Category Archives: E.coli O157:H7

Research – Occurrence of Escherichia coli O157:H7 in Pest Flies Captured in Leafy Greens Plots Grown Near a Beef Cattle Feedlot

Journal of Food Protection

ABSTRACT

Leafy greens are leading vehicles for Escherichia coli O157:H7 foodborne illness. Pest flies can harbor this pathogen and may disseminate it to produce. We determined the occurrence of E. coli O157:H7–positive flies in leafy greens planted up to 180 m from a cattle feedlot and assessed their relative risk to transmit this pathogen to leafy greens. The primary fly groups captured on sticky traps at the feedlot and leafy greens plots included house flies (Musca domestica L.), face flies (Musca autumnalisL.), stable flies (Stomoxys calcitrans L.), flesh flies (family Sarcophagidae), and blow flies (family Calliphoridae). E. coliO157:H7 carriage rates of house, face, flesh, and blow flies were similar (P > 0.05), ranging from 22.3 to 29.0 flies per 1,000 flies. In contrast, the carriage rate of stable flies was lower at 1.1 flies per 1,000 flies (P < 0.05). Differences in carriage rates are likely due to the uses of fresh bovine feces and manure by these different pest fly groups. E. coli O157:H7 carriage rates of total flies did not differ (P > 0.05) by distance (ranging from 0 to 180 m) from the feedlot. Most fly isolates were the same predominant pulsed-field gel electrophoresis types found in feedlot surface manure and leafy greens, suggesting a possible role for flies in transmitting E. coli O157:H7 to the leafy greens. However, further research is needed to clarify this role and to determine set-back distances between cattle production facilities and produce crops that will reduce the risk for pathogen contamination by challenging mechanisms like flies.

HIGHLIGHTS
  • E. coli O157:H7 was common in flies captured in leafy greens plots near a feedlot.

  • E. coli O157:H7 carriage rates of house, face, flesh, and blow flies were similar.

  • Stable flies had lower E. coli O157:H7 carriage than the other four fly groups.

  • E. coli O157:H7 carriage of total flies was not affected by distance up to 180 m.

  • Research is needed to determine risk for leafy green contamination by pest flies.

Research – Ultrasound treatment combined with fumaric acid for inactivating food-borne pathogens in apple juice and its mechanisms

Science Direct

Highlights

The combination of Ultrasound (US) and fumaric acid (FA) showed a synergistic bactericidal effect in apple juice.

US-FA combined treatment of apple juice did not affect quality.

Cell membrane damage was the main mechanism of US-FA synergistic lethal effect.

Abstract

The purpose of this study was to evaluate the synergistic bactericidal efficacy of combining ultrasound (US) and fumaric acid (FA) treatment against Escherichia coliO157:H7, Salmonella Typhimurium, and Listeria monocytogenes in apple juice and to identify the synergistic bactericidal mechanisms. Additionally, the effect of combination treatment on juice quality was determined by measuring the changes in color, pH, non-enzymatic browning index, and total phenolic content. A mixed cocktail of the three pathogens was inoculated into apple juice, followed by treatment with US (40 kHz) alone, FA (0.05, 0.1, and 0.15%) alone, and a combination of US and FA for 1, 2, 3, 4, and 5 min. Combined US and 0.15% FA treatment for 5 min achieved 5.67, 6.35, and 3.47 log reductions in E. coli O157:H7, S.Typhimurium, and L. monocytogenes, respectively, with the 1.55, 2.37, and 0.57 log CFU reductions attributed to the synergistic effect. Although the pH value slightly decreased as FA increased, there were no significant (P > 0.05) differences in color values, browning indices, and phenolic content between untreated and treated samples. To identify the mechanism of this synergistic bactericidal action, membrane integrity, malfunctions in the membrane efflux pump, and intracellular enzyme activity were measured. The analyses confirmed that damage to the cell envelope (membrane integrity and efflux pump) was strongly related to the synergistic microbial inactivation. These results suggest that simultaneous application of US treatment and FA is a novel method for ensuring the microbial safety of apple juice.

Research – Whole Genome Sequencing Characterization of Shiga Toxin–Producing Escherichia coli Isolated from Flour from Swiss Retail Markets

Journal of Food Protection

ABSTRACT

Shiga toxin–producing Escherichia coli (STEC) strains are often found in food and cause human infections. Although STEC O157:H7 is most often responsible for human disease, various non-O157 subtypes have caused individual human infections or outbreaks. The importance of STEC serogroup typing is decreasing while detection of virulence gene patterns has become more relevant. Whole genome sequencing (WGS) reveals the entire spectrum of pathogen information, such as toxin variant, serotype, sequence type, and virulence factors. Flour has not been considered as a vector for STEC; however, this product has been associated with several STEC outbreaks in the last decade. Flour is a natural product, and milling does not include a germ-reducing step. Flour is rarely eaten raw, but the risks associated with the consumption of unbaked dough are probably underestimated. The aim of this study was to determine the prevalence of STEC in flour samples (n = 93) collected from Swiss markets and to fully characterize the isolates by PCR assay and WGS. The prevalence of STEC in these flour samples was 10.8% as indicated by PCR, and a total of 10 STEC strains were isolated (two flour samples were positive for two STEC subtypes). We found one stx2-positve STEC isolate belonging to the classic serogroups frequently associated with outbreaks that could potentially cause severe disease. However, we also found several other common or less common STEC subtypes with diverse virulence patterns. Our results reveal the benefits of WGS as a characterization tool and that flour is a potentially and probably underestimated source for STEC infections in humans.

HIGHLIGHTS
  • Several STEC serotypes, including O26, were isolated from 8 (8.6%) of 93 flour samples.

  • STEC isolates from flour had a variety of virulence patterns.

  • Flour is a probably underestimated source of STEC infections in humans.

  • WGS for STEC characterization is more comprehensive than common serotyping.

Research – Conditions at the time of inoculation influence survival of attenuated Escherichia coli O157:H7 on field-inoculated lettuce

Science Direct

Highlights

Higher percentages of E. coli–positive plants recovered when inoculation was closer to harvest.

Higher relative humidity and leaf surface wetness were measured during night inoculation.

Short-term smaller initial population declines were observed after night inoculation.

E. coli population sizes were similar 2 or more days after night or day inoculation.

Probability of detecting E. coli was higher for longer times when inoculated at higher levels.

Abstract

The impact of plant development, environmental conditions at the time of inoculation, and inoculum concentration on survival of attenuated BSL1 Escherichia coli O157:H7 strain ATCC 700728 on field-grown romaine lettuce was evaluated over 3 years. E. coli 700728 was inoculated onto 4- and 6-week-old romaine lettuce plants in the Salinas Valley, CA, at night or the next morning with either low (5 log) or high (7 log) cell numbers per plant to simulate a single aqueous contamination event. At night, when leaf wetness and humidity levels were high, E. coli cell numbers declined by 0.5 log CFU/plant over the first 8–10 h. When applied in the morning, E. coli populations declined up to 2 log CFU/plant within 2 h. However, similar numbers of E. coli were retrieved from lettuce plants at 2 and 7 days. E. coli cell numbers per plant were significantly lower (P < 0.05) 7 days after application onto 4-week-old compared to 6-week-old plants. E. coli 700728 could be recovered by plating or enrichment from a greater proportion of plants for longer times when inoculated at high compared with low initial concentrations and after inoculation of 6-week-old plants compared with 4-week-old plants, even at the low initial inoculum. A contamination event near harvest or when leaf wetness and humidity levels are high may enhance survivability, even when low numbers of E. coli are introduced.

Research – Effects of metal oxide nanoparticles with plant extract on viability of foodborne pathogens

Wiley Online

Abstract

The present study tested the antibacterial activity, expressed as minimum bactericidal concentration (MBC), of zinc oxide nanoparticles (ZnO‐NPs), copper oxide nanoparticles (CuO‐NPs) and their combination with or without rosemary, clove or cinnamon extract against Escherichia coli O157:H7 and Listeria monocytogenes. The NPs were characterized by scanning electron microscopy. The sizes of ZnO‐NPs and CuO‐NPs were in the range of 56–71 and 171–204 nm, respectively. Results showed that ZnO‐NPs had a greater inhibitory effect against both E. coli O157:H7 and L. monocytogenes than CuO‐NPs. The MBC of ZnO‐NPs against E. coli O157:H7 and L. monocytogenes was 300 and 350 μg/mL, respectively, while the MBC of CuO‐NPs was >1,000 and 400 μg/mL, respectively. When combined, ZnO‐NPs and CuO‐NPs had additional inhibitory effects against L. monocytogenes, but not against E. coli O157:H7. In general, the antibacterial activity of the NPs against E. coli O157:H7 and L. monocytogenes was enhanced by rosemary or cinnamon extract. Incorporation of clove extract into the NPs improved the antibacterial effect against E. coli O157:H7, but not against L. monocytogenes. Thus, plant extracts may be useful adjuncts for the synthesis of ZnO‐NPs or CuO‐NPs which can be used to control foodborne pathogens.

Practical Application

Incorporation of plant extracts in the synthesis of metal oxide nanoparticles (NPs) can be applied to improve the antimicrobial activity of NPs against foodborne pathogens.

UK – Scotland – Salmonella and E. coli behind six outbreaks each last year in Scotland

Food Safety News

Shiga-toxin producing E. coli and Salmonella both caused six outbreaks last year in Scotland, according to figures from Health Protection Scotland.

Data comes from ObSurv, a surveillance system established in 1996 for general outbreaks of infectious intestinal disease in the country. It does not include those where infection is thought to have been acquired overseas.

The six outbreaks of Shiga-toxin producing E. coli (STEC) in 2018 were due to three different serogroups; three were O157, two were O145 and one was O26. A total of 22 people were affected with three outbreaks recording five cases. A source was not found for any of the outbreaks.

The total is comparable to the number of outbreaks in 2013 to 2017, when there was an average of five and a range of three to nine per year.

In five outbreaks the main mode of transmission was foodborne and in the sixth it was a combination of foodborne and person to person.

USA – Red Robin in Westminster Colorado link in E. coli O157 Outbreak

Food Poison Journal

Three individuals, including one adult and two children, tested positive for the bacteria E. coli O157:H7 with all persons having reported eating at the Red Robin restaurant located at 799 W. 146th Ave in Westminster, Colorado. Tri-County Health Department inspected the restaurant on July 9, 2019, after receiving information about the outbreak from the Colorado Department of Public Health and Environment. Two of the three individuals infected were hospitalized, and the investigation is ongoing.

Information – FDA issues new draft guidance to improve the safety of seeds for sprouting

FDA alfalfa

“Over the past 22 years, the FDA has investigated 50 reported outbreaks of foodborne illness associated with contaminated sprouts. Together, these outbreaks resulted in more than an estimated 2,600 cases of illness. Last year, there were two reported outbreaks associated with sprouts, resulting in more than an estimated 100 illnesses. Studies indicate that contaminated seed is the likely source of most sprout-related outbreaks, as this commodity is inherently more susceptible to these issues because they are grown in warm and humid conditions that are favorable for bacteria like Salmonella, Listeria and E. coli,” said FDA Deputy Commissioner for Food Policy and Response Frank Yiannas. “The FDA is committed to taking swift action to respond to outbreaks related to sprouts and keep our food supply safe, but we also know that measures to prevent issues from happening in the first place are an important element of protecting consumers. By studying outbreaks related to sprouts over the years, we have been able to recommend changes in the industry to help lower the incidence of sprout-related outbreaks. Today’s new draft guidance is another critical step, like the Sprout Safety Alliance or sprout-specific requirements of the Produce Safety Rule, the agency is taking to prevent illnesses related to sprouts.”

The U.S. Food and Drug Administration today released a proposed draft guidance, “Reducing Microbial Food Safety Hazards in the Production of Seed for Sprouting,” intended to make the sprout seed industry (seed growers, conditioners, packers, holders, suppliers, and distributors) aware of the agency’s serious concerns with the continuing outbreaks of foodborne illness associated with the consumption of raw and lightly-cooked sprouts.

Incorporating aspects of the Codex Code of Hygienic Practice for Fresh Fruits and Vegetables Annex II, Annex for Sprout Production; the International Sprout Growers Association-Institute for Food Safety and Health’s “U.S. Sprout Production Best Practices”; and Good Agricultural Practices, the FDA’s draft guidance issued today provides the agency’s recommendations to firms throughout the production chain of seed for sprouting. It states that if a grower, holder, conditioner, or distributor reasonably believes that its seeds are expected to be used for sprouting, we recommend that the grower, holder, conditioner, or distributor take steps that are reasonably necessary to prevent those seeds from becoming contaminated. We also recommend that firms throughout the supply chain – from seed production and distribution through sprouting – review their current operations related to seeds for sprouting.

During the 60-day comment period for this draft guidance, stakeholders will be able to provide comments on the draft provisions. For more information on this guidance, as well as instructions on how to submit your comments, please visit Draft Guidance for Industry: Reducing Microbial Food Safety Hazards in the Production of Seed for Sprouting.

Hong Kong – A kind of chilled raw beef product from US suspected to be contaminated with E. coli (O157:H7)

CFS

Source of Information Centre for Food Safety
Food Product Chilled raw beef product
Product Name and Description Product name: US ANGUS PRIME BEEF RIBEYE

Place of origin: US

Packer: Aurora Packing Company, Inc.

Importer: Yata Limited

Use-by-dates: May 7 to 13, 2019

Reason For Issuing Alert
  • The Centre for Food Safety (CFS), through its Food Incident Surveillance System, noted a notice issued by the US authorities concerned that raw beef products might have been contaminated with E. coli (O157:H7) and are being recalled.
  • Preliminary investigation by the CFS found that the above-mentioned local importer was suspected to have imported the affected product into Hong Kong.
Action Taken by the Centre for Food Safety
  • The CFS immediately contacted the importer concerned.
  • Follow-up investigation confirmed that the importer had imported around 150 kilograms of the above affected product. All had been sold out at its outlets.
  • The importer has initiated a recall according to the CFS’ advice.
  • The CFS will continue to monitor the incident and take appropriate follow-up action.
Advice to the Trade
  • Stop selling the affected product.
Advice to Consumers
  • Members of the public should stop consuming the product concerned immediately if they have bought it.
  • People can contract E. coli through consumption of contaminated water or undercooked and contaminated foods, resulting in gastro-intestinal diseases. Intestinal bleeding and serious complications such as hemolytic uraemic syndrome may also develop in some people.
  • Enquiries about the recall can be made to the importer’s hotline at 2694 1111 during office hours.
Further Information The CFS press release

Research – Rapid detection of single viable Escherichia coli O157:H7 cells in milk by flow cytometry

Wiley Online

kswfoodworld E.coli O157

Image CDC

 

Abstract

Escherichia coli O157:H7 (E coli O157:H7) is a highly virulent bacterial strain that is present in food, and as few as 10 cells can cause severe diseases. Rapid and sensitive bacterial detection is urgently required. In this study, we report a flow cytometry (FCM)‐based method for detecting E coli O157:H7 at the single‐cell level. Single E coli O157:H7 cells were obtained by a flow cytometric cell sorter and then artificially added to milk. Next, using BHI for 6.5 hr of enrichment, isolation of target cells, and dual staining, this method could be applied to detect single viable E coli O157:H7 cells in 25 mL of milk. The time to results (TTR) of the FCM‐based method was 7 hr.

Practical applications

The plate‐based method is the currently recommended method for detection of single E coli O157:H7 cells in milk because of the ease of operation. However, this method is time‐consuming, requiring enrichment of the target organism to attain quantifiable levels. Accordingly, rapid detection of microorganisms in milk would be of great benefit to public health. Flow cytometry (FCM) is a sensitive technique that can be used to rapidly analyze foodborne pathogens. Unfortunately, little attention has been paid to single‐cell detection in milk. This study provides a rapid method for detection of single viable E coliO157:H7 cells in milk. This method has the potential to provide effective protection against E coli O157:H7 contamination and is required for rapid detection of microorganisms in dairy products.