Browsing by Subject "Anti-infective agents"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Effects of feeding direct-fed microbials and prebiotics on receiving calf performance, health, and fecal shedding of pathogens(Texas Tech University, 2001-08) Abney, Michael D.Not availableItem Enhanced Purification of Platelet Beta-Lysin(Texas Tech University, 1982-05) Rickaby, Julia MarieExperimental alterations in the purification scheme established by Donaldson et al. for platelet B-lysin from rabbit serum were made with the objectives of enhanced bactericidal activity and increased stability. Either bovine serum albumin or reduced glutathione, when added to the filtrates in the purification scheme, increased bactericidal activity against Bacillus subtilis and Escherichia coli. In addition, ammonium bicarbonate was a more effective eluant than sodium chloride, which was used in the established procedure for removing 6-lysin from asbestos filter pads. The modified procedure, using glutathione and ammonium bicarbonate, yielded a stable 6-lysin preparation with increased bactericidal activity. Three UV absorbance peaks were obtained after filtration on a Sephadex G-50 column, with the third and largest peak showing substantial bactericidal activity. Bactericidal activity was also demonstrated in g-lysin samples after affinity chromatography on Affi-Gel blue. Analysis of the various 6-lysin preparations by polyacrylamide gel electrophoresis showed that the affinity chromatography step reduced albumin contamination in the samples of platelet 6-lysin.Item Investigation of antimicrobial drug resistance in bacterial isolates from commercial cattle processing systems: pre and post-harvest food safety issues(Texas Tech University, 2004-12) Fluckey, WadeTo determine the patterns of cross-contamination and antibiotic susceptibility, a total of 60 cattle were shipped to a commercial abattoir, 20 in each of three separate trial periods. The same animals were followed through the process and bacterial isolates were collected from these animals immediately before shipping, at the abattoir after exsanguination, after hide removal and in the cooler. Samples were cultured for Salmonella, non-type specific E. coli, and Enterococcus. Salmonella was identified in 33.9% («=20) of fecal samples and on 37.3% (n=22) of hides prior to shipment. At the abattoir, the proportion of hides from which Salmonella was isolated increased (P < 0.001) to 84.2% (n=48). Generic E. coli was recovered from 40.4 % of preevisceration carcass samples, while Salmonella was recovered from 8.3% and Enterococcus from 58.3% of these carcasses. No Salmonella or generic E. coli were recovered from hotbox carcass samples. Enterococcus however, was recovered from 8.3% of the hotbox carcass samples. Isolates were also tested for antimicrobial drug susceptibility. For generic E. coli 80.3% (n=270) of isolates were resistant to at least one antimicrobial. For Salmonella, 97% (n=101) of the isolates were resistant to at least one antimicrobial however only 4.0% were resistant to two or more. The most common resistance for gramnegative bacteria was to sulfamethoxazole. Antibiotic susceptibility patterns were fairly consistent across sampling points. Enterococcus isolates showed a higher degree of resistance to the antimicrobials tested. Of 279 confirmed Enterococcus all were resistant to at least one antimicrobial. Interestingly, 179 (64.15%) of these isolates were resistant to at least six agents tested. The most common resistance was to chloramphenicol (100%) followed by flavomycin (90.32%), hncomycin (87.81%), tylosin (78.49%), erythromycin (76.34%), tetracycline (58.87%), synercid or quinupristin/dalfopristin (47.67%), bacitracin (17.92), streptomycin (8.96%), ciprofloxacin (1.43%), linezolid (0.72%) and salinomycin (0.36%). Enterococcus spp. were also analyzed for pulsed-field gel electrophoresis profiles from all sampling points. Similar or identical PFGE patterns were found from isolates recovered at the feedlot and in the commercial abattoir. This presents strong evidence that bacterial isolates are being propagated from the feedlot to the processing environment and onto the final processed carcasses.Item Platelet B-Lysin: in vitro effects on intact E. coli K-12 and its associated antibacterial kinetics(Texas Tech University, 1980-08) Hubbard, Stephen PerryNot availableItem The regulation of Vibrio cholerae MDR efflux Pump in a TolC mutant of Escherichia coli(Texas Tech University, 2004-05) Ramasubramian, BhagavathiThe emergence of antibiotic-resistance among bacterial pathogens is becoming a serious threat to human health and welfare. One mechanism by which bacteria become resistant to antibiotics is to remove them via a multiple drug resistant (MDR) efflux pump. The first multidrug resistance pump was described in tumor cells that were resistant to chemotherapeutic agents. More recently, MDRs have been characterized in both Gram-negative and Gram-positive bacteria. Vibrio cholerae, a Gram-negative non-invasive enteric pathogen, is the causative agent of the severe diarrheal disease cholera. The first multi-drug efflux pump of V. cholerae, VceAB, was isolated and characterized by Colmer et al. In that study the authors cloned a 6.6 kb SalI-Hind III fragment of V cholerae into pBR322, pVC2 and demonstrated that this plasmid was capable of providing both V. cholerae and an Escherichia coli to/C mutant with resistance to a variety of toxic compounds and antibiotics. The authors also demonstrated that this 6.6 kb DNA fragment contained two genes, vceA and vceB, which encoded proteins whose amino acid sequences shared a high degree of similarity with the EmrA and EmrB proteins of E.coli, respectively. Since those studies were published, our laboratory has identified the outer membrane component of this efflux pump, OepX, whose gene resides in an operon with vceA and vceB and a regulatory gene vceR, whose product is a member of the TetR/AcrR transcriptional regulator family and which negatively regulates the oepX-vceA-vceB operon. During that study, the authors constructed an in-frame vceA::phoA gene fusion in pVC2 (pi328). In this construct the phoA gene is fused in-frame to the vceA gene at position 753 I have employed this reporter fusion to examine the regulation of the oepX-vceA- vceB (i.e., VceAB MDR) operon. The activity of this gene fusion, measured by alkaline phosphatase assay was found to be up regulated in the tolC mutant strain. The purpose of this study was to decipher the cause of this regulation which seems to be a tolC effect.Item Validation of antimicrobial treatments to reduce E.coli O157 and Salmonella spp. in beef trim and ground beef(Texas Tech University, 2004-05) Harris, Anna KristinaResearch determining the antimicrobial effects of interventions on beef trim has been limited. The objectives of this study were to validate the effectiveness of acidified sodium chlorite (1200 ppm), acetic and lactic acids (2% and 4%) in reducing pathogen levels in beef trim prior to grinding in a simulated processing environment. The reduction of pathogen loads, Salmonella spp. And Escherichia co//0157:H7, were determined prior to treatment (control) and at the following processing points: 1) trim just after treatment; 2) ground beef just after grinding, 3) ground beef 24 h after refrigerated storage; 4) ground beef 5 d after refrigerated storage; and 5) ground beef 30 d after frozen storage. Preparation of product for sensory testing was similar to the previous experimental design protocol except none of the trim was inoculated with pathogens. The organoleptic properties were evaluated during short-term (6 and 24 h; 5 d) refrigerated storage and during long-term (30 and 90 d) frozen storage. Ground products were vacuum packaged and stored at 4°C for 5 d or were stored frozen. Triangle tests for comparison of controls and treated samples were conducted on 6 and 24 h; 5, 30 and 90 d after treatment. Panelists (n=24) were given three coded samples, each set of three samples included two of the same samples and one odd sample. Panelists were asked to determine the odd sample. Equal numbers of the six possible combinations (ABB, BAA, AAB, BBA, BAB, ABA) for each treatment were randomly served to panelists. Raw patties were packaged on a supermarket Styrofoam tray, and displayed in a retail display case. Visual panelists were trained for color, color uniformity, percentage of discolorations and browning evaluations of the raw products for appearance and composition. Additionally, muscle luminance, redness and yellowness of the raw product were objectively measured using the Minolta Spectrophotometer. Biochemical composition of the product's percentage of moisture, fat, and protein were analyzed. Results conclude all antimicrobial interventions reduced the lower inoculation level of pathogens to a non-detectable level with significant reductions of the higher inoculation levels of pathogens on trim and in ground beef. There were not any visual differences assessed by a trained visual panel for patties undergoing short-term refrigerated storage, thus more indicative of consumer perceptions in the retail case. Four percent lactic acid was the only treatment to produce significantly different CIE L*, a*, b*, C, and H values for long-term frozen storage (90 day). A non-trained sensory panel utilizing a triangle test only detected differences between the controls and 4% lactic acid treatment for the 30-day long-term storage sampling period. The panel was not able to detect any adverse sensory differences between the controls or treatments for the short-term refrigerated storage periods, or 90-day frozen storage period. Thus, antimicrobial treatments did not have adverse sensory or visual characteristics during short-term storage.