and bacteriological testing

A Reservoir of Drug-Resistant Pathogenic Bacteria in Asymptomatic Hosts

The population genetics of pathogenic bacteria has been intensively studied in order to understand the spread of disease and the evolution of virulence and drug resistance. However, much less attention has been paid to bacterial carriage populations, which inhabit hosts without producing disease. Since new virulent strains that cause disease can be recruited from the carriage population of bacteria, our understanding of infectious disease is seriously incomplete without knowledge on the population structure of pathogenic bacteria living in an asymptomatic host. We report the first extensive survey of the abundance and diversity of a human pathogen in asymptomatic animal hosts. We have found that asymptomatic swine from livestock productions frequently carry populations of Salmonella enterica with a broad range of drug-resistant strains and genetic diversity greatly exceeding that previously described. This study shows how agricultural practice and human intervention may lead and influence the evolution of a hidden reservoir of pathogens, with important implications for human health