Foodsafetycentre.com.au

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 Salmonella enteritidis 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 isolates likely 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 Produced by tfor Meat & Livestock Australia
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