Effects of a siderophore receptor and porin proteins-based vaccination on fecal shedding of Escherichia coli O157:H7 in experimentally inoculated cattle.

The efficacy of a vaccine containing outer membrane siderophore receptor and porin (SRP) proteins for reducing fecal prevalence and shedding of Escherichia coli O157:H7 was evaluated in cattle inoculated with E. coli O157:H7. Thirty calves were randomly assigned to one of two groups, and on days 1 and 21 these calves were given subcutaneous injections of either a placebo (control) or the vaccine. Blood was collected weekly to monitor the serum anti-SRP antibody titers. Two weeks after the second vaccination, calves were orally inoculated with a mixture of five strains of nalidixic acid-resistant (NalR) E. coli O157:H7. Fecal samples and rectoanal mucosal swabs were collected daily for the first 5 days and then three times each week for the following 4 weeks to determine the presence and enumerate the fecal concentration of NalR E. coli O157:H7. At necropsy on day 35, gut contents and tissue swabs were collected to determine the presence and concentration of NalR E. coli O157:H7. Vaccinated cattle had significantly higher anti-SRP antibody titers than did control cattle, with a significant treatment x week interaction (P < 0.01). Vaccination of cattle with the SRP protein tended to decrease fecal concentration (1.9 versus 1.6 log CFU/g) of NalR E. coli O157:H7 (P = 0.10). The number of calves that were fecal culture positive for E. coli O157:H7 was lower (P = 0.05) in the vaccinated group than in the control group. The E. coli O157:H7 SRP vaccine tended to reduce fecal prevalence and concentration of E. coli O157:H7 in cattle orally inoculated with NalR E. coli 0157:H7 and may be a useful prehavest intervention strategy. Future research must be conducted on natural prevalence in feedlot operations to further evaluate the efficacy of this novel vaccine.

Subtype specific ELISA for the detection of antibodies against influenza A H1N1 and H3N2 in swine.

A subtype specific ELISA using purified hemagglutinin (HA) from influenza A H1N1 and H3N2 was developed to detect antibodies present in swine previously exposed to either H1N1 or H3N2 influenza viruses. The HA was extracted using the detergent octylglucoside followed by ion exchange chromatography. All HA preparations were free of contaminating nucleoprotein and matrix protein contamination. Monospecific swine anti-H1N1 and swine anti-H3N2 sera were used to demonstrate the subtype specificity of the assay. Monospecific rabbit anti-H1N1 or H3N2 was used to sterically block crossreacting determinants and thus enhance assay specificity. A linear relationship between single dilution point ELISA and the hemagglutination inhibition (HI) test was established. This enabled the accurate estimation of HI titer from ELISA. Further refinement of this ELISA based HI estimation system could allow it to replace the current HI procedures in instances where identification at the subtype level of specificity is acceptable. The substantial specificity requirements associated with the detection of strain specific antibody would still necessitate the use of the HI procedure.

Clonal diversity among strains of Escherichia coli incriminated in turkey colisepticemia.

The extent of genetic differentiation among 80 Escherichia coli isolates collected from turkeys with acute colisepticemia was assessed based on allelic variation at 20 enzyme-encoding loci detected by multilocus enzyme electrophoresis. Isolates were polymorphic at 17 loci and were classified into 32 multilocus genotypes, delineating clones, that differed on average at 36% of the loci. In the total sample, 29 (36%) of the isolates belonged to one of two closely related clones, differing only in a single electromorph, and 11 of these isolates were serogroup O78. Most isolates fell into one of 4 genetically distinct clusters of strains. Three of these clusters represent E. coli clone complexes that have been previously identified in avian diseases and a fourth cluster which is specific to colisepticemia in turkeys. Most (73%) isolates produced aerobactin, whereas none produced hemolysins. Assays for detecting K1 capsules, including the use of polyclonal antisera, monoclonal antibodies, and K1-specific bacteriophages, gave variable results, but showed that overall 18% of the strains from colisepticemia were K1 encapsulated with most of the K1+ isolates found in one clone cluster. The results show that many cases of colisepticemia in turkey flocks are caused by a small number of pathogenic clones representing at least three distinct clone complexes.

Effect of time and temperature on growth of Salmonella enteritidis in experimentally inoculated eggs.

Influence of time and temperature on Salmonella enteritidis multiplication in experimentally injected eggs was examined. There was an increase in the number of S. enteritidis with the increase in temperature of egg storage. There was less increase of S. enteritidis in eggs stored at 4 degrees C than in eggs held at temperatures higher than 4 degrees C (P less than 0.05). These results suggest a possible method for monitoring commercial eggs for the presence of S. enteritidis. It was concluded that the chances of recovery of S. enteritidis can be increased 10(6)-fold or more by holding the eggs at temperatures of 21 or 27 degrees C for more than 20 days and culturing their contents.

Virulence factors of Escherichia coli associated with colisepticemia in chickens and turkeys.

Four hundred twenty turkey and 80 chicken Escherichia coli isolates from colisepticemic birds were examined for the following properties: heat-labile toxin (LT), heat-stable enterotoxin, verotoxin, colicinogenicity, hemolysin, and hydroxamate/aerobactin production. Twenty-four (5.7%) of the 420 turkey isolates and six (7.5%) of the 80 chicken isolates produced an LT that was cytotoxic for both Vero and Y-1 cells. In contrast, 48 (11.4%) of the turkey isolates and 18 (22.5%) of the chicken isolates produced a distinct LT that was cytotoxic only for Vero cells. In addition, 64 (80.0%) of the chicken isolates and 309 (74.0%) of the turkey isolates produced aerobactin. Colicinogenicity occurred in 51 (64.0%) of the chicken isolates, with 41 (51.0%) producing colicin V. By contrast, 254 (61.0%) of the turkey isolates produced a colicin, of which 176 (42.0%) produced colicin V. None of the chicken and turkey isolates produced hemolysin or heat-stable enterotoxin.

Endotoxin lipopolysaccharide from Escherichia coli and its effects on the phagocytic function of systemic and pulmonary macrophages in turkeys.

The effect of Escherichia coli lipopolysaccharide (LPS) on the competence of pulmonary macrophages and phagocytic cells from the systemic circulation of turkeys was examined using luminol-enhanced zymosan-stimulated chemiluminescence. The results showed a rapid and accelerated oxidative burst in both systemic and pulmonary macrophages in LPS-treated turkeys that was significantly greater than in untreated controls. However, this increased oxidative metabolism induced by LPS was not associated with enhanced intracellular bacterial killing by pulmonary macrophages. Turkeys treated with LPS showed a highly significant decrease in pulmonary bactericidal activity against Staphylococcus aureus challenge, indicating a defect in pulmonary macrophage function induced by LPS.

In vitro evaluation of B-lymphocyte function in turkeys infected with hemorrhagic enteritis virus.

Studies were conducted on B-lymphocyte function in turkeys infected with hemorrhagic enteritis (HE) virus. Hemolytic plaque-forming technique was used to detect antibody-forming cells in turkeys. The plaque-forming cell responses in HE virus-infected and noninfected controls were compared. Results of this study indicated a decreased capability of HE virus-infected turkeys to produce antibodies to sheep RBC. The greatest inhibition of antibody-forming cell production was seen in the turkeys 19 days after exposure to the virus. However, after this period, the turkeys gradually recovered their immunocompetence to sheep RBC.

In vitro depression of the mitogenic response of lymphocytes from turkeys infected with hemorrhagic enteritis virus.

A depression in the mitogenic response of lymphocytes was demonstrated in turkeys inoculated with hemorrhagic enteritis virus. Blood samples were collected (in heparin) once a week, beginning 1 week after the turkeys were inoculated. The whole blood assay was used to study lymphoblastogenesis. Concanavalin-A and phytohemagglutinin were the mitogens used: the radioisotope used was (125I)deoxyuridine (125IudR; 125I, sp act 5 Ci/mg). Suppression in the lymphocyte response in vitro was seen up to 5 weeks after the inoculations were done, after which there was a gradual recovery from suppression in the lymphocyte blastogenesis.

Identification and isolation of somatic pili from pathogenic Escherichia coli of turkeys.

Transmission electron microscopy was performed to identify the presence of somatic pili on Escherichia coli pathogenic to turkeys. Three common pathogenic serotypes of E coli (Ola, O2a, and O78) were used. They were cultured in tryptic soy, veal infusion, and Minca medium broth and were incubated at 37 C with and without CO2 (5%). The cultures were examined for the expression of pili after 24, 48, and 72 hours of incubation. Pili were on all strains of the 3 serotypes examined. These pili were also isolated and purified.

Scanning electron microscopic studies of adverse effects of ammonia on tracheal tissues of turkeys.

Effects of 10 and 40 microliter of NH3/L of air (10 and 40 ppm) on the tracheal tissues of turkeys were examined under the scanning electron microscope. Turkeys maintained in the presence of either level of NH3 had deterioration of their normal mucociliary apparatus after prolonged exposure. Excessive mucous production, matted cilia, and areas of deciliation in the tracheal tissues were detected in birds exposed to NH3 concentrations as low as 10 microliters/L. The tracheal tissues of birds not exposed to NH3 appeared normal. The implications of respiratory tract damage caused by NH3 are discussed.

Effect of ammonia on the quantitative clearance of Escherichia coli from lungs, air sacs, and livers of turkeys aerosol vaccinated against Escherichia coli.

Turkeys were given an aerosol vaccine to determine their ability to clear a virulent inhaled pathogenic strain of Escherichia coli, while they were being maintained in the presence of atmospheric NH3. Turkeys were exposed to 2 concentrations of NH3 (10 and 40 microliters/L of air). More E coli was found in lungs, air sacs, and livers of turkeys exposed to NH3. Turkeys not exposed to NH3 had better clearance of E coli. Vaccination against E coli improved the rate of clearance of E coli in birds not exposed to NH3.

The effect of cyclic and constant ambient temperatures on feed consumption, egg production, egg weight, and shell thickness of hens.

Groups of 18 hens, 230 days of age, were housed in each of three climatic chambers with light schedules of 14L:10D. One was maintained at a constant temperature of 23.9 C, the second was cycled between 15.6 and 37.7 C (mean, 26.7 C), and the third was cycled between 21.1 and 37.7 C (mean, 29.4 C). In Experiment 1, the high temperature peaked during the dark period at 0200 hr and in Experiment 2, the high temperature peak was at 1400 hr during the light period. The birds had free access to a commercial breeder feed in these two experiments. The results from three 2-week observation periods indicated no significant differences in percent hen-day production, grams of feed per gram of egg mass, or overall body weight change but feed intake per day, egg weight, and shell thickness were significantly reduced by mean temperatures of 26.7 and 29.4 C in cycling chambers. The pair-feeding of birds in the 23.9 C constant chamber compared with those in the cycling 29.4 C chamber resulted in production of significantly heavier eggs with thicker shells without significantly influencing any of the other parameters. The reductions in egg weight and shell thickness observed at cyclic temperatures were not simply a result of a reduction in nutrient intake at high temperatures but also the direct effect of heat stress on the hens. In the 23.9 C constant temperature chambers, a reduction in AME of the feed for the hens fed ad libitum was observed but not for hens pair-fed to hens in the 29.4 C cyclic chamber.

Escherichia coli O157:H7 shedding in vaccinated beef calves born to cows vaccinated prepartum with Escherichia coli O157:H7 SRP vaccine.

Extensive research, intervention equipment, money, and media coverage have been directed at controlling Escherichia coli O157:H7 in beef cattle. However, much of the focus has been on controlling this pathogen postcolonization. This study was conducted to examine the performance, health, and shedding characteristics of beef calves that were vaccinated with an E. coli O157:H7 SRP bacterial extract. These calves had been born to cows vaccinated prepartum with the same vaccine. Cows and calves were assigned randomly to one of four treatments: (i) neither cows nor calves vaccinated with E. coli O157:H7 SRP (CON), (ii) cows vaccinated with E. coli O157:H7 SRP prepartum but calves not vaccinated (COWVAC), (iii) calves vaccinated with E. coli O157:H7 SRP but born to cows not vaccinated (CALFVAC), (iv) cows vaccinated with E. coli O157:H7 SRP prepartum and calves also vaccinated (BOTH). Calves born to vaccinated cows had significantly higher titers of anti-E. coli O157:H7 SRP antibodies (SRPAb) in circulation at branding time (P < 0.001). Upon entry to the feedlot, overall fecal E. coli O157:H7 prevalence was 23 % among calves, with 25 % in the CON treatment group, 19 % in the CALFVAC group, 32 % in the COWVAC group, and 15 % in the BOTH group (P > 0.05). Fecal shedding of E. coli O157 on arrival to the feedlot was not correlated with fecal shedding at slaughter (Spearman's rho = -0.02; P = 0.91). No significant effects of cow or calf E. coli O157:H7 SRP vaccination treatment were found on feedlot calf health or performance (P > 0.05), prevalence of lung lesions or liver abscess (P > 0.05), or morbidity, retreatment, or mortality numbers (P > 0.05). The findings of this study indicate that the timing of vaccination of calves against E. coli O157:H7 may be an important consideration for maximizing the field efficacy of this vaccine.