{"title":"大肠杆菌O157:H7在咸鱼中进入可存活但不可培养状态后热灭活的变化","authors":"M. Khezri, M. Rezaei, A. Mobarez, M. Zolfaghari","doi":"10.22124/CJES.2021.5130","DOIUrl":null,"url":null,"abstract":"Many species of non-sporulating bacteria including Escherichia coli can enter into a viable but non-culturable (VBNC) state under stress conditions. In this study, the change in thermal resistance of E. coli O157:H7 after entering into the VBNC state in salted silver carp, Hypophthalmichthys molitrix, was investigated. E. coli O157:H7 was inoculated on the fish control group (TF) and on those fish with 30% NaCl (TF + 30% NaCl) at room temperature. Culturability of bacteria was determined using routine culture and colony counting on Sorbitol MacConkey agar. When bacteria were non-cultivable, the RT-PCR of 16S rRNA gene (including direct extraction and purification of RNA, DNase I treatment for removing DNA contamination, cDNA synthesis and electrophoresis of PCR products of cDNA) was used to detect VBNC E. coli O157:H7. Also, cultivable and VBNC E. coli O157:H7 were individually heat-treated at 55, 62 and 70 °C for 5 min. The samples were cooled and after 24 h, the thermal resistance of bacteria was determined through viability detection using RT-PCR of 16S rRNA gene. The culturability of bacteria was kept in fish treatment but they were non-cultivable in fish under 30% NaCl after 5 days. The positive expression of 16S rRNA in all studied treatments indicated the entering of E. coli O157:H7 into the VBNC state in fish treatment under 30% NaCl. Moreover, the RT-PCR of 16S rRNA gene showed that only VBNC forms of E. coli O157:H7 showed viability at 62 °C for 5 min which indicated the increased resistant of VBNC bacteria to the thermal inactivation. The ability of E. coli O157:H7 to enter into VBNC state in salted fish and also the increase of its thermal resistance suggest that VBNC E. coli O157: H7 can be considered as critical threat to public health and food safety.","PeriodicalId":9640,"journal":{"name":"caspian journal of environmental sciences","volume":"19 1","pages":"629-637"},"PeriodicalIF":0.0000,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The change in heat inactivation of Escherichia coli O157:H7 after entering into the viable but non-culturable state in salted fish, Hypophthalmichthys molitrix\",\"authors\":\"M. Khezri, M. Rezaei, A. Mobarez, M. Zolfaghari\",\"doi\":\"10.22124/CJES.2021.5130\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Many species of non-sporulating bacteria including Escherichia coli can enter into a viable but non-culturable (VBNC) state under stress conditions. In this study, the change in thermal resistance of E. coli O157:H7 after entering into the VBNC state in salted silver carp, Hypophthalmichthys molitrix, was investigated. E. coli O157:H7 was inoculated on the fish control group (TF) and on those fish with 30% NaCl (TF + 30% NaCl) at room temperature. Culturability of bacteria was determined using routine culture and colony counting on Sorbitol MacConkey agar. When bacteria were non-cultivable, the RT-PCR of 16S rRNA gene (including direct extraction and purification of RNA, DNase I treatment for removing DNA contamination, cDNA synthesis and electrophoresis of PCR products of cDNA) was used to detect VBNC E. coli O157:H7. Also, cultivable and VBNC E. coli O157:H7 were individually heat-treated at 55, 62 and 70 °C for 5 min. The samples were cooled and after 24 h, the thermal resistance of bacteria was determined through viability detection using RT-PCR of 16S rRNA gene. The culturability of bacteria was kept in fish treatment but they were non-cultivable in fish under 30% NaCl after 5 days. The positive expression of 16S rRNA in all studied treatments indicated the entering of E. coli O157:H7 into the VBNC state in fish treatment under 30% NaCl. Moreover, the RT-PCR of 16S rRNA gene showed that only VBNC forms of E. coli O157:H7 showed viability at 62 °C for 5 min which indicated the increased resistant of VBNC bacteria to the thermal inactivation. The ability of E. coli O157:H7 to enter into VBNC state in salted fish and also the increase of its thermal resistance suggest that VBNC E. coli O157: H7 can be considered as critical threat to public health and food safety.\",\"PeriodicalId\":9640,\"journal\":{\"name\":\"caspian journal of environmental sciences\",\"volume\":\"19 1\",\"pages\":\"629-637\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2021-10-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"caspian journal of environmental sciences\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.22124/CJES.2021.5130\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"Agricultural and Biological Sciences\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"caspian journal of environmental sciences","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.22124/CJES.2021.5130","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Agricultural and Biological Sciences","Score":null,"Total":0}
The change in heat inactivation of Escherichia coli O157:H7 after entering into the viable but non-culturable state in salted fish, Hypophthalmichthys molitrix
Many species of non-sporulating bacteria including Escherichia coli can enter into a viable but non-culturable (VBNC) state under stress conditions. In this study, the change in thermal resistance of E. coli O157:H7 after entering into the VBNC state in salted silver carp, Hypophthalmichthys molitrix, was investigated. E. coli O157:H7 was inoculated on the fish control group (TF) and on those fish with 30% NaCl (TF + 30% NaCl) at room temperature. Culturability of bacteria was determined using routine culture and colony counting on Sorbitol MacConkey agar. When bacteria were non-cultivable, the RT-PCR of 16S rRNA gene (including direct extraction and purification of RNA, DNase I treatment for removing DNA contamination, cDNA synthesis and electrophoresis of PCR products of cDNA) was used to detect VBNC E. coli O157:H7. Also, cultivable and VBNC E. coli O157:H7 were individually heat-treated at 55, 62 and 70 °C for 5 min. The samples were cooled and after 24 h, the thermal resistance of bacteria was determined through viability detection using RT-PCR of 16S rRNA gene. The culturability of bacteria was kept in fish treatment but they were non-cultivable in fish under 30% NaCl after 5 days. The positive expression of 16S rRNA in all studied treatments indicated the entering of E. coli O157:H7 into the VBNC state in fish treatment under 30% NaCl. Moreover, the RT-PCR of 16S rRNA gene showed that only VBNC forms of E. coli O157:H7 showed viability at 62 °C for 5 min which indicated the increased resistant of VBNC bacteria to the thermal inactivation. The ability of E. coli O157:H7 to enter into VBNC state in salted fish and also the increase of its thermal resistance suggest that VBNC E. coli O157: H7 can be considered as critical threat to public health and food safety.