3.1. Phage Therapy in Livestock and Other Food-Producing Animals
3.1.家畜和其他食用动物的噬菌体治疗
Livestock may be the field where antibiotic use has become most abused, which has resulted in a major threat. Phage therapy has been successfully tested for the treatment of infections affecting especially cattle and swine [69]. In this section, we will mention some recent studies and examples of phage therapy in livestock.
畜牧业可能是滥用抗生素最多的领域，这造成了重大威胁。噬菌体疗法已成功用于治疗感染，特别是牛和猪[ 69]。在本节中，我们将提到一些最近的研究和例子噬菌体治疗牲畜。
Staphylococcus aureus has significant virulence properties, being able to cause several infections in both humans and animals [70]. In addition, S. aureus can acquire genes that confer resistance to different antimicrobials, the most frequent strains being methicillin-resistant [71]. This pathogenic bacterium is the cause of mastitis in cattle, a disease that can result in significant economic costs [72]. A recent study proposes the application of three phages against S. aureus, using mouse and Galleria mellonella models. The results are promising, showing 50% survival of larvae in G. mellonella within four days of in vivo treatment with the three phages. In the mouse model, incomplete recovery was obtained after 48 hours post-infection of a single phage [53]. The diminished effect may be explained by the possible interaction of the phages with proteins and lipids present in milk and by the use of a single phage [54]. However, this study demonstrates the potential usefulness of phage therapy as a treatment for mastitis caused by S. aureus [53]. Recently, more studies on phage therapy for mastitis in cattle have been developed with positive, significant results using phage cocktails in mouse models. They have shown a decrease in the number of colony-forming units and a significant improvement in mastitis pathology, even greater than in mice treated with a single phage [55,73].
金黄色葡萄球菌具有显著的毒力特性，能够在人类和动物中引起多种感染[ 70]。另外，S.金黄色葡萄球菌可以获得赋予对不同抗菌剂的抗性的基因，最常见的菌株是耐甲氧西林的[ 71]。这种致病细菌是牛乳腺炎的原因，这种疾病可能导致重大的经济损失[ 72]。最近的一项研究提出了应用三种方法对抗S。金黄色葡萄球菌，使用小鼠和Galleria mellonella模型。结果表明，在该条件下，幼虫存活率达50%。在用三种抗生素体内治疗的四天内，在小鼠模型中，在单个噬菌体感染后48小时后获得不完全恢复[ 53]。这种减弱的作用可能是由于该噬菌体与乳汁中存在的蛋白质和脂质之间可能的相互作用以及使用了单一噬菌体[ 54]。 然而，这项研究证明了噬菌体疗法作为治疗由链球菌引起的乳腺炎的潜在用途。aureus [ 53].最近，在小鼠模型中使用噬菌体鸡尾酒已经开发了更多关于牛乳腺炎的噬菌体治疗的研究，具有积极的、显著的结果。它们已经显示出集落形成单位数量的减少和乳腺炎病理学的显著改善，甚至比用单一噬菌体处理的小鼠中的改善更大[ 55，73]。
Mastitis is not the only bovine disease that has been proposed to be treated with phage therapy. Metritis is an acute systemic disease that affects cows during the 21 days after calving and has detrimental effects on reproduction [74,75,76]. A cocktail of four Escherichia coli phages has been designed and shown to be effective in inhibiting E. coli isolates in vitro. Ten phage particles per bacterial cell were sufficient to inhibit the growth of at least 50% of all isolates. These results indicated the potential of the phage cocktail to reduce the presence of E. coli in the uteri of dairy cows after calving in order to prevent metritis [56]. However, in vivo results did not show satisfactory results [76,77,78].
乳腺炎不是唯一提出用噬菌体疗法治疗的牛疾病。子宫炎是一种急性全身性疾病，在产犊后21天内影响奶牛，并对生殖产生不利影响[ 74，75，76]。设计了四种大肠杆菌的混合物，并显示出有效抑制大肠杆菌。大肠杆菌分离株。每个细菌细胞10个噬菌体颗粒足以抑制至少50%的所有分离株的生长。这些结果表明噬菌体混合物减少大肠杆菌存在的潜力。奶牛产犊后子宫内的大肠杆菌，以预防子宫炎[ 56]。然而，体内结果并未显示出令人满意的结果[ 76，77，78]。
Hemorrhagic septicemia is one of the most important epizootic diseases in India, a fatal disease caused by Pasteurella mutocida serogroup B:2. The phage PMP-GAD-IND has shown lytic behavior against several strains of P. mutocida, including B:2, making this phage potentially useful for phage therapy [57].
出血性败血症是印度最重要的动物流行病之一，是由多杀性巴氏杆菌血清群B：2引起的致死性疾病。噬菌体PMP-GAD-IND已显示出针对几种变形杀巴斯德氏菌菌株（包括B：2）的裂解行为，使得该噬菌体可能用于噬菌体治疗[ 57]。
Phage therapy has also been proposed to treat swine infections. Salmonella sp. can colonize pigs during transport. In a preliminary study, a group of 3- to 4-week-old pigs was administered an anti-Salmonella phage cocktail at the time of inoculation with Salmonella enterica serovar Typhimurium. Colonization was reduced by more than 99%. In a second experiment, sixteen naïve pigs were introduced into a contaminated pen with four pigs infected with S. enterica. One group of them was treated earlier with the phage cocktail. The phage-based treatment showed a significant preventive effect by reducing both cecal and ileal Salmonella concentrations [58].
噬菌体疗法也被提出来治疗猪感染。沙门氏菌可以在运输过程中在猪身上定植。在一项初步研究中，一组3至4周龄的猪在接种肠道沙门氏菌血清型鼠伤寒沙门氏菌时给予抗沙门氏菌噬菌体混合物。定植减少了99%以上。在第二个实验中，将16头未经处理的猪引入污染的围栏中，其中4头猪感染了S。肠的。其中一组在早期接受了噬菌体鸡尾酒治疗。基于噬菌体的治疗通过降低盲肠和回肠沙门氏菌浓度显示出显著的预防效果[ 58]。
Diarrhea caused by E. coli in pigs results in high mortality and morbidity rates as well as decreased growth rate, leading to significant economic losses. Due to the emergence of MDR strains, the search for antibiotic alternatives for this disease is a priority. Phage therapy has been suggested as an alternative due to its important results in human and animal infections [79].
E.猪大肠杆菌感染导致高死亡率和发病率以及生长速度下降，导致重大经济损失。由于MDR菌株的出现，寻找这种疾病的抗生素替代品是一个优先事项。噬菌体疗法由于其在人类和动物感染中的重要结果而被建议作为替代方案[ 79]。
Pigs have been also considered animal models for the design of human treatments. The successful results of these treatments mean that they may be useful for pigs as well. A recent study addresses the use of phages to eliminate bacterial biofilms in chronic wounds in porcine skin explants. Both phage and phage cocktails caused significant reductions in viable cells in porcine skin [59].
猪也被认为是设计人类治疗的动物模型。这些治疗的成功结果意味着它们也可能对猪有用。最近的一项研究讨论了使用抗菌素消除猪皮肤外植体慢性伤口中的细菌生物膜。噬菌体和噬菌体混合物均导致猪皮肤中活细胞的显著减少[ 59]。
It is worth mentioning that cattle are not the only food-producing animal for which phage therapy has been proposed as an alternative to antibiotics. There are several studies developed in poultry. Infections in these animals can cause economic and health problems in our society. Salmonella sp., E. coli, Campylobacter sp., Listeria sp., and Clostridium perfringens are the main pathogens in the poultry industry. A progressive increase in the number of multidrug-resistant bacteria has been experienced which has encouraged the use of bacteriophages as an alternative treatment for infections caused by these pathogens [80].
值得一提的是，牛并不是唯一一种提出噬菌体疗法作为抗生素替代品的食用动物。在家禽中开展了几项研究。这些动物的感染会给我们的社会带来经济和健康问题。沙门氏菌属，E.大肠杆菌，弯曲杆菌属，李斯特菌属、和产气荚膜梭菌是家禽业中的主要病原体。多重耐药细菌的数量逐渐增加，这鼓励使用噬菌体作为这些病原体引起的感染的替代治疗[ 80]。
Phages have also been proposed as a therapy in aquaculture. One example is Lactococcus garvieae, a pathogen affecting several marine fish species. A recent study has characterized three lytic phages against an L. garviae strain infecting marine fish species. This opens the possibility of a phage-based treatment against this aquaculture pathogen [81].
噬菌体也被提议作为水产养殖中的疗法。一个例子是Lactococcus garvieae，一种影响几种海洋鱼类的病原体。最近的一项研究已经确定了三种针对L.感染海洋鱼类的寄生虫菌株。这开启了针对这种水产养殖病原体的基于噬菌体的治疗的可能性[ 81]。
Some phage-based products to reduce bacterial contamination of food have already been accepted and commercialized in the USA, Canada, Australia, Israel, and some European countries. Some of these examples are ListShield™, EcoShield™, and SalmoFresh™, developed by Intralyx [82] and PhageGuard S™ products [69,83]. Previous acceptance of these products suggests the potential commercialization of phage-based products for the veterinary field.
一些基于噬菌体的产品，以减少食品中的细菌污染，已经被美国，加拿大，澳大利亚，以色列和一些欧洲国家接受和商业化。这些实例中的一些是由Intralyx开发的ListShield™、EcoShield™和SalmoFresh™ [ 82]和PhageGuard S™产品[ 69，83]。先前对这些产品的接受表明基于噬菌体的产品在兽医领域的潜在商业化。