The hygienic efficiency of conventional and inverted lamb dressing systems

R.G. BELL AND S.C. HATHAWAY. 1996. Aerobic plate counts (APC 37°C and APC 25°C) and Escherichia coli enumerations (Petrifilm) were used to determine sources of bacterial contamination during sheep dressing, determine the hygienic efficacy of hand wash and knife 'sterilization'procedures and compare the hygiene efficiency of conventional and inverted sheep dressing systems. The major slaughterline sources of microbial contamination were: fleece > workers' hands > faecal pellets > knife blades. Aerobic plate counts (APC 37°C) exceeding log 4.4 cfu cm^-2 were considered indicative of direct fleece contact, whereas E. coli numbers exceeding log 3.3 cfu cm^-2 were considered indicative of direct faecal contact. A 44°C water hand rinse removed 90% of the microbial contamination from workers' hands, but rinsed hands, particularly those contacting the fleece, still carried a microbial population exceeding log 4.0 cfu cm^-2. A 44°C rinse followed by an 82°C water dip reduced the contamination on knife blades to less than log 3.0 cfu cm^-2. Inverted dressing systems produced carcasses with a lower contamination level than conventional systems. With both systems little increase in contamination occurred after pelt removal. The areas of highest contamination were the forequarter region with inverted dressing and the hindquarter with conventional dressing. In both cases these regions are the sites where cuts are made through the skin. With both systems contamination around these cuts was entirely consistent with direct fleece contact resulting from 'rollback'.     

Effect of packaging conditions on the growth of micro-organisms and the quality characteristics of fresh mushrooms (Agaricus bisporus) stored at inadequate temperatures

Mushrooms were packed in two polymeric films (perforated and non-perforated PVC) and stored at 17 degrees C and 25 degrees C. The carbon dioxide and oxygen content inside the packages, aerobic mesophiles, Pseudomonas spp., faecal coliforms, Escherichia coli, anaerobic spores and major sensory factors (colour, texture, development stage and presence of moulds) were determined. The non-perforated packages had the highest contents of CO2 (6-7%), the lowest contents of O2 (0.013-0.17%) and the most desirable quality parameters (texture, development stage and absence of moulds). Pseudomonas spp. counts were around 1 logarithmic unit lower in mushrooms packaged in non-perforated film as the O2 concentrations were lower than in perforated film. The mushrooms themselves were inoculated with an enterotoxin A-producing strain of Staphylococcus aureus, packaged in overwrapped trays and stored at 17 and 25 degrees C. Staphylococcus aureus did not grow in the samples stored at 17 degrees C. Only slight growth was observed in mushrooms packaged with non-perforated film after 1 day at 25 degrees C. No enterotoxin was detected in any package. Faecal coliform counts were <2 log cfu g(-1). Escherichia coli was not isolated in any of the samples. At 25 degrees C, counts of anaerobic spores of around 2 log cfu g(-1) were detected in those mushrooms packaged in non-perforated film.     

Carvacrol and cinnamic acid inhibit microbial growth in fresh-cut melon and kiwifruit at 4 degrees and 8 degrees C

AIM: To establish whether or not carvacrol and cinnamic acid delay microbial spoilage of fresh-cut fruit. METHODS AND RESULTS: Dipping of fresh-cut kiwifruit in carvacrol solutions at 5-15 mM reduced total viable counts from 6.6 to < 2 log cfu g-1 for 21 d at 4 degrees C; however, undesirable colour and odour changes were also observed. Treatment with 1 mM of carvacrol or cinnamic acid reduced viable counts on kiwifruit by 4 and 1.5 log cfu g-1 for 5 d at 4 degrees C and 8 degrees C, respectively. Treatment of fresh-cut honeydew melon with 1 mM of carvacrol or cinnamic acid extended the lag phase of the microbial flora from less than 1 d in the untreated controls to 3 d at 8 degrees C and 5 d at 4 degrees C. Viable counts on the treated melon were 6 log cfu g-1 lower on Day 3 at 8 degrees C and 4 log cfu g-1 lower on Day 5 at 4 degrees C, compared with the untreated controls. IMPACT OF THE STUDY: Treatment with 1 mM of carvacrol or cinnamic acid delays spoilage of fresh-cut kiwifruit and honeydew melon at chill temperatures without adverse sensory consequences.     

Effectiveness of a steam-vacuum sanitizer for reducing Escherichia coli O157:H7 inoculated to beef carcass surface tissue

A steam-vacuum sanitizer reduced aerobic plate counts associated with bovine faecal contamination from 5.5 log₁₀ cfu cm⁻² to 3.0 ± 0.21 log₁₀ cfu cm⁻² on beef carcass short plates. The same beef carcass short plates inoculated wiht 7.6 ± 0.09 log₁₀ cfu cm⁻² Escherichia coli O157: H7 in faeces, yielded an average residual level of E. coli O157: H7 of 2.1 ± 0.21 log₁₀ cfu cm⁻² after steam-vacuum treatments. This study demonstrates the effectiveness of a steam-vacuum sanitizer for removing E. coli O157: H7 from beef carcasses.     

The effects of treating bovine hide with steam at subatmospheric pressure on bacterial numbers and leather quality

AIMS: To examine the effect of subatmospheric steam treatment on total viable counts (TVCs) on bovine hide and on the quality of derived leather. METHODS AND RESULTS: Pieces of bovine hide were heated to 75 degrees C (+/-2 degrees C) (n = 3) or 80 degrees C (+/-2 degrees C) (n = 3) for periods of 1, 10 or 20 s by the application of steam at subatmospheric pressure in a laboratory scale apparatus. Treated hide pieces and untreated controls were tanned and the quality of leather was assessed. Treatment at 80 degrees C (T80) reduced the TVC on hide pieces by 2.95 (1 s), 3.33 (10 s) and 3.99 (20 s) log10 CFU cm-2 (P > 0.05). Treatment at 75 degrees C (T75) reduced the TVC on hide pieces by 1.87 (1 s), 2.51 (10 s) and 2.56 (20 s) log10 CFU cm-2 (P > 0.05). The grain on all treated hides was damaged resulting in sueding on derived leather. Sueding was observed on 100% of surfaces from T80-treated samples and on 18 (1 s) to 84% (20 s) of the surfaces of T75 samples. CONCLUSIONS: The magnitude of TVC reductions achieved using T75 and T80 could limit the impact and scale of contamination transfer to the carcass during dehiding. However, because of the sueding observed on derived leather, it is unlikely that either T75 or T80 would be a commercially valid operation during routine slaughter operations. SIGNIFICANCE AND IMPACT OF THE STUDY: Hide decontamination would provide an important critical control point for beef processing, however there are currently no commercially available treatments.     

Detection and recovery rates achieved using direct plate and enrichment/immunomagnetic separation methods for Escherichia coli O157:H7 in minced beef and on bovine hide

AIMS: To assess the detection and recovery rates achieved with commonly used cultural methods for the enumeration and recovery of Escherichia coli O157:H7 from minced beef and bovine hide. METHODS AND RESULTS: Minced beef and bovine hide were inoculated with varying concentrations (log(10) 1.58-2.58 CFU g(-1) and log(10) 2.42-4.49 CFU 100 cm(2) respectively) of E. coli O157:H7 and recovered using a direct plate method or an enrichment/immunomagnetic separation (IMS) method and then plated onto SMAC or SMAC-CT in both cases. The direct plate method detected the pathogen consistently from minced beef samples with an average recovery of 69.2-91.2%. From faecal material on the bovine hide the recovery of the pathogen ranged from 1.80 to 64.5% with fresh faeces depending on the inocula while from dried faeces on hide the results ranged from no recovery at all to 25.1%. Enrichment/IMS recovered E. coli O157:H7 at all inocula levels tested in minced beef while the pathogen was only detected consistently at an average inocula level of log(10) 2.73 CFU 100 cm(2) from fresh faeces and log(10) 4.49 CFU 100 cm(2) from dried faeces on bovine hide. CONCLUSIONS: The direct count enumeration method for E. coli O157:H7 underestimated the numbers of pathogens present. The enrichment/IMS procedure consistently detected the pathogen from minced beef but did not always detect E. coli O157:H7 from faeces on bovine hide. SIGNIFICANCE AND IMPACT OF THE STUDY: Overall this study highlights that any microbial data, used in either predictive microbiology or risk assessment, must take account of the sensitivity and associated performance of the methods employed, in order to make an accurate reflection of the true microbiology of the examined sample.     

Washing and chilling as critical control points in pork slaughter hazard analysis and critical control point (HACCP) systems

AIMS: The aim of this research was to examine the effects of preslaughter washing, pre-evisceration washing, final carcass washing and chilling on final carcass quality and to evaluate these operations as possible critical control points (CCPs) within a pork slaughter hazard analysis and critical control point (HACCP) system. METHODS AND RESULTS: This study estimated bacterial numbers (total viable counts) and the incidence of Salmonella at three surface locations (ham, belly and neck) on 60 animals/carcasses processed through a small commercial pork abattoir (80 pigs d(-1)). Significant reductions (P < 0.05) in bacterial numbers were noted at some stages of the slaughter/dressing process, i.e. the process of hair removal (scalding-dehairing and singeing) resulted in an approx. 4.5 log10 cfu cm(-2) decrease in bacterial numbers. A significant increase (P < 0.05) in bacterial numbers was observed after pre-evisceration washing. Final washing increased the bacterial counts to between 3.6 and 3.8 log10 cfu cm(-2) while chilling effected a small but statistically significant (P < 0.05) increase to between 4.5 and 4.7 log10 cfu cm(-2). The incidence of Salmonella on pigs at the farm was 27%, decreasing to 10% after preslaughter washing. However, stunning and bleeding effected a considerable increase in Salmonella contamination and the incidence after these operations was 50%, which was reduced to 0% during the scalding-dehairing process. CONCLUSIONS: Washing the live animals and subsequent carcasses with cold water is not an effective control measure but chilling may be used as a CCP. SIGNIFICANCE AND IMPACT OF THE STUDY: Recent changes in European Union legislation legally mandate HACCP in pork slaughter plants. This research will provide a sound scientific basis on which to develop and implement effective HACCP in pork abattoirs.     

Enumeration of Salmonella and Escherichia coli O157:H7 in ground beef, cattle carcass, hide and faecal samples using direct plating methods

AIM: To develop and validate high throughput methods for the direct enumeration of viable and culturable Salmonella and Escherichia coli O157:H7 in ground beef, carcass, hide and faecal (GCHF) samples from cattle. METHODS AND RESULTS: The hydrophobic grid membrane filtration (HGMF) method and the spiral plate count method (SPCM) were evaluated as rapid tools for the estimation of pathogen load using GCHF samples spiked with known levels of Salmonella serotype Typhimurium. Validation studies showed that for a single determination of each sample type the low end of the detection limits were approx. 2.0 x 10(0) CFU g(-1) for ground beef, 5.0 x 10(-1) CFU (100 cm(2))(-1) for Salmonella and 8.0 x 10(-1) CFU (100 cm(2))(-1) for E. coli O157:H7 on carcasses, 4.0 x 10(1) CFU (100 cm(2))(-1) for hide and 2.0 x 10(2) CFU g(-1) for faecal samples. In addition, ground beef (n = 609), carcass (n = 1520) and hide (n = 3038) samples were collected from beef-processing plants and faecal samples (n = 3190) were collected from feed-lot cattle, and these samples were tested for the presence of Salmonella and E. coli O157:H7 by enrichment and enumeration methods. CONCLUSIONS: The direct enumeration methods described here are amenable to high throughput sample processing and were found to be cost-effective alternatives to other enumeration methods for the estimation of Salmonella and E. coli O157:H7, in samples collected during cattle production and beef processing. SIGNIFICANCE AND IMPACT OF THE STUDY: Use of the methods described here would allow for more routine testing and quantification data collection, providing useful information about the effectiveness of beef processing intervention strategies.     

The correlation method for rapid monitoring of Escherichia coli in foods

AIMS: A new rapid method was developed to rapidly monitor Escherichia coli counts in foods. MATERIALS AND RESULTS: One ml of modified selective broth with 4-methylumbelliferyl beta-D-glucuronide and 1 ml of food sample were mixed in a sterile test tube and incubated at 37 degrees C. The positive reaction (fluorescence under u.v. light) was monitored at regular 30 min intervals. The positive reaction times in test tubes were compared with actual E. coli numbers from tested samples. The growth of E. coli in test tubes (broth) was much faster than growth on agar. The first experiment was performed to evaluate the rapid correlation method using pure E. coli cultures. The correlation between E. coli counts by the conventional plating method and positive reaction (fluorescence production) times in test tubes was highly agreeable (r(2) = 0 x 95). In the case of low E. coli numbers, such as 2 x 0 log10 cfu ml(-1), the rapid correlation method detected their presence after 10 h incubation. When highly contaminated samples were assayed (8 log10 cfu ml(-1)), the rapid correlation method detected the presence of E. coli after 4 h incubation. In the ground beef experiment, the correlation between fluorescence production time and actual E. coli numbers was also strongly agreeable (r(2) = 0 x 92). CONCLUSIONS: From these results, it is obvious that the new rapid method can rapidly monitor E. coli counts in foods. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicated that the new method saved about 10-14 h incubation time compared to conventional plating methods. The rapid correlation method required much shorter incubation times compared to conventional plating methods for monitoring E. coli.     

Survival of faecal indicator bacteria in bovine manure incorporated into soil

AIMS: Survival of Escherichia coli and enterococci was evaluated in bovine manure incorporated into two Wisconsin soils. METHODS AND RESULTS: Silty clay loam (SCL) and loamy sand (LS) were mixed with fresh bovine manure, exposed daily to 10 h at 22 degrees C/14 h at 9 degrees C, and watered weekly for 12 weeks. Escherichia coli numbers increased 1-2 log cfu g(-1), then decreased < 1 and about 2 log cfu g(-1) in SCL and LS, respectively. Enterococci numbers rose less and then declined faster than those of E. coli. Watering intervals of 3, 7 and 14 days were evaluated in weeks 13-19, but did not affect the slow decline in numbers of E. coli or enterococci. CONCLUSION: Escherichia coli and enterococci may survive at least 19 weeks at 9-21 degrees C in bovine manure/soil, with E. coli surviving better. SIGNIFICANCE AND IMPACT OF THE STUDY: Quantification of E. coli or enterococci in late spring/early summer soil may be useful in indicating recent application of bovine manure.     

Comparison of two selective media for the detection and enumeration of Lactobacilli in human faeces

The enumeration of faecal bacteria is an important requirement for many studies of bowel health. One approach is the use of selective culture media for the culture and identification of genera or species from faeces. This study compares the culture of Lactobacilli from dilution series of faecal samples from six healthy human volunteers on two commonly used media, LAMVAB and Rogosa agar. Colonies were counted after a 72-h anaerobic incubation at 37 degrees C, and colony morphology recorded by a single observer. DNA was isolated from a representative number of colonies and genus-specific PCR, single-stranded conformation polymorphism (SSCP) and DNA sequencing performed. Total colony counts ranged from <3.00 to 7.48 log(10) cfu/g of faeces for LAMVAB and 5.09 to 7.66 log(10) cfu/g for Rogosa. For each subject, the total colony count was higher on Rogosa than that obtained with LAMVAB agar. SSCP analysis and DNA sequencing indicated that colony morphology was not an accurate predictor of genus identity. Growth of two species, Lactobacillus acidophilus and Lactobacillus gasseri, was not supported on LAMVAB medium. Rogosa agar was more likely to support growth of non-Lactobacillus species. Therefore, neither medium gave a fully accurate representation of the Lactobacilli species present in human faecal samples.     

Microbiological Contamination of Reindeer Carcass During Slaughter

Microbiological counts for 10 different sampling sites of 28 reindeer carcasses were studied in 3 reindeer slaughterhouses in Finland. On each carcass the hindshank, round, abdomen, flank, brisket, foreleg, shoulder, neck, foreback and back were sampled immediately after slaughter, using a nondestructive swabbing method. The overall mean bacterial count for 10 sampling sites of reindeer carcasses was 1.51 ± 0.51 log10 cfu/cm2. Statistically significant differences were detected between sampling sites. The back part of the reindeer carcass, i.e. hindshank, round, back and foreback, seemed to be relatively clean. The most contaminated parts were the foreleg, brisket and abdomen (2.05–2.95 log10 cfu/cm2); these could be used for monitoring the hygiene of the reindeer carcass after slaughter. Differences between the 3 slaughterhouses were detected for some sampling sites, which may be due to differences in slaughter techniques and hygiene.     

Survival of Salmonella in peanut butter and peanut butter spread

In 1996, the first documented outbreak of salmonellosis associated with the consumption of peanut butter was reported. This study was undertaken to determine survival characteristics of high (5.68 log10 cfu g(-1)) and low (1.51 log10 cfu g(-1)) inocula of a five-serotype mixture of Salmonella in five commercial peanut butters and two commercial peanut butter spreads. Populations in samples inoculated with 5.68 log10 cfu g(-1) and stored for 24 weeks at 21 or 5 degrees C decreased 4.14-4.50 log10 cfu g(-1) and 2.86-4.28 log10 cfu g(-1), respectively, depending on the formulation. The order of retention of viability was: peanut butter spreads > traditional (regular) and reduced sugar, low-sodium peanut butters > natural peanut butter. Differences in rates of inactivation are attributed to variation in product composition as well as size and stability of water droplets in the colloidal matrix, which may influence nutrient availability. With the exception of natural peanut butter, products initially inoculated with 1.51 log10 cfu of Salmonella g(-1) (32 cfu g(-1)) were positive for the pathogen after storage for 24 weeks at 5 degrees C. At 21 degrees C, however, with the exception of one peanut butter spread, all products were negative for Salmonella after storage for 24 weeks. Post-process contamination of peanut butter and spreads with Salmonella may to result in survival in these products for the duration of their shelf life at 5 degrees C and possibly 21 degrees C, depending on the formulation.     

Microbiological condition and shelf life of meat from hunted game birds

Hunted game birds (eight partridges, nine wood pigeons, 25 quails, 16 chilled and 16 frozen–thawed pheasants) were processed according to “Good Manufacturing Practice” rules. Microflora of skin, intestinal content and meat cuts (breast and thigh, both fresh and stored in vacuum package) was analysed. Listeria monocytogenes, Salmonella sp. and Campylobacter sp. were not recovered from any sample. Log microbial numbers on skin or in intestines were not significantly related to those on meat cuts. With the exception of pigeons, microbial numbers of the two meat cuts did not differ significantly (p > 0.05), and no significant increase in microbial numbers in vacuum-stored meat was found; the same applied to frozen–thawed compared to chilled pheasants. On meat, average total viable counts were <4.00 log cfu/cm² with a maximum of 6.48 log cfu/cm². Median Escherichia coli numbers were <2.00 log cfu/cm², maximum was 4.48 log cfu/cm². Meat cuts obtained from partridges, quails and pheasants demonstrated a shelf life of 1 week, provided they were kept vacuum-packaged at 0°C to 1°C.     

Monitoring the microbial contamination of beef carcass tissue with a rapid chromogenic Limulus amoebocyte lysate endpoint assay

A chromogenic Limulus amoebocyte lysate (LAL) endpoint assay was found to be an accurate and rapid means of gauging levels of beef carcass microbial contamination within 10 min. The assay demonstrated a high correlation with the total mesophilic bacterial and coliform surface populations from inoculated beef carcass surface tissues. This assay was tested on a set of actual beef carcass surface samples (n = 121) demonstrating the utility of the chromogenic LAL test as a means of monitoring carcass microbial contamination in a near real-time fashion. Classifying the chromogenic LAL results into four contamination groups was found to be a sound means of utilizing the resultant chromogenic LAL data for detecting carcasses with high levels of microbial contamination. For beef carcass testing, this assay can be used with no instrumentation other than the required 37 degrees C incubator and, as an option, a microplate reader.     

The role of visible faecal material as a vehicle for generic Escherichia coli,coliform, and other enterobacteria contaminating poultry carcasses during slaughtering

AIMS: A comparison of Enterobacteriaceae, coliform and Escherichia coli counts in chicken carcasses with and without visible faecal contamination was conducted to evaluate the role of contamination as a vehicle for generic E. coli, coliform and other enterobacteria contaminating broiler chicken carcasses when processed under routine commercial operations. METHODS AND RESULTS: Samples were removed from the processing line immediately after evisceration, inside-outside shower and chilling for microbiological analysis. After evisceration, mean counts were significantly different only for E. coli (P < or = 0.05) in chicken carcasses with and without visible faecal contamination. While the spray wash practice was not efficient enough for complete removal of the visible contamination from carcasses, leading to microbiological reduction percentages lower than expected, 25 ppm chlorinated water chilling did reduce the contamination level considerably in all samples. CONCLUSIONS: Carcasses with and without visible faecal contamination harboured E. coli and other potentially hazardous enterobacteria. E. coli was the predominant strain isolated in all samples, Enterobacter cloacae being next most frequent. SIGNIFICANCE AND IMPACT OF THE STUDY: The zero tolerance of visible faecal contamination requirement alone is not sufficient to assure safety and to improve the microbial quality of carcasses.     

Evaluation of a fluorescent antibody technique for the rapid enumeration of Bacteroides fragilis group of organisms in water

The Bacteroides fragilis group has been evaluated as a prospective rapid indicator of faecal contamination of water. Fluorescent antibody (FA) stained B. fragilis group bacteria were enumerated microscopically and compared with faecal coliform or Escherichia coli counts as indicators of faecal contamination. Environmental samples included surface waters (raw drinking water and known contaminated water). Laboratory disinfection experiments with ozone, chlorine and u.v. radiation were also performed. Bacteroides FA counts specifically detected recent human faecal contamination in field samples in 2-3 h. Samples with a high content of particulates or debris limited the sensitivity to about 10 FA counts/ml. Viable counts showed that the sensitivity to all three disinfection agents was essentially the same for Bacteroides and E. coli. Fluorescent antibody counts of Bacteroides, conversely, were not altered by any of the agents. Therefore, the Bacteroides FA method is not recommended for routine monitoring but may be useful for cases where extensive human faecal contamination is suspected (e.g. pipeline rupture or pollution of recreational water) and where rapid remedial action must be taken to protect the public health.     

The prevalence and spread of Escherichia coli O157:H7 at a commercial beef abattoir

AIMS: To investigate the prevalence and virulence characteristics of Escherichia coli O157:H7 after a number of beef process operations at a commercial Irish abattoir. METHODS AND RESULTS: Two 12-month studies were carried out. The first study (study 1) examined the prevalence of E. coli O157:H7 at up to six sites on carcasses at eight stages of the dressing, washing, chilling and boning process. The second study (study 2) examined the prevalence of E. coli O157:H7 in bovine faeces and rumen contents post-slaughter and on dressed, washed carcasses. Isolates from both studies were phage-typed and the presence of genes encoding verocytotoxin, enterohaemolysin and intimin production was determined. E. coli O157:H7 was isolated from four of 36 carcasses in study 1. E. coli O157:H7 was detected during hide removal and was detected at multiple carcass sites and multiple process stages, including boning. On two carcasses, contamination was first detected at the bung following its freeing and tying. All isolates from study 1 were phage type (PT) 2, eaeAO157 and ehlyA positive, but were verocytotoxin 1 (VT1) and verocytotoxin 2 (VT2) negative. In study 2, E. coli O157:H7 was isolated from 2.4% of faecal, 0.8% of rumen and 3.2% of carcass samples. In some cases, isolates recovered from the faeces of a particular animal, the resulting carcass and adjacent carcasses on the line had the same phage typing and virulence characteristic profile patterns. All isolates from study 2 were eaeAO157 and ehlyA positive and only one isolate was VT1 and VT2 negative. Most isolates were PT 32. A higher frequency of positive isolations was noted from samples taken during spring and late summer. CONCLUSION: These studies show that in a typical Irish beef abattoir, carcass contamination with E. coli O157:H7 can occur during hide removal and bung tying and this contamination can remain on the carcass during subsequent processing. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides data that is necessary for the understanding of how E. coli O157:H7 contamination of beef occurs.     

Effect of finishing diets on Escherichia coli populations and prevalence of enterohaemorrhagic E. coli virulence genes in cattle faeces

AIM: To determine the effect of different carbohydrate-based finishing diets on fermentation characteristics and the shedding of Escherichia coli and enterohaemorrhagic E. coli (EHEC) virulence genes in cattle faeces. METHODS AND RESULTS: The size of faecal E. coli populations and fermentation characteristics were ascertained in three experiments where cattle were maintained on a range of finishing diets including high grain, roughage, and roughage + molasses (50%) diets. Increased E. coli numbers, decreased pH and enhanced butyrate and lactate fermentation pathways were associated with grain diets, whereas roughage and roughage + molasses diets resulted in decreased concentrations of ehxA, eaeA and stx(1) genes, this trend remaining at lairage. In one experiment, faecal E. coli numbers were significantly lower in animals fed roughage and roughage + molasses, than animals fed grain (4.5, 5.2 and 6.3 mean log10 g(-1) digesta respectively). In a second experiment, faecal E. coli numbers were 2 log lower in the roughage and roughage + molasses diets compared with grain-fed animals prior to lairage (5.6, 5.5 and 7.9 mean log10 g(-1) digesta respectively) this difference increasing to 2.5 log at lairage. CONCLUSIONS: The type of dietary carbohydrate has a significant effect on E. coli numbers and concentration of EHEC virulence genes in faeces of cattle. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides a better understanding of the impact finishing diet and commercial lairage management practices may have on the shedding of E. coli and EHEC virulence factors, thus reducing the risk of carcass contamination by EHEC.     

Potential of an antibacterial ultraviolet-irradiated nylon film

The antibacterial effectiveness of an ultraviolet-irradiated nylon 6, 6 film was investigated for potential use as a food-packaging material to reduce the surface microbial contamination of foods. The film-surface analyses showed that UV irradiation induced conversion of surface amide groups to amines. Irradiation also increased the dimensional scale of the film surface topography (depth of valleys) approximately 5-fold on the scale of nanometers. The irradiated nylon demonstrated antagonistic activity against Staphylococcus aureus 25923 and Escherichia coli TV1058 with 4.5 and 6 log reductions, respectively, of an initial population of 10(6) cfu mL(-1). The irradiated nylon was ineffective against Pseudomonas fluorescens 13525 and Enterococcus faecalis 19433 under similar conditions. The film demonstrated increased antimicrobial activity against S. aureus 25923 with increasing temperatures up to 45 degrees C, the highest temperature tested. Protein and salt inhibited the antibacterial nature of the irradiated film. Amines in solution (4.31 x 10(-8) M; the calculated equivalent of amines on the film) killed at least 1 x 10(4) cfu mL(-1) E. coli TV1058, and 4. 31 x 10(-7) M amines killed up to 1 x 10(7) cfu mL(-1) E. coli TV1058. The amines in solution required similar exposure time to the bacteria for population reduction as was observed with the irradiated film.