The morphological differentiation between coastal and offshore ecotypes of bottlenose dolphins (g... more The morphological differentiation between coastal and offshore ecotypes of bottlenose dolphins (genus Tursiops) has been researched since the 1960s, particularly in T. truncatus (Montagu, 1821), although most morphological studies have focused on localized populations. Therefore, it is unclear how patterns observed in these individual populations integrate within the global morphological variation. Here we carry out a meta‐analysis of global morphological variation between coastal and offshore ecotypes from 532 museum specimens, using both linear measurements (LM; 282 specimens), and shape data using geometric morphometrics (GM; 290 specimens). Together these analyses show consistent differentiation in skull morphology between coastal and offshore ecotypes, and provide a detailed description of variation patterns within each ecotype. These patterns show high individual morphological variation in the coastal ecotype between locations, while the offshore ecotype appears morphologicall...
This study examined the effects of and interactions between pH, aw and temperature on the surviva... more This study examined the effects of and interactions between pH, aw and temperature on the survival of the top six non-O157 STECs and Escherichia coli O157:H7. All variables significantly affected the survival of all STEC serotypes. However, aw bore the most significant effect, followed by temperature and then pH. Examination of the effect of the interaction between these variables revealed that the interaction between aw and temperature was the most significant followed by the interaction between pH and temperature and then aw and pH. Decrease in aw resulted in population reduction of all serotypes studied. This reduction in population was significantly increased with the increase in temperature and was further significantly enhanced with decreasing pH. Examination of the differences in the survival among the individual serotypes revealed that the response of each serotype to aw or temperature changes was significantly different, while their response to pH changes was similar. Analysis of the relative survival of individual non-O157 STECs to O157:H7 revealed that the survival of O121 and O45 was not significantly different to O157:H7 while O103, O111, O145 and O26 showed less tolerance to the combined treatments, and their survival was significantly different from O157:H7. Results of this study estimate the interaction between pH, aw and temperature on the survival of the top six non-O157 STECs relative to Escherichia coli O157:H7 and provide important growth and no-growth condition which will offer risk assessors a means of estimating the likelihood of these pathogens, if present, would grow in response to the interaction between the three variables assessed.
Geographical variations of postcranial skeleton among the Yangtze,Yellow Sea and South China Sea ... more Geographical variations of postcranial skeleton among the Yangtze,Yellow Sea and South China Sea populations of the finless porpoise,Neophocaena phocaenoides,in CHi-nese waters were studied with t-test,covariance analysis(Table 2)and stepwise dis-criminant analysis(Tabie 3,Fig. 2)using 42 measurements based on 142 specimens ofall ages(38 from the Yangtze population,59 from the Yellow Sea population and 45from the South China Sea population)collected in 1974 to 1991 by the Cetacean Re-search Laboratory, Nanjing Normal University. The results showed that:(1 )Geo-graphical variations in the postcranial skeleton among the three Chinese populationswere demonstrated in all the ages even for the neonates(Table 2,Fig. 2).But the dif-ferences were interpreted by a group of variances. No single difference could be used asdiagnostic character for subspecies identification.(2)Summary of the results of thecomparison among the populations(Table 2 and 4)demonstrated that,the postcranialskeleton in...
Salmonella is one of the most frequent food-borne zoonoses, while Salmonella Typhimurium and Ente... more Salmonella is one of the most frequent food-borne zoonoses, while Salmonella Typhimurium and Enteritidis are the major serovars of concern in public health. 113 Salmonella strains including 38 S. Enteritidis (SE), 38 S. Typhimurium (ST) and 37 strains of 32 other Salmonella serovars (SG) were tested in quadruplicate by whole-cell MALDI-TOF MS. Ions were studied and aligned from the raw data of mzXML files using Mass-Up (http://www.sing-group.org/mass-up), resulting in 1,741 aligned peaks. Datasets of ions (presence/absence) selected using a home-developed criteria on their specificity and detectability were subjected to multivariate analyses and artificial intelligence tools. Principle Component Analysis based on 88 selected ions separated SE, ST and SG without overlap on the first three principle components. The network and forest based deep learning tools were more sophisticated than the decision tree-based models. Neural Network carried out consistently well in training model, bu...
Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2009
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn's disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitiv...
Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2005
Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease in cattle and it has been suggested that this organism may be associated with Crohn's disease in humans. Cows at the advanced stage of the disease shed this organism into both their milk and feces. The objective of this study was to develop a more efficient procedure for isolating MAP from bulk tank raw milk. Bulk tank raw milk (50 mL) samples 3 to 13 d old after collection without spiking were investigated to evaluate the effects of milk age on the efficacy of decontamination. Milk samples, 2 to 3 d old, were seeded with MAP at levels of 50 to 200 colony forming units/mL in experiments involving factorial design to evaluate 1) the effects of different decontaminating reagents and decontamination procedures on recovery of MAP, and 2) partition MAP in milk fractions after centrifugation in raw milk. Decontamination in 20 mL of 0.75% hexadecylpyridinium chloride (HPC) at room temperatur...
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn's disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitiv...
Background Bacterial enumeration data are typically log transformed to realize a more normal dist... more Background Bacterial enumeration data are typically log transformed to realize a more normal distribution and stabilize the variance. Unfortunately, statistical results from log transformed data are often misinterpreted as data within the arithmetic domain. Objective To explore the implication of slope and intercept from an unweighted linear regression and compare it to the results of the regression of log transformed data. Method Mathematical formulae inferencing explained using real dataset. Results For y=Ax+B+ε, where y is the recovery (CFU/g) and x is the target concentration (CFU/g) with error ε homogeneous across x. When B=0, slope A estimates percent recovery R. In the regression of log transformed data, logy=αlogx+β+εz (equivalent to equation y=Axα·ω), it is the intercept β=logyx=logA that estimates the percent recovery in logarithm when slope α=1, which means that R doesn’t vary over x. Error term ω is multiplicative to x, while εz or log(ω) is additive to log(x). Whether t...
Background: Ready-to-eat (RTE) meats, fruits, and vegetables contaminated by Shiga toxin producin... more Background: Ready-to-eat (RTE) meats, fruits, and vegetables contaminated by Shiga toxin producing Escherichia coli (STEC) raise serious concerns because they are often consumed directly without further processing. Objective: To evaluate a multiplex PCR for the detection of STEC across food categories. Methods: Samples (25 g) from seven RTE meat and nine fruit and vegetable matrices were inoculated with each of seven STEC (O157:H7, O26, O121, O145, O45, O103, O111) strains targeting 10 CFU/25 g, enriched in 225 mL of modified tryptone soya broth (mTSB), and tested by a multiplex real-time PCR for stx and eae genes, following U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) Microbiology Laboratory Guidebook (MLG) 5B, which was originally validated for meat products and environmental sponge. Results: The mTSB was successful at enriching for STEC in RTE meat, fruit, and vegetable matrices, except for sprouts; however, mEHEC resulted in successful enrichme...
Background: Estimation of measurement uncertainty (MU) has been extensively addressed in document... more Background: Estimation of measurement uncertainty (MU) has been extensively addressed in documents from standard authorities. In microbiology, bacterial counts are log transformed to get a more normal distribution. Unfortunately, the difference between using original and log-transformed data appears to not have been investigated even in publications focusing on MU estimation. Method: Statistical formulae inferencing and estimation of MU using real bacterial enumeration datasets. Results: Both mean and SD calculated from original data carry the same scale and unit as the original data. However, the mean of log-transformed data becomes a geometric mean in log, and the SD becomes the logarithm of a ratio. Furthermore, calculation of RSD obtained by dividing the SD by the mean is meaningless and misleading for log-transformed data. The ratio, the antilog of the SD of log-transformed data, copes with multiplicative and divisive relationships to geometric mean (without log), instead of th...
International journal of food microbiology, Jan 16, 2017
The study examined the relative fate of the top six non-O157 shiga-toxin producing Escherichia co... more The study examined the relative fate of the top six non-O157 shiga-toxin producing Escherichia coli (STEC) and E. coli O157:H7 during the manufacture of dry fermented sausages (DFS). Three separate batches of sausages containing a five-strain cocktail for each serogroup and uninoculated control were manufactured and subjected to identical fermentation, maturation and dry curing conditions. Changes in physicochemical properties and inoculated STEC numbers were enumerated during the DFS production stages and log reduction and log reduction rates were calculated. Inoculation of very high concentrations (8logCFUg(-1)) of STEC in the sausage batter did not significantly (P>0.05) affect the changes in the pH, aw, moisture, protein, fat content compared to the uninoculated DFS. There was a significant (P<0.05) reduction in counts within the 48h fermentation for all STEC serogroups inoculated by about 0.97- to 1.42-log units. However, during the sausage maturation stage, all serogroup...
Canadian Journal of Veterinary Research Revue Canadienne De Recherche Veterinaire, 2009
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease in ca... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn’s disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitivity than the milk culture method, the difference was not significant (P = 0.2473). The number of MAP colony-forming units (CFU) isolated by culture from fecal samples was, on average, higher than that isolated from milk samples (P = 0.0083). There was no significant correlation between the number of CFU cultured from milk and from feces (Pearson correlation coefficient = 0.1957, N = 63, P = 0.1243). The animals with high numbers of CFU in milk culture may not be detected by fecal culture at all, and vise versa. A significant proportion (29% to 41%) of the positive animals would be missed if only 1 culture method, instead of both milk and feces, were to be used for diagnosis. This suggests that the shedding of MAP in feces and milk is not synchronized. Most of the infected cows were low-level shedders. The proportion of low-level shedders may even be underestimated because MAP is killed during decontamination, thus reducing the chance of detection. Therefore, to identify suspected Johne’s-infected animals using the tests in this study, both milk and feces samples should be collected in duplicate to enhance the diagnostic rate. The high MAP kill rate identified in the culture methods during decontamination may be compensated for by using the nested PCR method, which had a higher sensitivity than the IS900 PCR method used.
National and international health agencies have recommended a significant reduction in daily inta... more National and international health agencies have recommended a significant reduction in daily intake of sodium by reducing the amount of NaCl in foods, specifically processed meats. However, sodium reduction could increase the risk of survival and growth of spoilage and pathogenic microorganisms on these products. Therefore, alternate processing technologies to improve safety of sodium reduced foods are necessary. This study examined the effects of three different salt types and concentrations on high-pressure inactivation of Listeria monocytogenes in pre-blended ground chicken formulations. Ground chicken formulated with three salt types (NaCl, KCl, CaCl2), at three concentrations (0, 1.5, 2.5%) and inoculated with a four strain cocktail of L. monocytogenes (10(8)CFUg(-1)) were subjected to four pressure treatments (0, 100, 300, 600MPa) and two durations (60, 180s) in an experiment with factorial design. Surviving cells were enumerated by plating on Oxford agar and analysed by factorial ANOVA. Pressure treatments at 100 or 300MPa did not significantly (P=0.19-050) reduce L. monocytogenes populations. Neither salt type nor concentration had a significant effect on L. monocytogenes populations at these pressure levels. At 600MPa, salt types, concentrations and duration of pressure treatment all had a significant effect on L. monocytogenes populations. Formulations with increasing concentrations of NaCl or KCl showed significantly lower reduction in L. monocytogenes, while increase in CaCl2 concentration resulted in a significantly higher L. monocytogenes reduction. For instance, increase in NaCl concentration from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 2.49 and 1.29, respectively, when exposed to 600MPa for 60s. In the case of CaCl2, increase from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 7.28 and 7.47, respectively. These results demonstrate that high-pressure processing is a viable process to improve microbial safety of sodium reduced poultry products.
The morphological differentiation between coastal and offshore ecotypes of bottlenose dolphins (g... more The morphological differentiation between coastal and offshore ecotypes of bottlenose dolphins (genus Tursiops) has been researched since the 1960s, particularly in T. truncatus (Montagu, 1821), although most morphological studies have focused on localized populations. Therefore, it is unclear how patterns observed in these individual populations integrate within the global morphological variation. Here we carry out a meta‐analysis of global morphological variation between coastal and offshore ecotypes from 532 museum specimens, using both linear measurements (LM; 282 specimens), and shape data using geometric morphometrics (GM; 290 specimens). Together these analyses show consistent differentiation in skull morphology between coastal and offshore ecotypes, and provide a detailed description of variation patterns within each ecotype. These patterns show high individual morphological variation in the coastal ecotype between locations, while the offshore ecotype appears morphologicall...
This study examined the effects of and interactions between pH, aw and temperature on the surviva... more This study examined the effects of and interactions between pH, aw and temperature on the survival of the top six non-O157 STECs and Escherichia coli O157:H7. All variables significantly affected the survival of all STEC serotypes. However, aw bore the most significant effect, followed by temperature and then pH. Examination of the effect of the interaction between these variables revealed that the interaction between aw and temperature was the most significant followed by the interaction between pH and temperature and then aw and pH. Decrease in aw resulted in population reduction of all serotypes studied. This reduction in population was significantly increased with the increase in temperature and was further significantly enhanced with decreasing pH. Examination of the differences in the survival among the individual serotypes revealed that the response of each serotype to aw or temperature changes was significantly different, while their response to pH changes was similar. Analysis of the relative survival of individual non-O157 STECs to O157:H7 revealed that the survival of O121 and O45 was not significantly different to O157:H7 while O103, O111, O145 and O26 showed less tolerance to the combined treatments, and their survival was significantly different from O157:H7. Results of this study estimate the interaction between pH, aw and temperature on the survival of the top six non-O157 STECs relative to Escherichia coli O157:H7 and provide important growth and no-growth condition which will offer risk assessors a means of estimating the likelihood of these pathogens, if present, would grow in response to the interaction between the three variables assessed.
Geographical variations of postcranial skeleton among the Yangtze,Yellow Sea and South China Sea ... more Geographical variations of postcranial skeleton among the Yangtze,Yellow Sea and South China Sea populations of the finless porpoise,Neophocaena phocaenoides,in CHi-nese waters were studied with t-test,covariance analysis(Table 2)and stepwise dis-criminant analysis(Tabie 3,Fig. 2)using 42 measurements based on 142 specimens ofall ages(38 from the Yangtze population,59 from the Yellow Sea population and 45from the South China Sea population)collected in 1974 to 1991 by the Cetacean Re-search Laboratory, Nanjing Normal University. The results showed that:(1 )Geo-graphical variations in the postcranial skeleton among the three Chinese populationswere demonstrated in all the ages even for the neonates(Table 2,Fig. 2).But the dif-ferences were interpreted by a group of variances. No single difference could be used asdiagnostic character for subspecies identification.(2)Summary of the results of thecomparison among the populations(Table 2 and 4)demonstrated that,the postcranialskeleton in...
Salmonella is one of the most frequent food-borne zoonoses, while Salmonella Typhimurium and Ente... more Salmonella is one of the most frequent food-borne zoonoses, while Salmonella Typhimurium and Enteritidis are the major serovars of concern in public health. 113 Salmonella strains including 38 S. Enteritidis (SE), 38 S. Typhimurium (ST) and 37 strains of 32 other Salmonella serovars (SG) were tested in quadruplicate by whole-cell MALDI-TOF MS. Ions were studied and aligned from the raw data of mzXML files using Mass-Up (http://www.sing-group.org/mass-up), resulting in 1,741 aligned peaks. Datasets of ions (presence/absence) selected using a home-developed criteria on their specificity and detectability were subjected to multivariate analyses and artificial intelligence tools. Principle Component Analysis based on 88 selected ions separated SE, ST and SG without overlap on the first three principle components. The network and forest based deep learning tools were more sophisticated than the decision tree-based models. Neural Network carried out consistently well in training model, bu...
Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2009
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn's disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitiv...
Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2005
Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease in cattle and it has been suggested that this organism may be associated with Crohn's disease in humans. Cows at the advanced stage of the disease shed this organism into both their milk and feces. The objective of this study was to develop a more efficient procedure for isolating MAP from bulk tank raw milk. Bulk tank raw milk (50 mL) samples 3 to 13 d old after collection without spiking were investigated to evaluate the effects of milk age on the efficacy of decontamination. Milk samples, 2 to 3 d old, were seeded with MAP at levels of 50 to 200 colony forming units/mL in experiments involving factorial design to evaluate 1) the effects of different decontaminating reagents and decontamination procedures on recovery of MAP, and 2) partition MAP in milk fractions after centrifugation in raw milk. Decontamination in 20 mL of 0.75% hexadecylpyridinium chloride (HPC) at room temperatur...
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease i... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn's disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitiv...
Background Bacterial enumeration data are typically log transformed to realize a more normal dist... more Background Bacterial enumeration data are typically log transformed to realize a more normal distribution and stabilize the variance. Unfortunately, statistical results from log transformed data are often misinterpreted as data within the arithmetic domain. Objective To explore the implication of slope and intercept from an unweighted linear regression and compare it to the results of the regression of log transformed data. Method Mathematical formulae inferencing explained using real dataset. Results For y=Ax+B+ε, where y is the recovery (CFU/g) and x is the target concentration (CFU/g) with error ε homogeneous across x. When B=0, slope A estimates percent recovery R. In the regression of log transformed data, logy=αlogx+β+εz (equivalent to equation y=Axα·ω), it is the intercept β=logyx=logA that estimates the percent recovery in logarithm when slope α=1, which means that R doesn’t vary over x. Error term ω is multiplicative to x, while εz or log(ω) is additive to log(x). Whether t...
Background: Ready-to-eat (RTE) meats, fruits, and vegetables contaminated by Shiga toxin producin... more Background: Ready-to-eat (RTE) meats, fruits, and vegetables contaminated by Shiga toxin producing Escherichia coli (STEC) raise serious concerns because they are often consumed directly without further processing. Objective: To evaluate a multiplex PCR for the detection of STEC across food categories. Methods: Samples (25 g) from seven RTE meat and nine fruit and vegetable matrices were inoculated with each of seven STEC (O157:H7, O26, O121, O145, O45, O103, O111) strains targeting 10 CFU/25 g, enriched in 225 mL of modified tryptone soya broth (mTSB), and tested by a multiplex real-time PCR for stx and eae genes, following U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) Microbiology Laboratory Guidebook (MLG) 5B, which was originally validated for meat products and environmental sponge. Results: The mTSB was successful at enriching for STEC in RTE meat, fruit, and vegetable matrices, except for sprouts; however, mEHEC resulted in successful enrichme...
Background: Estimation of measurement uncertainty (MU) has been extensively addressed in document... more Background: Estimation of measurement uncertainty (MU) has been extensively addressed in documents from standard authorities. In microbiology, bacterial counts are log transformed to get a more normal distribution. Unfortunately, the difference between using original and log-transformed data appears to not have been investigated even in publications focusing on MU estimation. Method: Statistical formulae inferencing and estimation of MU using real bacterial enumeration datasets. Results: Both mean and SD calculated from original data carry the same scale and unit as the original data. However, the mean of log-transformed data becomes a geometric mean in log, and the SD becomes the logarithm of a ratio. Furthermore, calculation of RSD obtained by dividing the SD by the mean is meaningless and misleading for log-transformed data. The ratio, the antilog of the SD of log-transformed data, copes with multiplicative and divisive relationships to geometric mean (without log), instead of th...
International journal of food microbiology, Jan 16, 2017
The study examined the relative fate of the top six non-O157 shiga-toxin producing Escherichia co... more The study examined the relative fate of the top six non-O157 shiga-toxin producing Escherichia coli (STEC) and E. coli O157:H7 during the manufacture of dry fermented sausages (DFS). Three separate batches of sausages containing a five-strain cocktail for each serogroup and uninoculated control were manufactured and subjected to identical fermentation, maturation and dry curing conditions. Changes in physicochemical properties and inoculated STEC numbers were enumerated during the DFS production stages and log reduction and log reduction rates were calculated. Inoculation of very high concentrations (8logCFUg(-1)) of STEC in the sausage batter did not significantly (P>0.05) affect the changes in the pH, aw, moisture, protein, fat content compared to the uninoculated DFS. There was a significant (P<0.05) reduction in counts within the 48h fermentation for all STEC serogroups inoculated by about 0.97- to 1.42-log units. However, during the sausage maturation stage, all serogroup...
Canadian Journal of Veterinary Research Revue Canadienne De Recherche Veterinaire, 2009
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease in ca... more Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease in cattle and other farm ruminants, and is also a suspected pathogen of Crohn’s disease in humans. Development of diagnostic methods for MAP infection has been a challenge over the last few decades. The objective of this study was to investigate the relationship between different methods for detection of MAP in milk and fecal samples. A total of 134 milk samples and 110 feces samples were collected from 146 individual cows in 14 MAP-infected herds in southwestern Ontario. Culture, IS900 polymerase chain reaction (PCR) and nested PCR methods were used for detecting MAP in milk; results were compared with those of fecal culture. A significant relationship was found between milk culture, direct PCR, and nested PCR (P < 0.05). The fecal culture results were not related to any of the 3 assay methods used for the milk samples (P > 0.10). Although fecal culture showed a higher sensitivity than the milk culture method, the difference was not significant (P = 0.2473). The number of MAP colony-forming units (CFU) isolated by culture from fecal samples was, on average, higher than that isolated from milk samples (P = 0.0083). There was no significant correlation between the number of CFU cultured from milk and from feces (Pearson correlation coefficient = 0.1957, N = 63, P = 0.1243). The animals with high numbers of CFU in milk culture may not be detected by fecal culture at all, and vise versa. A significant proportion (29% to 41%) of the positive animals would be missed if only 1 culture method, instead of both milk and feces, were to be used for diagnosis. This suggests that the shedding of MAP in feces and milk is not synchronized. Most of the infected cows were low-level shedders. The proportion of low-level shedders may even be underestimated because MAP is killed during decontamination, thus reducing the chance of detection. Therefore, to identify suspected Johne’s-infected animals using the tests in this study, both milk and feces samples should be collected in duplicate to enhance the diagnostic rate. The high MAP kill rate identified in the culture methods during decontamination may be compensated for by using the nested PCR method, which had a higher sensitivity than the IS900 PCR method used.
National and international health agencies have recommended a significant reduction in daily inta... more National and international health agencies have recommended a significant reduction in daily intake of sodium by reducing the amount of NaCl in foods, specifically processed meats. However, sodium reduction could increase the risk of survival and growth of spoilage and pathogenic microorganisms on these products. Therefore, alternate processing technologies to improve safety of sodium reduced foods are necessary. This study examined the effects of three different salt types and concentrations on high-pressure inactivation of Listeria monocytogenes in pre-blended ground chicken formulations. Ground chicken formulated with three salt types (NaCl, KCl, CaCl2), at three concentrations (0, 1.5, 2.5%) and inoculated with a four strain cocktail of L. monocytogenes (10(8)CFUg(-1)) were subjected to four pressure treatments (0, 100, 300, 600MPa) and two durations (60, 180s) in an experiment with factorial design. Surviving cells were enumerated by plating on Oxford agar and analysed by factorial ANOVA. Pressure treatments at 100 or 300MPa did not significantly (P=0.19-050) reduce L. monocytogenes populations. Neither salt type nor concentration had a significant effect on L. monocytogenes populations at these pressure levels. At 600MPa, salt types, concentrations and duration of pressure treatment all had a significant effect on L. monocytogenes populations. Formulations with increasing concentrations of NaCl or KCl showed significantly lower reduction in L. monocytogenes, while increase in CaCl2 concentration resulted in a significantly higher L. monocytogenes reduction. For instance, increase in NaCl concentration from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 2.49 and 1.29, respectively, when exposed to 600MPa for 60s. In the case of CaCl2, increase from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 7.28 and 7.47, respectively. These results demonstrate that high-pressure processing is a viable process to improve microbial safety of sodium reduced poultry products.
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