Biomedical subjects

D J Bolton

Publications and source records attributed to D J Bolton.

18 recordsLinked to original sources

PubMed2006

The development of a 'clean sheep policy' in compliance with the new Hygiene Regulation (EC) 853/2004 (Hygiene 2).

The aim of this research was to identify the risk factors associated with the transfer of bacterial contamination from the fleece to the ovine carcass thereby providing the scientific basis for the development and validation of a clean sheep policy. Two hundred sheep in lairage were graded into five categories each consisting of 40 sheep. The categories were as follows; (A) clean and dry; (B) clean and wet; (C) dirty and dry; (D) dirty and wet and (E) visible dags (dung-clotted tufts of wool) categorized by the chief veterinary inspector at the slaughter plant based on the visual inspection of the hygienic status of the fleece. Microbiological evaluations of the carcasses were conducted using swab sampling methods. Total viable counts (TVCs), Enterobacteriaceae and coliform counts were obtained from 40 animals per category at four separate sites (brisket, shoulder, flank and rump) immediately after pelt removal. Statistical analysis of TVC data obtained from the carcass indicated that the dirt level of the fleece had a significant effect on contamination levels when the fleece was dry. Enterobacteriaceae and coliform counts suggest that dirt was a contributing risk factor regardless of wetness or dryness of the animal. The clean sheep policy should therefore differentiate between clean and dirty sheep and mandate additional hygiene measures for the latter.

Abattoirs↗

PubMed2006

Thermal inactivation of Bacillus cereus and Clostridium perfringens vegetative cells and spores in pork luncheon roll.

The aim of this study was to design a thermal treatment(s) for pork luncheon roll, which would destroy Bacillus cereus and Clostridium perfringens vegetative cells and spores. B. cereus and C. perfringens vegetative and spore cocktails were used to inoculate luncheon meat. Samples were subjected to different temperatures and removal times. The decimal-reduction times (D-values) were calculated by linear regression analysis (D = -1/slope of a plot of log surviving cells versus time). The log(10) of the resulting D-values were plotted against their corresponding temperatures to calculate (-1/slope of the curve) the thermal resistance (z-values) of each cocktail. The D-values for vegetative cells ranged from 1 min (60 degrees C) to 33.2 min (50 degrees C) for B. cereus and from 0.9 min (65 degrees C) to 16.3 min (55 degrees C) for C. perfringens. The D-values for B. cereus spores ranged from 2.0 min (95 degrees C) to 32.1 min (85 degrees C) and from 2.2 min (100 degrees C) to 34.2 min (90 degrees C) for C. perfringens. The z-values were calculated to be 6.6 and 8.5 degrees C for B. cereus vegetative and spores, respectively, and 7.8 and 8.4 degrees C for C. perfringens vegetative cells and spores, respectively. The D-values of B. cereus and C. perfringens suggest that a mild cook of 70 degrees C for 12s and 1.3 min would achieve a 6 log reduction of B. cereus and C. perfringens vegetative cells, respectively. The equivalent reduction of B. cereus and C. perfringens spores would require the pork luncheon meat to be heated for 36 s at 105 and 110 degrees C, respectively. The results of this study provide the thermal inactivation data necessary to design a cooking protocol for pork luncheon roll that would inactivate B. cereus and C. perfringens vegetative cells and spores. The data may also be used in future risk assessment studies.

Animals↗

PubMed2006

Distribution of airborne microorganisms in commercial pork slaughter processes.

The objective of this research was to determine the prevalence and distribution of airborne bacterial contamination, with particular reference to Escherichia coli and Salmonella, at a number of stages in a pork slaughtering plant. Air samples (impaction and sedimentation) were recovered from seven locations before and during operations in a commercial pork processing plant. Aerobic mesophilic bacteria, E. coli counts and the incidence of Salmonella in the air were determined. Most sample locations which provided high impaction counts also provided high sedimentation counts. Before commencement of operations, there were no significant differences in aerobic mesophilic bacteria obtained from the sample locations. However, within 2 h of the commencement of operations, aerobic mesophilic bacteria in the wet room (3.14 log10 cfu/m3) were significantly higher (P < 0.05) than those in the clean room (2.66 log10 cfu/m3) and chiller (2.34 log10 cfu/m3). By the afternoon, similar aerobic mesophilic bacteria counts were recovered in the wet and clean rooms, although counts in both of these areas were significantly higher (P > 0.05) than in the chiller. In general there were no significant differences in E. coli counts between rooms (wet room, clean room and chiller) and these did not increase during the production day. Salmonella were detected at the locations of the dehairing and evisceration operations. Aerobic mesophilic bacteria in the air within the abattoir increased as production proceeded. In addition the air within the abattoir contained organisms such as Salmonella and E. coli. Positive correlations (P < 0.05-P < 0.001) between impaction and sedimentation samples were found suggesting that air may be an important source of carcass contamination.

Abattoirs↗

PubMed2005

Excision vs sponge swabbing - a comparison of methods for the microbiological sampling of beef, pork and lamb carcasses.

AIMS: The aim of this research was to compare excision sampling with polyurethane and cellulose acetate sponge swabbing for the recovery of total viable counts and Enterobacteriaceae on meat carcasses. METHODS AND RESULTS: Two sample types were used to compare the methods: (i) individual samples, taken from four sites on each carcass and (ii) composite samples, created by pooling the samples from four sites from an additional set of carcasses. When the polyurethane sponge and excision method were compared for individual sites, there were no significant differences in bacterial recovery on beef and pork carcasses and on two of four sites on lamb carcasses. However, when samples from each site were pooled, the excision method was more efficient than either swabbing method across the three animal species. CONCLUSIONS: Sampling using the polyurethane sponge represents an equivalent alternative method to excision for the bacteriological sampling of carcass surfaces which is nondestructive and less labour intensive. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides the scientific basis for using sponge swabbing instead of excision in compliance with 2001/471/EC.

Animals↗

PubMed2005

An investigation of the thermal inactivation of Staphylococcus aureus and the potential for increased thermotolerance as a result of chilled storage.

AIMS: The aims of this study were; (i) to provide thermal inactivation data for Staphylococcus aureus; (ii) to examine the kinetics, including decimal reduction times (D-value) and rate constants (k), that describe the thermal inactivation of Staph. aureus and to compare two different methods of calculating D-values and (iii) to determine whether or not chilled storage would toughen these microorganisms resulting in increased thermotolerance. METHODS AND RESULTS: Isolates of Staph. aureus recovered from domestic refrigerators were grown in shaken culture for 8 h at 37 degrees C, recovered and washed by centrifugation and combined to form a cocktail of five strains. Samples from this cocktail were (a) heat treated at 50, 55 and 60 degrees C or (b) held under simulated domestic refrigeration conditions for 72 h and then heat treated as above. The numbers of Staph. aureus in heat treated and chill held, heat treated samples were enumerated by direct selective plating onto Baird Parker Agar (BPA) and recovery plating on Tryptone Soya Agar (TSA) subsequently overlaid with BPA. D-values were obtained using two different methods both of which may be used when the thermal inactivation follows first order kinetics. In the first method D-values are obtained by plotting the Log(10) of the surviving cells against time and using the equation D = -1/slope. The second method uses the rate constant (k) which is obtained from the slope of a plot of ln N/N(0)vs time and D is obtained using the equation D = 2.303 k(-1). D(50), D(55) and D(60) values ranged from 94.3 to 127.9 min, 13 to 21.7 min and 4.8 to 6.5 min. Prechilling did not enhance thermal resistance. The method of calculation did not affect the D-values obtained because the thermal inactivation of Staph. aureus in this study followed first order kinetics with r(2) values of 0.91-0.99. CONCLUSIONS: The thermal inactivation of Staph. aureus in tryptone soya broth (TSB) follows first order kinetics and in general chilling of these bacteria does not increase the resistance to thermal destruction during subsequent thermal processes such as cooking. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides much needed data on the thermal resistance of Staph. aureus and validates chilling as a food storage activity which does not cause toughening of the microorganisms to subsequent cooking. However, the data generated strongly suggests that Staph. aureus is more thermotolerant than Listeria monocytogenes and should be used as the target microorganism in designing mild thermal treatments for food, in which case the current recommendations for pasteurization (70 degrees C for 2 min, minimum) should be revised.

Colony Count, Microbial↗

PubMed2005

Food safety knowledge of consumers and the microbiological and temperature status of their refrigerators.

The objectives of this study were to examine domestic food safety knowledge levels of consumers, establish the levels and incidence of bacterial contamination and operational temperatures in domestic refrigerators, and identify areas in which consumer food safety education is necessary in Ireland. A food safety knowledge questionnaire applied to a representative sample of households (n = 1,020) throughout the island of Ireland found the gaps in consumer food safety knowledge. Analysis of swab samples (n = 900) recovered from the domestic refrigerators in these households showed average total viable counts of 7.1 log CFU/cm2 and average total coliform counts of 4.0 log CFU/cm2. Analysis of swab samples also detected the incidence of Staphylococcus aureus (41%), Escherichia coli (6%), Salmonella enterica (7%), Listeria monocytogenes (6%), and Yersinia enterocolitica (2%). Campylobacter jejuni and E. coli O157:H7 were not detected in domestic refrigerators. The temperature profiles of a subset of the sampled refrigerators (100) were monitored for 72 h, and 59% were found to operate, on average, at temperatures above the recommended 5 degrees C. Knowledge and temperature survey results varied considerably, but consumers who scored better in terms of basic food safety knowledge had reduced levels of bacterial contamination in their refrigerators and reported a reduced incidence of food-associated illnesses. This study confirms the effect of basic food hygiene knowledge on hygienic practice and identifies specific areasfor emphasis in the development and delivery of effective food safety risk communication messages to consumers.

Adolescent↗

PubMed2004

Studies to determine the critical control points in pork slaughter hazard analysis and critical control point systems.

Aerobic mesophilic counts (AMC), coliform (CC) and coliform resuscitation counts (CRCs) were obtained by swabbing 50 cm(2) areas at three sites (ham, belly and neck) on pig carcasses, after each of seven stages of the slaughter/dressing process (bleeding, scalding, dehairing, singeing, polishing, evisceration and chilling). In most cases, there were no statistical differences (P>0.05) among the counts derived by these three methods. Reductions in counts at individual sites were observed after scalding (3.5 log(10) cfu cm(-2)), and singeing (2.5 log(10) cfu cm(-2)). Increases in counts at individual sites were observed after dehairing (2.0 log(10) cfu cm(-2)) and polishing (1.5 log(10) cfu cm(-2)). The incidence of Salmonella on pig carcasses was also obtained by swabbing the outside surfaces of 100 half carcasses. Information on the incidence of Salmonella in scald tank water (108 samples) was also investigated. Carcass swabs and scald tank water were examined for the presence of Salmonella using standard enrichment methods. Salmonella were detected on 31% of carcasses immediately after bleeding, 7% of carcasses immediately after dehairing and evisceration, and 1% of carcasses immediately after scalding. Serovars included Salmonella Typhimurium, Salmonella Hadar, Salmonella Infantis and Salmonella Derby. No Salmonella were recovered from samples of scald tank water. The impact of pig slaughter/dressing processes on carcass microbiology and their potential use as critical control points (CCPs) during pork production are discussed.

Abattoirs↗

PubMed2003

Decontamination of pork carcasses during scalding and the prevention of Salmonella cross-contamination.

AIMS: The objective of this study was to establish critical temperature limits to prevent cross-contamination of pork carcasses during scalding. METHODS AND RESULTS: Mixtures of antibiotic-resistant mutants of Salmonella species were heat treated at 50, 55 and 60 degrees C in samples of commercial scald tank water. Surviving cell numbers were estimated by plating treated suspensions on (i). tryptone soya agar (TSA) and (ii). on TSA, overlaid with brilliant green agar plus nalidixic acid and streptomycin sulphate and used to estimate D-values for the treated mixed cell suspensions. CONCLUSIONS: A time-temperature combination of 1.4 min at 60 degrees C is required to achieve a 1 log reduction in Salmonella in scald tank water. The predicted equivalent at 65 degrees C is 0.18 min. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides data and a model to enable pork processors to identify and apply processing parameters to limit the risks of transfer of Salmonella between pig carcasses during commercial scalding operations.

Animals↗

PubMed2002

The effect of commercial production and product formulation stresses on the heat resistance of Escherichia coli O157:H7 (NCTC 12900) in beef burgers.

The effects of commercial beef burger production and product formulation on the heat resistance of Escherichia coli O157:H7 (NCTC 12900) in beef burgers were investigated. Fresh beef trimmings were inoculated with E. coli O157:H7 to approximately log10 7.0 cfu g(-1) and subjected to standard beef burger production processes, including freezing, frozen storage and tempering. The tempered trimmings were processed in line with commercial practice to produce burgers of two formulations, a 'Quality' burger containing 100% beef and an 'Economy' burger containing 70% beef and 30% other ingredients (salt, seasoning, soya, onion and water). The burgers were then frozen and stored. Control 'unprocessed' burgers were produced to each of the above formulations using fresh beef trimmings. All burger types were heat-treated at 55, 60 or 65 degrees C. Samples were examined by plating on Tryptone Soya Agar (TSA), incubated at 37 degrees C for 2 h, before overlaying with SMAC (TSA/SMAC) and incubation at 37 degrees C. The resultant counts were used to derive D-values for E. coli O1 57:H7. At each treatment temperature, the D-values from each burger formulation using frozen tempered trimmings were significantly lower (P < 0.001) than the D-values from that formulation using fresh trimmings. At each treatment temperature, the D-values from Economy burgers using processed trimmings were significantly higher (P < 0.001) than the D-values from Quality burgers using processed trimmings. A similar trend of significantly higher (P<0.001) D-values for Economy burgers was observed using fresh trimmings. This study found that commercial processing and product formulation have profound effects on the heat resistance of E. coli O157:H7 in beef burgers.

Animals↗

PubMed2002

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.

Abattoirs↗

PubMed2002

Survival of Escherichia coli O157:H7 in farm water: its role as a vector in the transmission of the organism within herds.

AIMS: The study aimed to investigate the survival characteristics of Escherichia coli O157:H7 in farm water (FW), and in sterile distilled municipal water (SDW), stored outdoors under field conditions, with or without the addition of faeces (1% w/v), in a farmyard shed and the laboratory at 15 degrees C. METHODS AND RESULTS: Water samples were inoculated with E. coli O157:H7 at 10(3) and 10(6) ml(-1), and sampled over a 31-day period. In FW stored outdoors in a field, E. coli O157:H7 survived for 14 days at temperatures <15 degrees C, at both inoculation levels, while in the laboratory at 15 degrees C, the organism was still detectable at low levels (<1 log10 cfu ml(-1)) after 31 days. The addition of bovine faeces to water outdoors (1% w/v) resulted in survival for 24 days. In SDW inoculated at 10(6) ml(-1) and stored in the laboratory (15 degrees C), only a 2.5 log reduction was observed after 31 days, while the organism could not be detected after 17 days in the field. Preliminary screening of water samples stored outdoors isolated a bacterium which exhibited antimicrobial activity towards E. coli O157:H7. CONCLUSIONS: The survival of E. coli O157:H7 observed in this study illustrates the potential of farm water to act as a vehicle in the transfer of the organism across a herd. SIGNIFICANCE AND IMPACT OF THE STUDY: The difficulty in extrapolating results from controlled laboratory situations to on-farm conditions is also highlighted in this study.

Agriculture↗

PubMed2002

The ineffectiveness of organic acids, freezing and pulsed electric fields to control Escherichia coli O157:H7 in beef burgers.

AIMS: The objective of this study was to investigate the potential value of individual and combined applications of some GRAS (generally regarded as safe) additives with freezing and pulsed electric field (PEF) application, in reducing the risks associated with the presence of E. coli O157:H7 in beef burgers. METHODS AND RESULTS: Beef burgers, trimmings and filter paper were inoculated with E. coli O157:H7 and subjected to a range of chemical and physical treatments. Sequential application of 2% (v/v) lactic acid and freezing (at - 20 degrees C for 2 h) resulted in a decrease of approximately 6 log10 cfu cm(-1) in E. coli O157:H7, but only on filter paper. All other treatments were ineffective. CONCLUSIONS: Currently available methods for controlling E.coli O157:H7 in beef burgers during production are ineffective. SIGNIFICANCE AND IMPACT OF THE STUDY: Further research is needed to develop controls for E. coli O157:H7 during beef burger production.

Animals↗

PubMed2002

Fate of Escherichia coli O157:H7 during silage fermentation.

The survival characteristics of Escherichia coli O157:H7 in silage derived from contaminated grass were investigated. The survival of other enteric bacteria was also investigated to determine if E. coli O157:H7 demonstrates enhanced acid tolerance in comparison. Samples of chopped grass were treated as follows: (i) no additive (control); (ii) inoculation with E. coli O157:H7 to a final concentration of log10 4.0 CFU g(-1); (iii) addition of an 85% solution of formic acid at 3.0 ml kg(-1) grass; and (iv) addition of both E. coli O157:H7 and formic acid, at the above concentrations. Treated 6-kg grass samples were packed into laboratory silos, sealed, and stored at 15 degrees C for up to 180 days. Individual replicate silos were removed from storage periodically and subjected to microbiological and chemical analyses. Chemical analyses of the silage samples indicated that lactic acid-dominant fermentations, with a rapid drop in pH, occurred. Numbers of enteric bacteria decreased from log10 7.0 to 8.0 CFU g(-1) to undetectable levels within 19 days' storage. E. coli O157:H7 did not survive the silage fermentation process, with numbers declining from approximately log10 4.0 CFU g(-1) to undetectable levels within 19 days of ensiling. The pattern of decline in numbers of E. coli O157:H7 was the same as that for the enteric bacteria, indicating that under the conditions tested, the acid tolerance of E. coli O157:H7 was not significantly different from the acid tolerance of other enteric bacteria. This study found that E. coli O157:H7 did not survive a good silage fermentation process, indicating that properly ensiled grass that is correctly stored is unlikely to be a vector for the transmission of the pathogen among cattle.

Escherichia coli O157↗

PubMed2001

Beef HACCP: intervention and non-intervention systems.

While there are several generic beef HACCP documents available to the beef industry, these lack sufficient detail to be of any use other than as a general guide to HACCP. A document which clearly identifies and provides a sound scientific basis for potential critical control points (CCPs') and details critical limits, monitoring and corrective actions is clearly required. The objective of this paper is to provide such information. A detailed description of CCPs' for two different HACCP systems (an intervention and a non-intervention system) are presented and the advantages and disadvantages of each are discussed. Individual beef plants may then make an informed choice as to which HACCP system is most suitable for them and have all the specific information required for effective implementation.

Abattoirs↗

PubMed2001

The survival of Escherichia coli O157:H7 in slurry from cattle fed different diets.

AIMS: The survival characteristics of Escherichia Coli O157:H7 were investigated in bovine slurry from cattle fed two different diets: (i) silage and (ii) silage + concentrates. METHODS AND RESULTS: Slurry samples collected from freshly-agitated tanks were inoculated at a level of log10 6.0 cfu g(-1) and stored in the laboratory at 10 degrees C. Over a 12 week storage period, a 3.5 and 5.5 log reduction was observed in slurry from cattle fed a silage and silage plus concentrate diet, respectively. CONCLUSIONS: The persistence of E. coli O157:H7 in slurry over a 3 month storage period indicates its potential for transmitting the organism back into the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: The discussion concludes however, that despite pathogen survival in slurry, it may not represent a major source of transmission in the farm environment.

Animals↗

PubMed2000

Thermal inactivation of Listeria monocytogenes and Yersinia enterocolitica in minced beef under laboratory conditions and in sous-vide prepared minced and solid beef cooked in a commercial retort.

D-values were obtained for Listeria monocytogenes and Yersinia enterocolitica at 50, 55 and 60 degrees C in vacuum-packed minced beef samples heated in a laboratory water-bath. The experiment was repeated using vacutainers, which allowed heating of the beef to the desired temperature before inoculation. D-values of between 0.15 and 36.1 min were obtained for L. monocytogenes. Pre-heating the beef samples significantly affected (P < 0.05) the D60 value only. D-values for Y. enterocolitica ranged from 0.55 to 21.2 min and all the D-values were significantly different (P < 0.05) after pre-heating. In general, the D-values obtained for core inoculated solid beef samples were significantly higher (P < 0.05) than those generated in minced beef when heated in a Barriquand Steriflow commercial retort.

Animals↗

PubMed2000

The effects of preslaughter washing on the reduction of Escherichia coli O157:H7 transfer from cattle hides to carcasses during slaughter.

Fresh bovine faeces were inoculated with a non-toxigenic, antibiotic resistant strain of Escherichia coli O157:H7, spread on the rump areas of 30 heifers and allowed to dry for 24 h. Ten of the cattle then entered the normal slaughter process without further treatment. The remaining cattle were washed with a powerhose for 1 min (10 animals) and 3 min (10 animals) before entering the normal slaughter process. Both washing treatments removed all visible faecal materials on the live animals although a significant reduction (P < 0.05) in E. coli O157:H7 levels on the hides was only observed on those animals which were powerhosed for 3 min. After slaughter, E. coli O157:H7 was detected on carcasses and on the knives and hands of operatives. Preslaughter washing for 3 min did not statistically reduce the numbers of E. coli O157:H7 transferred from the hide to the carcass during slaughter. However, the organism was not detected on three of the four areas of the carcass sampled, indicating that washing may be a suitable method of decontamination animal hides before slaughter and as such deserves further investigation.

Abattoirs↗

PubMed1999

The survival characteristics of a non-toxigenic strain of Escherichia coli O157:H7.

The survival characteristics of a non-toxigenic, antibiotic-resistant strain of Escherichia coli O157:H7 in bovine faeces were investigated. Faecal samples were inoculated with 10(8-9) cfu g-1 of the organism and (i) stored in closed plastic containers at 10 degrees C, (ii) stored in closed plastic containers placed outside or (iii) decanted onto the surface of grazing land. Recovery and enumeration on Sorbitol MacConkey Agar (SMAC) and Tryptic Soya Agar (TSA) revealed that the E. coli O157:H7 numbers in both enclosed samples (i and ii) had decreased by 4.5-5.5 log10 cfu g-1 within 99 d. Numbers in samples decanted onto grassland (iii) decreased by 4.0-5.0 log10 cfu g-1 within 50 d but the organism was still detectable in the surrounding soil for up to 99 d. Persistence of E. coli O157:H7 in bovine faeces and contaminated pastures may therefore be an important factor in the initial infection and re-infection of cattle.

Animals↗