Oral Delivery Systems for Encapsulated Bacteriophages Targeted at O157:H7 in Feedlot Cattle

Abstract

Bacteriophages are natural predators of bacteria and may mitigate Escherichia coli O157:H7 in cattle and their environment. As bacteriophages targeted to E. coli O157:H7 (phages) lose activity at low pH, protection from gastric acidity may enhance efficacy of orally administered phages. Polymer encapsulation of four phages, wV8, rV5, wV7, and wV11, and exposure to pH 3.0 for 20 min resulted in an average 13.6% recovery of phages after release from encapsulation at pH 7.2. In contrast, untreated phages under similar conditions had a complete loss of activity. Steers (n = 24) received 10(11) CFU of naladixic acid-resistant E. coli O157:H7 on day 0 and were housed in six pens of four steers. Two pens were control (naladixic acid-resistant E. coli O157:H7 only), and the remaining pens received polymer-encapsulated phages (Ephage) on days -1, 1, 3, 6, and 8. Two pens received Ephage orally in gelatin capsules (bolus; 10(10) PFU per steer per day), and the remaining two pens received Ephage top-dressed on their feed (feed; estimated 10(11) PFU per steer per day). Shedding of E. coli O157:H7 was monitored for 10 weeks by collecting fecal grab and hide swab samples. Acceptable activity of mixed phages at delivery to steers was found for bolus and feed, averaging 1.82 and 1.13 x 10(9) PFU/g, respectively. However, Ephage did not reduce shedding of naladixic acid-resistant E. coli O157:H7, although duration of shedding was reduced by 14 days (P < 0.1) in bolus-fed steers as compared with control steers. Two successful systems for delivery of Ephage were developed, but a better understanding of phage-E. coli O157:H7 ecology is required to make phage therapy a viable strategy for mitigation of this organism in feedlot cattle.

Microencapsulation with alginate/CaCO3: A strategy for improved phage therapy

“…The materials used in bacteriophage encapsulation have been examined in several studies1213 and include alginate, alone or in combination with other materials810161718. However, few studies have described the in vivo use of alginate-encapsulated bacteriophages212227. Thus, our study is the first to test a cocktail of three alginate/CaCO 3 -encapsulated virulent bacteriophages (UAB_Phi20, UAB_Phi78, and UAB_Phi87)1123 as oral therapy in Salmonella -infected poultry under farm-like conditions.…”

Effects of purple prairie clover (Dalea purpurea Vent.) on feed intake, nutrient digestibility and faecal shedding of Escherichia coli O157:H7 in lambs

“…Contamination of carcasses during slaughter and processing is the primary manner in which E. coli O157:H7 is transferred to meat products (Elder et al, 2000;Duffy et al, 2006). Consequently, on-farm intervention strategies targeted at reducing levels of E. coli O157:H7 in the digestive tract prior to slaughter may reduce the incidences of foodborne illness associated with this pathogen (Elder et al, 2000;Stanford et al, 2010). Presently, there is no cost-effective means to consistently reduce the concentration of E. coli O157:H7 in the digestive tract of ruminants.…”

Four Escherichia coli O157:H7 Phages: A New Bacteriophage Genus and Taxonomic Classification of T1-Like Phages

“…Lytic phages offer promise in the prevention and therapy of bacterial infections in humans [9], livestock [10], [11] and plants [12] and have been employed to decontaminate processed foods and agricultural products [9], [10]. However, the use of phage therapy to target bacterial pathogens such as STEC O157:H7 [13], [14] and Salmonella [15], [16] in the digestive tract of livestock remains challenging. Factors such as the development of phage resistance, the complexity of predator-prey relationships between phages and hosts, the diversity and abundance of microflora in the gastro-intestinal tract all may undermine the effectiveness of phage therapy.…”