• A case of bovine raw milk contamination with Listeria monocytogenes

      Hunt, Karen; Drummond, Niall; Murphy, Mary; Butler, Francis; Buckley, James F.; Jordan, Kieran; Teagasc Walsh Fellowship Programme; Department of Agriculture, Food and the Marine, Ireland; European Union (Biomed Central, 06/07/2012)
      During routine sampling of bulk raw milk on a dairy farm, the pathogenic bacteria Listeria monocytogenes was found to be a contaminant, at numbers < 100 cfu/ml. A strain with an indistinguishable pulsed-field gel electrophoresis pattern was isolated from the bulk milk two months later. Environmental swabs taken at the dairy environment were negative for the presence of L. monocytogenes, indicating a possible case of excretion of the L. monocytogenes directly into the milk. Milk samples were collected from the individual cows and analysed, resulting in the identification of L. monocytogenes excretion (at 280 cfu/ml) from one of the 4 mammary quarters of one dairy cow out of 180. When the infected cow was isolated from the herd, no L. monocytogenes was detected from the remaining herd. The pulsed-field gel electrophoresis pattern of the strain from the individual cow was indistinguishable from that originally isolated from the bulk milk. The infected cow did not show any clinical signs of disease, nor did the appearance of the milk have any physical abnormalities. Antibiotic treatment of the infected mammary quarter was found to be ineffective. This study shows that there can be risks associated with direct contamination of raw milk with L. monocytogenes.
    • Cronobacter Sakazakii ISO 22964:2017 Testing of Milk Powders Using Commercially Available PCR

      Hunt, Karen; Jordan, Kieran; Legeay, Charlène (Teagasc, 2019-05)
      The detection of Cronobacter sakazakii in milk powder is important as a major health issue1 as it can survive for long periods in dry conditions2. Faster detection using PCR is possible and currently need to be compatible with traditionally standardised ISO methods. Viable cells are detected by PCR when dead cells and free DNA are diluted out, inhibited or destroyed. Biorad IQ–check DNA removal solution eliminates the detection of dead cells (based on endonuclease activity) or Biotecon Reagent D, (a light reactive aqueous reagent solution) is a dye designed to eliminate dead bacterial cell amplification, both avoid false-positive PCR results from dead cells. With ISO 20838: Real-Time PCR can be self-confirming and no further confirmation necessary with faster in house control and release of product quicker based on PCR results.
    • Determination of Listeria monocytogenes numbers at less than 10 cfu/g

      Hunt, Karen; Vacelet, M.; Jordan, Kieran; Department of Agriculture, Food and the Marine, Ireland; Dairy Processing Technology Centre; 11/F/008; TC 2014 0016. (Teagasc (Agriculture and Food Development Authority), Ireland, 09/06/2017)
      Listeria monocytogenes is a foodborne pathogen that causes a relatively rare foodborne disease called listeriosis, with a high mortality rate of 20%-30% and an undefined dose response. Current European Union regulations permit up to 100 colony-forming units (cfu)/g in food at the end of its shelf life, where the food has been shown not to support the growth of this pathogenic bacterium. Therefore, enumeration of L. monocytogenes at low numbers in food is important. The objective of this study was to reduce the detection limit of L. monocytogenes in food by a factor of 10. The International Organisation for Standardisation (ISO) 11290-2 method for enumeration of L. monocytogenes in food recommends spreading 0.1 mL of a 1:10 dilution of the food on the surface of an agar plate (detection limit 100 cfu/g), or 1.0 mL spread in equal parts on the surface of three agar plates (detection limit: 10 cfu/g). The pour-plate method (using 1 or 10 mL of an appropriate dilution) was compared to the spread-plate method using the ISO-approved chromogenic medium Agar Listeria according to Ottaviani and Agosti (ALOA). Using the pour-plate method, the colony morphology and halo formation were similar to the spread-plate method from pure cultures and inoculated foods. Using the pour-plate method in a 140 mm Petri dish, 10 mL of a 1:10 dilution of food allowed determination of numbers as low as 1 cfu/g. Applying this method, L. monocytogenes in naturally contaminated food samples were enumerated at numbers as low as 1-9 cfu/g.
    • Determination of the presence of pathogens and anthelmintic drugs in raw milk and raw milk cheeses from small scale producers in Ireland

      Lourenco, Antonio; Fraga-Corral, Maria; De Colli, Lorenzo; Moloney, Mary; Danaher, Martin; Jordan, Kieran; Depart of Agriculture, Food and the Marine; 15/F/690 (Elsevier, 2020-04-03)
      This aim of this study was to assess the microbiological and anthelmintic drug residue risks associated with raw milk used for cheesemaking and raw milk cheese, over an 18-month period. Samples of raw milk, milk filters, curd and cheese from nine raw milk artisan cheese producers in the south of Ireland were tested. Numbers of presumptive Bacillus cereus group, Escherichia coli, Salmonella spp., Staphylococcus aureus and Listeria monocytogenes were determined. The determination of anthelmintic drug residues, including benzimidazoles, flukicides, macrocyclic lactone (avermectin and milbemycins), levamisole and morantel was also performed. Neither L. monocytogenes, nor Salmonella spp. were detected in any of the samples tested and no anthelmintic drug residues were detected. Only one of the samples did not conform with regulatory numbers for other bacteria. This survey has shown a good microbiological and residue quality (and low risk) of the raw milk cheese and raw milk used for raw milk cheese produced in Ireland. Moreover, it has shown the importance of frequent assessment of raw milk used for cheesemaking and for raw milk cheese, as it allows the identification of potential problems facilitating resolution of these issues before they cause any public health threat.
    • Editorial: Microbial Food Safety along the Dairy Chain

      Fox, Edward M.; Fanning, Seamus; Corsetti, Aldo; Jordan, Kieran (Frontiers, 2017-08-23)
      Milk is susceptible to contamination with pathogenic and spoilage organisms and, therefore, Microbial food safety along the dairy chain is an important topic, from public health and industry perspectives. The dairy chain is an integral part of global food supply, with dairy food products a staple component of recommended healthy diets. The dairy food chain from production through to the consumer is complex, with various opportunities for microbial contamination of ingredients or food products, and as such interventions are key to preventing or controlling such contamination. Dairy foods often include a microbial control step in their production such as pasteurization, but in some cases may not, as with raw milk products. Microbial contamination may lead to a deterioration in food quality due to spoilage organisms, or may become a health risk to consumers should the contaminant be a pathogenic microorganism. As such food safety and food production are intrinsically linked.
    • Editorial: Microbial Food Safety along the Dairy Chain

      Fox, Edward M.; Fanning, Seamus; Corsetti, Aldo; Jordan, Kieran (Frontiers, 2017-08-23)
    • The effect of different precooling rates and cold storage on milk microbiological quality and composition

      Paludetti, L.F.; Kelly, Alan L.; O'Brien, Bernadette; Jordan, Kieran; Gleeson, David E (Elsevier, 2018-01-10)
      The objective of this study was to measure the effect of different milk cooling rates, before entering the bulk tank, on the microbiological load and composition of the milk, as well as on energy usage. Three milk precooling treatments were applied before milk entered 3 identical bulk milk tanks: no plate cooler (NP), single-stage plate cooler (SP), and double-stage plate cooler (DP). These precooling treatments cooled the milk to 32.0 ± 1.4°C, 17.0 ± 2.8°C, and 6.0 ± 1.1°C, respectively. Milk was added to the bulk tank twice daily for 72 h, and the tank refrigeration temperature was set at 3°C. The blend temperature within each bulk tank was reduced after each milking event as the volume of milk at 3°C increased simultaneously. The bacterial counts of the milk volumes precooled at different rates did not differ significantly at 0 h of storage or at 24-h intervals thereafter. After 72 h of storage, the total bacterial count of the NP milk was 3.90 ± 0.09 log10 cfu/mL, whereas that of the precooled milk volumes were 3.77 ± 0.09 (SP) and 3.71 ± 0.09 (DP) log10 cfu/mL. The constant storage temperature (3°C) over 72 h helped to reduce bacterial growth rates in milk; consequently, milk composition was not affected and minimal, if any, proteolysis occurred. The DP treatment had the highest energy consumption (17.6 ± 0.5 Wh/L), followed by the NP (16.8 ± 2.7 Wh/L) and SP (10.6 ± 1.3 Wh/L) treatments. This study suggests that bacterial count and composition of milk are minimally affected when milk is stored at 3°C for 72 h, regardless of whether the milk is precooled; however, milk entering the tank should have good initial microbiological quality. Considering the numerical differences between bacterial counts, however, the use of the SP or DP precooling systems is recommended to maintain low levels of bacterial counts and reduce energy consumption.
    • Evaluating the effect of storage conditions on milk microbiological quality and composition

      Paludetti, L.F.; Jordan, Kieran; Kelly, Alan L.; Gleeson, David E (Teagasc (Agriculture and Food Development Authority), Ireland, 2018-07-19)
      In this study, the effect of storage temperature (2 or 4°C) on the composition of milk and microbiological load was investigated over 96 h. Milk samples were collected from farm bulk milk tanks after one complete milking and stored at 2 or 4°C over 96 h. Total bacterial count (TBC), psychrotrophic bacterial count (PBC) and proteolytic bacterial count (PROT) were affected by storage time and temperature and varied significantly between farms (P < 0.05). The levels of TBC, PBC and PROT bacterial count increased from 4.37 to 6.15 log cfu/mL, 4.34 to 6.44 log cfu/mL and 3.72 to 4.81 log cfu/mL, respectively, when the milk was stored for 96 h at 2°C. The milk samples stored at 4°C had higher increases in these bacterial counts after 72 h in comparison to milk samples stored at 2°C. The casein fraction content was lower in milk samples stored at 4°C, which could be due to high levels of PROT bacteria or enzyme activity in these samples. Milk stored for 96 h at 2°C has less impact on composition or processability parameters compared to milk stored at 4°C.
    • Identification of existing and emerging chemical residue contamination concerns in milk

      Danaher, Martin; Jordan, Kieran; Department of Agriculture, Food and the Marine, Ireland (Teagasc (Agriculture and Food Development Authority), Ireland, 2013)
      In order to maintain the quality of Irish milk and meet increasingly demanding specifications, it is necessary to focus on chemical residues in milk, in addition to other quality issues. The objective of the work was to assess the current status of chemical contaminant analysis and to identify technological and knowledge needs. This was achieved through a review of literature with respect to chemical contaminants. Quaternary ammonium compounds (QACs) have been identified as an area of concern for the dairy industry because of the recent reports of QAC residues in dairy products internationally. Analytical support to analyse QAC residues in milk and dairy products on an ongoing basis is required. Furthermore, the source of QAC residues along the milk production chain needs to be identified. Similarly, analytical support and research is needed in the area of phthalates, to support the development of intervention strategies to reduce contamination, if present. Cephalosporin antibiotics have been a concern for the dairy industry because of the lack of suitable chemical tests to measure these substances.
    • Iodine concentrations in milk

      O'Brien, Bernadette; Gleeson, David E; Jordan, Kieran; Irish Dairy Levy Research Trust (Teagasc (Agriculture and Food Development Authority), Ireland, 2013)
      Iodine tends to be supplemented at farm level in the expectation of increasing cow health and fertility. There is concern that such practices may result in high milk iodine, which could affect ingredients for infant formula and, thus, dairy export markets. The objective of this study was to quantify the effect of iodine fortified feed and teat disinfection practices of dairy cows on milk iodine concentration. Thirty lactating cows were fed 7 kg, 3 kg (10 mg iodine/kg) and 0 kg of concentrate feed during 3 periods of 35 days each. During the first 14 days of each period, cows were on dietary iodine treatments only; during days 15–21, one of three teat disinfection treatments (n = 10) was applied (in addition to the dietary iodine treatments): non-iodine (chlorhexidine) post-milking spray; 0.5% iodine spray post-milking; 0.5% iodine spray pre- and post-milking. Cow milk yield was 21.3 kg/day. Individual cow milk samples were analysed for iodine concentration on 2 days at the end of each treatment period. Dietary supplementation of iodine at both 30 mg and 70 mg/day, when compared to the diet with no supplement, increased milk iodine concentrations significantly (P < 0.001) from 449 to 1034 and 915 μg/kg, respectively. Teat disinfection both pre- and post-milking increased milk iodine concentration at each of the dietary supplementation levels of 0, 30 and 70 mg/day compared with a non-iodine teat disinfectant (P < 0.001). In conclusion, both dietary iodine supplementation and teat disinfection iodine increased milk iodine concentrations in an additive manner, exceeding common target values of 250 μg/kg. As both iodine treatments can occur simultaneously on farm, supplementation strategies should be monitored.
    • Listeria monocytogenes in Milk Products

      Jordan, Kieran; Hunt, Karen; Dalmasso, Marion (Springer International Publishing, 2016-04-13)
      Milk and milk products are frequently identified as vectors for transmission of Listeria monocytogenes. Milk can be contaminated at farm level either by indirect external contamination from the farm environment or less frequently by direct contamination of the milk from infection in the animal. Pasteurisation of milk will kill L. monocytogenes, but post-pasteurisation contamination, consumption of unpasteurised milk and manufacture of unpasteurised milk products can lead to milk being the cause of outbreaks of listeriosis. Therefore, there is a concern that L. monocytogenes in milk could lead to a public health risk. To protect against this risk, there is a need for awareness surrounding the issues, hygienic practices to reduce the risk and adequate sampling and analysis to verify that the risk is controlled. This review will highlight the issues surrounding L. monocytogenes in milk and milk products, including possible control measures. It will therefore create awareness about L. monocytogenes, contributing to protection of public health.
    • A note on challenge trials to determine the growth of Listeria monocytogenes on mushrooms (Agaricus bisporus)

      Leong, Dara; Alvarez-Ordonez, Avelino; Jordan, Kieran; Safefood (Teagasc (Agriculture and Food Development Authority), Ireland, 30/12/2015)
      In the EU, food is considered safe with regard to Listeria monocytogenes if the number of micro-organisms does not exceed 100 colony forming units (cfu)/g throughout its shelf-life. Therefore, it is important to determine if a food supports growth of L. monocytogenes. Guidelines for conducting challenge tests for growth assessment of L. monocytogenes on foods were published by the European Union Reference Laboratory (EURL) in 2014. The aim of this study was to use these guidelines to determine if refrigerated, fresh, whole, closed-cap, prepackaged mushrooms (Agaricus bisporus) support the growth of L. monocytogenes. Three batches of mushrooms were artificially inoculated at approximately 100 cfu/g with a three-strain mix of L. monocytogenes and incubated for 2 days at 8°C followed by 4 days at 12°C. L. monocytogenes numbers were determined (in triplicate for each batch) on days 0, 2 and 6. Water activity, pH and total bacterial counts were also determined. There was no increase in the number of L. monocytogenes above the threshold of 0.5 log cfu/g in any of the replicates. In 8 of 9 replicates, the numbers decreased indicating that A. bisporus do not support the growth of L. monocytogenes. As the EU regulations allow < 100 cfu/g if the food cannot support growth of L. monocytogenes, the significance of this study is that mushrooms with < 100 cfu/g may be within the regulations and therefore, quantitative rather than qualitative determination may be required.
    • Occurrence and identification of spore-forming bacteria in skim-milk powders

      Li, Fang; Hunt, Karen; Van Hoorde, Koenraad; Butler, Francis; Jordan, Kieran; Tobin, John; Department of Agriculture, Food and the Marine; Enterprise Ireland; 14/F/883; TC 2014 0016 (Elsevier, 2019-05-28)
      The different customer and regulatory specifications for mesophilic and thermophilic aerobic and anaerobic spore numbers in skim-milk powder, in addition to some specifications on specific spore-forming bacteria, such as Bacillus cereus, can be challenging for the industry to meet. Twenty-two samples of medium-heat skim-milk spray-dried powder from eight sources were analysed in triplicate with 16 bacterial and spore enumeration tests to understand the variety of spore-forming bacteria population. Using 16S rDNA sequencing, the species were identified for 269 isolates that were representative of the various tests. Of the isolates identified, 68% were Bacillus licheniformis, a facultative anaerobe that can survive and grow at mesophilic and thermophilic temperatures, making it difficult to eliminate in manufacturing environments. Using whole genome sequencing, 16 of 23 isolates identified as B. licheniformis by 16S sequencing were confirmed as B. licheniformis, four were identified as Bacillus paralicheniformis and three were identified as Bacillus sp. H15-1.
    • Prevalence and persistence of Listeria monocytogenes in premises and products of small food business operators in Northern Ireland

      Madden, Robert H; Hutchison, Mike; Jordan, Kieran; Pennone, Vincenzo; Gundogdu, Ozan; Corcionivoschi, Nicolae; SafeFood, The Food Safety Promotion Board; 04–2014 (Elsevier, 2017-12-14)
      Listeriosis is a foodborne disease, with a high mortality rate, that predominantly affects the elderly. Under European Union legislation, EC 2073/2005, food business operators are encouraged to undertake sampling to ensure that the food processing environment, and required to ensure that food products, are free of Listeria monocytogenes. To determine the prevalence of L. monocytogenes in smaller food processing facilities in Northern Ireland, 24 companies submitted six processing environment swabs and two food samples every two months for eighteen months (July 2015 to November 2016) for L. monocytogenes examination. The prevalence of L. monocytogenes was 4.6% in food samples, and 6.3% in processing environment swabs. Over the duration of the study, 96 isolates of L. monocytogenes were obtained, one from each positive sample, except for two meat samples that had >100 cfu/g, where two isolates were obtained from each sample. No seasonality in occurrence of L. monocytogenes was seen for food isolates but significantly higher numbers of positive processing environment swabs were found in the warmer months of May, July and September (p = .007). Pulsed Field Gel Electrophoresis (PFGE) analysis revealed the presence of 27 pulsotypes; 9 pulsotypes were shared between different facilities and 9 were persistent. Based on a Combase predictive growth model, 77.5% (n = 130) of the foods tested were predicted to support the growth of L. monocytogenes. All of the isolates carried the pathogenicity genes inlA and actA and 71.4% carried qacH, which confers resistance to quaternary ammonium compounds which are frequently used in sanitizers. Whole genome sequencing of the isolates allowed multi-locus sequence typing to be undertaken. The data indicated that the sequence types identified included those with disease-causing ability, highlighting the disease-causing potential of the isolates.
    • Process environment sampling can help to reduce the occurrence of Listeria monocytogenes in food processing facilities

      Dalmasso, Marion; Jordan, Kieran; European Union; 265877 (Teagasc (Agriculture and Food Development Authority), Ireland, 2013)
      The occurrence and persistence of Listeria monocytogenes strains in food processing environments pose a risk of cross-contamination to food. The control of these strains is thus essential to ensure food safety. In the present study, 205 samples were collected from a food processing facility between May 2012 to February 2013 and analysed for the presence of L. monocytogenes by the ISO11290 standard method. L. monocytogenes isolates were differentiated using pulsed field gel electrophoresis. Up to 55% of the samples were positive for L. monocytogenes until October 2012. Advice was given on the implementation of corrective actions regarding cleaning and disinfection procedures and workflows. This resulted in a decrease in the number of positive samples, reflecting the reduction of L. monocytogenes in the processing environment. Eight pulsotypes were found in the food processing facility environment, mainly on non-food contact surfaces. One type was identified as persistent as it was isolated on each sampling occasion and constituted more than 71% of the isolates collected. It was the only type found in the processing environment after the implementation of corrective actions. This work demonstrates that processing environment sampling plans are effective to assess hygiene and implement corrective actions. This contributes to prevention of contamination events and consequently to assuring the safety of the food product.
    • Protocols and strategies to study the migration of veterinary drug residues into milk and dairy products in licensed trials

      Power, C.; Sayers, Riona; O'Brien, Bernadette; Furey, A.; Danaher, Martin; Jordan, Kieran (Teagasc (Agriculture and Food Development Authority), Ireland, 2013)
      In the interest of animal welfare, and in order that the results from animal trials are considered valid for inclusion in the development of regulations, it is necessary that such trials are undertaken in accordance with the appropriate licensing arrangements. In January 2013, new licensing arrangements were introduced in the European Union. The aim of this paper is to outline the legislative strategy required for obtaining licences for animal trials and based on live animal trials with flukicides, establishes a blueprint for obtaining the appropriate licences and undertaking the experiments.
    • Protocols and strategies to study the migration of veterinary drug residues into milk and dairy products in licensed trials – Corrigendum

      Power, C.; Sayers, Riona; O'Brien, Bernadette; Furey, A.; Danaher, Martin; Jordan, Kieran (Teagasc (Agriculture and Food Development Authority), Ireland, 2014)
      Corrigendum
    • Review of potential sources and control of thermoduric bacteria in bulk-tank milk

      Gleeson, David E; O'Connell, Aine; Jordan, Kieran; Irish Dairy Levy Research Trust (Teagasc (Agriculture and Food Development Authority), Ireland, 2013)
      Bacteria that contaminate milk include thermoduric bacteria that can survive pasteurisation and subsequently grow in the pasteurised milk or contaminate product. Elimination of thermodurics at milking is not feasible. Therefore, knowledge of their source and strategies for their reduction are important. The major sources of thermodurics in milk are contamination of the teat skin from soil and bedding, and subsequent contamination from deposits that can build up on milking equipment surfaces. Hygiene at milking can reduce the number of bacteria contaminating milk. Teat preparation at milking and a recommended plant cleaning procedure are critical to the prevention of the contamination of milk with thermoduric bacteria.
    • A Review on the Applications of Next Generation Sequencing Technologies as Applied to Food-Related Microbiome Studies

      Cao, Yu; Fanning, Seamus; Proos, Sinead; Jordan, Kieran; Srikumar, Shabarinath; Department of Agriculture, Food and the Marine, Ireland; 13/F/423 (Frontiers, 2017)
      The development of next generation sequencing (NGS) techniques has enabled researchers to study and understand the world of microorganisms from broader and deeper perspectives. The contemporary advances in DNA sequencing technologies have not only enabled finer characterization of bacterial genomes but also provided deeper taxonomic identification of complex microbiomes which in its genomic essence is the combined genetic material of the microorganisms inhabiting an environment, whether the environment be a particular body econiche (e.g., human intestinal contents) or a food manufacturing facility econiche (e.g., floor drain). To date, 16S rDNA sequencing, metagenomics and metatranscriptomics are the three basic sequencing strategies used in the taxonomic identification and characterization of food-related microbiomes. These sequencing strategies have used different NGS platforms for DNA and RNA sequence identification. Traditionally, 16S rDNA sequencing has played a key role in understanding the taxonomic composition of a food-related microbiome. Recently, metagenomic approaches have resulted in improved understanding of a microbiome by providing a species-level/strain-level characterization. Further, metatranscriptomic approaches have contributed to the functional characterization of the complex interactions between different microbial communities within a single microbiome. Many studies have highlighted the use of NGS techniques in investigating the microbiome of fermented foods. However, the utilization of NGS techniques in studying the microbiome of non-fermented foods are limited. This review provides a brief overview of the advances in DNA sequencing chemistries as the technology progressed from first, next and third generations and highlights how NGS provided a deeper understanding of food-related microbiomes with special focus on non-fermented foods.
    • A Review on the Applications of Next Generation Sequencing Technologies as Applied to Food-Related Microbiome Studies

      Cao, Yu; Fanning, Seamus; Proos, Sinead; Jordan, Kieran; Srikumar, Shabarinath; Department of Agriculture, Food and Marine; Enterprise Ireland; 13/F/423; IP 2015 0380 (Frontiers, 2017-09-21)
      The development of next generation sequencing (NGS) techniques has enabled researchers to study and understand the world of microorganisms from broader and deeper perspectives. The contemporary advances in DNA sequencing technologies have not only enabled finer characterization of bacterial genomes but also provided deeper taxonomic identification of complex microbiomes which in its genomic essence is the combined genetic material of the microorganisms inhabiting an environment, whether the environment be a particular body econiche (e.g., human intestinal contents) or a food manufacturing facility econiche (e.g., floor drain). To date, 16S rDNA sequencing, metagenomics and metatranscriptomics are the three basic sequencing strategies used in the taxonomic identification and characterization of food-related microbiomes. These sequencing strategies have used different NGS platforms for DNA and RNA sequence identification. Traditionally, 16S rDNA sequencing has played a key role in understanding the taxonomic composition of a food-related microbiome. Recently, metagenomic approaches have resulted in improved understanding of a microbiome by providing a species-level/strain-level characterization. Further, metatranscriptomic approaches have contributed to the functional characterization of the complex interactions between different microbial communities within a single microbiome. Many studies have highlighted the use of NGS techniques in investigating the microbiome of fermented foods. However, the utilization of NGS techniques in studying the microbiome of non-fermented foods are limited. This review provides a brief overview of the advances in DNA sequencing chemistries as the technology progressed from first, next and third generations and highlights how NGS provided a deeper understanding of food-related microbiomes with special focus on non-fermented foods.