Veterinary use of bacteriophage therapy in intensively-reared livestock

Zoonoses are infectious diseases transmitted directly or indirectly between animals and humans. Several important zoonotic pathogens colonize farm animals asymptomatically, which may lead to contamination of the food chain and public health hazards. Moreover, routine sampling of carcasses at retail by government authorities over the past 20 years suggests the prevalence of antibiotic resistance in foodborne pathogens has increased. If this continues, antibiotics may be ineffective against such pathogens in the future and alternative approaches, such as phage therapy, may be necessary. Intensive livestock farming is the only realistic way of meeting the demand for meat from an increasing global population and growth in middle class consumers in developing countries, particularly in Asia. This review elaborates on the use of phages to control zoonotic pathogens in intensively-reared livestock (poultry and pigs)

Bacteriophage control of Campylobacters in retail poultry

Food-borne disease continues to be a major cause of human morbidity and mortality. During the past few decades, Campylobacter jejuni has ascended to become the greatest cause of bacterial enteric disease worldwide. Anecdotal evidence suggests the majority of human campylobacteriosis in industrialised countries is caused by the consumption of undercooked chicken. Campylobacter continues to frustrate current control strategies throughout the food chain and in 2001 was responsible for over 56, 000 cases of food poisoning in the U.K. alone. The work presented in this thesis examined the potential of host-specific bacteriophage as a novel measure to control the population of Campylobacter in poultry production. Several surveys in this thesis revealed that campylobacters and their bacteriophage permeate the entire poultry meat supply chain, from chickens in the broiler house to packaged retail products. Characterisation of the bacteriophage recovered from such sources showed that retail poultry isolates exhibited greater similarities in host range than those originating from broiler houses, implying poultry processing selected for a subpopulation of phage. Additionally, broiler chickens harbouring bacteriophage in their gastrointestinal tract generally contained fewer campylobacters. All of the phage isolates studied belonged to the Myoviridae virus family as they possessed dsDNA genomes encapsulated in an icosahedral head with a rigid, contractile tail. Fragments of the phage genomes exhibited significant sequence homology with a number of genes involved in DNA replication from phage T4. Studies of the attachment and replication of the phage isolates in vitro suggested that adsorption to the host cell was efficient but the burst size was low (˂10 virions per cell). Campylobacter jejuni was found to produce membrane vesicles but these did not significantly affect bacteriophage replication in vitro. A series of trials using 'phage therapy' in broiler chickens revealed that Campylobacter colonisation can be reduced by ≥log[subscript]10 8.0 cfu g[superscript]-1 caecal contents by dosing with specific bacteriophage. However, both the timing and extent of the reduction in Campylobacter colonisation showed considerable variation. Additionally, the ability of bacteriophage to infect their host in vitro was not a reliable indicator of their efficacy in vivo. The direct application of bacteriophage to the surface of chicken skin artificially contaminated with Campylobacter led to a significant reduction in the number of recoverable host cells. Host resistance to bacteriophage infection was not detected in either the in vivo trials or when recovering Campylobacter cells from chicken skin treated with phage. The work presented in this thesis demonstrates that bacteriophage have considerable potential in the control of Campylobacter in poultry production. They already appear to constitute a limiting factor in Campylobacter colonisation of the chicken gastrointestinal tract and can be detected with their host on retail products. However, further research is required to fully realise their potential and optimising the timing, level and type of bacteriophage used in dosing will be important for their efficacy in vivo

Bacteriophage control of Campylobacters in retail poultry

Food-borne disease continues to be a major cause of human morbidity and mortality. During the past few decades, Campylobacter jejuni has ascended to become the greatest cause of bacterial enteric disease worldwide. Anecdotal evidence suggests the majority of human campylobacteriosis in industrialised countries is caused by the consumption of undercooked chicken. Campylobacter continues to frustrate current control strategies throughout the food chain and in 2001 was responsible for over 56, 000 cases of food poisoning in the U.K. alone. The work presented in this thesis examined the potential of host-specific bacteriophage as a novel measure to control the population of Campylobacter in poultry production. Several surveys in this thesis revealed that campylobacters and their bacteriophage permeate the entire poultry meat supply chain, from chickens in the broiler house to packaged retail products. Characterisation of the bacteriophage recovered from such sources showed that retail poultry isolates exhibited greater similarities in host range than those originating from broiler houses, implying poultry processing selected for a subpopulation of phage. Additionally, broiler chickens harbouring bacteriophage in their gastrointestinal tract generally contained fewer campylobacters. All of the phage isolates studied belonged to the Myoviridae virus family as they possessed dsDNA genomes encapsulated in an icosahedral head with a rigid, contractile tail. Fragments of the phage genomes exhibited significant sequence homology with a number of genes involved in DNA replication from phage T4. Studies of the attachment and replication of the phage isolates in vitro suggested that adsorption to the host cell was efficient but the burst size was low (˂10 virions per cell). Campylobacter jejuni was found to produce membrane vesicles but these did not significantly affect bacteriophage replication in vitro. A series of trials using 'phage therapy' in broiler chickens revealed that Campylobacter colonisation can be reduced by ≥log[subscript]10 8.0 cfu g[superscript]-1 caecal contents by dosing with specific bacteriophage. However, both the timing and extent of the reduction in Campylobacter colonisation showed considerable variation. Additionally, the ability of bacteriophage to infect their host in vitro was not a reliable indicator of their efficacy in vivo. The direct application of bacteriophage to the surface of chicken skin artificially contaminated with Campylobacter led to a significant reduction in the number of recoverable host cells. Host resistance to bacteriophage infection was not detected in either the in vivo trials or when recovering Campylobacter cells from chicken skin treated with phage. The work presented in this thesis demonstrates that bacteriophage have considerable potential in the control of Campylobacter in poultry production. They already appear to constitute a limiting factor in Campylobacter colonisation of the chicken gastrointestinal tract and can be detected with their host on retail products. However, further research is required to fully realise their potential and optimising the timing, level and type of bacteriophage used in dosing will be important for their efficacy in vivo

Predatory bacteria as living antibiotics – where are we now?

Antimicrobial resistance (AMR) is a global health and economic crisis. With too few antibiotics in development to meet current and anticipated needs, there is a critical need for new therapies to treat Gram-negative infections. One potential approach is the use of living predatory bacteria, such as Bdellovibrio bacteriovorus (small Gram-negative bacteria that naturally invade and kill Gram-negative pathogens of humans, animals and plants). Moving toward the use of Bdellovibrio as a ‘living antibiotic’ demands the investigation and characterization of these bacterial predators in biologically relevant systems. We review the fundamental science supporting the feasibility of predatory bacteria as alternatives to antibiotics

Fleas and smaller fleas: virotherapy for parasite infections

Bacteriophages are viruses of bacteria that are used for controlling bacterial food-borne pathogens and have been proposed for more extensive usage in infection control. Protists are now recognised to harbour viruses and virus-like particles. We propose that investigation of their prevalence in parasites be intensified. We also propose that such viruses might be considered for virotherapy to control certain parasite infections of man and animals

Pseudomonas spp. in Canine Otitis Externa

Canine otitis externa (OE) is a commonly diagnosed condition seen in veterinary practice worldwide. In this review, we discuss the mechanisms of the disease, with a particular focus on the biological characteristics of Pseudomonas aeruginosa and the impact that antibiotic resistance has on successful recovery from OE. We also consider potential alternatives to antimicrobial chemotherapy for the treatment of recalcitrant infections. P. aeruginosa is not a typical constituent of the canine ear microbiota, but is frequently isolated from cases of chronic OE, and the nature of this pathogen often makes treatment difficult. Biofilm formation is identified in 40–95% of P. aeruginosa from cases of OE and intrinsic and acquired antibiotic resistance, especially resistance to clinically important antibiotics, highlights the need for alternative treatments. The role of other virulence factors in OE remains relatively unexplored and further work is needed. The studies described in this work highlight several potential alternative treatments, including the use of bacteriophages. This review provides a summary of the aetiology of OE with particular reference to the dysbiosis that leads to colonisation by P. aeruginosa and highlights the need for novel treatments for the future management of P. aeruginosa otitis

Isolation and characterization of Campylobacter bacteriophages from retail poultry

The ability of phages to survive processing is an important aspect of their potential use in the biocontrol of Campylobacter in poultry production. To this end, we have developed a procedure to recover Campylobacter bacteriophages from chilled and frozen retail poultry and have validated the sensitivity of the method by using a characterized Campylobacter phage (i.e., NCTC 12674). By using this method, we have shown that Campylobacter phages can survive on retail chicken under commercial storage conditions. Retail chicken portions purchased in the United Kingdom were screened for the presence of endogenous Campylobacter phages. Thirty-four Campylobacter bacteriophages were isolated from 300 chilled retail chicken portions, but none could be recovered from 150 frozen chicken portions. The phage isolates were characterized according to their lytic profiles, morphology, and genome size. The free-range products were significantly more likely to harbor phages (P < 0.001 by single-factor analysis of variance) than were standard or economy products. This study demonstrates that Campylobacter bacteriophages, along with their hosts, can survive commercial poultry processing procedures and that the phages exhibited a wide range of recovery rates from chicken skin stored at 4°C

Investigation into the animal species contents of popular wet pet foods

Background: The use of the generic term “meat and animal derivatives” in declared ingredient lists of pet foods in the European Union is virtually universal. In the wake of the 2013 “horse meat scandal” in the human food chain, we examined the presence and authenticity of animal sources (cow, chicken, pig and horse) of proteins in a range of popular wet pet foods in the United Kingdom.Findings: Seventeen leading dog and cat foods were sampled for the relative presence of DNA from each of the four animal species by quantitative real-time polymerase chain reaction. No horse DNA was detected. However, there was detection at substantial levels of unspecified animal species in most products tested. In 14 out of 17 samples, bovine, porcine and chicken DNA were found in various proportions and combinations but were not explicitly identified on the product labels. Of the 7 products with prominent headline descriptions containing the term “with beef”, only 2 were found to contain more bovine DNA (>50%) than pig and chicken DNA combined.Conclusions: There is a need for the pet food industry to show greater transparency to customers in the disclosure of the types of animal proteins (animal species and tissue types) in their products. Full disclosure of animal contents will (a) allow more informed choices to be made on purchases which are particularly important for pets with food allergies, (b) reduce the risk of product misinterpretation by shoppers, and (c) avoid potential religious concerns

Application of a bacteriophage cocktail to reduce Salmonella Typhimurium U288 contamination on pig skin

Multidrug-resistant Salmonella Typhimurium U288 is a significant pathogen of pigs, accounting for over half of all outbreaks on UK pig production premises. The potential of this serovar, and other salmonellae, to enter the food chain during the slaughtering process requires that efforts be made to reduce the prevalence of these bacteria at both the pre- and post-harvest stages of production. A bacteriophage cocktail (PC1) capable of lysing various Salmonella enterica serovars was designed using the broad host-range phage Felix 01, and three phages isolated from sewage. PC1 applied to pig skin experimentally-contaminated with U288 achieved significant reductions (P 1 log10 unit were observed when the ratio of phage applied was in excess of the bacterial concentration. The treatment was found to be effective at a multiplicity of infection (MOI) of 10 or above, with no significant reductions taking place when the MOI was less than 10. Under these conditions U288 counts of log10 4.1–4.3 CFU were reduced to undetectable levels following the application of PC1 to pig skin (> 99% reduction). These data suggest phage cocktails could be employed post-slaughter as a means to reduce Salmonella contamination of pig carcasses

Complete genome sequences of seven Vibrio cholerae phages isolated in China

The complete genome sequences of seven closely related Vibrio cholerae phages isolated from environmental sites in southeastern China are reported here. Phages QH, CJY, H1, H2, H3, J2, and J3 are members of the Podoviridae family and are highly similar to the previously sequenced Vibrio phages VP2, VP5, and phiVC8