Determination of the changes in the gastric fluid endurance of O157 and non-O157 Shiga toxin-producing Escherichia coli
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ORIGINAL ARTICLE
Determination of the changes in the gastric fluid endurance of O157 and non-O157 Shiga toxin-producing Escherichia coli during storage of experimentally produced beef frankfurter ¨ NU ¨ L1 Su¨meyye Betu¨l BOZATLI1 • Abdullah DI˙KI˙CI˙2 • Bu¨lent ERGO
Revised: 8 September 2020 / Accepted: 17 September 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract Resistance of Shiga toxin-producing Escherichia coli (STEC) O157:H7 and serogroups O103, O26 and O145 to synthetic gastric fluid (SGF, pH 1.5) were investigated during frankfurter storage. Pathogens were inoculated (5 ± 1 log10 cfu g-1) on frankfurters and frankfurters were stored at 4 °C for 75 days in vacuum packages. Population changes of the competitive flora and STEC, changes in the pH of the frankfurters and resistance of STEC to SGF were monitored on days 0, 15, 30, 45, 60 and 75 of frankfurter storage. Direct synthetic gastric fluid (DSGF) challenges were also conducted to assess pathogen resistance without being effected by frankfurters, by inoculating pathogen cultures directly into SGF. Results showed that acid resistance of O145 and O26 was stronger than that of O103 and O157 during frankfurter storage. Resistance of O103 to SGF was better than that of O157 during frankfurter storage but, was similar to that of O157 during DSGF challenges. Results indicate that acid resistance of some strains of STEC pathogens might differentiate during storage of frankfurters. Different resistance capabilities to SGF were observed in the STEC strains when inoculated and stored on frankfurters than directly inoculated in the SGF. Keywords Acid resistance Competitive flora STEC Frankfurter Synthetic gastric fluid
¨ NU ¨L & Bu¨lent ERGO [email protected] 1
Department of Food Engineering, Faculty of Engineering, Manisa Celal Bayar University, Manisa, Turkey
2
Department of Food Engineering, Faculty of Engineering, Us¸ ak University, Us¸ ak, Turkey
Introduction Shiga toxin-producing E.coli (STEC) is a group of pathogenic E.coli which produce Shiga toxin and can cause illnesses with a wide range of symptoms, ranging from mild non-bloody diarrhea to hemolytic uremic syndrome (HUS) in humans (World Health Organization 2018). STEC serogroups other than O157:H7 are called non-O157 STECs and since the older laboratory practices did not identify non-O157 STECs, their role in STEC infections was unrecognized (CDC, 2014). The large O104:H4 outbreak in 2011 (originated from Germany) has gained more attention to non-O157 STECs (Burger 2012). The non-O157 STEC serogroups which frequently linked to diseases in the USA (O26, O45, O103, O111, O121 and O145) were named as the ‘‘big six’’ or ‘‘top six’’ (USDA 2010). The main source of transmission is cattle but other ruminants can also cause STEC transmission to humans. The infectious dose of STEC is notably low and adequate cooking of ground meat is advised in order to avoid STEC infections (Hunt 2010). Infection can occur via undercooked ground beef, unpasteurized milk or juic
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