title: Inactivation of Escherichia coli O157 Bacteriophages by Using a Mixture of Ferrous Sulfate and Tea Extract.
abstract: Bacteriophages (phages) have been used for biocontrol of Escherichia coli O157 and other pathogenic bacteria in many different matrices and foods, but few studies have included inactivation of residual phages in culture medium before plating and enumeration of surviving host bacteria for the assessment of phage efficacy. This oversight may lead to overestimation of phage efficacy. The ability of virucidal solution containing a mixture of ferrous sulfate [iron(II) sulfate, FeSO4] and tea extract [Fe(II)T] to inactivate residual T5-like, T1-like, T4-like, and rV5-like phages was assessed using E. coli O157 as the host. At concentrations of ≥10 mM FeSO4, all phages were not detected after 20 min in a broth culture model. Compared with the virucidal solution-free samples (1 to 96% recovery), Fe(II)T (10 mM FeSO4 plus 15% tea extract) recovered a greater (P < 0.01) number of E. coli O157 from phage-treated broth culture (97 to 100% recovery) and beef samples (52 to 100% recovery). Moreover, with the addition of Fe(II)T, the number of bacteria surviving after exposure to T5-like or T4-like phages was greater (P < 0.01) than that after exposure to T1-like or rV5-like phages. Consequently, use of a virucide for phage inactivation is recommended to improve the accuracy of evaluations of phage efficacy for biocontrol of E. coli O157.
authors.affiliation: China Institute of Food and Drug Control, Hohhot, Inner Mongolia, People's Republic of China, 010020; Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada T1J 4B1; Inner Mongolia Agricultural University, College of Animal Science, Hohhot, Inner Mongolia, People's Republic of China 010018.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: Inner Mongolia Agricultural University, College of Animal Science, Hohhot, Inner Mongolia, People's Republic of China 010018.
authors.forename: Ruiqiang
authors.initials: R
authors.lastname: Meng
authors.affiliation: Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada T1J 4B1; College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong, People's Republic of China 510642.
authors.forename: Jiaying
authors.initials: J
authors.lastname: Wang
authors.affiliation: Alberta Agriculture and Forestry, Agriculture Centre, Lethbridge, Alberta, Canada T1J 4V6. dongyan.niu@gov.ab.ca.
authors.forename: Yan D
authors.initials: YD
authors.lastname: Niu
authors.affiliation: Inner Mongolia Agricultural University, College of Animal Science, Hohhot, Inner Mongolia, People's Republic of China 010018.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Li
authors.affiliation: Alberta Agriculture and Forestry, Agriculture Centre, Lethbridge, Alberta, Canada T1J 4V6.
authors.forename: Kim
authors.initials: K
authors.lastname: Stanford
authors.affiliation: Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada T1J 4B1.
authors.forename: Tim A
authors.initials: TA
authors.lastname: McAllister
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry; D000998:Antiviral Agents / Q000737:chemistry; D002417:Cattle; D003090:Coliphages / Q000187:drug effects*; D024881:Drug Resistance, Bacterial; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary; D019453:Escherichia coli O157 / Q000821:virology*; D005296:Ferrous Compounds / Q000737:chemistry*; D005516:Food Microbiology; D008460:Meat / Q000382:microbiology; D015203:Reproducibility of Results; D013662:Tea / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D000998:Antiviral Agents; D005296:Ferrous Compounds; D013662:Tea; C020748:ferrous sulfate