Effect of translucency and eggshell color on broiler breeder egg hatchability and hatch chick weight.

A successful hatch has a considerable economic impact on all poultry companies. The aim of the current study was to describe the possible effects of shell translucency (T score) and coloration lightness (L* value) on shell thickness, hatchability, and chick weight. A total of 4,320 eggs from 4 commercial Ross 708 breeder flocks (50-55-wk old) were used. Eggs were selected for T score and L* value. A 3-point subjective scoring system was used for T score (1 = low, 2 = medium, 3 = high), and an electronic colorimeter for L* value, sorting the eggs as light (avg. L* = 80.7) or dark (avg. L* = 76.0). Data were analyzed using the GLIMMIX procedure of SAS (V9.4) and Tukey's HSD test was performed to separate means, a significant difference was considered when P ≤ 0.05. Results suggest that the color of the eggshell was related to the egg weight on the day of collection (P = 0.0056) and at transfer (P = 0.0211), in both cases dark eggs were 0.6 g heavier than light eggs. Dark eggs had a 3.8% increased hatchability of egg set (P = 0.0481) and yielded 6 µm thicker shells (P = 0.0019) when compared to light eggs. Regarding translucency, egg weight at transfer was 0.8 g heavier for T score 1 eggs compared to T score 3 (P = 0.0358). The translucency score of 1 had a 6.9% higher hatchability of eggs set (P = 0.0127) and 0.7 g heavier chick weight (P = 0.0385) compared to T score 3. However, T score 1 eggs had shells 28 µm thinner than the T score 2 and 34 µm thinner than T score 3 (P < 0.0001). An interaction effect was observed for eggshell thickness, L* value, and T score, where eggs classified as light with T score 1 had thinner eggshells compared to those that were dark with T score 3 (P = 0.0292). These results suggest that eggshell translucency and coloration lightness can be good noninvasive indicators of eggshell thickness, hatchability, and chick weight in broiler breeder flocks.

Phenelzine and Amoxapine Inhibit Tyramine and d-Glucuronic Acid Catabolism in Clinically Significant Salmonella in A Serotype-Independent Manner.

Non-typhoidal Salmonella ingeniously scavenges energy for growth from tyramine (TYR) and d-glucuronic acid (DGA), both of which occur in the host as the metabolic byproducts of the gut microbial metabolism. A critical first step in energy scavenging from TYR and DGA in Salmonella involves TYR-oxidation via TYR-oxidoreductase and production of free-DGA via ß-glucuronidase (GUS)-mediated hydrolysis of d-glucuronides (conjugated form of DGA), respectively. Here, we report that Salmonella utilizes TYR and DGA as sole sources of energy in a serotype-independent manner. Using colorimetric and radiometric approaches, we report that genes SEN2971, SEN3065, and SEN2426 encode TYR-oxidoreductases. Some Salmonella serotypes produce GUS, thus can also scavenge energy from d-glucuronides. We repurposed phenelzine (monoaminoxidase-inhibitor) and amoxapine (GUS-inhibitor) to inhibit the TYR-oxidoreductases and GUS encoded by Salmonella, respectively. We show that phenelzine significantly inhibits the growth of Salmonella by inhibiting TYR-oxidoreductases SEN2971, SEN3065, and SEN2426. Similarly, amoxapine significantly inhibits the growth of Salmonella by inhibiting GUS-mediated hydrolysis of d-glucuronides. Because TYR and DGA serve as potential energy sources for Salmonella growth in vivo, the data and the novel approaches used here provides a better understanding of the role of TYR and DGA in Salmonella pathogenesis and nutritional virulence.

Global transcriptional profiling of tyramine and d-glucuronic acid catabolism in Salmonella.

Salmonella has evolved various metabolic pathways to scavenge energy from the metabolic byproducts of the host gut microbiota, however, the precise metabolic byproducts and pathways utilized by Salmonella remain elusive. Previously we reported that Salmonella can proliferate by deriving energy from two metabolites that naturally occur in the host as gut microbial metabolic byproducts, namely, tyramine (TYR, an aromatic amine) and d-glucuronic acid (DGA, a hexuronic acid). Salmonella Pathogenicity Island 13 (SPI-13) plays a critical role in the ability of Salmonella to derive energy from TYR and DGA, however the catabolic pathways of these two micronutrients in Salmonella are poorly defined. The objective of this study was to identify the specific genetic components and construct the regulatory circuits for the TYR and DGA catabolic pathways in Salmonella. To accomplish this, we employed TYR and DGA-induced global transcriptional profiling and gene functional network analysis approaches. We report that TYR induced differential expression of 319 genes (172 up-regulated and 157 down-regulated) when Salmonella was grown in the presence of TYR as a sole energy source. These included the genes originally predicted to be involved in the classical TYR catabolic pathway. TYR also induced expression of majority of genes involved in the acetaldehyde degradation pathway and aided identification of a few new genes that are likely involved in alternative pathway for TYR catabolism. In contrast, DGA induced differential expression of 71 genes (58 up-regulated and 13 down-regulated) when Salmonella was grown in the presence of DGA as a sole energy source. These included the genes originally predicted to be involved in the classical pathway and a few new genes likely involved in the alternative pathway for DGA catabolism. Interestingly, DGA also induced expression of SPI-2 T3SS, suggesting that DGA may also influence nutritional virulence of Salmonella. In summary, this is the first report describing the global transcriptional profiling of TYR and DGA catabolic pathways of Salmonella. This study will contribute to the better understanding of the role of TYR and DGA in metabolic adaptation and virulence of Salmonella.

Prevalence, Antimicrobial Resistance, and Diversity of Salmonella along the Pig Production Chain in Southern Brazil.

Control of Salmonella spp. in food production chains is very important to ensure safe foods and minimize the risks of foodborne disease occurrence. This study aimed to identify the prevalence and main contamination sources of Salmonella spp. in a pig production chain in southern Brazil. Six lots of piglets produced at different farms were tracked until their slaughter, and samples were subjected to Salmonella spp. detection. The obtained isolates were serotyped, subjected to antimicrobial resistance testing, and pulsed field gel electrophoresis (PFGE). Salmonella spp. was detected in 160 (10.2%) samples, and not detected in pig carcasses after final washing or chilling. Among the 210 Salmonella spp. isolates, S. Typhimurium was the most prevalent (n = 101) and resistant to at least one antimicrobial. High resistance rates were detected against tetracycline (83.8%), chloramphenicol (54.3%), and trimethoprim-sulfamethoxazole (33.3%). The isolates that were non-susceptible to three or more classes of antimicrobials (n = 60) were considered multidrug-resistant (MDR), and isolates resistant to up to six of the tested antimicrobials were found. PFGE allowed the identification of genetic diversity and demonstrated that farm environment and feed supply may be sources for the dissemination of Salmonella spp. along the production chain. The results revealed the sources of Salmonella contamination in the pig production chain and highlighted the risks of antimicrobial resistance spread.

Genomic organization and role of SPI-13 in nutritional fitness of Salmonella.

Salmonella pathogenicity island 13 (SPI-13) contributes to the virulence of Salmonella. The majority of the SPI-13 genes encode proteins putatively involved in bacterial metabolism, however, their functions largely remain uncharacterized. It is currently unknown if SPI-13 contributes to metabolic fitness of Salmonella and, if so, what are the metabolic substrates for the protein encoded by genes within SPI-13. We employed Phenotype Microarray (Biolog, USA) to compare the metabolic properties of SPI-13 deficient mutant (ΔSPI-13) and the WT parent strain of non-typhoidal Salmonella enterica sub sp. enterica serovar Enteritidis (S. Enteritidis). The results of Phenotype Microarray revealed that SPI-13 is required for efficient utilization of two micronutrients, namely, d-glucuronic acid (DGA) and tyramine (TYR), as sole sources of carbon and/or nitrogen. By systematic deletion of the individual gene(s), we identified specific genes within SPI-13 that are required for efficient utilization of DGA (SEN2977-80) and TYR (SEN2967 and SEN2971-72) as sole nutrient sources. The results show that SPI-13 mediated DGA and TYR metabolic pathways afford nutritional fitness to S. Enteritidis. Comparative genomics analysis of the SPI-13 locus from 247 Salmonella strains belonging to 57 different serovars revealed that SPI-13 genes specifically involved in the metabolism of DGA and TYR are highly conserved in Salmonella enterica. Because DGA and TYR are naturally present as metabolic byproducts in the gastrointestinal tract and other host tissues, we propose a metabolic model that shows that the role of SPI-13 mediated DGA and TYR metabolism in the nutritional fitness of Salmonella is likely linked to nutritional virulence of this pathogen.

Influence of lactic acid and acetic acid on Salmonella spp. growth and expression of acid tolerance-related genes.

Salmonella spp. is an important foodborne pathogen, often associated with meat products. This pathogen presents a complex tolerance mechanism in the presence of organic acids, which is regulated by a diversity of genes, including rpoS, nlpD and clpP. The present study aimed to measure the expression of such genes by Salmonella strains subjected to acid stress conditions, and associate these data with microbial growth. A culture collection composed of 79 strains of Salmonella spp. obtained from bovine and swine production chains was subjected to PFGE using XbaI, and 3 strains (serovars Derby, Typhimurium and Meleagridis) were selected for acid tolerance trials. The selected strains were inoculated in meat extract broth (MEB) added to lactic or acetic acids at a final pH of 4.0, 5.0 or 6.0, and incubated at 37°C for 6, 12, 24 and 48h. As controls, Salmonella strains were inoculated in MEB at pH7.0, and incubated in the same conditions. Bacterial populations were monitored by direct plating and gene expression using qPCR. Salmonella presented similar populations to controls and evident expression of rpoS at pH5.0 and 6.0. However, Salmonella populations were not detectable after 6h at pH4.0. The adaptability of Salmonella to pH5.0 and 6.0 emphasizes the importance of adequate monitoring of pH reduction during cleaning procedures in food industries, such as organic acid spraying in bovine carcasses. The data obtained demonstrated the relevance of rpoS in the acid tolerance mechanism of Salmonella strains, prompting further studies to investigate its expression in meat systems.

Antimicrobial resistance and virulence profiles of Salmonella isolated from butcher shops in Minas Gerais, Brazil.

Salmonella can contaminate finished products of butcher shops, mainly through cross-contamination of utensils exposed to raw materials. To identify the main sources of contamination with this foodborne pathogen in four butcher shop environments, surface samples were obtained from employees' hands, cutting boards, knives, floor of the refrigeration room, meat grinders, and meat tenderizers (32 samples per area) and analyzed for Salmonella using the International Organization for Standardization method 6579, with modifications. Suspect isolates were identified by PCR (targeting ompC), and confirmed Salmonella isolates were subjected to pulsed-field gel electrophoresis (after treatment with restriction enzyme XbaI), analyzed for the presence of virulence genes (invA, sefA, and spvC), and screened for resistance to 12 antimicrobials. Salmonella isolates was identified only on cutting boards (five samples) from three butcher shops. Fifteen isolates were confirmed as Salmonella belonging to four pulse types (similarity of 71.1 to 100%). The invA gene was detected in 13 isolates, and the sefA was found in 8 isolates; no isolate carried spvC. All tested isolates were resistant to clindamycin and sensitive to amikacin and cefotaxine, and all isolates were resistant to at least 3 of the 12 antimicrobials tested. The results indicate the importance of cutting boards as a source of Salmonella contamination in butcher shops. The presence of multidrug-resistant Salmonella strains possessing virulence genes highlights the health risks for consumers.