Ultraviolet light (254 nm) inactivation of Listeria monocytogenes on frankfurters that contain potassium lactate and sodium diacetate.

Listeria monocytogenes, a psychrotrophic foodborne pathogen, is an occasional postprocess contaminant on ready-to-eat meat (RTE) products including frankfurters. Ultraviolet C light (UVC) is an FDA-approved technology for the decontamination of food surfaces. In this study, the ability of UVC to inactivate L. monocytogenes on frankfurters that contained potassium lactate (PL) and sodium diacetate (SDA), either before or after packaging, was investigated. UVC irradiation of frankfurters that were surface-inoculated with L. monocytogenes resulted in a 1.31, 1.49, and 1.93 log reduction at doses of 1, 2, and 4 J/cm(2), respectively. UVC treatment had no effect on frankfurter color or texture at UVC doses up to 4 J/cm(2). Frankfurter meat treated with UVC doses up to 16 J/cm(2) did not increase mutagenesis in bacterial or human cells, either with or without exogenous metabolic activation. UVC treatment of single-layer frankfurter packs at a dose of 2 J/cm(2) resulted in a 0.97 (+/- 0.14) log reduction of L. monocytogenes. Following 8 wk of refrigerated storage L. monocytogenes levels decreased by only 0.65 log in non-UVC-treated frankfurter packs compared with 2.5 log in the UVC-treated packs. Because the numbers of L. monocytogenes associated with contaminations of ready-to-eat meats are typically very low, the use of UVC in combination with potassium lactate and sodium diacetate has the potential to reduce the number of frankfurter recalls and foodborne illness outbreaks.

Inactivation of Listeria innocua on frankfurters by ultraviolet light and flash pasteurization.

Listeria monocytogenes, a psychrotrophic foodborne pathogen, is a recurring postprocess contaminant on ready-to-eat meat (RTE) products including frankfurters. Flash (Steam) Pasteurization (FP) and ultraviolet light (254 nm-UVC) has been shown to reduce levels of L. monocytogenes and L. innocua on frankfurters. In this study, the use of UVC light followed by FP to inactivate L. innocua, a nonpathogenic surrogate for L.monocytogenes, on frankfurters that contained sodium diacetate and potassium lactate (SDA/PL) in a pilot-plant setting was investigated. Application of UVC (1.0 J/cm2), followed by FP (0.75 s steam/121 degrees C) resulted in inactivation of 3.19 log L. innocua, while application of UVC (4.0 J/cm2), followed by FP (3 s steam/121 degrees C) resulted in inactivation of 3.89 log of L. innocua. A refrigerated storage study (8 degrees C) of frankfurters that contained SDA/PL that were treated with UVC followed by FP revealed the growth of L. innocua was inhibited for approximately 8 wk following application of the interventions. The use of UVC in combination with FP had little effect on frankfurter color and texture. The combination of UVC, FP, and SDA/PL was found to be an effective hurdle process for decontamination of frankfurter surfaces.

Inactivation of Listeria innocua on frankfurters that contain potassium lactate and sodium diacetate by flash pasteurization.

Listeria monocytogenes, a psychrotrophic foodborne pathogen, is a recurring postprocess contaminant on ready-to-eat meat (RTE) products, including frankfurters. Potassium lactate (PL) and sodium diacetate (SDA) are FDA-approved antimicrobials that inhibit the growth of L. monocytogenes when incorporated into the formulation of fine emulsion sausage. Flash (steam) pasteurization (FP) has been shown to reduce levels of L. monocytogenes, and its surrogate L. innocua, on frankfurter surfaces. The ability of FP to inactivate and prevent the growth of the L. monocytogenes surrogate L. innocua in a pilot plant setting was investigated. FP treatment (1.5 s, 121 degrees C) of single layers of frankfurters that were surface-inoculated with either 5, 4, or 3 log CFU/g of L. innocua immediately before FP (1.5 s, 121 degrees C) resulted in log reductions of 1.97 (+/- 0.11), 2.03 (+/- 0.10), or 2.07 (+/- 0.14), respectively. Inoculum level had no effect on the inactivation of L. innocua. Following 8 wk of refrigerated storage (4 degrees C), L. innocua levels decreased by 0.5 log in non-FP-treated frankfurter packs, while the 2 log reduction of L. innocua was maintained for FP-treated frankfurters. FP (1.5 s, 121 degrees C) had no effect on frankfurter color or texture. Because the numbers of L. monocytogenes associated with contaminations of ready-to-eat meats are typically very low, the use of FP in combination with PL and SDA has the potential to reduce the number of frankfurter recalls and foodborne illness outbreaks.

Inactivation of Escherichia coli JM109, DH5alpha, and O157:H7 suspended in Butterfield's Phosphate Buffer by gamma irradiation.

Food irradiation is a safe and effective method for inactivation of pathogenic bacteria, including Escherichia coli O157:H7, in meat, leafy greens, and complex ready-to-eat foods without affecting food product quality. Determining the radiation dose needed to inactivate E. coli O157:H7 in foods and the validation of new irradiation technologies are often performed through inoculation of model systems or food products with cocktails of the target bacterium, or use of single well-characterized isolates. In this study, the radiation resistance of 4 E. coli strains, 2 DNA repair deficient strains used for cloning and recombinant DNA technology (JM109 and DH5alpha) and 2 strains of serotype O157:H7 (C9490 and ATCC 35150), were determined. The D-10 values for C9490, ATCC 35150, JM109, and DH5alpha stationary phase cells suspended in Butterfield's Phosphate Buffer and irradiated at 4 degrees C were 229 (+/- 9.00), 257 (+/- 7.00), 61.2 (+/- 10.4), and 51.2 (+/- 8.82) Gy, respectively. The results of this study indicate that the extreme radiation sensitivity of JM109 and DH5alpha makes them unsuitable for use as surrogate microorganisms for pathogenic E. coli in the field of food irradiation research. Use of E. coli JM109 and DH5alpha, which carry mutations of the recA and gyrA genes required for efficient DNA repair and replication, is not appropriate for determination of radiation inactivation kinetics and validation of radiation processing equipment.

Modeling the irradiation followed by heat inactivation of Salmonella inoculated in liquid whole egg.

This study presents mathematical models that describe the inactivation of Salmonella Enteritidis, Salmonella Typhimurium, and Salmonella Senftenberg suspended in liquid whole egg (LWE) by irradiation followed by heat treatments (IR-H treatments). These models also enable prediction of cell injury in Salmonella after exposure to IR-H. Salmonella viability decreased exponentially (primary model) with heat treating time for all the radiation doses (0, 0.1, 0.3, 0.5, 1.0, and 1.5 kGy) and temperatures investigated (55, 57, and 60 degrees C). Two secondary models that related the D(T) values (time required to eliminate 90% of viable cells at a given temperature) with radiation dose, heating temperature, and recovery medium after treatments were also developed. The developed final equations enabled to establish the process criterion (combinations of irradiation doses, temperature, and heat treatment times) required to achieve a given reduction (performance criterion) in Salmonella spp. suspended in LWE or the cell damage caused by the treatments. Process criteria to obtain the established performance criteria (a 5-log(10) reduction) on any of the investigated Salmonella serovars were determined to be, 57.7 degrees C/3.5 min following 1.5 kGy when treated cells were recovered in tryptic soy agar and 59.3 degrees C/3.5 min following 0.5 kGy when cells were recovered in tryptic soy agar amended with 3% NaCl. Based on our results, current industrial LWE heat treatments (60 degrees C/3.5 min) would inactivate 3 log(10) cycles of the Salmonella population. The results of this study can be applied to engineering design and for the evaluation and optimization of the IR-H process as a new technique to obtain Salmonella-free LWE.

Irradiation inactivation of four Salmonella serotypes in orange juices with various turbiditiest.

Reconstituted orange juice inoculated with Salmonella Anatum, Salmonella Infantis, Salmonella Newport, or Salmonella Stanley was treated with gamma radiation at 2 degrees C. To determine the relationship between juice antioxidant power and Dgamma (dose required to achieve 90% mortality), juice solids were removed prior to inoculation by centrifugation and/or filtration to create juice preparations of varying turbidity. In unadulterated orange juice, Salmonella Anatum (Dgamma = 0.71 kGy) was significantly more resistant than the other species tested. Salmonella Newport (Dgamma = 0.48 kGy) and Salmonella Infantis (Dgamma = 0.35 kGy) were significantly different, while Salmonella Stanley (Dgamma = 0.38 kGy) was intermediate between the two. Neither the resistance of each isolate nor the pattern of relative resistance among isolates was altered in reduced turbidity juice preparations. Although total antioxidant power was associated with the level of juice solids resuspended in phosphate buffer, antioxidant power was not significantly associated with turbidity in the juice preparations or with Dgamma of any species. The variable resistance to irradiation of the Salmonella isolates suggests this as a more significant factor than turbidity or antioxidant power in designing antimicrobial juice irradiation protocols.

Comparison of responses of base-specific Salmonella tester strains with the traditional strains for identifying mutagens: the results of a validation study.

The ability of a TA7000 series of Salmonella his- mutant tester strains to detect mutagens as classified by the traditional tester strains (TA100, TA98, TA1535, TA1537, TA97, TA102 and TA104) was evaluated using 30 coded chemicals, 5 of which were duplicates with different code numbers. The TA7000 series of tester strains were TA7001, TA7002, TA7003, TA7004, TA7005 and TA7006, each of which reverts by a specific base substitution. In addition, each chemical was tested in a mixture of the base-specific strains (the Mix), plus the traditional strains, TA98 and TA1537. A liquid version of the Salmonella mutagenicity assay was performed in microtiter plates to allow partial automation for increased throughput. The results were compared to those in the National Toxicology Program (NTP) database, which were obtained from the traditional strains in the preincubation assay. In the two strains common to both protocols, TA98 and TA1537, the agreement was 80% and 85%, respectively. When compared to the NTP results for TA100, the Mix gave a 72% concordance, while the addition of the frameshift tester strain, TA98, increased the agreement to 76%. The overall agreement on positive or negative classifications of mutagenicity was 88% for the 25 chemicals tested. There were three notable exceptions to the overall agreement. Benzaldehyde was detected as a mutagen in TA7005 in contrast to its classification as a non-mutagen in the NTP database. This does not necessarily contradict the NTP results because the base-specific strains may respond to different mutagens. Two weak mutagens in the NTP database, 1-chloro-2-propanol and isobutyl nitrite, were not detected as mutagens in the base-specific new strains in the liquid protocol. While there are a number of major differences in the two assays, it was concluded that the results from each procedure are comparable.

Conditional lethality of null mutations in RTH1 that encodes the yeast counterpart of a mammalian 5'- to 3'-exonuclease required for lagging strand DNA synthesis in reconstituted systems.

A 5'- to 3'-exonuclease of about 45 kDa has been purified from various mammalian sources and shown to be required for the completion of lagging strand synthesis in reconstituted DNA replication systems. RTH1 encodes the yeast Saccharomyces cerevisiae counterpart of the mammalian enzyme. To determine the in vivo biological role of RTH1-encoded 5'- to 3'-exonuclease, we have examined the effects of an rth1 delta mutation on various cellular processes. rth1 delta mutants grow poorly at 30 degrees C, and a cessation in growth occurs upon transfer of the mutant to 37 degrees C. At the restrictive temperature, the rth1 delta mutant exhibits a terminal cell cycle morphology similar to that of mutants defective in DNA replication, and levels of spontaneous mitotic recombination are elevated in the rth1 delta mutant even at the permissive temperature. The rth1 delta mutation does not affect UV or gamma-ray sensitivity but enhances sensitivity to the alkylating agent methyl methanesulfonate. The role of RTH1 in DNA replication and in repair of alkylation damage is discussed.

DNA repair gene RAD3 of S. cerevisiae is essential for transcription by RNA polymerase II.

The RAD3 gene of Saccharomyces cerevisiae is required for excision repair of ultraviolet-damaged DNA and is essential for cell viability. The RAD3-encoded protein shares a high degree of homology with the human ERCC2(XPD) gene product. Mutations in XPD, besides causing the cancer-prone syndrome xeroderma pigmentosum, can also result in Cockayne's syndrome and trichothiodystrophy. To investigate the role of RAD3 in viability, we examined here the effect of a recessive, temperature-sensitive (ts) conditional lethal mutation of the gene on transcription by RNA polymerase II. Upon transfer to the restrictive temperature, the rad3-ts mutant rapidly ceases growth and poly(A)+ RNA synthesis is inhibited drastically. Messenger RNA levels of all the genes examined, HIS3, TRP3, STE2, MET19, RAD23, CDC7, CDC9 and ACT1, decline rapidly upon loss of RAD3 activity. The synthesis of heat-shock-inducible HSP26 mRNA and galactose-inducible GAL7 and GAL10 mRNAs is also drastically inhibited in the rad3-ts mutant at the restrictive temperature. The RNA polymerase II transcriptional activity in extract from the rad3-ts14 strain is thermolabile, and this in vitro transcriptional defect can be fully corrected by the addition of homogeneous RAD3 protein. These findings indicate that RAD3 protein has a direct and essential role in RNA polymerase II transcription.

Specific complex formation between proteins encoded by the yeast DNA repair and recombination genes RAD1 and RAD10.

The RAD1 and RAD10 genes of Saccharomyces cerevisiae are required for excision repair of ultraviolet light-damaged DNA, and they also function in a mitotic recombination pathway that is distinct from the double-strand-break recombination pathway controlled by RAD52. Here, we show that the RAD1 and RAD10 proteins are complexed with each other in vivo. Immunoprecipitation of yeast cell extracts with either anti-RAD1 antibody or anti-RAD10 antibody coprecipitated quantitative amounts of both RAD1 and RAD10 proteins. The level of coprecipitable RAD1 and RAD10 increased when both proteins were overproduced together, but not if only one of the proteins was overproduced. The RAD1/RAD10 complex is highly stable, being refractory to 1 M NaCl and to low concentrations of SDS. By hydroxylamine mutagenesis, we have identified a rad1 mutant allele whose encoded protein fails to complex with RAD10. The interaction-defective rad1 mutant resembles the rad1 or rad10 null mutant in defective DNA repair and recombination, implying that complex formation is essential for the expression of biological activities controlled by RAD1 and RAD10.

Once a soldier, always a dependent.

Why are veterans entitled to special benefits, such as free medical care? Not because such a benefit is an inducement to military service, or because a soldier accepts risk. Rather, the relationship of the Army, to use one service as an example, to a soldier is like that of a parent to a child. The right to health care, even carried beyond the term of service, is an extension of this quasi-familial relationship.

KIE: Comparing the military personnel-Army relationship to the relationship between children and parents, Sommers offers a rationale for the provision of health care during active military service and for service-connected disabilities beyond active duty. For disabilities or conditions that are not service-connected, Congress may take a step in the right direction by requiring veterans to show financial need before receiving care from the Veterans Administration. This would follow the parent-child analogy--a parent may choose to support or assist an adult child, but the child has no right to such care.