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.

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 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 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.

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%.

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.

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 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.

Complex formation with damage recognition protein Rad14 is essential for Saccharomyces cerevisiae Rad1-Rad10 nuclease to perform its function in nucleotide excision repair in vivo.

Nucleotide excision repair (NER) in eukaryotes requires the assembly of a large number of protein factors at the lesion site which then coordinate the dual incision of the damaged DNA strand. However, the manner by which the different protein factors are assembled at the lesion site has remained unclear. Previously, we have shown that in the yeast Saccharomyces cerevisiae, NER proteins exist as components of different protein subassemblies: the Rad1-Rad10 nuclease, for example, forms a tight complex with the damage recognition protein Rad14, and the complex of Rad1-Rad10-Rad14 can be purified intact from yeast cells. As the Rad1-Rad10 nuclease shows no specificity for binding UV lesions in DNA, association with Rad14 could provide an effective means for the targeting of Rad1-Rad10 nuclease to damage sites in vivo. To test the validity of this idea, here we identify two rad1 mutations that render yeast cells as UV sensitive as the rad1Delta mutation but which have no effect on the recombination function of Rad1. From our genetic and biochemical studies with these rad1 mutations, we conclude that the ability of Rad1-Rad10 nuclease to associate in a complex with Rad14 is paramount for the targeting of this nuclease to lesion sites in vivo. We discuss the implications of these observations for the means by which the different NER proteins are assembled at the lesion site.

Inactivation of avirulent Yersinia pestis in Butterfield's phosphate buffer and frankfurters by UVC (254 nm) and gamma radiation.

Yersinia pestis is the causative agent of plague. Although rare, pharyngeal plague in humans has been associated with consumption or handling of meat prepared from infected animals. The risks of contracting plague from consumption of deliberately contaminated food are currently unknown. Gamma radiation is a penetrating form of electromagnetic radiation, and UVC radiation is used for decontamination of liquids or food surfaces. Gamma radiation D10-values (the radiation dose needed to inactivate 1 log unit pathogen) were 0.23 (+/-0.01) and 0.31 (+/-0.03) kGy for avirulent Y. pestis inoculated into Butterfield's phosphate buffer and onto frankfurter surfaces, respectively, at 0 degree C. A UVC radiation dose of 0.25 J/cm2 inactivated avirulent Y. pestis suspended in Butterfield's phosphate buffer. UVC radiation doses of 0.5 to 4.0 J/cm2 inactivated 0.97 to 1.20 log units of the Y. pestis surface inoculated onto frankfurters. A low gamma radiation dose of 1.6 kGy could provide a 5-log reduction and a UVC radiation dose of 1 to 4 J/cm2 would provide a 1-log reduction of Y. pestis surface inoculated onto frankfurters. Y. pestis was capable of growth on frankfurters during refrigerated storage (10 degrees C). Gamma radiation of frankfurters inhibited the growth of Y. pestis during refrigerated storage, and UVC radiation delayed the growth of Y. pestis.

Radiation sensitization and postirradiation proliferation of Listeria monocytogenes on ready-to-eat deli meat in the presence of pectin-nisin films.

In this study, the ability of pectin-nisin films in combination with ionizing radiation to eliminate Listeria monocytogenes and inhibit its postirradiation proliferation was evaluated. Pectin films containing 0.025% nisin were made by extrusion. The surface of a ready-to-eat turkey meat sample was inoculated with L. monocytogenes at 10(6) CFU/cm2 and covered with a piece of pectin-nisin film. The samples were vacuum packaged and irradiated at 0, 1, and 2 kGy. The treated samples were stored at 10 degrees C and withdrawn at 0, 1, 2, 4, and 8 weeks for microbial analysis. Reductions in L. monocytogenes viability of 1.42, 1.56, 2.85, 3.78, and 5.36 log CFU/cm2 were achieved for the treatments of 1 kGy, pectin-nisin film, 2 kGy, 1 kGy plus pectin-nisin film, and 2 kGy plus pectin-nisin film, respectively. The greatest reduction (5.5 log CFU/cm2) was observed at 1 week for the 2 kGy plus pectin-nisin film treatment, suggesting that nisin was further released from the film to the surface of meat samples. Pectin-nisin films used in this study did not prevent but did significantly slow (P < 0.05) the proliferation of the L. monocytogenes cells that survived irradiation during 8 weeks of storage at 10 degrees C. These data indicate the potential use of pectin-nisin films alone or in combination with ionizing radiation for preventing listeriosis due to postprocessing contamination of ready-to-eat meat products.

Draft Genomic Sequence of Multidrug-Resistant Klebsiella pneumoniae B8S35, Isolated from Retail Chicken Skin.

Here, we report the draft genome sequence of Klebsiella pneumoniae strain B8S35, isolated from retail chicken skin. It carries genes for resistance to multiple antibiotics, as well as quaternary ammonium compounds used by the food and health care industries.

Draft Genomic Sequences of Nine Extraintestinal Pathogenic Escherichia coli Isolates from Retail Chicken Skin.

Extraintestinal pathogenic Escherichia coli strains were isolated from retail chicken skin. Here, we report the draft genomic sequences for these nine E. coli isolates, which are currently being used in agricultural and food safety research.

Draft Genome Sequences of Seven Strains of Shiga Toxin-Producing Escherichia coli O111 with Variation in Their Sensitivity to Novobiocin.

Inclusion of novobiocin as a selective agent for enrichment media and selective agars inhibits the growth of some Shiga toxin-producing Escherichia coli (STEC) strains, particularly non-O157 STEC, which can yield false-negative detection results. Here, we report the draft genomic sequences of seven STEC O111 isolates with different sensitivities to novobiocin.

Draft Whole-Genome Sequences of Seven Listeria monocytogenes Strains with Variations in Virulence and Stress Responses.

Listeria monocytogenes is an important foodborne pathogen that causes listeriosis. Here, we report the draft genome sequences of seven L. monocytogenes strains isolated from food, environmental, and clinical sources. Sequence differences at the genome level may help in understanding why these strains displayed different virulence and stress response characteristics.

Inactivation of Salmonella enteritidis and Salmonella senftenberg in liquid whole egg using generally recognized as safe additives, ionizing radiation, and heat.

The effect of combining irradiation and heat (i.e., irradiation followed by heat [IR-H]) on Salmonella Enteritidis and Salmonella Senftenberg inoculated into liquid whole egg (LWE) with added nisin, EDTA, sorbic acid, carvacrol, or combinations of these GRAS (generally recognized as safe) additives was investigated. Synergistic reductions of Salmonella populations were observed when LWE samples containing GRAS additives were treated by gamma radiation (0.3 and 1.0 kGy), heat (57 and 60 degrees C), or IR-H. The presence of additives reduced the initial radiation Dgamma -values (radiation doses required to eliminate 90% of the viable cells) by 1.2- to 1.5-fold, the thermal decimal reduction times (D,-values) by up to 3.5- and 1.8-fold at 57 and 60 degrees C, respectively, and the thermal D,-values after irradiation treatments by up to 3.4- and 1.5-fold at 57 and 60 degrees C, respectively, for both Salmonella serovars. Of all the additives investigated, nisin at a concentration of 100 IU/ml was the most effective at reducing the heat treatment times needed to obtain a 5-log reduction of Salmonella. Thus, while treatments of 21.6 min at 57 degrees C or of 5 min at 60 degrees C should be applied to achieve a 5-log reduction for Salmonella in LWE, only 5.5 min at 57 degrees C or 2.3 min at 60 degrees C after a 0.3-kGy radiation pretreatment was required when nisin at a concentration of 100 IU/ml was used. The synergistic reduction of Salmonella viability by IR-H treatments in the presence of GRAS additives could enable LWE producers to reduce the temperature or processing time of thermal treatments (current standards are 60'C for 3.5 min in the United States) or to increase the level of Salmonella inactivation.

Effect of benzene and its closed ring metabolites on intrachromosomal recombination in Saccharomyces cerevisiae.

Genome rearrangements, such as DNA deletions, translocations and duplications, are associated with cancer in rodents and humans, and clastogens are capable of inducing such genomic rearrangements. The clastogen benzene and several of its toxic metabolites have been shown to cause cancer in animals. Benzene is associated with leukemia and other blood related disorders in humans. Benzene and metabolites tested negative in short-term bacterial mutation assays such as the Salmonella Mutagenicity Test and the Escherichia coli Tryptophan Reversion Assay. These assays, while reliable for the detection of point-mutagenic carcinogens, are incapable of detecting DNA strand break inducing xenobiotics. The yeast DEL assay is based on intrachromosomal recombination events resulting in deletions and is very sensitive in detecting DNA strand breaks. In previous results the DEL assay detected 17 Salmonella positive as well as 25 Salmonella negative carcinogens [Bishop, Schiestl, Hum. Mol. Genet. 9 (2000) 2427-2434]. The carcinogen benzene and its metabolites including phenol, catechol, p-benzoquinone and hydroquinone induced DEL recombination. The benzene metabolite 1,2,4-benzenetriol was negative. Interestingly, p-benzoquinone induced DEL recombination at a dose 300-fold lower than any of the other metabolites, suggesting that it might be responsible for much of benzene's genotoxicity. In addition, an excision repair deficient strain was used, but no difference was detected compared to the wildtype, indicating that DNA adducts subject to excision repair were not formed by benzene or its metabolites.

Production of mutagenic metabolites by Metarhizium anisopliae.

NG-391 (1) and NG-393 (2), previously reported from undescribed Fusarium species as nerve-cell growth stimulants, were identified from fermentation extracts of the entomopathogenic fungus Metarhizium anisopliae. These compounds are 7-desmethyl analogues of fusarin C and (8Z)-fusarin C, mutagenic toxins from Fusarium species that contaminate corn. A mutant strain of M. anisopliae (KOB1-3) overproduces 1 and 2 by ca. 10-fold relative to the wild-type strain, ARSEF 2575, from which it was derived. Overproduction of these compounds in KOB1-3 imparts a yellow pigmentation to the culture medium of the fungus. These compounds were inactive at 100 mug/disk in antimicrobial disk diffusion assays. Compound 1 was inactive at 100 ppm in a mosquitocidal assay. However, like their fusarin analogues, 1 and 2 exhibited potent S9-dependent mutagenic activity in the Salmonella mutagenicity test. Discovery of these highly mutagenic mycotoxins in M. anisopliae suggests that screening for production of NG-391 and NG-393 in strains that are used as biocontrol agents would be a prudent course of action. The impact of these findings on the use of M. anisopliae as a biocontrol agent is currently unknown and requires further investigation.