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Acid and heat tolerance of persistent and nonpersistent Listeria monocytogenes food plant strains
Author(s) -
Lundén J.,
Tolvanen R.,
Korkeala H.
Publication year - 2008
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.2007.02305.x
Subject(s) - listeria monocytogenes , strain (injury) , biology , persistence (discontinuity) , contamination , microbiology and biotechnology , food science , bacteria , ecology , genetics , geotechnical engineering , engineering , anatomy
Aims: Acid and heat tolerance of 17 persistent and 23 nonpersistent Listeria monocytogenes strains, recovered from three meat‐processing plants, were investigated. Methods and Results: The isolates were genotyped by pulsed‐field gel electrophoresis and categorized into persistent strains according to the frequency of the strain and duration of the contamination. The persistent and nonpersistent strains were challenged to acidic conditions (pH 2·4 for 2 h, 1 mol l −1 HCl were used to acidify the suspension) and to heat (55°C for 40 min) to receive a reduction in cell count. Listeria monocytogenes strains showed large variation in acid tolerance (over 6 log units) and in heat tolerance (3 log units). The persistent strains showed higher tolerance to acidic conditions than the nonpersistent strains (Student’s t ‐test, P = 0·02), but significant differences in heat tolerance between persistent and nonpersistent strains were not observed. Conclusions: The results indicate that acid tolerance may have an effect on the persistence of L. monocytogenes contamination. Significance and Impact of the Study: This study highlights the fact that there are great differences in acid and heat tolerances between L. monocytogenes strains, and the preventive measures should be designed to be effective against the most tolerant strains.