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A Focus on Listeria monocytogenes
Listeria monocytogenes (Lm) is the causative
bacteria of listeriosis, a very dangerous and
often deadly disease.
The CDC reports approximately 2,500 cases a
year, 500 of which are fatal. This is more than
Salmonella and Botulism.
Due to the ubiquitous nature of the bacteria, it
is among the most highly researched and
investigated foodborne pathogens in the
United States, Canada, and many other
countries.
Federal and state governments, universities,
and industries are actively conducting
research.
Effectively controlling Listeria monocytogenes
is challenging and requires intensive
management and resources.
Although, the risk of developing listeriosis is
low, the consequences are devastating for
both consumers and processors.
Research over the past decade has
concentrated on testing and detection
methods, control methods, and risk
assessments.


In 1998, one of the largest outbreaks of
Listeria monocytogenes occurred with a large
hot dog manufacturer.
The result was 15 adult deaths, six
stillbirths, and over one million pounds of
product recalled.
Listeria innocua transformed with an
antibiotic resistance plasmid as a thermalresistance indicator for Listeria
monocytogenes ( Document )
WVuJjMzPWRvY3VtZW50cyYzNz1pbmZv.
Journal of Food Protection 54(7) 519-523.
Listeria innocua PFEI is a chloramphenicol- and
erythromycin-resistant organism obtained by
electrotransforming L. innocua ATCC 33091 with
the plasmid pGK12.
L. innocua ATCC 33091 and L. innocua PFEI
were more heat resistant between 56 and 66
degC than Listeria monocytogenes F5069
and Scott A when evaluated in sterile
phosphate buffer or milk.
Decimal reduction times of each L. innocua strain were
1.5 to 3 times longer in either heating menstruum than
were D-values of the most heat resistant L.
monocytogenes strain studied (F5069).
L. innocua PFEI retained the plasmid during heating so
that, of 300 survivors evaluated, 100% were resistant
to chloramphenicol and 98% were resistant to
erythromycin.
Thus L. innocua ATCC 33091 or PFEI would be useful
indicator organisms to evaluate the lethality of thermal
processes with repect to L. monocytogenes.
L. innocua PFEI has the advantages that it could
easily be selected and enumerated among a large,
complex, background microflora, but it may not be
appropriate for application in a food processing
environemnt. LISTMO
http://www.onefish.org/servlet/CDSServlet?status=ND
0zODE5Mi50b3JsaWJJUEUyOTIyMSY2P
Gene disruption by plasmid integration in
Listeria monocytogenes: insertional
inactivation of the listeriolysin determinant lisA.
Wuenscher MD, Kohler S, Goebel W,
Chakraborty T.
Institut fur Genetik und Mikrobiologie, Universitat
Wurzburg, Federal Republic of Germany.
Mol Gen Genet. 1991 Aug;228(1-2):177-82.
A plasmid integration technique was
developed for insertional inactivation of
chromosomal Listeria monocytogenes genes.
A Listeria-Escherichia coli shuttle vector
(pLSV1) was constructed which carried the
temperature-sensitive gram-positive
replication origin from plasmid pTV32(Ts).
An internal fragment of the listeriolysin gene
(lisA) was cloned into pLSV1 to create
pLSV2.
In L. monocytogenes pLSV2 transformants,
plasmid pLSV2 integrated into the L.
monocytogenes chromosome at a frequency
of 2 x 10(-3) via lisA homology and these
cells could be selected at 42 degrees C
using a plasmid-encoded erythromycin
resistance.
Plasmid integration resulted in disruption of the
lisA gene, production of a truncated,
immunologically cross-reactive listeriolysin
protein and loss of the hemolytic phenotype.
An improved Listeria protoplast transformation
method is also described which facilitates
genetic manipulation of Listeria species.
PMID: 1909419 [PubMed - indexed for
MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?c
md=Retrieve&db=PubMed&list_uids=1909419&
dopt=Abstract
Institution: KING FAISAL SPECIALIST HOSP
Conjugative Mobilization of the Rolling-Circle Plasmid
pIP823 from Listeria monocytogenes BM4293 among
Gram-Positive and Gram-Negative Bacteria
Emmanuelle Charpentier, Guy Gerbaud, and Patrice
Courvalin*
Unité des Agents Antibactériens, Institut Pasteur,
75724 Paris Cedex 15, France
Received 19 October 1998/Accepted 3 April 1999
http://jb.asm.org/cgi/content/abstract/181/11/3368
We determined the sequence and genetic
organization of plasmid pIP823, which contains the
dfrD gene; dfrD confers high-level trimethoprim
resistance to Listeria monocytogenes BM4293 by
synthesis of dihydrofolate reductase type S2. pIP823
possessed all the features of the pUB110/pC194
plasmid family, whose members replicate by the
rolling-circle mechanism.
The rep gene encoded a protein identical to RepU,
the protein required for initiation of the replication of
plasmids pTB913 from a thermophilic Bacillus sp.
and pUB110 from Staphylococcus aureus.
The mob gene encoded a protein with a high
degree of amino acid identity with the Mob
proteins involved in conjugative mobilization
and interplasmidic recombination of pTB913
and pUB110. The host range of pIP823 was
broad and included L. monocytogenes,
Enterococcus faecalis, S. aureus, Bacillus
subtilis, and Escherichia coli. In all these
species, pIP823 replicated by generating
single-stranded DNA and was stable.
Conjugative mobilization of pIP823 was
obtained by self-transferable plasmids between
L. monocytogenes and E. faecalis, between
L. monocytogenes and E. coli, and between
strains of E. coli, and by the streptococcal
conjugative transposon Tn1545 from
L. monocytogenes to E. faecalis, and from
L. monocytogenes and E. faecalis to E. coli.
These data indicate that the gene flux observed
in nature from gram-positive to gram-negative
bacteria can occur by conjugative mobilization.
Our results suggest that dissemination of
trimethoprim resistance in Listeria spp. and
acquisition of other antibiotic resistance
determinants in this species can be
anticipated.
* Corresponding author. Mailing address:
Unité des Agents Antibactériens, Institut
Pasteur, 28 rue du Dr. Roux, 75724 Paris
Cedex 15, France. Phone: (33) (1)
45 68 83 20. Fax: (33) (1) 45 68 83 19. Email: [email protected] .
Present address: New York University
Medical Center, Department of Cell Biology,
New York, NY 10016
Subtyping of Listeria monocytogenes on
the basis of plasmid profiles and arsenic
and cadmium susceptibility
J. McLauchlin, M.D. Hampton, S. Shah, E.J.
Threlfall, A.A. Wieneke & G.D.W. Curtis
The susceptibilities to arsenic and cadmium
together with the detection of plasmid DNA
were evaluated for use as epidemiological
markers for the subtyping of Listeria
monocytogenes. Plasmid DNA was detected
in 34% of 322 apparently unrelated isolates of
L. monocytogenes.
The resistance to cadmium and arsenic
differentiated 565 apparently unrelated cultures
into four groups, the smallest being 5% of
cultures resistant to both agents, and the largest
(53%) being sensitive to cadmium and resistant
to arsenic.
The resistance patterns to these agents and the
presence of plasmid DNA varied markedly
between the serotypes of the cultures. The
detection of plasmid DNA was strongly
associated with cadmium resistance in serogroup
1/2 cultures, but not within those of serogroup 4.
Arsenic resistance was not associated with
plasmid DNA. All methods were sufficiently
stable to be useful for epidemiological
investigations. The techniques described here
offer simple methods which can be easily
utilized in laboratories without a specialized
expertise for this bacterium.
http://www.blackwellsynergy.com/doi/abs/10.1046/j.13652672.1997.00238.x
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