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Evaluation of ALOA plating medium for its suitability to recover high pressure‐injured Listeria monocytogenes from ground chicken meat
Author(s) -
Jantzen M.M.,
Navas J.,
De Paz M.,
Rodríguez B.,
Da Silva W.P.,
Nuñez M.,
MartínezSuárez J.V
Publication year - 2006
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.2006.01950.x
Subject(s) - listeria monocytogenes , agar , incubation , food science , microbiology and biotechnology , listeria , biology , chromogenic , growth medium , agar plate , isolation (microbiology) , plating (geology) , bacteria , chemistry , chromatography , biochemistry , genetics , paleontology
Aims: To evaluate a chromogenic plating medium for the isolation of sublethally injured cells of Listeria monocytogenes from processed foods. Methods and Results: The inactivation of L. monocytogenes at pressures up to 400 MPa and 12°C in ground chicken meat was employed to examine the recovery of high‐pressure injured cells. Before and after different repair incubation periods at 30°C in a nonselective broth, samples were plated onto a selective and differential agar [Agar Listeria according to Ottaviani and Agosti (ALOA)] and in the same medium supplemented with 4% sodium chloride (ALOA‐S), and incubated at 37°C. Sublethally injured cells were able to grow when directly plated onto the ALOA medium, without a previous repair incubation period. However, only uninjured cells grew on the ALOA‐S medium. Conclusions: Sublethally injured cells of L. monocytogenes can be quantified by subtracting counts on ALOA‐S medium from counts on ALOA medium. Significance and Impact of the Study: Possible applications include direct enumeration on ALOA of stressed cells of L. monocytogenes in foods with more than 100 colony forming units per gram.