|KIM, GWANG HEE - KANGWON NATIONAL UNIVERSITY|
|OH, DEOG HWAN - KANGWON NATIONAL UNIVERSITY|
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2015
Publication Date: 8/5/2015
Citation: Kim, G., Breidt, F., Fratamico, P.M., Oh, D. 2015. Acid Resistance and molecular characterization of Escherichia coli O157:H7 and different non-O157 Shiga toxin-producing E. coli serogroups. Journal of Food Science. doi: 10.1111/1750.3841.12996.
Interpretive Summary: Harmful bacteria found as food contaminants that are known as Shiga toxin-producing Escherichia coli (STEC) can cause serious illnesses and death. E. coli O157:H7 is an important STEC; however, in recent years, other types of STEC bacteria have caused illnesses similar to those caused by O157:H7. One reason why STEC O157:H7 is able to cause illness is because it is not easily inactivated when exposed to acidic conditions in certain foods and also the acidic conditions in the human stomach. Research was conducted to understand whether eight different types of STEC, including O157:H7, could tolerate highly acidic conditions. The results showed similar survival of the eight types of STEC in acid solutions; however, some STEC bacteria were able to survive better than STEC O157:H7. This research enhances the understanding of the disease-causing potential of non-O157:H7 STEC bacteria and provides information to develop intervention strategies to control these harmful pathogens in food.
Technical Abstract: The objective of this study was to compare the acid resistance (AR) of seven non-O157 Shiga toxin-producing E. coli (STEC) strains belonging to serogroups O26, O45, O103, O104, O111, O121 and O145 with O157:H7 STEC isolated from various sources in 400 mM acetic acid solutions (AAS) at pH 3.2 and 30°C for 25 min with or without glutamic acid. Furthermore, the genetic relatedness of the STEC strains was analyzed with the repetitive sequence-based PCR (rep-PCR) method using a DiversiLabTM system. Results for a total of 52 strains ranged from 0.31-5.45 log reduction CFU/mL in the absence of glutamic acid and 0.02-0.33 CFU/mL in the presence of glutamic acid except for B0447 (O26:H11), B0452 (O45:H2), and B0466 (O104:H4) strains. Particularly, strains belonging to serogroups O111, O121 and O103 showed higher AR than serotype O157:H7 strains in the absence of glutamic acid. STEC O157:H7 and strains belonging to serogroups O111 and O121 exhibited similar DNA patterns for each serogroup/serotype with more than 95% similarity in the rep-PCR results. Surprisingly, the DNA pattern of B0458 (O103:H2) was similar to that of O157:H7 strains with 85% similarity, and the O103:H2 strain showed the highest AR to AAS among the O103 strains with 0.44 log reduction CFU/mL without glutamic acid. These results suggest that some non-O157 STEC strains may have higher AR than STEC O157:H7 strains under acidic conditions at different temperatures.