Evaluation of ALOA plating medium for its suitability to recover high pressure-injured Listeria monocytogenes from ground chicken meat.
OBJECTIVE
To evaluate a chromogenic plating medium for the isolation of sublethally injured cells of Listeria monocytogenes from processed foods.


RESULTS
The inactivation of L. monocytogenes at pressures up to 400 MPa and 12 degrees 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 degrees 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 degrees 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.


CONCLUSIONS
Possible applications include direct enumeration on ALOA of stressed cells of L. monocytogenes in foods with more than 100 colony forming units per gram.
Jantzen
M M
MM
Departamento de Tecnología de Alimentos, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain.
Navas
J
J
de Paz
M
M
Rodríguez
B
B
da Silva
W P
WP
Nuñez
M
M
Martínez-Suárez
J V
JV
D000818:Animals; D002645:Chickens; D015169:Colony Count, Microbial; D003470:Culture Media; D005516:Food Microbiology; D005519:Food Preservation; D008089:Listeria monocytogenes / Q000254:growth & development / Q000302:isolation & purification*; D008460:Meat / Q000382:microbiology; D011202:Poultry Products / Q000382:microbiology*; D011312:Pressure
D003470:Culture Media