Subsequent Toxin Production Research Articles

Impact of temperature, nutrients, pH and cold storage on the germination, growth and resistance of Bacillus cereus spores in egg white

B. cereus spores are a concern to the food industry, especially to the producers of heat sensitive food products like egg white or precooked and stored food such as fried rice. This study investigated the impact of nutrients, temperature (4, 8, 15 and 25 °C), pH (4, 5, 7 and 9), and cold storage on the germination, growth and resistance of B. cereus spores. In egg white held at 4 °C for 12 days spore germination was not apparent, however the addition of egg yolk (5%) resulted in a 2 Log colony forming units (CFU)/mL increase in vegetative cells (p < .05). Adding l-alanine (0.9 mg/mL) to egg white did not induce germination unless the spores were simultaneously heat activated at 70 °C for 30 min. On incubation at 15 or 25 °C in egg white, spore germination increased by 3.0 Log and 3.7 Log CFU/mL on day 12. The presence of 5% yolk further enhanced germination and subsequent sporulation during storage at 15 and 25 °C. Acidification (pH 4) of 10% egg white solution prevented germination at 4, 8, 15 and 25 °C. Spores held at 4 °C for 6 days in phosphate buffer (50 mM, pH 4) had visible deformations on their surface (scanning electron microscopy) and a significant reduction in D88, and D92 values of 13.9 and 8.2 min respectively. A better understanding of how spores sense and respond to changing environmental conditions will help in the development of processing strategies, involving multiple hurdles to ensure the prevention of germination and subsequent toxin production.

A novel Eulerian approach for modelling cyanobacteria movement: Thin layer formation and recurrent risk to drinking water intakes

Toxic cyanobacteria (CB) blooms are being reported in an increasing number of water bodies worldwide. As drinking water (DW) treatment can be disrupted by CB, in addition to long term management plans, short term operational decision-making tools are needed that enable an understanding of the temporal variability of CB movement in relation to drinking water intakes. In this paper, we propose a novel conservative model based on a Eulerian framework and compare results with data from CB blooms in Missisquoi Bay (Québec, Canada). The hydrodynamic model considered the effects of wind and light intensity, demonstrated that current understanding of cell buoyancy in relation to light intensity in full-scale systems is incomplete and some factors are yet to be fully characterized. Factors affecting CB buoyancy play a major role in the formation of a thin surface layer that could be of ecological importance with regards to cell concentrations and toxin production. Depending on velocities, wind contributes either to the accumulation or to the dispersion of CB. Lake recirculation effects have a tendency to create zones of low CB concentrations in a water body. Monitoring efforts and future research should focus on short-term variations of CB throughout the water column and the characterization of factors other than light intensity that affect cell buoyancy. These factors are critical for understanding the risk of breakthrough into treatment plants as well as the formation of surface scums and subsequent toxin production.

Inhibition of Fusarium Growth and Mycotoxin Production in Culture Medium and in Maize Kernels by Natural Phenolic Acids

The possible role of natural phenolic compounds in inhibiting fungal growth and toxin production has been of recent interest as an alternative strategy to the use of chemical fungicides for the maintenance of food safety. Fusarium is a worldwide fungal genus mainly associated with cereal crops. The most important Fusarium mycotoxins are trichothecenes, zearalenone, and fumonisins. This study was conducted to evaluate the potential of four natural phenolic acids (caffeic, ferulic, p-coumaric, and chlorogenic) for the control of mycelial growth and mycotoxin production by six toxigenic species of Fusarium . The addition of phenolic acids to corn meal agar had a marked inhibitory effect on the radial growth of all Fusarium species at levels of 2.5 to 10 mM in a dose-response pattern, causing total inhibition (100%) in all species except F. sporotrichioides and F. langsethiae . However, the effects of phenolic acids on mycotoxin production in maize kernels were less evident than the effects on growth. The fungal species differed in their responses to the phenolic acid treatments, and significant reductions in toxin concentrations were observed only for T-2 and HT-2 (90% reduction) and zearalenone (48 to 77% reduction). These results provide data that could be used for developing pre- and postharvest strategies for controlling Fusarium infection and subsequent toxin production in cereal grains.

Methods for the determination of deoxynivalenol and other trichothecenes in foods.

Trichothecene mycotoxins are secondary metabolites of Fusarium moulds that routinely infect cereal crops. Processing can reduce, but not eliminate, trichothecenes from cereal-based foods, and the potential presence of the trichothecenes in cereal foods poses a significant health risk to consumers. Deoxynivalenol (vomitoxin, DON) is the most common of the trichothecenes detected in cereal crops and is subject to government regulation in many countries. Sensitive (ng/g) methods for the detection of trichothecenes in cereal grains and food products are needed to protect consumers, to provide data for dietary exposure estimates, and to support research into the control of moulds and subsequent toxin production. Laboratories require simple, rugged and reliable methods for routine testing, with unequivocal identification of suspect mycotoxins. A method employing gas chromatography-negative ion chemical ionisation/mass spectrometry (GC-NICI/MS) has been developed and used for the routine determination of eight of the most significant trichothecenes in a variety of commodities. This chapter discusses GC, liquid chromatographic (LC) and supercritical fluid chromatographic methods that are currently used for the analysis of trichothecene mycotoxins.

HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype.

AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual.

Growth and Aflatoxin Production by Aspergillus parasiticusNRRL 2999 as Affected by the Fungicide Iprodione

Spores of Aspergillus parasiticus strain NRRL 2999 were inoculated into yeast extract sucrose broth containing different levels of iprodione (0, 1, 3, 5, 10, 15, and 20 (μg/ml) and incubated at 25°C for 4, 7, 10, 14, and 21 d. Iprodione inhibited mold growth and subsequent toxin production, beginning at the 5 μg/g level up to 7 d of incubation. Results showed that as the iprodione level increased, more time was required by the organism to initiate mycelial development. At any given time, the lower the iprodione level, the more dry mycelial weight and aflatoxin production (B1, B2, G1, and G2) were observed.

Status of the Aflatoxin Problem in Corn

AbstractAflatoxin, a potent carcinogenic metabolite produced by the fungus Aspergillus flavus, has been clearly demonstrated to be a kernel contaminant in both preharvest and postharvest corn. Research has been conducted on: (i) fungus invasion of the ear; (ii) effects of the environment on aflatoxin levels; and (iii) methods of control.A. flavus infects developing ears in both southern and corn belt regions but growing conditions in the southern U.S. are more conducive to the fungal infection process and subsequent toxin production. Most observations indicated that a break in the pericarp is necessary for fungal establishment. Insects, particularly larvae of the second European corn borer, corn earworm, and fall armyworm, have been implicated in causing breaks as well as serving as vehicles for carrying the inoculum to the potential infection site. Conditions of stress such as those caused by drought have been shown to enhance the aflatoxin contamination problem. Suggested control methods are: (i) plant only adapted hybrids with the highest level of resistance against ear‐damaging insects; (ii) employ management practices that will either reduce stress or shift the ear development stage to miss a likely stress period.Preliminary results suggest that either A. flavus growth or aflatoxin levels are under genetic control, but corn genotypes cannot be recommended at this time that would entirely eliminate the aflatoxin contamination problem in corn.

INHIBITION OF GROWTH AND AFLATOXIN PRODUCTION BY CINNAMON AND CLOVE OILS. CINNAMIC ALDEHYDE AND EUGENOL

ABSTRACTPrevious work indicated that cinnamon was inhibitory to the growth of aflatoxin‐producing molds. The objective of this study was to determine the specific components of cinnamon and cloves that may be effective against mold growth and toxin production. The effects of cinnamon oil, clove oil, cinnamic aldehyde and eugenol on growth and aflatoxin production by Aspergillus parasiticus were studied using yeast‐extract sucrose broth as the substrate. All four substances inhibited mold growth and subsequent toxin production. Cinnamon and clove oils were inhibitory at 200–250 ppm, cinnamic aldehyde at 150 ppm and eugenol at 125 ppm. Since cinnamic aldehyde and eugenol are the respective major components of cinnamon and clove oils, it was concluded that these are the major active antifungal ingredients of these two essential oils. The inhibitory effect of these substances was judged to be inhibition of growth rather than of toxin production. When growth occurred after a delay, aflatoxin production occurred when the cultures reached secondary metabolism. Given sufficient time, cultures which were inhibited initially, but which subsequently grew, produced toxin levels equivalent to control cultures. Levels of the oils above 250 ppm and of cinnamic aldehyde and eugenol above 200 ppm completely inhibited mold growth, or permitted only a small amount of growth that never reached secondary metabolism and never produced aflatoxins during the time of this study.