Category Archives: Research

Research – Antibiofilm Efficacy of Peptide 1018 against Listeria monocytogenes and Shiga Toxigenic Escherichia coli on Equipment Surfaces

Posted on October 31, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Listeria monocytogenes and Shiga toxigenic Escherichia coli (STEC) are important foodborne bacterial pathogens that can form biofilms on equipment surfaces at food processing facilities. Pathogens in biofilms are resistant to conventional antimicrobials and require higher antimicrobial concentrations to be inactivated. In this study, the efficacy of a synthetic innate defense regulator peptide 1018 (peptide 1018) for inactivating L. monocytogenes and STEC (O26, O111, O145, O157) biofilms on stainless steel and polycarbonate surfaces was investigated. Stainless steel and polycarbonate coupons (12 mm in diameter) were used in a Centers for Disease Control and Prevention biofilm reactor containing 400 mL of 10% tryptic soy broth (TSB) that had been inoculated with an individual strain of L. monocytogenes or STEC to obtain 6 log CFU/mL populations. The reactor was set with a constant flow rate at 50 mL/h of 10% TSB for 48 h. After 48 h, coupons were treated with peptide 1018 at 0, 10, 20, or 50 μg/mL in phosphate buffer saline (PBS) for 24 h. Surviving bacterial populations were determined by scraping off the coupons and spiral plating on selective media. Significantly higher levels of pathogens in biofilms formed by certain bacterial strains, including L. monocytogenes F6854, E. coli O157:H7 RM4407 and NADC5713, and non-O157 E. coli NADC3629, were recovered on polycarbonate surfaces than on stainless steel. Antibiofilm efficacy of peptide 1018 against pathogens was concentration-dependent and varied with the type of pathogen and material surfaces. Peptide 1018 at 50 μg/mL significantly inactivated all tested bacterial biofilms on both surfaces compared with the PBS control (P < 0.05). L. monocytogenes was the bacterium most sensitive to peptide 1018; on stainless steel surfaces treated with 50 μg/mL peptide 1018, there was a 3.7- to 4.6-log CFU/cm2 reduction in Listeria populations compared with a 1.0- to 3.5-log CFU/cm2 reduction of STEC. Results suggest that peptide 1018 may be used to inactivate L. monocytogenes and STEC biofilms on equipment surfaces.

HIGHLIGHTS

  • Bacteria attach at higher levels on polycarbonate surfaces than on stainless steel.

  • L. monocytogenes is more sensitive than STEC to peptide 1018.

  • Peptide 1018 can be used to inactivate biofilms on equipment surfaces.

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Posted in Biofilm, E.coli, E.coli O111, E.coli O145, E.coli O157:H7, E.coli O26, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, STEC, STEC E.coli, Technology, Uncategorized

Research – Outbreaks of Shiga Toxin–Producing Escherichia coli Linked to Sprouted Seeds, Salad, and Leafy Greens: A Systematic Review

Posted on October 29, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Shiga toxin–producing Escherichia coli (STEC) outbreaks involving ready-to-eat salad products have been described in the scientific literature since 1995. These products typically do not undergo a definitive control step such as cooking to eliminate pathogens. To reduce the number of STEC infections from salad products, efforts will need to focus on preventing and reducing contamination throughout the food chain. We performed a systematic review of STEC outbreaks involving sprouted seeds, salad, or leafy green products to determine whether there were recurrent features, such as availability of microbiological evidence or identification of the contamination event, which may inform future investigations and prevention and control strategies. Thirty-five STEC outbreaks linked to contaminated leafy greens were identified for inclusion. The outbreaks occurred from 1995 to 2018 and ranged from 8 to more than 8,500 cases. Detection of STEC in the food product was rare (4 of 35 outbreaks). For the remaining outbreaks, the determination of leafy greens as the source of the outbreak mainly relied on analytical epidemiology (20 of 35) or descriptive evidence (11 of 35). The traceback investigation in 21 of 32 outbreaks was not able to identify possible routes leading to where the STEC bacteria came from or how the leaves were contaminated. Investigations in eight outbreaks found poor practice during processing that may have contributed to the outbreak, such as insufficient postharvest disinfection of the product. Six outbreak investigations were able to identify the outbreak strain in animal feces near the growing fields; two of these were also able to find it in irrigation water on the farms, providing a likely route of contamination. These results highlight the limitations of relying on microbiological confirmation as a basis to initiate investigations of upstream production to understand the source of contamination. This review also demonstrates the importance of, and difficulties associated with, food-chain traceback studies to inform control measures and future prevention.

HIGHLIGHTS

  • Systematic review identified 35 STEC outbreaks linked to contaminated leafy greens.

  • Most (20 of 35) outbreaks relied on epidemiological evidence to identify leafy greens.

  • In 21 of 35 studies, no evidence was found for how original contamination occurred.

  • In 11 studies, water was identified as the probable vector in the contaminating product.

  • Only two studies were able to identify the likely source and route of contamination.

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Posted in E.coli, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, microbial contamination, Microbiology, Research, STEC, Uncategorized

Research – UK study: Food not likely source of drug resistant E coli.

Posted on October 28, 2019 by | Leave a comment

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CDC E.coli

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A large genomic epidemiology study by scientists in the United Kingdom has found that most bloodstream infections caused by drug-resistant Escherichia coli involve human-associated strains of the pathogen, with little contribution from the food chain.

The study, published yesterday in The Lancet Infectious Diseases, found that the extended-spectrum beta-lactamase-producing (ESBL) E coli sequence type (ST) 131 was the predominant strain found in bloodstream isolates, as well as in samples collected from human feces and sewage, while isolates from meat, veterinary diagnostic samples, and farm runoff were dominated by other ESBL E coli sequence types. Few drug-resistant E coli strains were shared among the animal and human isolates.

The authors of the study say the findings suggest that while ESBL E coli strains are widespread in humans, animals, and the environment, there’s little crossover between these strains, and efforts to reduce invasive ESBL E coli infections should focus on limiting human transmission.

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Posted in Drug Resistance, drug resistant, E.coli, ESBL, food contamination, Food Hygiene, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Testing, Multi Drug Resistant, Research, Uncategorized

Research – Characterization of Virulence and Persistence Abilities of Listeria monocytogenes Strains Isolated from Food Processing Premises

Posted on October 27, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

We report the characterization of 15 Listeria monocytogenes strains isolated from various food processing plants by multivirulence locus sequence typing to determine virulence types (VTs) and epidemic clones. Molecular mechanisms involved in adaptation to food processing environments and related to virulence were also studied. Phenotypic behaviors associated with various antimicrobials, biofilm formations, and invasiveness were assessed. There were 11 VTs among the 15 L. monocytogenes strains. Strains belonging to six VTs were stress survival islet 1 (SSI-1) and one strain of VT94 was SSI-2. Tn6188 was found in VT6 and VT94 strains, and bcrABC cassette genes were identified in VT21, VT60, and VT63 strains. Only one strain, in VT20, showed llxS, whereas a full-size inlA was detected in strains belonging to VT8, VT20, VT21, and VT63. VT10, VT20, VT21, VT60, and VT63 strains were the most tolerant to studied disinfectants. A VT6 strain showed the strongest biofilm formation ability in polyvinyl chloride, and strains belonging to VT10, VT11, VT20, and VT94 had moderate abilities. Antimicrobial sensitivity tests showed that all the L. monocytogenes strains were multidrug resistant. F tests revealed that only strains of VT10, VT60, and VT94 were significantly noninvasive (P < 0.05) in Caco-2 cells. Our findings illustrate how L. monocytogenes isolates exploit diverse mechanisms to adapt to adverse conditions. Consequently, detailed characterization of L. monocytogenes isolates is required for comprehensive elimination of this pathogenic bacterium in food processing environments.

HIGHLIGHTS

  • Virulence types of epidemic clones are multidrug resistant and tolerant to disinfectants.

  • Presence of SSI-1, SSI-2, Tn6188, and ability to form biofilm support persistent strains.

  • Strains unable to invade Caco-2 cells have higher tolerance to disinfectants exposure.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Uncategorized

Research – Recalls of Foods due to Microbial Contamination Classified by the Canadian Food Inspection Agency, 2000 to 2017

Posted on October 27, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Recall of microbial-contaminated food products is an important intervention in preventing the transmission of foodborne illness. Here, we summarize the number and nature of foods recalled as a result of microbial contamination, classified by the Canadian Food Inspection Agency, for the period 1 January 2000 through 31 December 2017. A total of 10,432 food products were recalled from 2,094 recall events in Canada because of microbial contamination during this period. The meat, meat products and poultry category, followed by fishery and seafood products and nuts and edible seeds, contained the food products most commonly associated with microbial contamination. Most microbial-contaminated food products reported were recalled because of the presence bacterial pathogens. Salmonella contamination was responsible for the largest number of recall events, whereas Listeria monocytogenes contamination accounted for the greatest number of food products recalled because of microbial contamination. L. monocytogenes contamination was also most commonly associated with major food recall events, although records may be inflated because of an invested effort to prevent future L. monocytogenes outbreaks following a 2008 deli meat recall. The findings and data we present in this study will support future surveillance and analysis of microbial-contaminated food recalls in Canada.

HIGHLIGHTS

  • Top microbial-contaminated food products were meat, seafood, and nuts and edible seeds.

  • Salmonella contamination was responsible for the largest number of recall events.

  • L. monocytogenes accounted for the largest number of recalled food products.

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Posted in food contamination, Food Hygiene, Food Inspections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Pathogen, Food Poisoning, food recall, Food Safety, Food Testing, Listeria, Listeria monocytogenes, Research, Uncategorized

Research – Sanitization of Chicken Frames by a Combination of Hydrogen Peroxide and UV Light To Reduce Contamination of Derived Edible Products

Posted on October 26, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

Chicken carcass frames are used to obtain mechanically separated chicken (MSC) for use in other further processed food products. Previous foodborne disease outbreaks involving Salmonella-contaminated MSC have demonstrated the potential for the human pathogen to be transmitted to consumers via MSC. The current study evaluated the efficacy of multiple treatments applied to the surfaces of chicken carcass frames to reduce microbial loads on noninoculated frames and frames inoculated with a cocktail of Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium. Inoculated or noninoculated frames were left untreated (control) or were subjected to treatment using a prototype sanitization apparatus. Treatments consisted of (i) a sterile water rinse, (ii) a water rinse followed by 5 s of UV-C light application, or (iii) an advanced oxidation process (AOP) combining 5 or 7% (v/v) hydrogen peroxide (H2O2) with UV-C light. Treatment with 7% H2O2 and UV-C light reduced numbers of aerobic bacteria by up to 1.5 log CFU per frame (P < 0.05); reductions in aerobic bacteria subjected to other treatments did not statistically differ from one another (initial mean load on nontreated frames: 3.6 ± 0.1 log CFU per frame). Salmonella numbers (mean load on inoculated, nontreated control was 5.6 ± 0.2 log CFU per frame) were maximally reduced by AOP application in comparison with other treatments. No difference in Salmonella reductions obtained by 5% H2O2 (1.1 log CFU per frame) was detected compared with that obtained following 7% H2O2 use (1.0 log CFU per frame). The AOP treatment for sanitization of chicken carcass frames reduces microbial contamination on chicken carcass frames that are subsequently used for manufacture of MSC.

HIGHLIGHTS

  • Chicken carcass frames were sanitized using an advanced oxidation process.

  • Salmonella was reduced by 1.1 log CFU per frame with H2O2 and UV-C light.

  • Aerobic bacteria were reduced by up to 1.5 log CFU per frame with 7% H2O2 plus UV-C light.

  • Advanced oxidation processing produced greater reductions than water or UV-C light alone.

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Posted in food bourne outbreak, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, foodborne outbreak, foodbourne outbreak, microbial contamination, Microbiology, Research, Uncategorized, UV Microbiology

Research -Characterization of bacterial pathogens associated with milk microbiota in Egypt

Posted on October 26, 2019 by | Leave a comment

Academic Journals

Abstract

Milk is a substantial source of nutrients needed by all humans across lifespan development. Given its nutritional composition, milk is considered a vehicle for various microbes including beneficial and pathogenic bacteria. In this study, 270 milk samples comprising raw cow and buffalo milk and pasteurized milk with different shelf-life durations were tested along with pasteurized organic milk for the presence of Staphylococcus aureus and Escherichia coli. Collectively, 21 E. coli and 14 S. aureus isolates were cultivated and identified from total milk samples. All E. coli and S. aureus isolates exhibited resistance to erythromycin and penicillin, respectively. Serogroups O26, O128, and O111 were the most frequently identified amongst E. coli isolates, whereas staphylococcal enterotoxins (SEs) were inconsistently produced across S. aureus isolates. The molecular profile showed clustering of 6 isolates of E. coli by harboring stx1, stx2, eaeA genes, and 5 isolates of S. aureus by mecA gene. Findings revealed the bacteriological quality of popularly consumed milk in Egypt, including raw and pasteurized milk with preference to pasteurized organic milk and 7-day shelf life (7DSL) pasteurized milk. However, raw milk and 3MSL pasteurized milk were the major sources of E. coli and S. aureus, posing a serious public health issue.

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Posted in E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Microbiology, Raw Milk, Research, Staphylococcus aureus, Uncategorized

Research -Occurrence, Seasonal Distribution, and Molecular Characterization of Vibrio vulnificus, Vibrio cholerae, and Vibrio parahaemolyticus in Shellfish (Mytilus galloprovincialis and Ruditapes decussatus) Collected in Sardinia (Italy)

Posted on October 25, 2019 by | Leave a comment

Journal of Food Protection

ABSTRACT

In this study, we investigated the occurrence, seasonal distribution, and molecular characterization of pathogenic vibrios in Mediterranean mussels (Mytilus galloprovincialis) and grooved carpet shells (Ruditapes decussatus) from two harvesting areas of Sardinia (Italy). Samples collected before and after depuration were submitted for qualitative and quantitative determination of Vibrio spp. Vibrio spp. isolates were presumptively identified by means of biochemical methods. Identification and virulence profile of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus were performed by molecular methods. The prevalence of Vibrio spp. in M. galloprovincialis and R. decussatus was, respectively, 96 and 77%. The averaged enumeration (mean ± standard deviation) of Vibrio spp. in samples of M. galloprovincialis and R. decussatus collected at the harvesting time was 2.04 ± 0.45 and 2.51 ± 0.65 log CFU/g, respectively. The average contamination levels in samples collected after purification were 2.28 ± 0.58 log CFU/g (M. galloprovincialis) and 2.12 ± 0.67 log CFU/g (R. decussatus). Four potentially pathogenic V. parahaemolyticus isolates (tdh+ or trh+) were recovered from grooved carpet shells samples. No isolate was tdh+/trh+. The presence of potentially pathogenic vibrios in Sardinian waters strengthens the need for rational purification practices under controlled conditions to guarantee the protection of consumers.

HIGHLIGHTS

  • Occurrence and pathogenicity characteristics of Vibrio pathogens were investigated.

  • Prevalence of Vibrio spp. in M. galloprovincialis was 96% and in R. decussatus was 77%.

  • Environmental conditions influence the occurrence of Vibrio spp.

  • Four V. parahaemolyticus isolates carried tdh or trh genes.

  • Rational purification practices are needed to guarantee the protection of consumers.

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Posted in Contaminated water, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, microbial contamination, Microbiology, Research, Uncategorized, Vibrio, Vibrio cholera, Vibrio parahaemolyticus, Vibrio vulnificans, Vibrio vulnificus, Water, water microbiology

Research – Potential Ad Hoc Markers of Persistence and Virulence in Canadian Listeria monocytogenes Food and Clinical Isolates

Posted on October 25, 2019 by | Leave a comment

Food Protection Journal

ABSTRACT

The Listeria monocytogenes gene inlA, encoding a surface virulence protein, was examined for the presence of premature stop codon (PMSC) mutations in 82 isolates obtained by the Canadian Food Inspection Agency (CFIA) from foods and food contact surfaces. These mutations were coanalyzed for the presence of stress survival islet 1 (SSI-1) and for the abilities of the isolates to invade Caco-2 intestinal epithelial cells and form biofilms on polystyrene. PMSC mutations were present in one-third of the isolates (predominantly those of serogroup 1/2a), and their presence was correlated with a noninvasive phenotype. The presence of SSI-1 and the ability to form biofilms were also linked to the 1/2a serogroup. Serogroup 4b isolates lacked inlA PMSC mutations and were invasive, but neither formed biofilms nor carried SSI-1. To expand upon these experimental findings, an in silico analysis was performed on L. monocytogenes genomes from Canadian databases of 278 food isolates and 607 clinical isolates. The prevalence of inlA PMSC mutations in genomes of food isolates was significantly higher (P < 0.0001) than that in clinical isolates. Also, a three-codon deletion in inlA associated with a hyperinvasive phenotype was more prevalent in genomes from clinical isolates (primarily of clonal complex 6, serogroup 4b) than in those from food isolates (P < 0.001). In contrast, SSI-1 was significantly overrepresented (P < 0.001) in genomes from food isolates. We propose the hypothesis that SSI-1 and inlA play a role in the evolution of Canadian L. monocytogenes strains into either a virulent (represented by serogroup 4b clinical isolates) or an environmentally persistent (represented by serogroup 1/2a food isolates) phenotype. The combined presence of SSI-1 and inlA PMSC mutations have potential for use as genetic markers for risk assessment when L. monocytogenes is recovered from foods, indicating low potential for pathogenesis.

HIGHLIGHTS

  • Numerous Canadian food isolates of L. monocytogenes have attenuated virulence.

  • Food but not clinical Canadian L. monocytogenes strains often have inlA mutations.

  • Listeria strains carry potential markers of virulent or persistent phenotypes.

  • SSI-1 and inlA may be phenotypic markers for Canadian L. monocytogenes strains.

  • SSI-1 and inlA may indicate the health risk associated with L. monocytogenes food isolates.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Listeria, Listeria monocytogenes, microbial contamination, Microbiology, Research, Uncategorized

Research -Tiny droplets allow bacteria to survive daytime dryness on leaves

Posted on October 19, 2019 by | Leave a comment

Science Daily

Microscopic droplets on the surface of leaves give refuge to bacteria that otherwise may not survive during the dry daytime, according to a new study published today in eLife.

Understanding this bacterial survival strategy for dry conditions may enable scientists to develop practices that support healthy plant microbiomes in agricultural and natural settings.

The surface of an average plant leaf is teeming with about 10 million microbes — a population comparable to that of large cities — that contribute to the health and day-to-day functioning of the plant. Scientists have long wondered how bacteria are able to survive as daytime temperatures and sunlight dry off leaf surfaces.

“While leaves may appear to be completely dry during the day, there is evidence that they are frequently covered by thin liquid films or micrometre-sized droplets that are invisible to the naked eye,” says co-lead author Maor Grinberg, a PhD student at Hebrew University’s Robert H. Smith Faculty of Agriculture, Food, and Environment in Rehovot, Israel. “It wasn’t clear until now whether this microscopic wetness was enough to protect bacteria from drying out.”

To answer this question, Grinberg, together with co-lead author and Research Scientist Tomer Orevi and their team, recreated leaf surface-like conditions in the laboratory using glass plates that were exposed to various levels of humidity. They then conducted experiments with more than a dozen different bacteria species in these conditions.

They observed that while these surfaces appeared dry to the naked eye, under a microscope bacteria cells and aggregates were safely shielded in miniscule droplets. Interestingly, larger droplets formed around aggregates of more than one cell, while only tiny droplets formed around solitary cells. This microscopic wetness is caused by a process called deliquescence — where hygroscopic substances, such as aerosols, that are prevalent on leaves absorb moisture from the atmosphere and dissolve within the moisture to form the droplets.

“We found that bacteria cells can survive inside these droplets for more than 24 hours and that survival rates were much higher in larger droplets,” Orevi explains. “Our results suggest that through methods of self-organisation, for example by aggregation, these cells can improve their survival chances in environments frequently exposed to drying.”

These findings could have important implications for agriculture as human practices may inadvertently interfere with this bacterial survival mechanism, endangering the health of crops and natural vegetation, according to senior author Nadav Kashtan, PhD, Assistant Professor at Hebrew University’s Robert H. Smith Faculty of Agriculture, Food, and Environment. “A greater understanding of how microscopic leaf wetness may protect the healthy plant microbiome and how it might be disrupted by agricultural practices and human aerosol emissions is of great importance,” he says.

Kashtan also notes that similar microscopic surface wetness likely occurs in soil, in the built environment, on human and animal skin, and potentially even in extra-terrestrial systems where conditions might allow, suggesting such bacterial survival strategies are not limited to leaf surfaces.

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Materials provided by eLife.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, microbial contamination, Microbiology, Microbiome, Research, Uncategorized, water microbiology