Modeling the effect of simultaneous use of allyl isothiocyanate and cinnamaldehyde on high hydrostatic pressure inactivation of Uropathogenic and Shiga toxin-producing Escherichia coli in ground chicken.

BACKGROUND: A combination of high-pressure processing (HPP) and antimicrobials is a well-known approach for enhancing the microbiological safety of foods. However, few studies have applied multiple antimicrobials simultaneously with HPP, which could be an additional hurdle for microbial inactivation. The present study applied a full factorial design to investigate the impact of HPP (225-325 MPa; 10-20 min), allyl isothiocyanate (AITC) (0.3-0.9 g kg-1 ) and trans-cinnamaldehyde (tCinn) (1.0-2.0 g kg-1 ) on the inactivation of Shiga toxin-producing Escherichia coli (STEC) O157:H7 and uropathogenic E. coli (UPEC) in ground chicken meat. RESULTS: The regulatory requirement of 5-log reduction was achieved at 305 MPa, 18 min, 0.8 g kg-1 AITC and 1.7 g kg-1 tCinn for STEC O157:H7 and at 293 MPa, 16 min, 0.6 g kg-1 AITC and 1.6 g kg-1 tCinn for UPEC, as specified by response surface analysis and verified via experiments. The surviving population was eliminated by post-treatment storage of 9 days at 10 °C. The developed linear regression models showed r2 > 0.9 for the E. coli inactivation. The developed dimensionless non-linear regression models covered a factorial range slightly wider than the original experimental limit, with probability Pr > F (< 0.0001). CONCLUSION: Simultaneous use of AITC and tCinn reduced not only the necessary concentration of each compound, but also the intensity of high-pressure treatments, at the same time achieving a similar level of microbial inactivation. STEC O157:H7 was found to be more resistant than UPEC to the HPP-AITC-tCinn stress. The developed models may be applied in commercial application to enhance the microbiological safety of ground chicken meat. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

The evaluation of gamma irradiation and cold storage for the reduction of Campylobacter jejuni in chicken livers.

Recent outbreaks of Campylobacter mediated disease attributed to undercooked chicken livers have highlighted a continuing need for methods to reduce Campylobacter numbers in these types of food products. In this study, gamma irradiation is evaluated for its effectiveness in reducing Campylobacter jejuni numbers in experimentally contaminated chicken livers. A wide range of radiation doses were evaluated in conjunction with cold storage parameters, before and after irradiation. Storage of chicken livers at -20 °C prior to radiation treatment, as expected, increased C. jejuni radiation resistance. Livers previously stored at -20 °C exhibited D10 values of 0.748 kiloGray (kGy) compared to livers without previous storage that had a significantly lower D10 value of 0.361 kGy. Cold storage conditions post-irradiation at both 4 °C and -20 °C further reduced the C. jejuni numbers over those reduced by the initial irradiation. The largest reduction (3.8 logs) of C. jejuni numbers in livers produced by combining irradiation and cold storage was achieved using 0.8 kGy of radiation followed by 1 week storage at -20 °C. This reduction of 3.8 logs was not determined to be significantly different from the 3.5 log reduction achieved with the same radiation dose (0.8 kGy) after only 48 h of subsequent storage at -20 °C.

Inactivation of extraintestinal pathogenic E. coli clinical and food isolates suspended in ground chicken meat by gamma radiation.

Extraintestinal pathogenic Escherichia coli are common contaminants in retail poultry and involved inflammatory bowel disease, urinary tract infections and meningitis in both animals and humans. They cause significantly more illnesses and deaths in humans than Shiga toxin-producing E. coli (STEC). Ionizing radiation is used commercially for improving the safety and shelf-life of foods. In this study we inoculated ground chicken meat with 25 individual isolates of clinical uropathogenic E. coli (UPEC) and newborn meningitis causing E. coli (NMEC), isolates from retail chicken meat (CM), as well as retail chicken-skin isolates identified in our laboratory (CS). We then determined their gamma radiation inactivation kinetics (D10-value). The mean D10-value for all isolates (n = 25) was 0.30 kGy. The mean D10-value for the UPEC, NMEC, CM, and CS isolates were 0.25, 0.29, 0.29, and 0.39 kGy, respectively. The mean D10-value for the clinical isolates was 0.27 kGy vs. 0.34 kGy for the non-clinical isolates. There was no correlation between presence of virulence factors, antibiotic resistance, and radiation resistance. ExPEC were similar to that of STEC which were previously evaluated in our laboratory. The radiation doses needed to kill STEC poultry meat should also kill ExPEC.

Inactivation of Salmonella spp., pathogenic Escherichia coli, Staphylococcus spp., or Listeria monocytogenes in chicken purge or skin using a 405-nm LED array.

Raw poultry are sometimes contaminated with foodborne pathogens, which can lead to illness in humans. In recent years research has focused on a variety of light technologies to decontaminate food and food contact surfaces during meat and poultry processing. In this study we evaluated the ability of 405-nm light generated from an LED array to inactivate multi-isolate cocktails of either Salmonella spp., pathogenic Escherichia coli, Staphylococcus spp., or Listeria monocytogenes suspended in chicken purge or skin. When exposed to 180 J/cm2 405-nm light at two separate light intensities (300 mW/cm2/s or 150 mW/cm2/s) the maximum pathogen reduction on chicken skin was ca. 0.4 log. When the pathogens were suspended in chicken purge the maximum log reductions ranged from 0.23 to 0.68 log (180 J/cm2; 150 mW/cm2/s) versus 0.69 to 1.01 log (180 J/cm2; 300 mW/cm2/s). Log reductions of each pathogen, when they were subjected to heat shock prior to 405-nm light treatment, were reduced, indicating that thermal effects accounted for much of the bacterial inactivation.

The Effects of 405-nm Visible Light on the Survival of Campylobacter on Chicken Skin and Stainless Steel.

Campylobacter spp. are foodborne pathogens responsible for a significant portion of human cases of bacterial-mediated gastrointestinal disease. A primary method for the introduction of Campylobacter into the food supply is through poultry products. Reducing the number of Campylobacter on poultry products may reduce the incidence of human disease. Research has been conducted on the use of light to inactivate Campylobacter on poultry products and processing environments. More recently, the use of high intensity visible 405-nm light has been proposed for the elimination of pathogenic bacteria. This study investigated the ability of 405-nm light to reduce Campylobacter jejuni and Campylobacter coli in poultry products. Campylobacter in chicken exudate were placed onto chicken skin or food-grade stainless steel before treatment with 405-nm light. A range of 405-nm light doses were applied to cocktails of six C. jejuni or six C. coli strains in exudate at 10°C to minimize thermal effects. Little difference was observed between inactivation of C. jejuni and C. coli on poultry skin with only minor average reductions of 1.7 logs and 2.1 logs, respectively, at the maximal dose of 184-186 J/cm(2). More noticeable differences were observed when the samples were placed on stainless steel and treated with a dose of 89 J/cm(2), producing an average reduction of 3.0 logs for C. coli but only 1.1 logs for C. jejuni. The maximal dose (181-183 J/cm(2)) applied to Campylobacter on stainless steel produced significant (p ≤ 0.05) reductions for C. jejuni and C. coli of 4.9 logs and 5.1 logs, respectively. However, significant 405-nm-mediated reductions in Campylobacter numbers required exposure times to achieve necessary dose levels that might be impractical under processing conditions. In addition, the most potent exposure times likely produced secondary thermal effects by raising sample surface temperatures above 48°C.

Inactivation of avirulent Yersinia pestis on food and food contact surfaces by ultraviolet light and freezing.

Yersinia pestis, the causative agent of plague, can occasionally be contracted as a naso-pharyngeal or gastrointestinal illness through consumption of contaminated meat. In this study, the use of 254 nm ultraviolet light (UV-C) to inactivate a multi-isolate cocktail of avirulent Y. pestis on food and food contact surfaces was investigated. When a commercial UV-C conveyor was used (5 mW/cm(2)/s) 0.5 J/cm(2) inactivated >7 log of the Y. pestis cocktail on agar plates. At 0.5 J/cm(2), UV-C inactivated ca. 4 log of Y. pestis in beef, chicken, and catfish, exudates inoculated onto high density polypropylene or polyethylene, and stainless steel coupons, and >6 log was eliminated at 1 J/cm(2). Approximately 1 log was inactivated on chicken breast, beef steak, and catfish fillet surfaces at a UV-C dose of 1 J/cm(2). UV-C treatment prior to freezing of the foods did not increase the inactivation of Y. pestis over freezing alone. These results indicate that routine use of UV-C during food processing would provide workers and consumers some protection against Y. pestis.

Inactivation of a diverse set of shiga toxin-producing Escherichia coli in ground beef by high pressure processing.

Shiga toxin-producing Escherichia coli (STEC) are regularly implicated in foodborne illness outbreaks and recalls of ground beef. In this study we determined the High Pressure Processing (HPP) D10 value (the processing conditions needed to reduce the microbial population by 1 log) of 39 STEC isolates, including the "big six" serovars, O104 and O157:H7. STEC isolates included those isolated from animals and environmental sources in addition to those associated with illness in humans. Individual STEC were inoculated into 80% lean ground beef and treated with HPP (350 MPa, 4 °C, up to 40 min). The mean D10 was 9.74 min, with a range of 0.89-25.70 min. The D10 of the STEC involved in human illness was 9.25 vs. 10.40 min for those not involved in human illness (p > 0.05). The presence or absence of genes encoding virulence factors (e.g. Shiga toxin 1 or 2, intimin, or enterohemolysin) had no effect on the HPP D10 (p > 0.05). The high D10 of some STEC involved in human illness should be considered in selecting HPP processing parameters for ground beef. This study demonstrates the heterogeneity of STEC resistance to HPP. Risk assessors and the food industry can use this information to provide safer meat products to consumers.

Effect of high pressure processing on the survival of Shiga toxin-producing Escherichia coli (Big Six vs. O157:H7) in ground beef.

High pressure processing (HPP) is a safe and effective technology for improving food safety. Non-O157:H7 Shiga Toxin-producing Escherichia coli (STEC) have been increasingly implicated in foodborne illness outbreaks and recalls, and the USDA Food Safety Inspection Service (FSIS) has designated them as adulterants in meat (e.g. ground beef). In this study we compared the inactivation of multi-isolate cocktails of E. coli O157:H7 versus the non-O157:H7 STEC "Big Six" (i.e. O26, O45, O103, O111, O121, and O145) in ground beef (83% lean) using HPP at refrigeration temperature (4-7 °C). A >5-log CFU/g inactivation of both the Big Six and O157:H7 cocktails were observed at 450 MPa for 15 min. In general, the Big Six cocktail was found more sensitive to pressure stress (p < 0.05). In contrast, HPP treatment at 250 MPa (30 min) inactivated only 2.3 log of the Big Six versus 1.0 log of O157:H7. HPP treatment at 350 MPa (30 min) inactivated 4.7 log of the Big Six vs. 3.2 log of O157:H7. Multiple-cycle HPP cycles (250 or 350 MPa, three 5 min treatments) did not result in a 5 log reduction of the non-O157:H7 or O157:H7 STEC. Our results indicate that HPP inactivation parameters which are effective for O157:H7 STEC can be used for the non-O157:H7 Big Six isolates in ground beef.

Inactivation of Shiga toxin-producing Escherichia coli in lean ground beef by gamma irradiation.

In this study the radiation resistance of 40 Shiga Toxin-Producing Escherichia coli (STEC) isolates which contained various combinations of the shiga toxin 1 (stx1), shiga toxin 2 (stx2), intimin (eae), and hemolysin (ehx) genes were determined. The STEC were suspended in lean ground beef and irradiated at 4 °C. D10 values, the radiation dose needed to reduce 1 log (90%) of a microorganism, ranged from 0.16 to 0.48 kGy, with a mean of 0.31 kGy for the 40 isolates. Isolates associated with illness outbreaks had a mean D10 of 0.27 kGy, while non-outbreak isolates had a mean D10 of 0.36 kGy (p < 0.05). The presence or absence of stx1, stx2, or both stx1 and 2 had no affect on D10 (p > 0.05). The presence (0.30 kGy) or absence (0.35 kGy) of ehx had no affect on D10 (p > 0.05). However, the mean D10 of isolates lacking eae (0.37 kGy) were significantly higher than those containing eae (0.27 kGy) (p < 0.05). There was no difference in D10 for isolates lacking eae regardless of whether or not they were associated with a foodborne illness outbreak (p > 0.05). It may be possible to use some of the STEC isolates which lacked eae, ehx, or both (D10 > 0.30) as avirulent surrogates in food irradiation research. The data presented in this study provides risk assessors data for metagenomic analysis as well as food and radiation processors with valuable information to control of STEC in meat.

The effects of high-pressure treatments on Campylobacter jejuni in ground poultry products containing polyphosphate additives.

Marinades containing polyphosphates have been previously implicated in the enhanced survival of Campylobacter spp. in poultry product exudates. The enhanced Campylobacter survival has been attributed primarily to the ability of some polyphosphates to change the pH of the exudate to one more amenable to Campylobacter. In this study a ground poultry product contaminated with a 6 strain Campylobacter jejuni cocktail was utilized to determine if the efficiency of high-hydrostatic-pressure treatments was negatively impacted by the presence of commonly utilized polyphosphates. Two polyphosphates, hexametaphosphate and sodium tripolyphosphate, used at 2 concentrations, 0.25 and 0.5%, failed to demonstrate any significant negative effects on the efficiency of inactivation of C. jejuni by high-pressure treatment. However, storage at 4°C of the ground poultry samples containing C. jejuni after high-pressure treatment appeared to provide a synergistic effect on Campylobacter inactivation. High-pressure treatment in conjunction with 7 d of storage at 4°C resulted in a mean reduction in C. jejuni survival that was larger than the sum of the individual reductions caused by high pressure or 4°C storage when applied separately.

Inactivation of avirulent pgm(+) and Δpgm Yersinia pestis by ultraviolet light (UV-C).

Yersinia pestis is the causative agent of bubonic plague. Though not considered a foodborne pathogen, Y. pestis can survive, and even grow, in some foods, and the foodborne route of transmission is not without precedent. As such, concerns exist over the possible intentional contamination of foods with this deadly pathogen. Here we report the inactivation of avirulent (pYV-minus) strains of Y. pestis by ultraviolet light (UV-C, 254 nm). Two strains of Y. pestis containing an intact pgm virulence locus (pgm(+)) and strains from which the pgm locus was spontaneously deleted (Δpgm) were tested using cells grown in both logarithmic and stationary phase. The D10 values for inactivation (the UV-C dose required to inactivate one log of bacterial cells) of Y. pestis on the surface of agar plates ranged from 0.69 to 1.09 mJ/cm(2). A significant difference was observed between the inactivation of cells of Y. pestis strain Yokohama grown in logarithmic and stationary phases, but no significant difference between growth phase sensitivity to UV-C was observed in Y. pestis strain Kuma. No difference in D10 values was observed between pgm(+) and Δpgm strains of Yokohama grown to either logarithmic or stationary phase. A measurable difference was observed between the D10 of Kuma pgm(+) and Kuma Δpgm grown in logarithmic phase, but this difference was diminished in the Kuma strains grown to stationary phase. Though strain variations exist, the results showing that UV-C can inactivate Y. pestis cells on agar surfaces suggest that UV-C would be effect in inactivating Y. pestis on food surfaces, particularly foods with a smooth surface.

Draft genomic sequence for uropathogenic Staphylococcus saprophyticus ATCC 49453.

Staphylococcus saprophyticus, a common contaminant of foods, causes urinary tract infections in humans. Here, we report the draft genomic sequence for S. saprophyticus ATCC 49453, which is currently being used in food safety research.

Identifying reference conditions and quantifying biological variability within benthic macroinvertebrate communities in perennial and non-perennial northern California streams.

Identification of minimally disturbed reference sites is a critical step in developing precise and informative ecological indicators. We tested procedures to select reference sites, and quantified natural variation (inter-site and -annual variability) among reference conditions using a macroinvertebrate data set collected from 429 mediterranean-climate stream reaches in the San Francisco Bay Area, California (USA). We determined that a landscape GIS-based stressor screen followed by a local field-based stressor screen effectively identified least-disturbed reference sites that, based on NMS ordination results, supported different biological communities than sites identified with only landscape (GIS) or local (field) stressors. An examination of least-disturbed reference sites indicated that inter-site variability was strongly associated with stream hydrology (i.e., perennial vs. non-perennial flow) and annual precipitation, which highlights the need to control for such variation when developing biological indicators through natural gradient modeling or using unique biological indicators for both non-perennial and perennial streams. Metrics were more variable among non-perennial streams, indicating that additional modeling may be needed to develop precise biological indicators for non-perennial streams. Among 192 sites sampled two to six times over the 8-year study period, the biological community showed moderate inter-annual variability, with the 100 point index of biotic integrity scores varying from 0 to 51 points (mean = 11.5). Variance components analysis indicated that inter-annual variability explained only a fraction (5-18 %) of the total variation when compared against site-level variation; thus efforts to understand causes of natural variation between sites will produce more precise and accurate biological indicators.

Draft Genomic Sequence for Klebsiella pneumoniae 060517CS3-g, a Bacterium Harboring Multidrug Resistance Genes, Isolated from Retail Ground Chicken Meat.

Klebsiella pneumoniae is an important foodborne pathogen that can cause human infections. Here, we report the draft genomic sequence for K. pneumoniae 060517CS3-g, isolated from retail ground chicken meat, which has several antibiotic resistance genes, multiple plasmids, and genes that may result in its hypervirulence based on the sequence data.

Complete Genome Sequence of Escherichia coli Strain FEX669, a ColV Plasmid-Containing Isolate from Retail Chicken Meat.

Escherichia coli strain FEX669 was isolated from retail ground chicken and shown to contain the extraintestinal pathogenic E. coli (ExPEC) virulence genes sfaD, focC, and iutA Because this presumptive ExPEC strain was isolated from a retail food item and it was a weak biofilm former, it was characterized using whole-genome sequencing using the PacBio RS II platform. Genomic analysis showed that the FEX669 chromosome is 4,973,943 bp long, with a GC content of 50.47%, and is accompanied by a ColV plasmid that is 237,102 bp long, with a GC content of 50.49%.

Survival Evaluation of Salmonella and Listeria monocytogenes on Selective and Nonselective Media in Ground Chicken Meat Subjected to High Hydrostatic Pressure and Carvacrol.

High pressure processing (HPP) and treatment with the essential oil extract carvacrol had synergistic inactivation effects on Salmonella and Listeria monocytogenes in fresh ground chicken meat. Seven days after HPP treatment at 350 MPa for 10 min, Salmonella treated with 0.75% carvacrol was reduced to below the detection limit (1 log CFU/g) at 4°C and was reduced by ca. 6 log CFU at 10°C. L. monocytogenes was more sensitive to these imposed stressors, remaining below the detection limit during storage at both 4 and 10°C after HPP treatment at 350 MPa for 10 min following treatment with 0.45% carvacrol. However, pressure-injured bacterial cells may recover and lead to an overestimation of process lethality when a selective medium is used without proper justification. For HPP-stressed Salmonella, a 1- to 2-log difference was found between viable counts on xylose lysine Tergitol 4 agar and aerobic plate counts, but no significant difference was found for HPP-stressed L. monocytogenes between polymyxin-acriflavine-lithium chloride-ceftazidime-esculin-mannitol (PALCAM) agar and aerobic plate counts. HPP-induced bacterial injury and its recovery have been investigated by comparing selective and nonselective agar plate counts; however, few investigations have addressed this issue in the presence of essential oil extracts, taking into account the effect of high pressure and natural antimicrobial compounds (e.g., carvacrol) on bacterial survival in various growth media. Use of selective media may overestimate the efficacy of bacterial inactivation in food processing evaluation and validation studies, and the effects of various media should be systematically investigated.

Draft Genome Sequence of Red-Heat-Causing Halomonas eurihalina MS1, a Moderately Halophilic Bacterium Isolated from Saline Soil in Alicante, Spain.

Here, we report the draft genome sequence of Halomonas eurihalina MS1, which was isolated from saline soil in Alicante, Spain, and causes the condition known as "red heat" in salt-packed cured hides, decreasing their commercial value for leather production.

Solid-phase micro extraction of food irradiation marker 2-dodecylcyclobutanone (2-DCB) from chicken jerky treated with glycerol.

The food irradiation marker, 2-dodecylcyclobutanone (2-DCB), assayed by SPME provides a fast and simple method to estimate the irradiation history of fat-containing food products. The SPME conditions were optimized to maximize the extraction of 2-DCB from chicken jerky treats (CJT) irradiated at low (5 kGy) and high (50 kGy) doses. The extracted 2-DCB was measured using GC-MS in selected ion mode (m/z 98, and 112). Water dilution (1:5) was needed to mobilize 2-DCB and allow partition to the headspace form the CJT matrix. Increasing the incubation temperature to 80 °C resulted in higher response. Spiking control jerky samples with 2-DCB from 10 to 150 ng/g CJT compared with spiking water revealed a significant food matrix effect. This method provides a fast, simple, and environmental friendly alternative for the existing solvent extraction methods.

An analysis of cellulose- and dextrose-based radicals in sweet potatoes as irradiation markers.

Dried sweet potatoes (SPs) are often irradiated for improved safety and shelf life. Formation of irradiation-derived radicals was analyzed using electron paramagnetic resonance (EPR) spectroscopy. These irradiation-specific radicals can be used to characterize the irradiation history of dry plant-based foods containing cellulose and sugars. The signal characteristics (intensity and peak shape) were evaluated at different sample locations (skin and flesh), as a function of sample preparation method (grinding, sieving, and pelletizing). The signal intensity was quantified using a double integration method of the peaks based on the area under the curve. The sieving caused ca. 50% decrease in total signal intensity as compared to nonsieved samples due to loss of cellulose-based radicals. The flesh of irradiated SP showed complex EPR spectra with multiple satellite peaks of cellulose radicals (333.5 and 338.8 mT) and split peak of dextrose radicals (337.4 mT); while skin spectra were distinctive of cellulose radicals. In this study, we demonstrated the effects of sample composition and preparation method on formation and analysis of irradiation-specific radicals based on EPR. PRACTICAL APPLICATION: In the last decade or so, there have been health concerns related to the consumption of irradiated pet food products. Electron paramagnetic resonance spectroscopy can be used to analyze the irradiation history of dry products containing cellulose and sugar, such as the popular dog treat dried sweet potatoes, to ensure the products were irradiated within safe limits. This work demonstrates that the formation of irradiation-specific radicals is affected by the sample location (skin and flesh) and moisture content.

Draft Genomic Sequences of Three Escherichia coli Sequence Type 131 Isolates (H45, H43ii, and H43iii) from Patients in Lagos, Nigeria.

Escherichia coli sequence type 131 (ST131) has recently emerged as a leading multidrug-resistant pathogen that causes urinary tract and bloodstream infections in humans. Here, we report the draft genomic sequences of three E. coli ST131 isolates, H45, H43ii, and H43iii, from urine samples of patients in Lagos, Nigeria.