Abbreviated identification scheme for Eschericia coli in swine feces

Antimicrobial susceptibility profiles of Escherichia coli (EC) are often used to monitor the effect of antimicrobial use regimens on the antimicrobial resistance (AR) reservoir in animal species. Epidemiological studies of AR may involve the identification of thousands of bacterial isolates, so complete biochemical identification of EC can be prohibitively expensive and time consuming. In this study an abbreviated biochemical scheme using colony phenotype and the indole test results in a sensitivity and specificity of 91.7% and 100% respectively for identification of EC as compared to a commercial biochemical identification kit. This abbreviated scheme results in over US$500 savings per 100 candidate EC isolates identified. These savings have significant benefits to the economics of conducting epidemiologic investigations of AR

Effect of chlortetracycline on the distribution of resistance genes

The objective of this study was to compare the distribution of tetracycline resistance genes in the Gram-negative fecal flora between swine that werer fed subtherapeutic chlortetracycline as compared to pigs that did not receive in feed antimicrobials

Prevalence of Yersinia enterocolitica across phases of swine production

The objective of this study was to describe the prevalence of Yersinia enterocolitica (YE) in different swine production phases. In this cross-sectional study, individual pigs on eight farrow-to-finish farms were sampled for YE by collection of both feces and oral-pharyngeal swab

Effect of cleaning and subtherapeutic chlortetracycline on Salmonella

The objective of this study was to evaluate the effect of stringent cleaning and subtherapeutic chlortetracycline (CTC) on Salmonella enterica (SE) prevalence in market age swine

Association between Salmonella sp. and Yersinia enterocolitica infection in swine

Swine are known reservoirs for both Salmonella and Yersinia enterocolitica. Both are foodborne pathogens and can result in zoonotic disease if contamination of pork products occurs during harvest. The epidemiology of Y. enterocolitica and Salmonella in swine is not well understood. Previous reports from experimental studies in mice suggest that, vai quorum-sensing, Salmonella detects Y. enterocolitical signals, increasing Salmonella colonization

Leaf Traits and Performance Vary with Plant Age and Water Availability in \u3cem\u3eArtemisia californica\u3c/em\u3e

Background and aims Leaf functional traits are strongly tied to growth strategies and ecological processes across species, but few efforts have linked intraspecific trait variation to performance across ontogenetic and environmental gradients. Plants are believed to shift towards more resource-conservative traits in stressful environments and as they age. However, uncertainty in how intraspecific trait variation aligns with plant age and performance in the context of environmental variation may limit our ability to use traits to infer ecological processes at larger scales. Methods We measured leaf physiological and morphological traits, canopy volume, and flowering effort for Artemisia californica (California sagebrush), a dominant shrub species in the coastal sage scrub community, under conditions of 50%, 100%, and 150% ambient precipitation for three years. Key Results Plant age was a stronger driver of variation in traits and performance than water availability. Older plants demonstrated trait values consistent with a more conservative resource-use strategy and trait values were less sensitive to drought. Several trait correlations were consistent across years and treatments; for example, plants with high photosynthetic rates tended to have high stomatal conductance, leaf nitrogen concentration, and light-use efficiency. However, the trade-off between leaf construction and leaf nitrogen evident in older plants was absent for first-year plants. While few traits correlated with plant growth and flowering effort, we observed a positive correlation with leaf mass per area and performance in some groups of older plants. Conclusions Overall, our results suggest that trait sensitivity to the environment is most visible during earlier stages of development, after which intraspecific trait variation and relationships may stabilize. While plant age plays a major role in intraspecific trait variation and sensitivity (and thus trait-based inferences), the direct influence of environment on growth and fecundity is just as critical to predicting plant performance in a changing environment

Molecular Epidemiology of Salmonella enterica and Subtyping Using Phenotypic and Genotypic Approaches

The aim of this study was to evaluate the discriminatory power of two phenotyping and three genotyping methods commonly used to subtype Salmonella in swine and other hosts. We found AFLP and PFGE to have the highest and comparable discriminatory power to each other. Among the 202 isolates analyzed in this study, using AFLP, 16 cluster types of S. Typhimurium were identified. Vertical spread in the production chain, from nursery to finishing farms and vertical as well as horizontal spread among finishing farms appeared to be important means of Salmonella serovar Typhimurium dissemination in swine units

Plant Traits are Differentially Linked to Performance in a Semiarid Ecosystem

A central principle in trait‐based ecology is that trait variation has an adaptive value. However, uncertainty over which plant traits influence individual performance across environmental gradients may limit our ability to use traits to infer ecological processes at larger scales. To better understand which traits are linked to performance under different precipitation regimes, we measured above‐ and belowground traits, growth, and reproductive allocation for four annual and four perennial species from a coastal sage scrub community in California under conditions of 50%, 100%, and 150% ambient precipitation. Across water treatments, annual species displayed morphological trait values consistent with high rates of resource acquisition (e.g., low leaf mass per area, low root tissue density, high specific root length), and aboveground measures of resource acquisition (including photosynthetic rate and leaf N concentration) were positively associated with plant performance (reproductive allocation). Results from a structural equation model demonstrated that leaf traits explained 38% of the variation in reproductive allocation across the water gradient in annual species, while root traits accounted for only 6%. Although roots play a critical role in water uptake, more work is needed to understand the mechanisms by which root trait variation can influence performance in water‐limited environments. Perennial species showed lower trait plasticity than annuals across the water gradient and were more variable as a group in terms of trait–performance relationships, indicating that species rely on different functional strategies to respond to drought. Our finding that species identity drives much of the variation in trait values and trait–performance relationships across a water gradient may simplify efforts to model ecological processes, such as productivity, that are potentially influenced by environmentally induced shifts in trait values

Quantifying tetracycline resistance

This study’s goal was to evaluate the impact of sub-therapeutic feeding of chlortetracycline (CTC) on the fecal concentration of tet(C), a gene that confers tetracycline resistance via an efflux mechanism. We developed a real-time quantitative PCR assay to measure the quantity of tet(C) in whole fecal DNA samples. The vast proportion of variability in tet(C) (91%) was associated with differences in concentration between the individual pigs, and there was no significant difference in the copy number of tet(C)/mg of feces between the treatment and control pigs (p\u3e0.05, linear regression, SPSS 11.0.5)

Salmonella serovar distribution and risk factors associated with persistence of shedding in finishing pigs

The objectives of this study were to describe the Salmonella serovar distribution and to identify risk factors associated with serovar persistence in finisher pigs. A longitudinal study was conducted in 18 cohorts of pigs. Fecal culture and serotyping were conducted using standard methods