Asit ve tuza adapte edilmiş Escherichia coli O157:H7 ve Listeria monocytogenes'in Türk sucuklarında yaşama düzeylerinin belirlenmesi
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Date
2010
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Fen Bilimleri Enstitüsü
Abstract
In this research, acid resistance levels of E. coli O157:H7 and L. monocytogenes have been examined under the conditions of acid and salt adaptations. In addition, the effect of acid and salt adaptations on the survival of E. coli O157:H7 and L. monocytogenes in Turkish sucuk have also been determined. E. coli O157:H7 and L. monocytogenes were adapted to pH 4.5; 5.0 and 5.5 for the periods of 1, 2, 3 and 4 hours. The survival of E. coli O157:H7 and L. monocytogenes that were adapted to acid have been ascertained at pH 3.0 and 3.5, and at pH 2.5, 3.0 and 3.5 respectively. The effects of organic acids (acetic, lactic and citric acids) and inorganic acids (HCl) on acid adaptation have also been studied.At the adaptation tests that were carried out on E. coli O157:H7, it has been found that 3 and 4 hours adaptation at pH 5.5 in case of using HCl; 3 hours adaptation in case of using acetic acid, and 3 and 4 hours adaptation in case of using lactic acid have been caused highest survival (p<0.01). On the other hand, in case of using citric acid, any notable increase was recorded in survival.It has been found that HCl, acetic acid and lactic acid adaptations at pH 3.5 have resulted in no increase in the survival of L. monocytogenes. In case of citric acid experiments, it has been found that maximal acid resistance was realized at the 3 hours adaptation at pH 4.5, 5.0 and 5.5 (p<0.05). It has been found that 3 hours adaptation at pH 4.5, and 1, 2, 3, and 4 hours adaptation at pH 5.0 and 5.5 have resulted in maximum increases in the survival of L. monocytogenes at pH 2.5 and pH 3.0 respectively (p<0.01).At the cross resistance tests, 2, 3, and 4 hours adaptation to acetic acid have been caused maximum level of increases in the cross resistance of E. coli O157:H7 to lactic acid (p<0.05). But, no significant increase has been observed in case of using HCl. It has been determined that HCl and citric acid adaptation did not increase the cross resistance of L. monocytogenes to lactic acid.In the salt adaptation tests, the cultures that were adapted to 3.5% NaCl for the period of 1 hour were left to incubation for 25 days, in 8% NaCl solution, at the temperatures of 4 ?C and 25 ?C. At the end of these tests, it has been determined that L. monocytogenes has not gained any resistance to salt, and salt resistance of E. coli O157:H7 in the culture, which was kept at 25 ?C (p<0.05), increased while the resistance in the culture, which was kept at 4 ?C did not increase.While acid adaptation enhanced the survival of E. coli O157:H7 in Turkish sucuk (p<0.01), not significant difference occur at the survival of L. monocytogenes. In addition, salt adaptation did not enhanced the survival of E. coli O157:H7 in Turkish sucuk.
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Mikrobiyoloji, Asit, sucuk