Inactivation of hepatitis A virus, feline calicivirus, and Tulane virus on Formica coupons using ultraviolet light technologies.

Contaminated fomites can lead to hepatitis A virus (HAV) and human norovirus (HuNoV) disease outbreaks. Improved decontamination methods that are user-friendly, cost-effective, and waterless are being researched for sustainability. Traditional ultraviolet light (UV-C) technologies though effective for surface decontamination have drawbacks, using mercury lamps, that pose user-safety risk and environmental hazards. Therefore, UV-C light emitting diode (LED) systems are being designed for delivering required antiviral doses. The objective of this research was to determine the ability of UV-C LED (279 nm) systems to inactivate HuNoV surrogates, feline calicivirus (FCV-F9) and Tulane virus (TV), and HAV on Formica coupons in comparison to UV-C (254 nm) systems. FCV-F9 (∼6 log PFU/mL), TV (∼7 log PFU/mL), or HAV (∼6 log PFU/mL) at 100 µL were surface-spread on sterile Formica coupons (3 × 3 cm2), air-dried, and treated for up to 2.5 min with both systems. Each experiment was replicated thrice. Recovered infectious plaque counts were statistically analyzed using mixed model analysis of variance. FCV-F9, TV, and HAV showed D10 values of 23.37 ± 0.91 mJ/cm2, 16.32 ± 3.6 mJ/cm2, and 12.39 ± 0.70 mJ/cm2 using 279 nm UV-C LED, respectively and D10 values of 9.97 ± 2.44 mJ/cm2, 6.83 ± 1.13 mJ/cm2 and 12.40 ± 1.15 mJ/cm2, respectively with 254 nm UV-C. Higher 279 nm UV-C LED doses were required to cause HuNoV surrogate reduction than 254 nm UV-C, except similar doses with both systems were needed for HAV inactivation on Formica surfaces. It remains critical to measure UV intensity of optical sources and optimize exposure times for desired log reduction on surfaces.

Microbiological Profile, Prevalence, and Characterization of Salmonella enterica in Peanuts, Pecans, Raisins, Sun-Dried Tomatoes, and Chocolate Sprinkles Sold in Bulk in Markets in Querétaro, Mexico.

ABSTRACT: In Mexico, the prevalence of Salmonella enterica in low-water-activity foods and its link to outbreaks are unknown. The aim of this study was to determine the microbiological profile and the prevalence of S. enterica in several low-water-activity foods, including peanuts, pecans, raisins, sun-dried tomatoes, and chocolate sprinkles, purchased in retail establishments in Querétaro, Mexico. Seventy samples of each food item sold in bulk were purchased. Aerobic plate count, molds, yeasts, total coliforms, Escherichia coli, and Staphylococcus aureus were quantified in 10-g samples. The prevalence of S. enterica in 25-g samples was determined. From positive samples, S. enterica isolates (60) were characterized based on their antimicrobial susceptibility to 14 antibiotics, the presence-absence of 13 virulence genes, and serotype. The concentration of aerobic plate count, molds, yeasts, total coliforms, and E. coli ranged from 3.1 to 5.2 log CFU g-1, from 2.0 to 2.4 log CFU g-1, from 2.0 to 3.0 log CFU g-1, from 0.6 to 1.1 log most probable number (MPN) g-1, and from 0.5 to 0.9 log MPN g-1, respectively. S. aureus was not detected in any sample (<10 CFU g-1). The prevalence of S. enterica in chocolate sprinkles, raisins, peanuts, pecans, and sun-dried tomatoes was 26, 29, 31, 40, and 52%, respectively. Most isolates (68.3%) were resistant to at least one antibiotic. Chromosome-associated virulence genes were found in all isolates, and only one strain had sopE, and 98.3% of the isolates were grouped in the same virulotype. Among the isolates, the most frequent serotype was Tennessee (51 of 60). According to the characteristics evaluated, we grouped the isolates into 24 clusters. The elevated prevalence of S. enterica highlights the role of low-water-activity food items sold in bulk at markets as potential vehicles for pathogen transmission. Regardless of the low variability among S. enterica isolates, their characterization could be helpful to elucidate which strains are circulating in these foods for improving epidemiological surveillance.

Value-added switchgrass extractives for reduction of Escherichia coli O157:H7 and Salmonella Typhimurium populations on Formica coupons.

Recurring outbreaks linked to Escherichia coli O157:H7-contaminated lettuce and Salmonella enterica-contaminated sprouts highlight the need for improved food safety measures. The aim of this study was to determine the ability of a bio-based antimicrobial extract prepared from switchgrass, a dedicated energy crop, to reduce E. coli O157:H7 and S. Typhimurium populations on Formica coupons, a model food-contact surface. Overnight cultures of ~7 log CFU/mL E. coli O157:H7 and S. Typhimurium, air-dried on Formica coupons were treated with 0.625% NaClO, 70% ethanol, sterile water or different batches of switchgrass extractives (SE1, SE2, and SE3) for up to 30 min. E. coli O157:H7 was reduced by 4.43 log CFU/mL after 1 min by SE3, and to non-detectable levels after 1 min by all other treatments. Populations of S. Typhimurium LT2 (15-min drying) were reduced by 3.30 log CFU/mL with 70% ethanol, 5.38 log CFU/mL with SE1, and to non-detectable levels with 0.625% NaClO after 1 min, while S. Typhimurium ATCC 23564 (1-h drying) was non-detectable after 1 min by all treatments. Under soiled conditions, 10-min treatment with SE1 and 70% ethanol reduced both bacteria to non-detectable levels. Studies with concentrated switchgrass extractives combined with various other natural disinfectants or in hurdle approaches warrant further investigation.

Thermal inactivation kinetics of hepatitis A virus in homogenized clam meat (Mercenaria mercenaria).

AIMS: Epidemiological evidence suggests that hepatitis A virus (HAV) is the most common pathogen transmitted by bivalve molluscs such as clams, cockles, mussels and oysters. This study aimed to generate thermal inactivation kinetics for HAV as a first step to design adequate thermal processes to control clam-associated HAV outbreaks. METHODS AND RESULTS: Survivor curves and thermal death curves were generated for different treatment times (0-6 min) at different temperatures (50-72°C) and Weibull and first-order models were compared. D-values for HAV ranged from 47·37 ± 1·23 to 1·55 ± 0·12 min for the first-order model and 64·43 ± 3·47 to 1·25 ± 0·45 min for the Weibull model at temperatures from 50 to 72°C. z-Values for HAV in clams were 12·97 ± 0·59°C and 14·83 ± 0·0·28°C using the Weibull and first-order model respectively. The calculated activation energies for the first-order and Weibull model were 145 and 170 kJ mole(-1) respectively. CONCLUSION: The Weibull model described the thermal inactivation behaviour of HAV better than the first-order model. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides novel and precise information on thermal inactivation kinetics of HAV in homogenized clams. This will enable reliable thermal process calculations for HAV inactivation in clams and closely related seafood.

Nucleic acid sequence based amplification for the rapid and sensitive detection of Salmonella enterica from foods.

AIMS: The purpose of this study was to apply nucleic acid sequence-based amplification (NASBA) for the detection of Salmonella enterica serovar Enteritidis (S. Enteritidis) in representative foods. METHODS AND RESULTS: A previously reported primer and probe set based on mRNA sequences of the dnaK gene of Salmonella were used in this study. To test for possible food matrix inhibition and assay detection limits, 25-g samples of representative food commodities (fresh meats, poultry, fish, ready-to-eat salads and bakery products) were pre-enriched with and without S. Enteritidis inoculation. The NucliSens(R) Basic Kit, supplemented with enzymes from various other commercial sources, was used for RNA isolation, NASBA amplification and electrochemiluminescent (ECL) detection. The end point detection limit of the NASBA-ECL assay was equivalent to 101 CFU of S. Enteritidis per amplification reaction. When the assay was tested on noncontaminated foods, none of the food matrices produced false-positive results. Some of the food matrices inhibited the NASBA-ECL reaction unless the associated RNA was diluted 10-fold prior to amplification. CONCLUSIONS: For all food items tested, positive ECL signals were achieved after 18 h of pre-enrichment and subsequent NASBA at initial inoculum levels of 102 and 101 CFU per 25 g food sample. SIGNIFICANCE AND IMPACT OF THE STUDY: This rapid, semi-automated detection method has potential for use in the food, agricultural and public health sectors.

Zirconium hydroxide effectively immobilizes and concentrates human enteric viruses.

BACKGROUND: Detection of human enteric viruses in foods and environmental samples requires concentration of viruses from complex matrices before application of molecular or cultural methods. Previous studies have described the use of zirconium hydroxide to concentrate bacteria from clinical, environmental, and food samples. AIMS: Our study describes the application of zirconium hydroxide to concentrate human enteric viruses. METHODS: Poliovirus type 1, hepatitis A virus (HAV) strain HM-175, and Norwalk virus (NV) were used as models. Virus recovery was evaluated both as loss to discarded supernatants and as recovery in the precipitated pellets. RESULTS: Poliovirus type 1, based on the plaque assay recoveries, ranged from 16 to 59% with minimal loss to the supernatant (1-5%). For both HAV and NV, RT-PCR amplicons of appropriate sizes were detected and confirmed in the pellet fraction with no visible amplicons from the supernatant. SIGNIFICANCE AND IMPACT OF THE STUDY: This rapid and inexpensive method shows promise as an alternative means to concentrate enteric viruses.

Human Enteric Viruses as Causes of Foodborne Disease.

Recent epidemiological evidence indicates that enteric viruses are the leading cause of foodborne disease in the U.S.A. and, indeed, worldwide. Certainly, advances in epidemiology and molecular biology have improved the ability to study this previously elusive group of foodborne pathogens. The purpose of this article is to review the agents, transmission routes, epidemiology, persistence, diagnosis, and detection of foodborne viruses and their diseases, with specific reference to the role that contemporary technologies have had in improving our understanding of this important group of emerging foodborne pathogens.

Aflatoxin B1 degradation by flavobacterium aurantiacum in the presence of reducing conditions and seryl and sulfhydryl group inhibitors.

This study was undertaken to determine the effects of reducing conditions (L-cysteine) and seryl (phenylmethylsulfonyl fluoride) and sulfhydryl (divalent cadmium) group inhibitors on aflatoxin B1 (AFB1) degradation by Flavobacterium aurantiacum. High-performance liquid chromatography was used to determine AFB1 concentrations in 72-h cultures of F. aurantiacum. The addition of 0.1, 1, or 10 mM L-cysteine did not have any significant effect on AFB1 degradation by these cultures after incubation for 4, 24, or 48 h (P > 0.05). The addition of 0.1 mM phenylmethylsulfonyl fluoride did not significantly decrease AFB1 degradation (P > 0.05), but 1 mM phenylmethylsulfonyl fluoride significantly decreased AFB1 degradation after 4, 24, and 48 h of incubation (P < or = 0.05). No significant difference in AFB1 degradation was obtained with 0.1 mM Cd2+ after 4, 24, or 48 h of incubation (P > 0.05). The addition of 1 and 10 mM Cd2+ significantly decreased AFB1 degradation compared with the cells containing AFB1 alone after 4 and 24 h (P < or = 0.05). The addition of chelators, 1 mM EDTA and 1 mM o-phenanthroline, did not result in removal of inhibition of AFB1 degradation observed with 1 and 10 mM Cd2+. Higher concentration of chelators (>1 mM) are necessary to overcome the inhibitory effect. Further work on the cellular fractions and/or crude enzyme preparations is necessary to determine if indeed sulfhydryl and seryl groups of the enzymes are involved in AFB1 degradation (by maintaining either the structure or function of the enzyme).

The influence of divalent cations and chelators on aflatoxin B1 degradation by Flavobacterium aurantiacum.

The influence of divalent cations (Mg2+ and Ca2+) and chelators (EDTA and 1,10-phenanthroline) on aflatoxin B1 (AFB1) degradation by Flavobacterium aurantiacum was determined in an effort to elucidate the possible manner by which this organism degrades AFB1. AFB1 (10 microg/ml) was added to 72-h cultures of F. aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). High-performance liquid chromatography was used to determine AFB1 concentration in these cultures. Incubating cells with 0.1, 1, and 10 mM Ca2+ for 48 h significantly increased AFB1 degradation by 11.8, 13.5, and 14.0%, respectively, compared with F. aurantiacum cells alone. Likewise, incubation with 0.1, 1, and 10 mM Mg2+ for 48 h significantly increased AFB1 degradation by 13.8, 13.3, and 13.1%, respectively. Incubating the bacterium with either divalent cation for 16 and 24 h did not significantly affect AFB1 degradation (P < or = 0.05). Addition of 0.1, 1, and 10 mM EDTA and 0.1 and 1 mM 1,10-phenanthroline resulted in significant increases in AFB1 degradation after 24 h. Significantly less AFB1 degradation was observed using 10 mM 1,10-phenanthroline after 24-h incubation. These results suggest the involvement of Mg2+ and Ca2+ cations in AFB1 degradation by F. aurantiacum.

The role of trace metal ions in aflatoxin B1 degradation by Flavobacterium aurantiacum.

Flavobacterium aurantiacum NRRL B-184 possesses the ability to degrade aflatoxin B1 in solution and in several food items. Aflatoxin B1 is a potent carcinogen that causes significant economic losses to the agricultural and food industry. The role of trace metal ions (Cu2+, Mn2+, Zn2+, and Co2+) were studied in an effort to understand the enzymatic system involved in aflatoxin B1 degradation by F aurantiacum. The effect of divalent chelators (EDTA and 1,10-phenanthroline [OPT]) in the presence of the trace metal ions was studied as well. Aflatoxin B1 (10 microg/ml) was added to 72-h cultures of F aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). HPLC was used to determine aflatoxin B1 concentration in these cultures. Incubating cells at 30 degrees C with 1 and 10 mM Cu2+, Mn2+, and Zn2+ significantly decreased aflatoxin B degradation after 4 and 24 h (P < 0.05). Decreased degradation was also observed with 1 and 10 mM Cu2+ and Zn2+ after 48 h and with 0.1 mM Cu2+ after 24 and 48 h. Co2+ did not have a significant effect on aflatoxin B1 degradation. EDTA and OPT did not counter the inhibition in the presence of Cu2+. The addition of 1 mM EDTA countered the inhibition by 1 mM Mn2+ after 4 and 24 h, but 1 mM OPT did not counter the inhibition by 10 mM Mn2+ after 4 and 24 h. OPT countered the inhibition by 1 mM Zn2+ after 4 and 48 h. These trace elements inhibit aflatoxin B1 degradation by F aurantiacum. In addition, their presence necessitates higher concentrations (>1 mM) of EDTA and OPT for the removal of their inhibitory effect.