Selection and identification of a Listeria monocytogenes target strain for pulsed electric field process optimization.
Nine Listeria monocytogenes strains were treated individually with a continuous pulsed electric field (PEF) apparatus, and their sensitivities to the treatment were compared at 25 kV/cm. When cell suspensions of these strains in 0.1% NaCl (pH 7.0) were treated at 23 degrees C for 144 micro s, inactivation ranged from 0.7 to 3.7 log(10) CFU/ml. Inactivation by 72- micro s PEF treatments at 37 degrees C ranged from 0.3 to 2.5 log(10) CFU/ml. L. monocytogenes OSY-8578 was substantially more resistant than other strains when cells were PEF treated in 0.1% NaCl, whereas Scott A was one of the most sensitive strains. The superiority of OSY-8578's resistance to that of Scott A was confirmed in 50% diluted acid whey (pH 4.2). Changes in sensitivity to PEF during phases of growth were minimal in OSY-8578 and substantial in Scott A. Use of L. monocytogenes OSY-8578, therefore, is recommended in studies to optimize PEF processes that target L. monocytogenes. The nine L. monocytogenes strains were genotyped with pulsed-field gel electrophoresis (PFGE) and arbitrarily primed PCR (AP-PCR) techniques. These strains were better differentiated with PFGE than with AP-PCR. The target strain (OSY-8578) was characterized by both molecular typing techniques, but resistance to PEF, in general, was not associated with a particular genotype group.
Lado
Beatrice H
BH
Department of Food Science and Technology, The Ohio State University, Columbus 43210, USA.
Yousef
Ahmed E
AE
D015169:Colony Count, Microbial; D003470:Culture Media; D004558:Electric Stimulation / Q000379:methods*; D016521:Electrophoresis, Gel, Pulsed-Field; D005516:Food Microbiology; D005838:Genotype; D008089:Listeria monocytogenes / Q000145:classification* / Q000235:genetics / Q000254:growth & development*; D016133:Polymerase Chain Reaction / Q000379:methods*
D003470:Culture Media