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Research Project: CONTROL OF HUMAN PATHOGENS ASSOCIATED WITH ACIDIFIED PRODUCE FOODS

Location: Food Science Research

Title: Escherichia coli O157:H7 bacteriophage (phi)241 isolated from an industrial cucumber fermentation at high acidity and salinity

Author
item LU, ZHONGING - Kennesaw State University
item Breidt, Frederick

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2015
Publication Date: 2/17/2015
Publication URL: http://handle.nal.usda.gov/10113/60640
Citation: Lu, Z., Breidt, F. 2015. Escherichia coli O157:H7 bacteriophage (phi)241 isolated from an industrial cucumber fermentation at high acidity and salinity. Frontiers in Microbiology. 6:67. doi: 10.3389/fmicb.2015.00067.

Interpretive Summary: Bacterial viruses only infect bacteria (not humans) and are widespread in nature, perhaps the most common form of life on earth. We isolated a bacterial virus from a vegetable fermentation that infects and kills a disease causing bacterium (Escherichia coli). We determined that the virus only infects one type of E. coli, which are designated O157:H7, which can cause fatal infections in humans. We found that other closely related strains of E. coli are not infected and the virus uniquely attacks O157:H7 strains of these bacteria. The bacterial virus can survive in salt and acid conditions typical of vegetable fermentations, and may be stable in a variety of foods. We characterized the virus to determine the rate of reproduction in host cells, analyzed the virus structure and the viral DNA. Because of the stability of the virus in salt and acidic foods, it may have use in killing the O157:H7 strains of E. coli which may be present in a variety of foods, including acidic foods.

Technical Abstract: A novel phage, (phi)241, specific for Escherichia coli O157:H7 was isolated from an industrial cucumber fermentation where both acidity (pH less than or equal to 3.7) and salinity (greater than or equal to 5% NaCl) were high. The phage belongs to the Myoviridae family. Its latent period was 15 min and average burst size was 53 phage particles per infected cell. The phage was able to lyse 48 E. coli O157:H7 strains, but none of the 18 non-O157 strains (including E. coli O104:H7) or the 2 O antigen-negative mutants of O157:H7 strain, 43895 (delta) per (also lacking H7 antigen) and F12 (still expressing H7 antigen). However, the phage was able to lyse a per-complemented strain (43895 (delta) perComp) which expresses O157 antigen. These results indicated that phage (phi)241 is specific for O157 antigen, and E. coli strains lacking O157 antigen were resistant to the phage infection, regardless of the presence or absence of H7 antigen. SDS-PAGE profile revealed at least 13 structural proteins of the phage. The phage DNA was resistant to many commonly used restriction endonucleases, suggesting the presence of modified nucleotides in the phage genome. At the multiplicity of infection of 10, 3, or 0.3, the phage caused a rapid cell lysis within 1 or 2 h, resulting in 3.5- or 4.5-log-unit reduction in cell concentration. The high lytic activity, specificity and tolerance to low pH and high salinity make phage (phi)241 a potentially ideal biocontrol agent of E. coli O157:H7 in various foods. To our knowledge, this is the first report on E. coli O157:H7 phage isolated from high acidity and salinity environment.