January 2010 Issue 23 Meat Safety News Digest A collection of recent news relevant to the safety of red meat prepared by the Food Safety Program of Meat & Livestock Australia, for SAFEMEAT Stakeholders PREVALENCE
Results from the study showed that L. monocytogenes was present in both faecal
The risk of Listeria monocytogenes
and environmental samples, with greatest
contamination in beef cattle operations
prevalence observed in samples collected
nature and ability to persist within food
makes this organism a serious concern for
reservoirs can lead to confounding routes
of transmission to food environments. As
Prevalence of Escherichia coli O157:H7
such, knowledge of the distribution within
in gut contents of beef cattle at slaughter
essential for the development of effective
prevalence of L. monocytogenes in
contamination of the hide is a likely source
of E. coli O157:H7 transmission. As such,
and to identify factors associated with risk
controls, knowledge on the prevalence of
work looked at cow–calf and feedlot beef
E. coli O157:H7 throughout these sites is
operations three times per year over three
recently investigated the prevalence of E. coli O157:H7 in the contents of the rumen,
cecum, colon and rectum of beef cattle at
unambiguous identification of the target
CONTAMINATION AND CONTROL
plating on selective medium, agglutination
Field tests planned for E. coli vaccines
detection of virulence genes. This lengthy
A vaccine targeting E. coli O157:H7
in cattle would provide a valuable addition
identification. In addition to identification,
promising new vaccine against E. coli
O157:H7 is set to undergo extensive field
(pulsed-field gel electrophoresis). This
the recovered E. coli O157:H7 isolates
2001. The vaccine will be administered to
approximately 400,000 cattle in the tests.
suggesting persistent rather than sporadic
to be effective at reducing the prevalence
of E. coli O157:H7 in cattle by 65–75%, it
gastric locations were subjected to an acid
challenge to determine resistance to low
assessing this, and represents one of the
determining if the strains were adapted to
life within specific regions of the beef
release. However, at $3 (US) a dose, with
costly at this stage for wide spread use.
highest prevalence overall. The majority of
Does acid resistance give E. coli an advantage in beef cattle and can adding probiotics inhibit them?
localisation within the gastrointestinal tract
survival of E. coli strains within the acidic
of beef cattle, and highlights potential
gastrointestinal tract. This could facilitate
intervention strategies targeted at E. coli
reservoir of “acid resistant” E. coli strains
cleaning/sanitising treatments. In a recent
whether acid resistant E. coli strains
the ruminant digestive tract and whether
reduction efficacy at each exposure time
probiotics (beneficial microbial strains)
was found to be: strong acidic electrolysed
affects the survival of these E. coli strains.
water > sodium hypochlorite> slightly
acidic electrolysed water. This was found
resistant strains did indeed survive longer
to increase with exposure time (90 s > 60
s > 30 s) for all of the sanitisers tested.
which is commonly used in food industry,
incubations killed all of the strains tested,
independent of acid resistance. However,
the addition of probiotics had no effect on
survival of the E. coli strains in digestive
targeting the rumen compartment to limit
toxigenic E. coli. This could decrease
further passage through the digestive tract
influences E. coli O157:H7 biofilm formation E. coli has a range of mechanisms
molecular components of E. coli, under
the direction of the organism’s genetic
Comparison of the sanitisation potency of slightly acidic electrolysed water with other food sanitisers
effectiveness of sanitisers and sanitising
investigated the efficacy of slightly acidic
A well known survival strategy by E. coli is the ability to form biofilms. Biofilms
available chlorine) for sanitisation of pure
cultures of Staphylococcus aureus and E. coli in comparison to strong acidic
electrolyzed water (pH<5.0) and sodium
preservation, cleansing and sanitisation
that a specific E. coli H7:O157 genetic
element (plasmid O157) plays a role in the
these structures. This is the first time that
CHARACTERISATION
means of screening for high risk E. coli
populations, and could lead to a target for
Assessment of the ability of E. coli
the removal and control of biofilms within
O157:H7 strains isolated from human infections and cattle to cause disease and survive adverse environmental conditions
characterised as either clinical (has the
Responses of E. coli O157:H7, L.
ability to cause serious disease due to the
monocytogenes Salmonella
presence of shigatoxin genetic material)
enteritidis to pH, water activity and
and bovine–biased (absence of shigatoxin
temperature stress combinations monocytogenes and Salmonellaenteritidis
investigated whether the infective potential
are bacteria capable of surviving under a
of these broad groups actually differed.
range of adverse conditions. This can lead
production facilities despite apparently
that each type produced. In addition, the
recent study investigated the effects of
water activity) on growth and inactivation
parameters of E. coli O157:H7, L.
clinical and bovine–biased E. coli strains.
temperature was the greatest determinant
activity also had a measurable effect. L.
conditions, while the clinical group was
more likely to cause serious disease. The
inactivation levels of the organisms tested.
The work may help evaluate the safety of
of the ecology of E. coli, supports the
current broad grouping of E. coli O157:H7
types and importantly, clearly identifies
containing high numbers of E. coli are a
high risk E. coli O157:H7 strains.
bacteria to beef carcasses. In addition, the
study found that the truckload may be an
important factor for transmission of E. coli Does faecal shedding of Escherichia coli O157 isolates form beef cattle
isolates from different trucks and harvest
contaminate the beef carcasses?
Faecal shedding of E. coli O157:H7
alone is not responsible for transmission
on the transmission of E. coli from farm-to-
molecular techniques to see if E. coli
carcass. It identified high shedding cattle
O157:H7 isolated from cattle faeces were
the same strains as those recovered from
highlighted truck transport as a focal point
pre-intervention beef carcasses. This was
essential intervention step in the farm–to–
Farm-to-fork characterisation of E. coli associated with feedlot cattle with a
observable genetic profiles of E. coli known history of antimicrobial use
the prevalence of antimicrobial resistant E. coli recovered from cattle fed antimicrobial
contamination and faecal shedding of E. coli O157:H7 at harvest. Those with the
One hundred and seventy-four E. coli
envisceration, ground beef stored at 5°C
for 1 and 8 days, the abattoir environment
evisceration carcasses (39), faeces (139)
and air. Prevalence of E. coli isolates
resistant to ampicillin and tetracycline
researchers tested the recovered E. coli
isolates on their susceptibility to eleven
multiple samples, from different trucks,
resistant E. coli had a high prevalence
(resistance to ampicillin was greater than
presence of high shedder faecal isolates
tetracycline, with resistance to up to nine
concluded that the antimicrobial resistant
E. coli isolateslikely contaminate meat
products during slaughter, and enter the
food chain irrespective of the cattle being
Effect of frozen storage conditions on microbiological and sensory quality of beef at different states of ageing
microbiological and sensory quality of a
specific beef type (Morucha x Charolais)
PACKAGING AND STORAGE Effects of temperature and pH on the growth of bacteria isolated from blown
microbiological quality of the beef. The
packs of vacuum-packaged beef
temperatures tested (-20 and -80 degrees
parameter. The microbiological quality of
and the effects of temperature and pH on
the beef was acceptable in all instances,
tolerant microbes was observed after both
Leuconostoc mesenteroides, Lactococcus lactis, Carnobacterium maltaromaticum,
and Clostridium estertheticum, with L.
increased storage time, as did tenderness
mesenteroides being the most prevalent.
All of the bacterial species grew well in
medium. Only L. mesenteroides and L.
growth by spoilage bacteria and provides
insight into the ecology of meat spoilage
microorganisms. The results suggest that
primarily by fluctuations in the pH within
to a lesser extent, the storage temperature.
The work has implications in the storage
Pulsed light inactivation of Listeria
evident after 11 days in the nisin-activated
monocytogenes different
packaging, with similar results observed
plastic films
for enterobacteria after 22 and 32 days.
determine the spoilage populations to the
species level. Results indicated that the
technology through different plastic films
and was specifically targeted at Listeria monocytogenes.A 12-μm polyethylene
film, a 48-μm polyamide/polyethylene/vinyl
preservation of microbiological quality in
detailed the spoilage populations during
pulsed light treatment achieved the same
chilled storage of beef. The work supports
degree of inactivation (5 – 5.5 log colony
the use of nisin for extending the shelf-life
forming units / cm2) in both wrapped and
unwrapped samples for all of the plastic
films. These results indicate that pulsed
Development of spoilage microbiota in nisin-activated packaging
microbial populations causing spoilage of chilled beef during storage, and the
ANTIMICROBIAL RESISTANCE AND SUSCEPTIBILITY
packaging material in preventing spoilage.
Nisin is a polycyclic peptide produced by
Prevalence and antibiotic susceptibility Lactococcus lactis. It is used to extend the
of Listeria spp. isolated from raw meat and retail foods
activated packaging materials were tested
during storage of beef at 1°C. Spoilage
and antibiotic resistance of Listeria spp.
media. A significant reduction (1 – 3 logs)
recovered from raw meats and other retail
products in the country. Prevalence in raw
dominant species recovered was E.
to first and second class antibiotics (1st
faecalis (87%), followed by E. faecium
and 2nd choice by doctors for Listeria
(10%). A total of 199 isolates were
resistance was detected, with >90% of the
antimicrobial resistance, the researchers
E. faecalis isolates resistant to lincomycin
state that increased resistance of Listeria
from all sample sites. Differences in both
species to antimicrobials in recent years
the antimicrobial resistance profiles and
the level of resistance were noted among
proportion of the E. faecalis isolates
antimicrobial resistance in Enterococcus
processing with evidence for the transfer
of resistance to locations throughout the
plant. Importantly, the study highlights the
Characterisation antimicrobial
need for increased focus on antimicrobial
resistance Enterococcus
resistance within these facilities, and a
recovered from a commercial beef
review of transmission and contamination
processing plant
animals. These bacteria cause a range of
clinical infections in humans, and are often
Characterisation of resistant E. coli in faecal deposits from cattle fed sub-
antimicrobials. The organism is commonly
therapeutic levels of antimicrobials
examined faecal deposits from cattle fed
that were and were not fed antimicrobial
resistance of Enterococcus spp recovered
tetracycline) for the persistence of total E.
from a commercial beef processing plant.
coli and numbers and proportions of
Enterococcus spp. including conveyers
resistant E. coli. The deposits were
12 times during this period. All E. coli
number of tetracycline-resistant E. coli
antibiotic showed a significant effect on the numbers of ampicillin and tetracycline
resistant E. coli. The study concluded that
antimicrobial resistant E. coli, and that
antimicrobial resistant E. coli for prolonged
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antibiotic showed a significant effect on the numbers of ampicillin and tetracycline
resistant E. coli. The study concluded that
antimicrobial resistant E. coli, and that
antimicrobial resistant E. coli for prolonged
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