Parker W Drew, Lungu Bwalya, Berghaus Roy D, Sellers Holly S, Alvarado Ivan Ricardo, Hofacre Charles L
Department of Population Health, Poultry Diagnostic and Research Center, University of Georgia, 953 College Station Road, Athens, GA 30602, USA.
Avian Dis. 2011 Jun;55(2):248-54. doi: 10.1637/9561-100410-Reg.1.
The efficacy of a live attenuated Salmonella Typhimurium Megan Vac 1 vaccine (MV1) was evaluated against Salmonella Enteritidis in chicken pullets with the use of PCR and culture methods. Two hundred Hyline W-32 white leghorn chicks were obtained from a local hatchery and divided into four treatment groups. Two of the groups served as positive and negative controls. The MV1 vaccine was administered to the chicks in the remaining two groups at 1 and 35 days old by either the coarse spray (field) or the oral route (laboratory) method. The chicks were challenged with a high dose of a Salmonella Enteritidis strain at 10 wk old and euthanatized 3 days postinoculation. Samples for PCR analysis were collected prior to enrichment, after pre-enrichment in buffered peptone water (BPW) and after primary enrichment from the ceca, liver, and spleen. None of the samples tested yielded positive results for the Salmonella Typhimurium vaccine strain by either the culture or PCR methods. Results from the standard culture method showed that vaccinating the birds with MV1 reduced the counts of Salmonella Enteritidis recovered from the challenged birds. In addition, fewer pre-enriched samples tested positive for Salmonella Enteritidis among the challenged groups that were vaccinated when compared to the unvaccinated challenged group. Under the conditions of this study, MV1 was unable to prevent colonization of other internal organs such as the liver and spleen. Real-time PCR was significantly more sensitive than conventional PCR (C-PCR) prior to enrichment, but after enrichment the sensitivities of the two methods were similar. Enrichment significantly increased the sensitivity of both PCR methods for the detection of Salmonella Enteritidis in cecal samples, but did not significantly increase the sensitivity for detection of Salmonella Enteritidis in liver and spleen samples that were pre-enriched in BPW. There was no significant difference between the laboratory or field vaccination methods with respect to either the prevalence of Salmonella Enteritidis isolation or the bacterial loads in culture-positive samples. Collectively, the data suggest that MV1 offered some protection against Salmonella Enteritidis in commercial layer chick pullets under the conditions of this study. Given the labor and time required to perform the C-PCR and culture methods, the real-time PCR method may prove to be a more useful method to use in diagnostics.
利用聚合酶链式反应（PCR）和培养方法，对减毒活鼠伤寒沙门氏菌Megan Vac 1疫苗（MV1）针对蛋鸡雏鸡肠炎沙门氏菌的效力进行了评估。从当地孵化场获取200只海兰W-32白来航雏鸡，并将其分为四个处理组。其中两组作为阳性和阴性对照。其余两组雏鸡在1日龄和35日龄时通过粗喷雾（田间）或口服途径（实验室）方法接种MV1疫苗。雏鸡在10周龄时用高剂量肠炎沙门氏菌菌株进行攻毒，并在接种后3天实施安乐死。在富集前、在缓冲蛋白胨水（BPW）中预富集后以及从盲肠、肝脏和脾脏进行初次富集后，采集用于PCR分析的样本。通过培养或PCR方法，所检测的样本均未对鼠伤寒沙门氏菌疫苗株得出阳性结果。标准培养方法的结果表明，用MV1疫苗接种雏鸡可减少从攻毒雏鸡中回收的肠炎沙门氏菌数量。此外，与未接种疫苗的攻毒组相比，在接种疫苗的攻毒组中，预富集样本检测出肠炎沙门氏菌呈阳性的数量更少。在本研究条件下，MV1无法预防肝脏和脾脏等其他内部器官的定植。在富集前，实时PCR比传统PCR（C-PCR）显著更灵敏，但富集后，两种方法的灵敏度相似。富集显著提高了两种PCR方法检测盲肠样本中肠炎沙门氏菌的灵敏度，但未显著提高检测在BPW中预富集的肝脏和脾脏样本中肠炎沙门氏菌的灵敏度。在肠炎沙门氏菌分离率或培养阳性样本中的细菌载量方面，实验室或田间接种方法之间没有显著差异。总体而言，数据表明在本研究条件下，MV1为商品蛋鸡雏鸡提供了针对肠炎沙门氏菌的一定保护。鉴于进行C-PCR和培养方法所需的人力和时间，实时PCR方法可能被证明是一种更适用于诊断的有用方法。
