Biomedical subjects

S C Ricke

Publications and source records attributed to S C Ricke.

At least 55 records · Page 3Linked to original sources

PubMed2003

The gastrointestinal tract ecology of Salmonella enteritidis colonization in molting hens.

There is an interaction between feed withdrawal induced-molting and foodborne Salmonella Enteritidis colonization and invasion in susceptible laying hens. Less is known about the ecology of the indigenous microflora and their response to feed removal, the response of S. Enteritidis to feed removal (virulence expression), and the interaction between the gastrointestinal tract microenvironment and S. Enteritidis. Because the crop is the first host environment encountered by S. Enteritidis after ingestion, it can influence the survival and virulence of S. Enteritidis. Feed withdrawal alters the microenvironment of the crop by causing alterations in the indigenous microbial population along with lactate and short-chain fatty acids (SCFA) concentrations and an increase in pH. This altered crop environment is accompanied by increased S. Enteritidis colonization of the crop and ceca along with invasion of the spleen and liver. The observation that crop composition influences the virulence of S. Enteritidis has important implications for understanding the gastrointestinal factors necessary for protection against S. Enteritidis infection. Consequently, an important aspect for minimizing S. Enteritidis colonization during molting is to maintain the crop microflora and their fermentative activities as similar as possible to that of crop microflora and fermentation activities of birds with fully active gastrointestinal microbial populations.

Animal Feed↗

PubMed2003

Poultry digestive microflora biodiversity as indicated by denaturing gradient gel electrophoresis.

Populations of digestive microflora in chickens change with age and are affected by diet, stressors, and performance enhancers. Culturing techniques used to profile a bacterial community inadvertently select for some organisms while excluding others. Several molecular-based techniques have been used to profile mixed microbial populations on the basis of DNA extracted from the entire community. Denaturing gradient gel electrophoresis was used in the present study to examine PCR-amplified fragments (amplicons) of a 16S ribosomal DNA variable region from predominant digestive bacteria. The objective of the study was to examine changes in digestive microbial communities of developing Leghorn chicks and molted Leghorn hens. Dendrograms of amplicon patterns indicated approximately 51% similarity between cecal bacteria composition in Leghorn chicks less than 20 d old and chicks greater than 20 d old. Cecal communities in Leghorn chicks given a competitive exclusion culture exhibited 21% correlation at all ages with those in control chicks. Nonmolted and molted hens had 40% similarity between cecal communities, whereas diets with low calcium (0.8% wt/wt) and excess zinc (2,800 mg/kg) lessened population differences (90% similarity). Results indicated the potential usefulness of the molecular-based denaturing gradient gel electrophoresis to monitor changes in digestive bacterial communities in chickens.

Aging↗

PubMed2002

Comparison of media and a liquid detergent extraction step on bacterial recovery from animal feeds.

The objective of this study was to evaluate the recovery of Tryptic soy agar (TSA) or low nutrient R2 bacterial populations from fresh feeds and animal feeds held in long-term cold storage after extraction with a detergent-based solution combined with repeated centrifugation. Repeated centrifugation after exposure to a detergent-based solution resulted in recoveries generally no more than 10% of the microbial population in the original feed. Feed R2A populations were significantly correlated (P<0.01) with TSA populations enumerated from the feed and feed extracts, as well as R2A populations from feed extracts. Similarly, TSA bacterial populations from feed were significantly correlated with TSA populations from extracts.

Animal Feed↗

PubMed2002

Methionine auxotroph Escherichia coli growth assay kinetics in antibiotic and antifungal amended selective media.

The objective of this work was to determine if Escherichia coli methionine bioassay characteristics were influenced by selective media amended with antibiotics and the antifungal compound cycloheximide. Bacterial cells were grown in minimal media with increasing concentrations of methionine and were incubated at 37 degrees C with vigorous agitation for 6 hours. Addition of antistatic agents to the media did not change the growth kinetic response (P>0.05) to methionine concentration (3.4 to 26.8 microM). This supports the utility of this strain as a methionine bioassay organism for feed and other environmental sources.

Animal Feed↗

PubMed2001

Effects of ammonia nitrogen of H2 and CH4 production during anaerobic digestion of dairy cattle manure.

A number of researchers have verified the inhibitory effects of elevated H2 concentrations on various anaerobic fermentation processes. The objective of this work was to investigate the potential for using hydrogen gas production to predict upsets in anaerobic digesters operating on dairy cattle manure. In an ammonia nitrogen overload experiment, urea was added to the experimental digesters to obtain increased ammonia concentrations (600, 1,500, or 3,000 mg N/l). An increase in urea concentration resulted in an initial cessation of H2 production followed by an increase in H2 formation. Additions of 600, 1,500, or 3,000 mg N/l initially resulted in the reduction of biogas H2 concentrations. After 24 h, the H2 concentration increased in the 600 and 1,500 mg N/l digesters, but production remained inhibited in the 3,000 mg N/l digesters. Both methane and total biogas production decreased following urea addition. Volatile solids reduction also decreased during these periods. The digester effluent pH and alkalinity increased due to the increased NH4 formed with added urea. Based on these results, changes in H2 concentration could be a useful parameter for monitoring changes due to increased NH3 in dairy cattle manure anaerobic digesters.

Ammonia↗

PubMed2001

Response of foodborne Salmonella spp. marker strains inoculated on egg shell surfaces to disinfectants in a commercial egg washer.

The objective of this study was to determine the effectiveness of an iodine based disinfectant (IBD, Iocide, Biomedical Development Corporation, San Antonio, TX) on Salmonella enteritidis and S. typhimurium inoculated on egg shell surfaces under simulated industry egg processing conditions with a commercial egg washer used as the sanitizer delivery system. Re-circulated egg washer water containing 1.40-2.85 g/l total dissolved solids was obtained from a commercial egg processing. Sanitizing treatments consisted of distilled deionized water (DDW), IBD, and chlorine (CL; 200 ppm). All treatments (DDW, IBD and CL) significantly (p < 0.05) decreased Salmonella spp. populations on the shell compared to dry (no spray) egg controls. However, efficacy of egg sanitizers appeared to be dependent on the level of total dissolved solids in the egg wash water.

Animals↗

PubMed2001

Presence of bacteriophages in animal feed as indicators of fecal contamination.

The objectives of this study were to determine if indigenous male specific and somatic bacteriophages could be detected in animal feeds and if isolated phages contained RNA or DNA. Seven fresh feeds, 2 fresh feed ingredients, 7 stored feeds, 2 stored feed ingredients, and 8 samples of poultry diets suspected to contain Salmonella spp. were enriched and spot plated for indigenous phages using Escherichia coli Famp and CN-13 as hosts. Bacteriophage numbers were below detection without enrichment, but both male specific and somatic coliphages were detected in all animal feeds, feed ingredients, and poultry diets after 16 h of enrichment, even after the samples had been stored for 14 months of storage at -20 C. Five out of 9 fresh feeds and 7 out of 8 stored feeds contained RNA somatic phages.

Animal Feed↗

PubMed2000

A bioluminescent Escherichia coli auxotroph for use in an in vitro lysine availability assay.

Microbiological methods have been used to determine the amino acid availability of a variety of animal feed and human food protein sources. Growth of Escherichia coli auxotrophs have been shown to yield a consistent linear response to lysine concentration when compared to chemical measures. Extent of total growth of E. coli lysine mutant (American Type Culture Collection #23812) when measured as optical density (OD) displays a lysine-dependent growth response that can be used to estimate lysine in feed proteins. However, typical OD-based growth studies for amino acid quantitation using the mutant may require anywhere from 12 to over 40 h. To develop an improved rapid method for lysine quantitation in protein sources, the plasmid pJHD500 carrying genes that encode for expression of bioluminescence and ampicillin resistance was transformed into the E. coli mutant by electroporation (set at 1.80 kV). The luminescence measured during early exponential growth allowed detectable differentiation of lysine concentration in the media in 4 h. When the luminescence method was compared with the conventional optical density lysine growth assay, the correlation coefficient was 0.989. Lysine availability valued for enzymatically hydrolyzed protein sources were comparable with availability measures using animal methods for lysine availability. This research shows potential applications for more rapid quantitative measurement of bioavailable lysine.

Animal Feed↗

PubMed2000

Efficient amplification of multiple transposon-flanking sequences.

Transposon mutagenesis is a very useful tool for gene identification in bacteria. Once the transposon mutants of interest are isolated, it is often necessary to identify the sequences that flank the transposon insertions. We devised an efficient method for specific amplification of transposon-flanking sequences that requires the sequence information of only transposon-specific sequences. The basic steps for this method consists of (1) digestion with a restriction enzyme, (2) ligation with a Y-shaped linker and (3) polymerase chain reaction amplification using a transposon-specific primer and a primer specific to the Y-shaped linker. The feasibility of this method was demonstrated with mini-Tn5 mutants of Salmonella typhimurium. We also found that this method can be used for simultaneous amplification of multiple transposon-flanking sequences.

3' Untranslated Regions↗

PubMed2000

Expression of the hilA Salmonella typhimurium gene in a poultry Salm. enteritidis isolate in response to lactate and nutrients.

Pathogens express virulence genes in response to the combination of environmental conditions present in the host environment. The crop is the first gastrointestinal environment encountered in birds. However, feed withdrawal alters the crop environment resulting in an increased pH, and decreased concentrations of lactate, glucose and amino acids compared with unmoulted birds. Salmonella enteritidis infections increase significantly in hens that have been force moulted by feed withdrawal. The present study examined the effects of pH, carbohydrate sources, amino acids and lactate on expression of Salm. enteritidis virulence by measuring expression of hilA. The hilA gene encodes a transcriptional activator that regulates expression of Salmonella virulence genes in response to environmental stimuli. HilA expression was determined using a poultry isolate of Salm. enteritidis carrying a hilA-lacZY transcriptional fusion from Salm. typhimurium. The media used were Luria Bertani (LB) broth and LB broth diluted 1:5 (DLB). The expression of hilA was 2.9-fold higher in DLB broth compared with LB broth which suggested that there is a nutritional component to the regulation of hilA. Addition of 0.2% glucose, fructose or mannose to LB and DLB reduced hilA expression 1.5 to twofold. Addition of 0.2% Casaminoacids, arabinose, fucose, or lactose had little effect on hilA expression. Lactate (25 and 50 mmmol 1-1) reduced hilA expression at pH 6, 5 and 4, with the lowest expression occurring at pH 4. Based on these results it appears that the composition of the crop lumen could potentially influence Salm. enteritidis virulence expression.

Amino Acids↗

PubMed2000

Efficacy of a commercial polymerase chain reaction-based assay for detection of Salmonella spp. in animal feeds.

Salmonellosis is a cyclic problem in the food industry, to which animal feed has been contributory. Current conventional methods of Salmonella spp. detection require 96 h for detection and confirmation. With modern and just-in-time production schedules, a 96-h hold represents a significant expense in storage and decontamination. The commercially available assay, 'BAX for Screening/Salmonella' (BAX), is based on the principle of the polymerase chain reaction and may represent a significant decrease in assay time. Seven fresh feed formulations, two fresh feed ingredients, seven stored feeds and two stored feed ingredients were artificially contaminated with a primary poultry isolate of Salmonella typhimurium and analysed by conventional and BAX methodology. The results of BAX agreed with conventional plating results for 16 of 18 samples spiked with 1200 cfu 10 g(-1) of feed and 13 of 18 samples spiked with 40 cfu 10 g(-1) of feed. Indigenous Salmonella spp. were detected in five of eight samples of poultry diets by conventional methods. With BAX, Salmonella spp. could not be detected in any of the samples after only 7 h of enrichment but could be detected in two dietary samples after 13 h of enrichment and four dietary samples after 24 h of enrichment. Specific sequences of salmonella DNA that were extracted from poultry diets could be detected with BAX.

Animal Feed↗

PubMed2000

Glutamine synthetase and protease enzyme activities and growth response of ruminal bacterium Prevotella ruminicola strain B(1)4 to nitrogen source and concentration.

The objective of this study was to determine the effects of varying nitrogen sources and concentrations upon glutamine synthetase and protease activities in Prevotella ruminicola strain B(1)4. Based on growth response it appears that ammonium chloride or pepticase limited P. ruminicola becomes nitrogen limited when nitrogen concentration is at 0.5 mM. However, when casein was provided as the sole source of nitrogen P. ruminicola becomes nitrogen limited at 2.5 mM. Glutamine synthetase activity was measured from mid-log phase cells grown in either nitrogen-limited or non-limited conditions. No activity was detectable in the non-limited treatments. However, in the N-limited treatments, pepticase had the highest activity (20.76 units), followed by ammonium chloride (18.72 units) and casein (14.42 units). Protease activity assays indicated that nitrogen-limited cultures had higher proteolytic activity than non-limited cultures. Moreover, these activities appeared to follow the same response pattern as the previously observed glutamine synthetase activities. The results of this study indicate that P. ruminicola strain B(1)4 protease activity may be influenced by nitrogen concentration such that activity increases when nitrogen availability decreases.

Animals↗

PubMed2000

Response of selected poultry cecal probiotic bacteria and a primary poultry Salmonella typhimurium isolate grown with or without glucose in liquid batch culture.

The objective of this study was to determine whether fermentation by a cecal probiotic co-culture of an Enterococcus sp. and Veillonella sp. would inhibit the in vitro growth of a S. typhimurium poultry isolate. The growth rates of S. typhimurium and Enterococcus were significantly reduced at pH 5. At the two pH levels, there was a significant (p < 0.001) increase at 24 h in colony forming units for each of the bacteria enumerated from the mixed culture compared to the respective pure culture enumerations. S. typhimurium was not inhibited in mixed cultures. The mixed cultures produced more acetate than any of the pure cultures and lactate produced by Enterococcus appeared to be utilized by Veillonella.

Animals↗

PubMed2000

Recovery of a marker strain of Salmonella typhimurium in litter and aerosols from isolation rooms containing infected chickens.

Screening of poultry flocks for foodborne pathogen Salmonella contamination is critical for Salmonella control in preharvest stages of poultry production. In this study, two sampling methods (litter and air filter) were compared for detection of S. typhimurium from experimentally infected chicks some of which had received either a probiotic competitive exclusion culture or transfer of cecal contents from salmonellae-free adult birds. At 4, 9, and 11 days after inoculation, S. typhimurium samples were enumerated by selective plating. For both types of sampling, the control birds yielded the greatest levels of environmental contamination followed by the samples from the probiotic inoculated birds with the birds receiving the cecal transfer culture having the lowest levels of contamination. Although the two sampling methods responded in a similar fashion, detection sensitivity needs to be increased for air filter sampling.

Aerosols↗

PubMed2000

Salmonella enteritidis hilA gene fusion response after incubation in spent media from either S. enteritidis or a poultry Lactobacillus strain.

The purpose of this study was to determine if growth of a poultry probiotic lactobacilli strain can influence S. enteritidis virulence expression by measuring the response of a hilA-lacZY transcriptional fusion. beta-galactosidase activity was not detected when S. enteritidis was incubated in Lactobacillus-spent medium (24 h growth, pH 4.1, 50.4 mM lactate) but was detectable in spent medium from 4 h growth cultures of Lactobacillus sp. (final OD of 0.213, pH 5.7, 12 mM lactate) when pH and lactate were adjusted to that of the 24 h-pH 4 spent media levels. Adjusting the pH of the 24 h spent medium from 4 to 6, resulted in a measurable beta-galactosidase activity that was significantly higher than expression in LB broth. When S. enteritidis was grown in Salmonella-spent media (24 h growth, pH 4.2, 78 mM acetate), hilA expression was increased 4-fold over expression in the LB broth.

Animals↗

PubMed2000

Assessment of demand for a job placement service for the Poultry Science Association.

A placement service for the membership of the Poultry Science Association (PSA) is a possible future consideration. This service should provide a formal national platform that could aid membership and their employers in position services. A survey was conducted with the objective of determining the interest of the membership in such a placement service and the maximum expense that members would be willing to pay for the service. Ten questions in an undisguised questionnaire format, covering demographic, historical, and interest points was devised with survey questions designed for a forced response on most of the questions. A total of 2,050 surveys was mailed to PSA members in the US, including 1,850 regular members and 200 student members; 518 responded to the survey. A majority of all age groups favored the construction of a placement service, but the respondents' willingness to use the service depended upon age, education, and work experience and whether or not they believed a placement service was needed. Sources of information used in finding a position varied with age; trade journals and publications were the most frequent sources for the responses. It appears that the membership likes the idea of a placement service, is willing to pay something for it, and would use it if it were available.

Adult↗

PubMed2000

Short-chain volatile fatty acids modulate the expression of the hilA and invF genes of Salmonella typhimurium.

The ability of Salmonella typhimurium to invade the intestinal mucosal cells is an important step in pathogenesis. This invasion process requires genes encoded on the Salmonella pathogenicity island 1 (SPI1). Two transcriptional activators, HilA and InvF, encoded in SPII regulate the expression of invasion genes in response to environmental stimuli such as osmolarity, oxygen tension, and pH. During its pathogenic life cycle, Salmonella typhimurium is also exposed to short-chain fatty acids (SCFA), especially acetate, propionate, and butyrate, in the intestinal lumen, as well as the SCFA used as food preservatives. The effects of SCFA on the expression of hilA and invF-lacZY transcriptional fusions were examined to determine the potential role of SCFA in the pathogenesis of Salmonella typhimurium. Growth rates were reduced by increasing SCFA concentrations at pH 6 but not at pH 7. At pH 7, hilA and invF expression was induced by acetate but not by propionate or butyrate, while at pH 6, all SCFA induced hilA and invF expression at 1 h. In general, hilA and invF expression levels when compared to respective control responses were higher at 1 h than at 4 and 8 h in the presence of most SCFA concentrations at pH 6. However, expression levels at 4 and 8 h were either similar or higher than the 1-h responses for the hilA-lacZY fusion strain in the presence of acetate while exposure to 20 mM propionate yielded similar levels of expression at 1, 4, and 8 h. The pH-dependent manner of induction suggests that entry of SCFA into the cell was necessary for induction. We speculate that SCFA may serve as an environmental signal that triggers the expression of invasion genes in the gastrointestinal tract.

Bacterial Proteins↗

PubMed1999

Antibiotic amendment for suppression of indigenous microflora in feed sources for an Escherichia coli auxotroph lysine assay.

Growth responses of lysine auxotrophic mutants of Escherichia coli have been used as a measurement of bioavailable lysine in protein sources and animal feeds. Sterilizing feed samples by autoclaving to eliminate non-specific background growth of indigenous feed micro-organisms prior to conducting the bacterial assay may introduce chemical and physical alterations to the feeds, influencing the estimation of available feed lysine. In this study, an antibiotic- and antifungal-supplemented medium was constructed to support growth of an E. coli lysine auxotroph assay organism, and was tested for its ability to repress indigenous bacterial and fungal growth in feed samples. To determine which antibiotics to include, an ampicillin-sensitive E. coli lysine mutant strain (ATCC no. 23812) was screened for antibiotic resistance and transformed with a plasmid carrying an ampicillin resistance gene. Maximum optical density quantitative response of the E. coli auxotroph to lysine was not altered by the antibiotic medium amendments (ampicillin, novobiocin and cycloheximide). Indigenous microfloral growth in a variety of typical animal feeds was suppressed in the presence of the antistatic agents. The estimated lysine recovery was 91.6% and 98.1% when the medium was used in an assay of available lysine in a lysine-supplemented feed. This indicates that the antibiotic-amended basal medium can be used for the E. coli-determined lysine availability of a variety of animal feeds without prior sterilization of the feed sources.

Ampicillin Resistance↗