Shehata Awad A, Tarabees Reda, Elsayed Mohamed, Wareth Gamal, Basiouni Shereen
Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, University of Sadat City, 32897, Sadat City, Egypt.
Research and Development Section, PerNaturam GmbH, Gödenroth, Germany.
Heliyon. 2020 Aug 28;6(8):e04810. doi: 10.1016/j.heliyon.2020.e04810. eCollection 2020 Aug.
is one of the most frequent food-borne pathogens and remains public health threat globally. The control of in poultry, the main reservoir of non-typhoidal salmonellae, is a fundamental approach to ensure the safety of poultry products for human consumption. In the present study, a new live attenuated enterica serovar Enteritidis vaccine candidate containing three attenuating markers based on streptomycin-independent (Sm-id) suppressor, and metabolic drift antibiotic resistance (MD- "res") was developed. The streptomycin dependent (Smd) mutants were derived from Enteritidis wild-type strain using streptomycin. Then the Sm-id mutants were derived from the isolated Smd mutants and designated "Smd→Sm-id". A third MD- "res" marker was generated from Smd→Sm-id using rifampicin (Rif) and designated "Smd→Sm-id→Rif". The colony sizes of these mutants were stable after more than 50 serial passages on blood agar; reversion to virulence can be almost excluded. The safety and efficacy of Smd→Sm-id and Smd→Sm-id→Rif were evaluated in one-day-old commercial layer chicks. Both mutants proved to be safe in terms of clinical signs, mortalities, lesion scores of visceral organs and rapid clearance when administered orally at a dose of 10 colony forming unit (CFU), whereas birds inoculated with 10 CFU Enteritidis wild-type strain showed diarrhea, mortalities (3/40) and necrosis in liver and spleen. Chickens vaccinated with the developed mutants showed no seroconversion; however, wild-type strain induced a significant seroconversion at 3-week-postvaccination (wpv). The developed mutants protected chickens against challenge with 10 CFU of Enteritidis wild-type strain at 3-wpv. Vaccinated birds showed neither clinical signs nor mortalities during two-week post-challenge. In addition, the challenge strain could not be detected in pooled liver and spleen samples (0/5) at 7 day post-inoculation (dpi). However, non-vaccinated challenged birds showed diarrhea and the challenge strain was re-isolated from pooled liver and spleen samples (3/5) at 7 dpi. In conclusion, the developed mutants are safe and fully protected immunized chickens following heterologous challenge. It is obvious that the genetic characterization of these mutants and evaluation of different vaccination regimes are still in demand.
是最常见的食源性病原体之一，在全球范围内仍然是对公共卫生的威胁。在家禽中控制非伤寒沙门氏菌，家禽是其主要宿主，是确保供人类食用的家禽产品安全的基本方法。在本研究中，开发了一种新的减毒肠炎沙门氏菌肠炎血清型候选活疫苗，其含有基于链霉素非依赖（Sm-id）抑制子和代谢漂移抗生素抗性（MD-“res”）的三个减毒标记。链霉素依赖（Smd）突变体是使用链霉素从肠炎沙门氏菌野生型菌株衍生而来。然后从分离出的Smd突变体衍生出Sm-id突变体，并命名为“Smd→Sm-id”。使用利福平（Rif）从Smd→Sm-id产生第三个MD-“res”标记，并命名为“Smd→Sm-id→Rif”。这些突变体在血琼脂上连续传代50多次后菌落大小稳定；几乎可以排除回复毒力的情况。在一日龄商品蛋鸡中评估了Smd→Sm-id和Smd→Sm-id→Rif的安全性和有效性。当以10个菌落形成单位（CFU）的剂量口服给药时，两种突变体在临床症状、死亡率、内脏器官病变评分和快速清除方面都被证明是安全的，而接种10 CFU肠炎沙门氏菌野生型菌株的鸡出现腹泻、死亡（3/40）以及肝脏和脾脏坏死。用所开发的突变体接种的鸡没有出现血清转化；然而，野生型菌株在接种后3周（wpv）诱导了显著的血清转化。所开发的突变体在3 wpv时保护鸡免受10 CFU肠炎沙门氏菌野生型菌株的攻击。接种疫苗的鸡在攻击后两周内既没有出现临床症状也没有死亡。此外，在接种后7天（dpi），在合并的肝脏和脾脏样本中未检测到攻击菌株（0/5）。然而，未接种疫苗的攻击鸡出现腹泻，并且在7 dpi时从合并的肝脏和脾脏样本中重新分离出攻击菌株（3/5）。总之，所开发的突变体是安全的，并且在异源攻击后能完全保护免疫的鸡。显然，仍需要对这些突变体进行基因特征分析以及评估不同的疫苗接种方案。
