Department of Clinical Veterinary Science, University of Bristol, Langford, UK.
Present Address: School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington, Leicestershire, LE12 5RD, UK.
Virol J. 2020 Jul 9;17(1):98. doi: 10.1186/s12985-020-01368-0.
Enteric infections caused by Salmonella spp. remain a major public health burden worldwide. Chickens are known to be a major reservoir for this zoonotic pathogen. The presence of Salmonella in poultry farms and abattoirs is associated with financial costs of treatment and a serious risk to human health. The use of bacteriophages as a biocontrol is one possible intervention by which Salmonella colonization of chickens could be reduced. In a prior study, phages Eϕ151 and Tϕ7 significantly reduced broiler chicken caecal colonization by S. Enteritidis and S. Typhimurium respectively.
Salmonella-free Ross broiler chickens were orally infected with S. Enteritidis P125109 or S. Typhimurium 4/74. After 7 days of infection, the animals were euthanased, and 25cm sections of skin were collected. The skin samples were sprayed with a phage suspension of either Eϕ151 (S. Enteritidis), Tϕ7 phage suspension (S. Typhimurium) or SM buffer (Control). After incubation, the number of surviving Salmonellas was determined by direct plating and Most Probable Number (MPN). To determine the rate of reduction of Salmonella numbers on the skin surface, a bioluminescent S. Typhimurium DT104 strain was cultured, spread on sections of chicken breast skin, and after spraying with a Tϕ11 phage suspension, skin samples were monitored using photon counting for up to 24 h.
The median levels of Salmonella reduction following phage treatment were 1.38 log MPN (Enteritidis) and 1.83 log MPN (Typhimurium) per skin section. Treatment reductions were significant when compared with Salmonella recovery from control skin sections treated with buffer (p < 0.0001). Additionally, significant reduction in light intensity was observed within 1 min of phage Tϕ11 spraying onto the skin contaminated with a bioluminescent Salmonella recombinant strain, compared with buffer-treated controls (p < 0.01), implying that some lysis of Salmonella was occurring on the skin surface.
The results of this study suggest that phages may be used on the surface of chicken skin as biocontrol agents against Salmonella infected broiler chicken carcasses. The rate of bioluminescence reduction shown by the recombinant Salmonella strain used supported the hypothesis that at least some of the reduction observed was due to lysis occurred on the skin surface.
由沙门氏菌引起的肠道感染仍然是全球范围内的一个主要公共卫生负担。众所周知，鸡是这种人畜共患病病原体的主要宿主。在养鸡场和屠宰场中存在沙门氏菌与治疗的经济成本有关，并对人类健康构成严重威胁。噬菌体作为一种生物防治剂的使用是减少鸡沙门氏菌定植的一种可能干预措施。在先前的一项研究中，噬菌体 Eϕ151 和 Tϕ7 分别显著降低了肉鸡盲肠中肠炎沙门氏菌和鼠伤寒沙门氏菌的定植。
无沙门氏菌的罗斯肉鸡通过口服感染肠炎沙门氏菌 P125109 或鼠伤寒沙门氏菌 4/74。感染 7 天后，对动物进行安乐死，并采集 25cm 皮肤段。将噬菌体 Eϕ151（肠炎沙门氏菌）或 Tϕ7 噬菌体悬浮液或 SM 缓冲液（对照）喷洒在皮肤样本上。孵育后，通过直接平板计数和最可能数（MPN）确定存活沙门氏菌的数量。为了确定噬菌体处理后鸡皮表面沙门氏菌数量的减少率，培养发光鼠伤寒沙门氏菌 DT104 菌株，将其铺展在鸡胸皮段上，并用 Tϕ11 噬菌体悬浮液喷洒后，使用光子计数法监测皮肤样本长达 24 小时。
噬菌体处理后，每段皮肤的沙门氏菌减少中位数水平分别为 1.38 log MPN（肠炎沙门氏菌）和 1.83 log MPN（鼠伤寒沙门氏菌）。与用缓冲液处理的对照皮肤段中沙门氏菌的恢复相比，处理后的减少具有统计学意义（p<0.0001）。此外，与用缓冲液处理的对照相比，在用发光重组沙门氏菌污染的皮肤上喷洒噬菌体 Tϕ11 后 1 分钟内，观察到光强度显著降低（p<0.01），这意味着在皮肤表面发生了一些沙门氏菌的裂解。
本研究结果表明，噬菌体可作为生物控制剂用于鸡皮表面，以控制感染肠炎沙门氏菌的肉鸡胴体。发光重组沙门氏菌菌株显示的生物发光减少率支持这样的假设，即观察到的减少至少部分是由于在皮肤表面发生的裂解。
