No abstract

Astaxanthin (AX) is one of the commonly used feed supplements to enhance the growth performance and provide antioxidant and immune functions of several aquatic animals. In the current study, juveniles of white-leg shrimp (Litopenaeus vannamei) with mean initial weight of 0.340 ± 0.041 g were fed with diets supplemented with 0 (control), 25, 50, 100, and 200 mg/kg feed for 8 weeks. At the end of the feeding trial, shrimps were exposed to Vibrio harveyi, and their mortality rates were observed for additional 10 days. The growth indices in the AX-fed groups were significantly (P < 0.05) higher than what were observed in shrimps in the control group. Dietary AX stimulated the final weight, weight gain, and specific growth rate and optimum growth levels were achieved at 100–200 mg AX/kg feed. Furthermore, the AX-enriched diets significantly enhanced feed intake more than the control diet, and the amount of AX had no effects on feed conversion ratios. In comparison to the control group, the AX-fed animals had significantly (P < 0.05) higher villi length, villi width, and absorption area and their optimum values were observed at 100–200 mg AX/kg feed treatments. Moreover, the intestinal morphometry especially villi and its crypt, both internal and external tunica muscularis, and submucosal tissues did not show any inflammatory and/or degenerative changes in AX-fed shrimp. Furthermore, the dietary AX at escalating levels linearly and quadratically enhanced (P < 0.05) the activities of serum superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and increased levels of total antioxidant capacity and reduced glutathione. In addition, malondialdehyde levels decreased significantly in AX-fed animals, and the highest levels were observed in the control group (without AX). The expression levels of cMn-SOD, CAT, and GPx genes were significantly upregulated in the hepatopancreas of L. vannamei fed with AX-enriched diets (especially in the 200-mg/kg feed treatment) as compared with the control diet. The immunity indices of the AX treatments (hematocyte count, total protein, lysozyme, phagocytic activity, and phenoloxidase) of L. vannamei were linearly (P < 0.05) and quadratically (P < 0.05) increased. This study revealed the antibacterial activity of AX against V. harveyi abundance. After the bacterial challenge, feeding L. vannamei with dietary AX significantly increased (P < 0.05) the relative percentage of survival, especially in the treatment of 200-mg/kg diet (82.7%). The findings of the current study demonstrate that dietary AX (100–200 mg/kg feed) was effective in enhancing the growth, antioxidant status, immune response, and increasing the resistance of L. vannamei against V. harveyi infection.

No abstract

A prevalent bacterial intestinal infection with severe economic damage is salmonellosis. Our study was carried out to diagnose Salmonella from chickens and calves, to determine its resistance to antimicrobials’ phenotypic and genotypic characterization of integrons and β lactamase genes in the multidrug resistance of different Salmonella serotypes, and to detect the genetic relationship between Salmonella isolates collected from different origins using an ERIC PCR. In total, 200 samples from diseased chicken and diarrheic calves were obtained from 50 various farms from Kafr El-sheikh, Egypt. Salmonella poultry isolates were characterized as S. Typhimurium (3/8), S. Enteritidis (3/8), and S. Kentucky (2/8), but Salmonella isolates from cattle were S. Enteritidis (1/2) and S. Kentucky (1/2). When antibiotic susceptibility testing was completed on all of the isolates, it showed that there was multidrug resistance present (MDR). A PCR was applied for identifying the accompanying class 1 integrons and ESBLs from MDR Salmonella isolates (two isolates of S. Kentucky were divided as one from calf and one from poultry). Our results detected blaTEM and class 1 integron, but were negative for bla IMP, bla VIM, and bla SHV. An ERIC PCR was conducted for understanding the clonal relation between various β-lactamase-producing MDR Salmonella isolates. The same four previously mentioned isolates were also tested. The two isolates of S. Enteritidis isolated from poultry and calves had 100% similarity despite indicating that there were interactions between broilers and calves living on the same farm that caused infection from the same Salmonella strains, while the other two isolates of S. Kentucky showed only 33% serovarities.

Vibrio alginolyticus and Streptococcus agalactiae are important bacterial pathogens that yielded high losses in Nile tilapia in Egypt. The present study aimed to check the protective efficacy of inactivated whole-cell bivalent vaccines against these pathogens using incomplete Freund’s adjuvant and Montanide™ IMS 1312 VG as adjuvants. The antibody titers have been determined at different weeks post-vaccination (WPV). Moreover, the protection levels against the challenged bacterial pathogens have also been examined in relation to the time-dependent protection at different WPV. The results revealed that serum antibodies were generated in all immunized fish at 1st WPV, peaked at 4th WPV, continued, and gradually decreased from 6th WPV to 14th WPV in all vaccinated groups. In addition, vaccines induced significantly higher protection of the immunized tilapia, manifested by higher survival rates. We noticed that the antibody levels and survival rates of the vaccinated fish by a vaccine adjuvanted by Montanide™ IMS 1312 VG were higher than those produced by a vaccine adjuvanted by incomplete Freund’s adjuvant at different time points. Moreover, no external clinical signs, visceral adhesions, or internal lesions were recorded in the vaccinated tilapia, demonstrating the safety of the formulated vaccines. According to the aforementioned findings, we could suggest that the prepared bivalent vaccines, using the two adjuvant types, are safe and highly protective and could be utilized as promising candidate vaccines to increase the resistance of Nile tilapia against V. alginolyticus and S. agalactiae infections. Moreover, Montanide™ IMS 1312 VG enhanced the immuno-protectivity and exhibited optimum immune response and earlier protection compared to the vaccine adjuvanted by incomplete Freund’s adjuvant, demonstrating its added value during the preparation of tilapia vaccines.