Veterinary Research Forum

Abstract Quorum sensing (QS) is a cell density-dependent mechanism used by many pathogenic bacteria for regulating virulence gene expression. Inhibition or interruption of QS by medicinal plant remedies has been suggested as a new strategy for fighting against antibiotic-resistant bacteria. This study aimed to assess the impact of sub-inhibitory concentrations of licochalcone A (LAA) and epigallocatechin-3-gallate (EGCG) as natural plant products on the QS-associated genes(sdiA and luxS)expression. The PCR test was used to confirm the presence of sdiA and luxS genes in 23 S. Typhimurium isolates from poultry. The quantitative real-time PCR assay was used to analyze the expression of sdiA and luxS in S. Typhimurium isolates in response to the treatment with sub-inhibitory concentrations of LAA and EGCG at 45-min time point. All S. Typhimurium isolates showed the presence of sdiA and luxS genes (100%). As result, the expression of QS-related genes was significantly reduced in S. Typhimurium isolates following treatment with LAA and EGCG. In conclusion, LAA and EGCG showed anti-QS activity with down-regulation of both sdiA and luxS genes in S. Typhimurium, suggesting potential therapeutic use of them against salmonellosis. However, it must be pointed out that the safety and efficiency of these compounds need more thorough research.

Abstract Drop plate technique has a priority and preference compared with the spread plate procedure, because of less time, quantity of media, effort requirement, little incubator space, and less labor intensive. The objective of this research was to compare the accuracy and fidelity of drop plate method vs. spread plate method by parametric and nonparametric statistical tests. For bacterial enumeration by drop and spread plate methods, successive dilutions of second subculture of Lactobacillus casei and Salmonella Typhimurium were transferred to selective agar. The correlation of agreement between both methods was evaluated by using statistical proofs. Results showed that mean value (parametric unpaired t-test) comparison at 95 percent confidence level did not reject null hypothesis, which it meant that the equality of the mean data could not be ruled out. Nonparametric method was used because of approximately Gaussian pattern of data distribution. For this purpose, Mann-Whitney test (equivalent nonparametric t-test) was used. It meant that the equality of medians obtained from two methods were similar. Spearman’s rho correlation coefficient (r) via both methods due to data distribution patterns for enumeration of S. Typhimurium and L. casei were 0.62 and 0.87, respectively; which represented moderately strong and strong relationship between two methods, respectively. Besides, there was a significant and strong positive correlation (p < 0.001) between spread and drop plate procedures. Because of aforementioned reasons, the spread plate method can be replaced by drop plate method.

Abstract Salmonella enterica serovar Typhimurium and S.enterica serovar Enteritidis are the most frequently isolated serovars from food-borne diseases throughout the world. According to their antigenic profiles, salmonella shows different disease syndromes and host specificities. It is necessary and important to discriminate salmonella serovars from each other in order to ensure that each pathogen and its epidemiology are correctly recognized. Many PCR-based methods have been developed to identify salmonella serovars. The objective of present study was to identify S. Typhimurium in avians from different regions including: North, Northwest and capital city (Tehran) of Iran. Also in this research, the quality of CHROMagar™ Salmonella medium (CAS medium) in veterinary medicine was evaluated. The results of present study showed that out of 1870 intestine samples, fifty two S. Typhimurium including broiler (n=13), layer (n=12), duck (n=5), goose (n=5), sparrow (n=8), canary (n=3), pigeon (n=5) and African grey parrot (n=1) were identified using serotyping as well as multiplex-PCR. In conclusion, important measures must be taken on prevention and propagation of S. Typhimurium among avians. CHROMagar™ Salmonella medium has high levels of sensitivity and specificity and reduced the time to final identification of salmonella spp. in comparison with biochemical tests.