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ABSTRACT
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The effect of irradiation (2 kGy) on growth of and toxin production by Staphylococcus aureus and Bacillus cereus in roast beef and gravy during storage at abuse temperatures (15 and 22 degrees C) was assessed by inoculation studies.... more
The effect of irradiation (2 kGy) on growth of and toxin production by Staphylococcus aureus and Bacillus cereus in roast beef and gravy during storage at abuse temperatures (15 and 22 degrees C) was assessed by inoculation studies. Irradiation resulted in a 3-4 log10 reduction in numbers of both pathogens. Whenever B. cereus and S. aureus numbers reached 10(6) and 10(7) cfu/g, respectively, during storage their toxins were detectable. As the time taken to attain these levels was longer in irradiated than in unirradiated samples, toxin production by both pathogens was delayed by irradiation. When samples initially containing low levels (10(2)/g) of S. aureus were irradiated no toxin was produced during subsequent storage at 15 or 22 degrees C. Diarrhoeal toxin produced by B. cereus was detected after 2 days at 22 degrees C, but not at 15 degrees C, in samples containing 10(2) cells/g prior to irradiation. When higher numbers (10(6)/g) of either pathogen were present prior to irradiation, toxins were produced by both pathogens at 22 degrees C, but not at 15 degrees C. Microbial competition had an effect on the growth of B. cereus and S. aureus after irradiation when a low initial inoculum was applied. However, when a higher inoculum was used the pathogens outnumbered their competitors and competition effects were less important. It was concluded that low-dose irradiation would improve the microbiological safety of roast beef and gravy.
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ABSTRACT
Research Interests: Microbiology, Biotechnology, Biology, Zoonoses, Applied microbiology, and 15 moreMedicine, Multidisciplinary, Humans, Mycobacterium, Animals, Meat, Milk, Cattle, Applied Microbiology and Biotechnology, Water Microbiology, Crohn Disease, Mycobacterium avium, Paratuberculosis, Macrolides, and Mycobacterium avium subsp. paratuberculosis (MAP)
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The thermal inactivation of Mycobacterium avium, Myco. bovis, Myco. fortuitum, Myco. intracellulare and Myco. kansaii in milk at 63.5 degrees C was investigated. Survivors were enumerated after heating for 0, 5, 10, 15, 20 and 30 min and... more
The thermal inactivation of Mycobacterium avium, Myco. bovis, Myco. fortuitum, Myco. intracellulare and Myco. kansaii in milk at 63.5 degrees C was investigated. Survivors were enumerated after heating for 0, 5, 10, 15, 20 and 30 min and thermal death curves were constructed for each species. Mycobacterium bovis and Myco. fortuitum were found to exhibit linear thermal death curves and neither species demonstrated any survival after heating at 63.5 degrees C for 30 min (equivalent to holder pasteurization). In contrast, Myco. avium, Myco. intracellulare and Myco. kansasii yielded thermal death curves which exhibited significant 'tailing' and all three strains survived holder pasteurization.
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Research Interests: Microbiology, Biology, Bacteriophages, Medicine, Veterinary, and 15 moreClinical Microbiology, Biological Sciences, Virus, Mycobacterium, Animals, Bacteria, Milk, Cattle, Feces, Bacterial Load, Sensitivity and Specificity, Microbial Viability, Paratuberculosis, Medical and Health Sciences, and Mycobacterium avium subsp. paratuberculosis (MAP)
Research Interests: Microbiology, Food Science, Biotechnology, Biology, Ecology, and 15 moreMedicine, Multidisciplinary, Enumeration, Mycobacterium, Animals, Applied Environmental Microbiology, Bacteria, Efficiency, Milk, Cattle, Applied Microbiology and Biotechnology, Sensitivity and Specificity, Biotinylation, Paratuberculosis, and Immunomagnetic separation
Four chemical decontamination protocols for milk were compared with respect to mean percentage recovery of spiked Mycobacterium avium subsp. paratuberculosis, minimum detection limit and ease of application. Raw milk spiked with 106 cfu... more
Four chemical decontamination protocols for milk were compared with respect to mean percentage recovery of spiked Mycobacterium avium subsp. paratuberculosis, minimum detection limit and ease of application. Raw milk spiked with 106 cfu M.a. paratuberculosis was decontaminated prior to culture by: (1) treatment with 0.75% (w/v) hexadecylpyridinium chloride (HPC) for 5 h; (2) and (3) Cornell methods employing brain heart infusion broth containing 0.75% (w/v) and 0.9% (w/v) HPC, respectively; and (4) a C18-carboxypropylbetaine (CB-18) The 0.75% HPC method yielded the highest mean percentage recovery of M.a. paratuberculosis (28.7%) and was capable of detecting the lowest number of cells (30 cfu/40 ml). Treatment of milk with 0.75% HPC for 5 h was shown to be superior to the other methods for decontaminating milk prior to culture for M.a. paratuberculosis. Certain chemical decontamination protocols are too harsh for application to milk. The "best" decontamination protocol only recovered a fraction of the M.a. paratuberculosis cells present in a milk sample.
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Research Interests: Microbiology, Biology, Medicine, Multidisciplinary, Enumeration, and 15 moreOptimization, Methods, Incubation, Correlation, Mycobacterium, Applied Environmental Microbiology, Bacteria, Incubation Period, Food Contamination, Mycobacteriophages, Bioassays, Agar, Sensitivity and Specificity, Paratuberculosis, and Mycobacterium smegmatis
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Research Interests: Biotechnology, Culture, Biology, Enumeration, Escherichia coli, and 15 moreAnimals, Applied Environmental Microbiology, Bacteria, Drinking Water, Iron, Applied and Environmental Microbiology, Disinfection, Cattle, Food irradiation, Growth rate, Culture Media, Fruit Juice, Cumulant, Cryptosporidium parvum, and Egg yolk
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The non-radiometric Mycobacterium Growth Indicator Tube (MGIT) culture system has not previously been evaluated for the culture of Mycobacterium avium subsp. paratuberculosis (Map) from milk. A study was undertaken to compare the... more
The non-radiometric Mycobacterium Growth Indicator Tube (MGIT) culture system has not previously been evaluated for the culture of Mycobacterium avium subsp. paratuberculosis (Map) from milk. A study was undertaken to compare the detection capabilities and detection times of the MGIT system with those of the radiometric BACTEC 460 system currently used in our laboratory. UHT milk samples were spiked with a range of Map concentrations (10-10 cells/ml). MGIT tubes supplemented with MGIT OADC, MGIT PANTA and mycobactin J, and BACTEC vials supplemented with PANTA and mycobactin J, were inoculated with 500 μl of triplicate milk samples at each Map concentration. MGIT tubes were read manually using a UV transilluminator and BACTEC vials on the BACTEC 460TB machine. Time to detection of growth in days was recorded for each system. A corresponding BACTEC count was determined from the BACTEC growth index readings using a published formula. A further experiment assessed the recovery of Map from milk by both culture systems following decontamination with 0.75 % (w/v) cetylpyridinium chloride for 5 h. In the absence of any decontamination step both the MGIT and BACTEC culture systems were capable of detecting growth from milk samples containing 10100 Map cells within 30-40 d. The correlation coefficient between MGIT and BACTEC detection times was 0.826. MGIT detection times tended to be shorter than BACTEC detection times when low numbers of Map were present in a milk sample and slightly longer when high numbers of Map were present. After decontamination only milk samples originally spiked with > 10-10 Map exhibited growth in both culture systems. Decontamination caused a significant reduction (mean 1.44 log) in numbers of viable Map in all spiked milk samples. Overall, the MGIT system was shown to have similar detection capabilities to the BACTEC system for recovering Map from milk.
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Research Interests: Microbiology, Biology, Medicine, Clinical Microbiology, Biological Sciences, and 15 moreMice, Animals, Bovine Tuberculosis, Monoclonal Antibodies, Peptides, Cattle, Polyclonal Antibodies, Monoclonal Antibody, Rabbits, Protein Binding, Mycobacterium bovis, Antigen, Lymph nodes, Medical and Health Sciences, and Immunomagnetic separation
The objective of this study was to develop a novel screening method for detection of viable Mycobacterium avium subsp. paratuberculosis (Map) in milk and faeces, as a rapid alternative to Map culture. The new method couples Map-specific... more
The objective of this study was to develop a novel screening method for detection of viable Mycobacterium avium subsp. paratuberculosis (Map) in milk and faeces, as a rapid alternative to Map culture. The new method couples Map-specific peptide-mediated magnetic separation technique with an optimized phage amplification assay followed by detection of released progeny phage by ELISA in a competition assay format using polyclonal antibody produced against the D29 mycobacteriophage involved in the phage assay. Sample matrices were found not to interfere with the developed method, and the dynamic range of the assay was 3 × 10(2) -6 × 10(8 ) phage ml(-1) . When low numbers of Map were present (10(2) CFU ml(-1) ), the burst size of a single host Map cell was maximal (10(3) phage per cell) resulting in a highly sensitive screening assay. A rapid, sensitive immuno-based screening method suitable for the detection of viable Map in milk and faeces was developed. The novel PMS-phage-ELISA permits sensitive, qualitative detection of viable Map in milk or faeces samples within 48 h, representing a substantial decrease in time to detection compared with current culture methods for Map.
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SummaryThe safety of irradiated pork packed in 25% CO2:75% N2 and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia... more
SummaryThe safety of irradiated pork packed in 25% CO2:75% N2 and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens. Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of 102 cells g‐1. When higher inoculum levels were used (106 cells g‐1) irradiation at 1.75 kGy reduced pathogen numbers by 1 –>5 log10 cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.In all cases when high numbers (106 to 107g‐1) of spoilage and/or pathogenic bacteria were present initially on the pork the meat appeared spoiled, and although irradiation reduced the number of microorganisms, the meat was still unacceptable from a sensory viewpoint after treatment.It was concluded that the microbiological safety of irradiated, modified atmosphere packaged (MAP) pork is better than that of unirradiated MAP pork.
Research Interests: Microbiology, Chemistry, Food Science, Refrigeration, Food Pathogens, and 15 moreFood Science and Technology, Food Preservation, Listeria monocytogenes, Bacteria, Colour, Salmonella, Ionization, Warehousing, Irradiation, Modified atmosphere packaging, Food Sciences, Radiation resistance, Clostridium perfringens, Modified Atmosphere Packing of Fruits, and Yersinia Enterocolitica
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Is there a common water-activity limit for the three domains of life?
ABSTRACTMycobacterium avium subsp. paratuberculosis (MAP) causes paratuberculosis (Johne's disease) in ruminants and is suspected to be involved in the development of Crohn's disease and several autoimmune disorders. As such,... more
ABSTRACTMycobacterium avium subsp. paratuberculosis (MAP) causes paratuberculosis (Johne's disease) in ruminants and is suspected to be involved in the development of Crohn's disease and several autoimmune disorders. As such, sensitive and specific MAP detection methods are required to confirm infection in animals and identify potential sources of animal and human exposure. Despite recent developments in immunological and nucleic acid-based detection methods, culture-based detection of MAP remains the ‘gold standard’ against which the sensitivity and specificity of other detection methods are measured. However, not all culture-based approaches are equivalent in terms of detection capability, which can lead to errors in the evaluation of other detection methods. This review will provide an overview of the chronological development of culture methods for MAP, and will consider the unique growth requirements of MAP, the merits of solid versus liquid culture media, the relative ...
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<p>Beads were coated separately with different MAP binders (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147870#pone.0147870.t001" target="_blank">Table 1</a>) and then... more
<p>Beads were coated separately with different MAP binders (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147870#pone.0147870.t001" target="_blank">Table 1</a>) and then evaluated for MS individually (10 μl of beads per ml of sample) and as 50:50 combinations (5 μl of each bead type per ml of sample). Ability to capture MAP was evaluated by IS900 PCR; the expected PCR product size was 394 bp and intensity of signal was used to assess degree of MAP capture. Key: Lanes 1 and 16, MAP 806PSS suspension before MS; Lane 2–10, coated beads 1–9 tested individually; Lane 11, beads 1 and 2; Lane 12, beads 1 and 3; Lane 13, beads 2 and 3; Lane 14, beads 1 and 4;. Lane 15, biotinylated aMp3 and aMptD peptide-coated beads (control) currently employed for MAP capture at QUB; Lane 17, beads 2 and 4; Lane 18, beads 3 and 4; Lane 19, beads 1 and 5; Lane 20, beads 2 and 5; Lane 21, beads 3 and 5; Lane 22, beads 4 and 5; Lane 23, beads 1 and 7; Lane 24, beads 2 and 7; Lane 25, beads 3 and 7; Lane 26, beads 1 and 6; Lane 27, beads 2 and 6; Lane 28, beads 3 and 6; Lane 29, beads 4 and 7. Lane 30, biotinylated aMp3 and aMptD peptide-coated beads (control). Lanes MW indicate a 100 bp DNA ladder (TrackIt™, Life Technologies).</p
Research Interests: Biochemistry, Immunology, Biotechnology, Cancer, Cell Biology, and 6 moreInfectious Diseases, Space Science, PCR, Magnetic Beads, D, and G
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When advising farmers on how to control Johne's disease, the number 1 recommendation is to avoid feeding waste milk to calves and instead to feed them calf milk replacer (CMR). Obviously, this advice is based on the assumption that... more
When advising farmers on how to control Johne's disease, the number 1 recommendation is to avoid feeding waste milk to calves and instead to feed them calf milk replacer (CMR). Obviously, this advice is based on the assumption that milk replacer is free of live Mycobacterium avium subsp paratuberculosis (MAP) organisms capable of causing infection. No one has ever challenged this assumption. Preliminary work on CMR sourced in Wisconsin found that 1 of 8 (12.5%) samples tested positive for live MAP organisms by the peptide-mediated magnetic separation-phage assay (PMS-PA). Previously, 30 of 68 ( 44%) powdered milk products intended for human consumption were positive for live MAP by the same assay. The study objective was to expand the survey of CMR and to test for MAP as well as standard measures of microbiological quality.
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Dipeptidyl peptidase-4 (DPP-4) plays an important role in the enzymatic inactivation of incretin hormones. In this context, drugs that inhibit DPP-4 have been developed and clinically approved as therapies for type 2 diabetes. As the... more
Dipeptidyl peptidase-4 (DPP-4) plays an important role in the enzymatic inactivation of incretin hormones. In this context, drugs that inhibit DPP-4 have been developed and clinically approved as therapies for type 2 diabetes. As the primary substrates of DPP-4 are produced in the intestinal lining, we investigated whether lactobacilli colonizing the gut could inhibit this enzyme. Fifteen Lactobacillus strains (Lb 1–15) from human infant faecal samples were isolated, identified, extracted and screened for inhibitory activity against DPP-4. Activity was compared against Lactobacillus reference strains (Ref 1–7), a Gram-positive control (Ctrl 1) and two Gram-negative controls (Ctrl 2–3). A range of DPP-4 inhibitory activity was observed (10–32 %; p < 0.05–0.001). Strains of L. plantarum (12–25 %) and L. fermentum (14 %) had significant inhibitory activity. However, we noted that Escherichia coli (Ctrl 2) and Salmonella Typhimurium (Ctrl 3) had the greatest inhibitory activity (30–32 %). Contrastingly, some isolates (Lb 12–15) and reference cultures (Ref 1–4), instead of inhibiting DPP-4, actually enhanced it, perhaps indicating the presence of X-prolyl-dipeptidyl-amino-peptidase (PepX). This provides a future rationale for using probiotic bacteria or their components for management of type 2 diabetes via DPP-4 inhibition.
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White chick hatchery disease is an emerging disease of broiler chicks with which the virus, chicken astrovirus, has been associated. Adult birds typically show no obvious clinical signs of infection, although some broiler breeder flocks... more
White chick hatchery disease is an emerging disease of broiler chicks with which the virus, chicken astrovirus, has been associated. Adult birds typically show no obvious clinical signs of infection, although some broiler breeder flocks have experienced slight egg drops. Substantial decreases in hatching are experienced over a two-week period, with an increase in mid-to-late embryo deaths, chicks too weak to hatch and pale, runted chicks with high mortality. Chicken astrovirus is an enteric virus, and strains are typically transmitted horizontally within flocks via the faecal–oral route; however, dead-in-shell embryos and weak, pale hatchlings indicate vertical transmission of the strains associated with white chick hatchery disease. Hatch levels are typically restored after two weeks when seroconversion of the hens to chicken astrovirus has occurred. Currently, there are no commercial vaccines available for the virus; therefore, the only means of protection is by good levels of bio...
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The high mortality rate associated with Listeria monocytogenes and its ability to adapt to the harsh conditions employed in food processing has ensured that this pathogen remains a serious problem in the ready-to-eat food sector.... more
The high mortality rate associated with Listeria monocytogenes and its ability to adapt to the harsh conditions employed in food processing has ensured that this pathogen remains a serious problem in the ready-to-eat food sector. Bacteriophage-derived enzymes can be applied as biocontrol agents to target specific foodborne pathogens. We investigated the ability of a listeriophage endolysin and derivatives thereof, fused to polyhydroxyalkanoate bionanoparticles (PHA_BNPs), to lyse and inhibit the growth of L. monocytogenes. Turbidity reduction assays confirmed the lysis of L. monocytogenes cells at 37 °C upon addition of the tailored BNPs. The application of BNPs also resulted in the growth inhibition of L. monocytogenes. BNPs displaying only the amidase domain of the phage endolysin were more effective at inhibiting growth under laboratory conditions (37 °C, 3 × 107 CFU/mL) than BNPs displaying the full-length endolysin (89% vs. 83% inhibition). Under conditions that better represen...
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The focus of the present study was to evaluate the copper ions treatment on the viability of Mycobacterium avium subsp. paratuberculosis (MAP) and other bacterial communities in cow’s milk.