The effect of transportation stress on excretion rates of campylobacters in market-age broilers

We determined the effects of transportation distance and holding times at a commercial slaughter facility on excretion rates of Campylobacter spp. in broilers. Fecal samples from broilers in each of 10 flocks were obtained at the following three sampling points: at the farms, following transportation, and after holding at the plant. The farms examined were divided into two groups based on distances and transport times to the plant. The prevalence and levels of Campylobacter spp. were evaluated for all specimens taken at the three sampling points. A statistically significant increase in counts was observed in samples from both groups following transportation (P < 0.05). The resting period at the abattoir prior to slaughter did not significantly reduce rates of Campylobacter spp. shedding in the flocks examined. Differences in distance travelled and transport durations between the two groups was not found to be a statistically significant factor in altering excretion rates of the organism. The present study demonstrated that transport-induced stress increased shedding of Campylobacter spp. in fecal material of broilers that may subsequently result in extensive carcass contamination.

Distribution and prevalence of airborne microorganisms in three commercial poultry processing plants

Airborne microbial contaminants and indicator organisms were monitored within three poultry processing plants (plants A, B, and C). In total, 15 cubic feet (c.f.) of air was sampled per location during 15 visits to each plant and quantitatively analyzed for total mesophilic and psychrophilic aerobic counts, thermophilic campylobacters, Escherichia coli, and Enterobacteriaceae. The prevalence of Salmonella spp. in air samples was also evaluated. Significant reductions in total aerobic counts were observed between defeathering and evisceration areas of the three plants (P < 0.05). Mesophilic plate counts were highest in the defeathering areas of all plants compared to equivalent psychrophilic plate counts. Enterobacteriaceae counts were highest in the defeathering areas of all three plants with counts of log10 1.63, 1.53, and 1.18 CFU/15 c.f. recovered in plants A, B, and C, respectively. E. coli enumerated from air samples in the defeathering areas exhibited a similar trend to those obtained for Enterobacteriaceae with log10 1.67, 1.58, and 1.18 CFU for plants A, B, and C, respectively. Thermophilic campylobacters were most frequently isolated from samples in the defeathering areas followed by the evisceration areas. The highest mean counts of the organism were observed in plant A at 21 CFU/15 c.f. sample with plants B and C at 9 and 8 CFU/sample, respectively. With the exception of low levels of Enterobacteriaceae recovered from samples in the on-line air chill in plant A, E. coli, Enterobacteriaceae, or Campylobacter spp. were not isolated from samples in postevisceration sites in any of the plants examined. Salmonella spp. were not recovered from any samples during the course of the investigation.

Quantitative investigation of the effects of chemical decontamination procedures on the microbiological status of broiler carcasses during processing

The effects of elevated chlorine concentrations (25 ppm) added to water in the final carcass washing equipment on total viable counts (TVCs 22 degrees C) and Escherichia coli and Enterobacteriaceae levels on poultry carcasses were investigated. Mean TVC counts on neck skin samples were significantly reduced when pre-evisceration and postwash samples were compared with log10 4.98 to 4.52 CFU/g recovered, respectively (P < or = 0.05). No significant reductions in TVC counts were observed in control samples at corresponding sampling points subjected to wash water containing 1 to 2 ppm chlorine. E. coli and Enterobacteriaceae counts were not significantly altered following final carcass washing in the processing plant. A second trial assessed the microbial decontamination capabilities of sodium triphosphate (TSP) on broiler carcasses. Neck skin samples from carcasses were obtained before final washing (control), following a 15-s dip in potable water and after dipping in a 10% TSP solution (pH 12) for 15 s. Reductions in E. coli and Enterobacteriaceae counts were all statistically significant for both water and TSP-treated samples when compared with corresponding controls (P < or = 0.01). The TSP treatment resulted in higher reductions of log10 1.95 and 1.86/g for E. coli and Enterobacteriaceae, respectively. In contrast, reductions of log10 0.37 and 0.3 l/g were observed for E. coli and Enterobacteriaceae counts when water-dipped carcasses were compared with corresponding controls. Significantly, Salmonella was not detected in any of the TSP-treated carcasses, while log10 1.92 and 1.04/g were found in control and water-dipped samples, respectively. Thermophilic Campylobacter counts were significantly lower in both treatment groups when compared with corresponding controlsresulting in log10 0.55 and 1.71/g reductions for water- and TSP-dipped carcasses, respectively (P < or = 0.01).

Expression, purification, and characterization of recombinant alpha-N-acetylgalactosaminidase produced in the yeast Pichia pastoris

alpha-N-Acetylgalactosaminidase (alpha NAGAL, EC 3.2.1.49) purified from chicken liver has been used in seroconversion of human erythrocytes. Blood group A, defined by the terminal alpha-linked N-acetylgalactosamine, can be cleaved in vitro by alpha NAGAL, resulting in the underlying penultimate blood group H (O) epitope structure. In order to produce sufficient quantities of recombinant alpha NAGAL (r alpha NAGAL) for such studies, we expressed the cDNA encoding chicken liver alpha NAGAL in Pichia pastoris, a methylotrophic yeast strain. The alpha NAGAL coding sequence was cloned into the EcoRI site of the vector pPIC 9 such that the protein was in the same reading frame as the secretion signal of yeast alpha-mating factor derived from the vector. After P. pastoris transformation, colonies were screened for high-level expression of r alpha NAGAL based on enzyme activity. As a result of methanol induction of high-density cell cultures in a fermentor, enzymatically active r alpha NAGAL was produced and secreted into the culture medium. The recombinant enzyme was purified over 150-fold by chromatography on a cation exchange column followed by an affinity column. Its homogeneity was confirmed by Coomassie blue-stained SDS-PAGE, Western blot, and N-terminal sequencing. The purified r alpha NAGAL has a molecular mass of approximately 50 kDa while its native counterpart has a molecular mass of 43 kDa. This discrepancy in size was eliminated by endoglycosidase treatment, suggesting that the recombinant protein was hyperglycosylated by the host P. pastoris cells. r alpha NAGAL was further characterized in terms of specific activity, pH profile, kinetic parameters, and thermostability by comparing with alpha NAGAL purified from chicken liver. The data presented here suggest that by overexpressing r alpha NAGAL in P. pastoris and purifying with affinity chromatography one can readily obtain the quantity of enzyme needed for seroconversion studies.

Trp-16 is essential for the activity of alpha-galactosidase and alpha-N-acetylgalactosaminidase

By expressing site-directed mutants in the methylotrophic yeast strain Pichia pastoris, the role of a tryptophan residue at position 16 in the activity of alpha-galactosidase and alpha-N-acetylgalactosaminidase, two closely related exoglycosidases, was studied. A substitution of Trp-16 with an arginine residue in alpha-N-acetylgalactosaminidase abolished the enzyme activity, which was confirmed by replacing a 600 bp fragment containing the mutation with the corresponding wild-type sequence. The same tryptophan residue was then substituted with an alanine in both enzymes by site-directed mutagenesis to reveal a possible relationship between their active sites. The purified alpha-N-acetylgalactosaminidase mutant demonstrated a specific activity of 2.8 x 10(-2) U/mg and a Vmax/K(m) of 4.3 x 10(-2), which were both more than a thousandfold lower than corresponding values for the wild-type enzyme. Furthermore, the mutant failed to bind to an affinity resin, suggesting the involvement of Trp-16 in substrate-binding. In addition, the purified alpha-galactosidase mutant resulted in more than a 10(4)-fold decrease in specific activity. Thus our data suggest that Trp-16 in both alpha-galactosidase and alpha-N-acetylgalactosaminidase is critical for enzymatic activity, which in turn supports the hypothesis that these two enzymes may share a catalytic mechanism involving similar residues in their active sites.

Characterization of recombinant alpha-galactosidase for use in seroconversion from blood group B to O of human erythrocytes

Alpha-Galactosidase (alpha-GAL) purified from green coffee bean cleaves the terminal galactose residues from the surface of group B erythrocytes, thereby converting these cells serologically to group O cells. Such enzymatically converted red cells have been transfused into group A and O recipients as part of the first phase of FDA-approved clinical trials. Recently we expressed the recombinant alpha-GAL (r)alpha-GAL) in large quantities in a methylotrophic yeast strain Pichia pastoris and purified the protein to apparent homogeneity by chromatography on a macro prep S50 column. Purified (r)alpha-GAL, migrating as a single band of 41 kDa on a SDS-PAGE, appears to be identical to its native counterpart in specific activity (32 U/mg) and kinetic parameters (K(m) =0.363 mM and V(max) = 46.9 U/mg). Both enzymes demonstrate the same pH profile in the pH range from 2 to 9, with an optimal pH at 6.4 when tested with the substrate p-nitrophenol-alpha-D-galactopyranoside. Furthermore, as with its native counterpart, (r)alpha-GAL specifically cleaves alpha-linked terminal galactose residues from group B red cells without affecting other major antigens on the red cell surface. In addition, we developed a method for using RT-PCR to detect possible DNA contamination in the purified protein preparation, which is one of the concerns for in vivo studies. Thus, with a simple procedure for over-expression and purification of (r)alpha-GAL from P. pastoris culture, one can readily obtain the enzyme needed for large-scale sero-conversion of red cells.

High-level expression and purification of coffee bean alpha-galactosidase produced in the yeast Pichia pastoris

alpha-Galactosidase isolated from coffee beans cleaves the terminal alpha-galactose residues from oligosaccharide chains on blood group B red cells, thus generating group O cells. Such enzymatically converted red cells not only maintain full erythrocyte integrity and viability in vitro, but also demonstrate immune tolerance and a normal life span in vivo. In order to produce large quantities of recombinant alpha-galactosidase for use in the study of blood-type conversion, we subcloned the cDNA coding for coffee bean alpha-galactosidase into the EcoRI site of the vector pPIC9 in order to express the enzyme in Pichia pastoris, a methylotrophic yeast strain. After P. pastoris transformation, colonies were screened for high-level expression of alpha-galactosidase, based on enzyme activity. In order to increase enzyme production, the growth conditions in the shake flask culture and fermentor culture were optimized. Under the conditions applied, biologically active alpha-galactosidase was produced and secreted into the culture medium at a level of approximately 0.4 g per liter of the fermentor culture. The protein was purified to apparent homogeneity by a simple chromatography procedure, as suggested by a single band of 41 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its homogeneity was further confirmed by chromatofocusing and N-terminal sequencing. P. pastoris appears to be the choice as host for the large-scale production of recombinant alpha-galactosidase used for blood type conversion.

Language learning and retention in young language-disordered children

Simultaneous sign and spoken language training was conducted with young, language-disordered children under standardized training and follow-up conditions with a stringent learning criterion to determine if language learned was stable over time. Twenty-one children between 36 and 86 months with no or nonfunctional language participated in the study. Diagnoses included autism, mental retardation, combined autism and mental retardation, and developmental aphasia. Children completed a mean of 74 signed speech training sessions. Sessions were twice daily, 5 days a week. Follow-up evaluations were made approximately 6 months after training. Of the 21 children, 17 learned at least one word and 7 children learned multiple-word phrases during the training. Most language learned in training was found to be retained at follow-up approximately 6 months later. Gestural imitation, play style, language age, developmental age, and fine motor skills had strong correlations with language learning and retention.

A prospective double-blind study of side effects associated with the administration of amantadine for influenza A virus prophylaxis

During a study of efficacy of amantadine prophylaxis of influenza A virus infection in young adults, gross and subtle side effects were monitored. Eighty-eight students were randomly selected to receive either amantadine or placebo for four weeks or both in a sequential crossover design of two weeks each. Side effects (i.e., dizziness, nervousness, and insomnia) occurred in 33% of those receiving amantadine and in 10% of those receiving placebo (P less than 0.005). Although side effects were well tolerated by most subjects, six volunteers discontinued amantadine because of marked complaints. Cessation of side effects occurred in more than half of those continuing amantadine. Sixteen students receiving amantadine had decreased performance on sustained attention tasks as compared with ones receiving placebo (P less than 0.05). Gross and subtle side effects of amantadine observed in this study on currently recommended dosage are higher than previously reported, which may be an important factor in consideration of mass prophylaxis.