We investigated the ability of an antibody-specific, O antigen-based ELISA to document Salmonella typhimurium herd infections by screening of milk samples. Three cattle populations, 20 herds with no history of salmonellosis, 8 herds with history of S. typhimurium episodes within the previous 7 months, and 220 herds of unknown disease status, were tested. A herd was considered ELISA positive if at least 5% of the cows had OD values > 0.3. Among the 20 herds without history of salmonellosis, only 2 herds were ELISA positive, whereas all 8 herds with a known history of salmonellosis were ELISA positive (herd specificity, 0.9 and herd sensitivity, 1.0). A significant correlation (P < 0.001) was found between the OD values of serum and milk samples from cows in the herds with a history of salmonellosis. It was concluded that ELISA testing of individual milk samples can be used for surveillance of herds for S. typhimurium infections, but further modifications are needed to test bulk tank milk samples.

When Salmonella typhimurium and Clostridium perfringens were tested in conventional chickens, larger numbers of S typhimurium and C perfringens adhered to Eimeria tenella-infected ceca than to uninfected ceca. In germ-free chickens, S typhimurium and C perfringens adhered to the E tenella-infected cecal mucosa more than to the uninfected cecal mucosa, but fewer Bacteroides vulgatus and Bifidobacterium thermophilum adhered to the E tenella-infected ceca than to the uninfected ceca. Many bacteria adhered to the lesions caused by E tenella as observed by scanning electron microscopy. On the basis of our findings, we suggest that infection with E tenella upsets the balance of competitive adherence of bacteria, allowing more colonization of S typhimurium and C perfringens.

A series of experiments was conducted to document tumor necrosis factor-alpha (TNF) activity in serum of swine after inoculation with Salmonella spp endotoxin and after oral or respiratory tract challenge exposure with live Salmonella spp. For experiment 1, a potentially lethal dose of S typhimurium endotoxin (25 microgram/kg of body weight) was administered IV, and serum TNF activity was measured. High TNF (approx 700 IU/ml) activity at 1 to 2 hours after administration of the inoculum was associated with death, whereas lower TNF (approx 30 IU/ml) activity was associated with a general prolonged state of shock. For experiment 2, pigs were administered a nonlethal dose (5 microgram/kg, IV) of either S typhimurium or S choleraesuis endotoxin. Difference in the ability to induce porcine serum TNF activity was not observed between strains. During experiment 3, pigs were inoculated with 104 colony-forming units of S typhimurium chi4232 either orally by gelatin capsule (GC) or by intranasal (IN) instillation. A late serum TNF response (17 IU/ml) was measured at 6 weeks after IN inoculation. A serum TNF response was not detected in GC-inoculated pigs. All tissues and feces were test-negative for S typhimurium prior to the 6-week TNF response. Serum TNF activity may be related to clearance of S typhimurium after respiratory tract exposure, but it is not important to or indicative of clearance of orally presented S typhimurium in swine. During experiment 4, pigs were inoculated with 106 colony-forming units of S typhimurium chi4232 similarly as for experiment 3. Challenge exposure with this medium-size dose of inoculum induced a prolonged peak serum TNF response (37 IU/ml) between 2 and 4 weeks after IN inoculation Again, serum TNF activity was not detected in GC-inoculated pigs. Data suggest that clearance of a medium-size dose (106) of inoculum may be influenced by the prolonged higher serum TNF activity. For experiments 5 and 6, pigs were inoculated IN with 103, 106, 108.

Polymyxin B and an antiserum against an Re mutant Salmonella typhimurium were evaluated for protective effect in an equine model of endotoxemia. Six 3- to 5-month-old foals were given endotoxin (0.25 micrograms/kg of body weight) IV after no pretreatment, or pretreatment with polymyxin B (6,000 U/kg, IV) or S typhimurium antiserum (1.5 ml/kg, IV). When given without pretreatment, endotoxin caused transient recumbency and increases in rectal temperature, and heart and respiratory rates. In addition, leukopenia and increases in circulating tumor necrosis factor (TNF) and interleukin 6 (IL-6) activities were detected. Compared with results obtained when endotoxin was given alone, pretreatment with polymyxin B resulted in significantly (P < 0.05) lower maximal plasma TNF and IL-6 activities, and significantly lower rectal temperature and respiratory rate. In contrast, compared with effects of endotoxin given without pretreatment, use of antiserum was associated with significantly (P < 0.05) higher respiratory rate, maximal plasma IL-6 activity, and total TNF response (as determined by areas under curves of plasma TNF vs time). These results indicate that polymyxin B may have potential as a treatment for equine endotoxemia. Salmonella typhimurium antiserum had no positive effect in this model, and, under certain conditions, may exacerbate the actions of endotoxin.

The current study evaluated the efficacy of Selenium Nanoparticles (Se-NPs) on hemato-biochemical, antioxidant biomarkers, and immunological responses induced by S. Typhimurium in broiler chickens. Chicks (N=120) were divided into six groups. Group 1: received no treatment and set as a control group. Group 2: fed Se-NPs enriched diet (0.5 mg/kg diet). Group 3: subjected to oral challenge with 3.5x108 CFU/mL/1 ml/bird of S. Typhimurium. Group 4: administrated Se-NPs (0.5 mg/kg diet) then on day 21 was subjected to 3.5x108 CFU/mL/1 ml/bird of S. Typhimurium. Group 5: vaccinated by a SERVAC Tri Sal. 0.1ml subcutaneous (s/c) injection on day 3 then subjected to 3.5x108 CFU/mL/1 ml/bird of S. Typhimurium on day 21. Group 6: treated from day 1 with Se-NPs (0.5 mg/kg diet) till the end of the experiment and vaccinated by a SERVAC Tri Sal. 0.1ml (s/c) on day 3 and then subjected to 3.5x108 CFU/mL/1 ml/bird of S. Typhimurium on day 21. The results showed that S. Typhimurium significantly decreased erythrogram, lymphocytes count, total protein, albumin, A/G ratio, glucose, cholesterol, triglyceride, serum iron, and TIBC, GPX, SOD, TAC, and IL-10 expression compared to the control.  Meanwhile, S. Typhimurium significantly increased TLC, heterophils, monocytes, serum ferritin, liver enzymes (ALT, AST), renal products (creatinine, uric acid), MDA, IL6 expression. Conversely, the dietary Se-NPs supplementation and/or Salmonella vaccine to the infected broiler induced, to various degrees, improvement in hemato-biochemical, antioxidant biomarkers, and proinflammatory responses compared to challenged group. In conclusion, dietary Se-NPs supplementation offered a direct protection against S. Typhimurium infection for sustaining poultry production and correspondingly protecting human health.

In this study, a genetically engineered live attenuated Salmonella Enteritidis (SE) vaccine was evaluated for its ability to protect against Salmonella Typhimurium (ST) infection in chickens. The birds were orally primed with the vaccine on the 1st day of life and given an oral booster at 5 wk of age. Control birds were orally inoculated with phosphate-buffered saline. Both groups of birds were orally challenged with a virulent ST strain at 9 wk of age. Compared with the control chickens, the vaccinated chickens had significantly higher levels of systemic IgG and mucosal IgA against specific ST antigens and a significantly greater lymphoproliferative response to ST antigens. The excretion of ST into the feces was significantly lower in the vaccinated group than in the control group on days 9 and 13 d after challenge. In addition, the vaccinated group had significantly fewer pronounced gross lesions in the liver and spleen and lower bacterial counts in the internal organs than the control group after challenge. These data indicate that genetically engineered live attenuated SE may induce humoral and cellular immune responses against ST antigens and may confer protection against virulent ST challenge.

Objective—To evaluate effects of quaternary benzo(c)phenanthridine alkaloids (QBAs) against Salmonella spp and determine effects on growth performance, organism shedding, and gastrointestinal tract integrity in pigs inoculated with Salmonella enterica serovar Typhimurium. Sample—36 Salmonella isolates and twenty 5-week-old pigs. Procedures—Minimum inhibitory concentration of QBAs against the Salmonella isolates was determined. Pigs were allocated to 4 groups and inoculated with Salmonella organisms. Pigs received diets supplemented with 1.5 g of QBAs/1,000 kg of feed, 0.75 g of QBAs/1,000 kg of feed, or 59.4 g of chlortetracycline/1,000 kg of feed or a nonsupplemented (control) diet. Pigs were weighed on day 0 and then weekly for 40 days. Fecal samples were collected to quantify Salmonella organisms. Gastrointestinal tract integrity was evaluated by measuring transepithelial resistance. Results—In vitro, 9 of 36 (25%) Salmonella isolates were inhibited at 90 μg of QBAs/mL; all 36 were inhibited at 179 μg of QBAs/mL. Diets containing QBAs significantly decreased Salmonella spp shedding; shedding was lower 40 days after inoculation for pigs fed diets containing QBAs or chlortetracycline than for pigs fed the control diet. Growth performance was similar for pigs fed diets containing QBA or chlortetracycline. Gastrointestinal tract integrity was improved in pigs fed the diet containing 1.5 g of QBAs/1,000 kg of feed. Conclusions and Clinical Relevance—QBAs and chlortetracycline decreased Salmonella spp shedding but did not differ with regard to growth performance. Gastrointestinal tract integrity was better, albeit not significantly, in pigs fed diets containing QBAs. Further investigation into the role of QBAs and their mechanism as an immunomodulator is necessary.

Avian pathogenic Escherichia coli (APEC) are known to cause extraintestinal disease in poultry, leading to substantial losses in the industry. IutA, iron-regulated aerobactin receptor is firmly associated with APEC. To assess the potential of IutA to induce protective immune responses, attenuated Salmonella Typhimurium strain expressing IutA was constructed and administered orally to BALB/c mice. The IutA-specific immune responses were measured with sera, vaginal and fecal samples by an enzyme-linked immunosorbent assay. We found that the Salmonella-IutA vaccine induced significantly higher immune responses as compared to the control inoculated with the attenuated S. Typhimurium containing the plasmid only. The IutA-specific immune responses were increased by second immunization at third week after initial immunization, whereas triple immunization induced lower immune responses than those induced by the double immunization. The Salmonella-IutA vaccine induced a nature of immunity biased to the Th1- type, as judged by the ratio of IutA-specific IgG isotypes (IgG2a/IgG1). Overall, these results suggest that the Salmonella-IutA vaccine appear to be suitable candidate for a vaccine against APEC. Keywords :

Salmonella enterica subsp. enterica serovar Typhimurium was isolated from diarrheic piglets in 2 periods, 2000–2001 (n = 25) and 2005–2006 (n = 17). To compare the characteristics of the isolates collected during the 2 periods, all isolates were tested for antimicrobial resistance, the presence of virulence genes, and pulsed-field gel electrophoresis (PFGE) patterns. All 42 isolates were resistant to at least 1 of the 20 antimicrobials tested, and 39 (93%) were resistant to 2 or more antimicrobials. One isolate was resistant to 12 antimicrobials. Profiles of antimicrobial resistance revealed 20 resistance types. Several isolates were also resistant to quinolones and expanded-spectrum cephalosporins. Ten isolates (24%) were resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT); only one isolate had been isolated in 2000–2001, indicating that this type of resistance has rapidly disseminated. Polymerase chain reaction (PCR) assays revealed that all the isolates carried invA. Among the 25 strains isolated in 2000–2001, all carried the sipA, sopA, sopD, sopE2, and ssaR genes, and 96% carried sopB and sifA. Among the 17 strains isolated in 2005–2006, all carried sifA, and approximately 90% carried sipA, sopA, sopB, sopD, sopE2, and ssaR. However, only 6 (14%) of the 42 isolates carried spvC. By PFGE analysis, all 42 strains were classified into 4 major clusters, basically by collection period. The genetic similarity according to PFGE suggests that the strains isolated from diarrheic piglets of this region within the same period may be closely related.

A clinical field trial was performed to determine the effectiveness of an autogenous Salmonella Typhimurium bacterin compared with a commercial live S. Choleraesuis vaccine in pigs. The association between Salmonella shedding and weight gain was also investigated. Nine cohorts of weaned pigs, (330 to 350 pigs per cohort), were randomly assigned to 1 of 3 treatment groups (injection with S. Typhimurium bacterin, vaccination via water with S. Choleraesuis vaccine, or a control group receiving no vaccine). In each cohort, the average daily gain was calculated for a selected pen throughout the production stage. Pen (pooled) fecal samples were collected bi-weekly and cultured. The odds of Salmonella shedding in both vaccinated groups was higher than in the control group (P < 0.05). The prevalence of Salmonella shedding declined overall as pigs aged (P = 0.04). However, the control pigs showed the smallest decrease in Salmonella shedding over the entire production stage, while prevalence of Salmonella shedding in the vaccinated groups decreased twice as much as the control group over the entire production stage. Salmonella Typhimurium var. Copenhagen DT104, S. Cerro, and S. Agona, which had been isolated on the study farm previously, were recovered from pigs in this study. Shedding of S. Typhimurium var. Copenhagen decreased over time in both vaccine treatment groups. On the other hand, S. Cerro shedding rate was lower in the control pigs compared with vaccinated pigs and S. Agona could be recovered only from the samples collected from S. Choleraesuis vaccinated pigs. The pigs from pens with a higher Salmonella recovery rate experienced slower growth compared with pigs from pens where Salmonella was not isolated. This latter finding indicates that there might be an economic incentive for producers to try to control endemic salmonellosis if effective programs could be developed.