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Abstract - Phenotypic and genetic characterization of a non-hemolytic variant of
Listeria monocytogenes from cold-smoked salmon, Food Microbiology 15:329-337, 1998
Phenotypic and genetic characterization of a non-hemolytic variant of
Listeria monocytogenes from cold-smoked salmon
Strom, M. S. 1998. Food Microbiol. 15:329-337.
The identity of 11 strains of Listeria monocytogenes and L. innocua isolated
from various processed seafood products was confirmed by the polymerase chain
reaction (PCR). All species identities determined by a combination of selective
media, beta-hemolysis, and biochemical fermentation profiles were confirmed by PCR,
with one exception. One strain (4-4), previously identified as L. innocua
because of the lack of hemolysis on blood agar, was shown to be L.
monocytogenes. In order to determine whether this isolate was a weakly
hemolytic variant and thus potentially virulent, or whether it was truly unable
to express listeriolysin (LLO), a number of phenotypic and genetic
characterizations were performed. The strain was competent for expression of
other L. monocytogenes virulence factors and characteristics such as the
phosphatidylinositol-specific phospholipase C and the ability to adhere to and
invade Caco-2 and J774 cells, but could not grow intracellularly and was
avirulent in mice. DNA sequencing of the LLO gene (hly) from strain 4-4 showed
that the genetic lesion was a single base-pair deletion, resulting in a
frame-shift and subsequent stop codon in the translated open reading frame.
Such a mutation is unique from those seen in previously described naturally
occurring non-hemolytic L. monocytogenes strains.
last modified
01/05/2006
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