Wanda Smoragiewicz

Trichothecene mycotoxins in the dust of ventilation systems in office buildings

SummaryAnalysis of trichothecene mycotoxins in dust samples from ventilation systems of office buildings was applied as a rapid and inexpensive method for the detection of mycotoxins. Dust samples from three different office spaces of the Montreal urban area, reportedly affected by the “sick buildings syndrome”, were analysed by thin-layer chromatography (TLC). Positive colour reaction on TLC plates with 4-(p-nitrobenzyl) pyridine, specific for the 12,13-epoxy group in the trichothecene nucleus, was obtained for the extracts of 0.5- to 50-g dust samples. The dust samples contained at least four trichothecenes: T-2 toxin, diacetoxyscirpenol, roridine A and T-2 tetraol. The results were confirmed by high-performance liquid chromatography analysis. Screening of dust samples from air ventilation systems of reportedly affected buildings provided direct evidence of trichothecene mycotoxins, with the detection limit estimated as 0.4-4 ng/mg dust. Thus, the dust sample analysis is suggested as a rapid technique for detecting the presence of mycotoxins in the dust of ventilation systems.

Antibacterial activity of Lactobacillus acidophilus and Lactobacillus casei against methicillin-resistant Staphylococcus aureus (MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant microorganism and the principal nosocomial pathogen worldwide. The antibacterial activity of lactic acid bacteria against MRSA from ten human clinical isolates as well as MRSA standard strain ATCC 43300 was tested in vitro. The Lactobacillus (Lb.) strains (Lb. acidophilus CL1285(®) and Lb. casei LBC80R) as pure cultures, which came from commercial food products were employed. The growth inhibitory effect produced by the antimicrobial activity of the lactic acid bacteria on the MRSA strains was tested on solid medium using agar diffusion methods as well as a using a liquid medium procedure that contained a mixture of MRSA and lactic acid bacteria cultures. In the latter instance, we were able to demonstrate that the direct interaction of lactic acid bacteria and MRSA in such a mixture led to the elimination of 99% of the MRSA cells after 24 h of their incubation at 37°C.

Combined effect of gamma irradiation, ascorbic acid, and edible coating on the improvement of microbial and biochemical characteristics of ground beef.

This study was conducted to evaluate the combined effect of gamma irradiation and the incorporation of natural antimicrobial compounds in cross-linked films on the microbiological and biochemical characteristics of ground beef. Medium-fat (23% fat) ground beef patties were divided into three separate treatment groups: (i) control samples without additives, (ii) ground beef samples containing 0.5% (wt/wt) ascorbic acid, and (iii) ground beef samples containing 0.5% ascorbic acid and coated with a protein-based cross-linked film containing immobilized spice powders. Meat samples were irradiated at doses of 0, 1, 2, and 3 kGy and stored at 4 +/- 2 degrees C. Microbial growth (based on total aerobic plate counts [APCs] and total coliforms) was evaluated, as were the content of thiobarbituric acid-reactive substances (TBARS) and that of free sulfydryl groups. At the end of the storage period, Enterobacteriaceae, presumptive Staphylococcus aureus, presumptive Pseudomonas spp., Brochothrix thermosphacta, and lactic acid bacteria were enumerated. Regardless of the treatment group, irradiation significantly (P < or = 0.05) reduced the APCs. Irradiation doses of 1, 2, and 3 kGy produced immediate APC reductions of 2, 3, and 4 log units, respectively. An APC level of 6 log CFU/g was reached after 4, 7, and 10 days for samples irradiated at 1, 2, and 3 kGy, respectively. Lactic acid bacteria and B. thermosphacta were more resistant to irradiation than were Enterobacteriaceae and Pseudomonas. The TBARS and free sulfydryl contents were stabilized during postirradiation storage for samples containing ascorbic acid and coated with the protein-based cross-linked film containing immobilized spice powders.

Interaction of Bifidobacterium and Salmonella during associated growth

Interaction of 15 Bifidobacterium (belonging to species B. animalis, B. globosum and B. breve) and six Salmonella (belonging to species S. enteritidis and S. typhimurium) strains was examined during associated growth at optimum conditions for the two genera. All strains of Bifidobacterium investigated were antagonistic to Salmonella. Three strains of Bifidobacterium bactericidal to Salmonella were identified. The kinetics of Salmonella inhibition was as follows: growth of Salmonella was inhibited before the end of the exponential phase, then succeeded by a rapid decrease of live-cell numbers at the beginning of the stationary phase, after which the cell death rate was lower. Growth of Bifidobacterium in the associated cultures was similar to that in monocultures.

Role of probiotics in the prevention and treatment of meticillin-resistant Staphylococcus aureus infections

Meticillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant micro-organism and is the principal nosocomial pathogen worldwide. Following initial in vitro experiments demonstrating that Lactobacillus acidophilus CL1285(®) and Lactobacillus casei LBC80R(®) commercial strains exhibit antibacterial activity against clinical MRSA isolates, we conducted a literature search to find any evidence of probiotic efficacy in decolonisation or treatment of S. aureus infection. As summarised below, many strains of lactobacilli and bifidobacteria isolated from a variety of sources inhibited the growth of S. aureus and clinical isolates of MRSA in vitro. The most active strains were Lactobacillus reuteri, Lactobacillus rhamnosus GG, Propionibacterium freudenreichii, Propionibacterium acnes, Lactobacillus paracasei, L. acidophilus, L. casei, Lactobacillus plantarum, Lactobacillus bulgaricus, Lactobacillus fermentum and Lactococcus lactis. Their effects were mediated both by direct cell competitive exclusion as well as production of acids or bacteriocin-like inhibitors. L. acidophilus also inhibited S. aureus biofilm formation and lipase production. In vitro antimicrobial activity did not necessarily assure efficacy in vivo in animal infectious models, e.g. S. aureus 8325-4 was most sensitive in vitro to L. acidophilus, whilst in vivo Bifidobacterium bifidum best inhibited experimental intravaginal staphylococcosis in mice. On the other hand, L. plantarum, which showed the highest inhibition activity against S. aureus in vitro, was also very effective topically in preventing skin wound infection with S. aureus in mice. Very few clinical data were found on the interactions between probiotics and MRSA, but the few identified clinical cases pointed to the feasibility of elimination or reduction of MRSA colonisation with probiotic use.

Protein quality and microbiological changes in aerobically- or vacuum-packaged, irradiated fresh pork loins

The effect of gamma-irradiation on the physicochemical, organoleptic and microbiological properties of pork was studied, during 43 days of storage at 4±1°C. Irradiation treatments were carried out under air or vacuum packaging on fresh pork loins at a dose of 6 kGy, at two different dose rates: 2 kGy/h and 20 kGy/h. The loins were evaluated for protein sulphydryl content and emulsifying capacity, surface hydrophobicity of proteins and sensorial evaluation. Regardless of the type of packaging and dose rate of irradiation, all irradiated pork samples were effectively prevented from bacterial spoilage for at least 43 days. Meat redness and texture of irradiated loins were relatively well preserved during the storage period, especially when samples were stored under vacuum. Overall, the physicochemical and organoleptic changes in pork loins appeared to be relatively little affected by the 6 kGy dose. No marked changes in emulsifying capacity and protein sulphydryl content of proteins were noted throughout the storage period. However, the hydrophobicity was reduced (P⩽0.05) by the faster dose rate of irradiation and by longer storage.

Prevention of lipid radiolysis by natural antioxidants from rosemary (Rosmarinus officinalis L.) and thyme (Thymus vulgaris L.)

Abstract Radiolysis of unsaturated linoleic fatty acid and subsequent generation of volatile alkane and alkene hydrocarbons was studied following relatively low, 3–9 kilo-Gray (kGy) gamma-irradiation, i.e. within the accepted 10 kGy limit for commercial food pasteurization. The low-dose irradiation generated relatively low quantities of hydrocarbons, totalling 83 ± 1–140 ± 4ng/mg for saturated myristic and stearic fatty acids. As expected, unsaturated fatty acids (UFA) were more susceptible to the gamma-irradiation; at 9 kGy dose, the total amount of C10–C19 volatile hydrocarbons were, respectively, 602 ± 18 ng/mg for arachidonic acid and 751 ± 60 ngmg−1 for linoleic acid. Addition of powdered (unextracted) rosemary or thyme, at 1/0.1 g lipid/plant ratio, decreased by 52.5–80.5% the radiolytic generation of C10–C19 hydrocarbons. In conclusion, rosemary and thyme, both known to contain natural antioxidants, markedly reduced the gamma-radiolysis of linoleic acid, when irradiated within the accepted 10 kGy limit for commercial food processing.

Antimicrobial potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 against selected bacteria.

Immobilization of living cells of lactic acid bacteria could be an alternative or complementary method of immobilizing organic acids and bacteriocins and inhibit undesirable bacteria in foods. This study evaluated the inhibition potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 on selected bacteria by a modified method of the agar spot test. L. lactis was immobilized in calcium alginate (1 to 2%)-whey protein concentrate (0 and 1%) beads. The antimicrobial potential of immobilized L. lactis was evaluated in microbiological media against pathogenic bacteria (Escherichia coli, Salmonella, and Staphylococcus aureus) or Pseudomonas putida, a natural meat contaminant, and against seven gram-positive bacteria used as indicator strains. Results obtained in this study indicated that immobilized L. lactis inhibited the growth of S. aureus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus sakei, Kocuria varians, and Pediococcus acidilactici. Only 4 h of incubation at 35 degrees C resulted in a clear inhibition zone around the beads that increased with time. With the addition of 10 mM of a chelating agent (EDTA) to the media, results showed growth inhibition of E. coli; however, P. putida and Salmonella Typhi were unaffected by this treatment. These results indicate that immobilized lactic acid bacteria strains can be successfully used to produce nisin and inhibit bacterial growth in semisolid synthetic media.

Airborne fungal ecological niche determination as one of the possibilities for indirect mycotoxin risk assessment in indoor air

Based on the microbiological analysis of air samples from occupied spaces, some possibilities for indirect risk assessment of mycotoxin‐related health problems are proposed. Airborne fungi could be classified on the basis of the relationship between the two environmental factors and their combinations, i.e., temperature and water requirements (water activity aw). One type involves three different groups of molds, selected on the basis of the quantitative and qualitative information about the ability of fungi to sporulate under different environmental conditions: group (i), represented by Aspergillus nidulans, A. niger, and A. ochraceus, and characterized by sporulation which was more dependent on temperature than on water activity; (ii), represented by A. flavus and A. versicolor, in which sporulation was approximately equal and depended on both the temperature changes and aW alterations; and (iii), represented by Cladosporium sp., Penicillium cyclopium, and P. citrinum, in which sporulation depended more on alteration of the aw conditions than on temperature changes. Another type is characterized by four sporulation rates with two levels of mycotoxin risk accumulation in the spores (conidia) of each mold species: large (Ia) and moderate (Ib) sporulation rates with a risk of mycotoxin accumulation (aw≥86; t≥12°C); rare sporulation (IIa) and absence of sporulation (IIb), without risk of mycotoxin accumulation (aw≤86; t≤12°C). In conclusion, providing a useful guide for two dimensions, temperature and water activity for each of the three phases of fungal growth, i.e. germination, growth, and sporulation, could be important for determination of the fundamental niche of each fungus and its ability to form or accumulate mycotoxin. Special emphasis should be given to the indirect mycotoxin risk assessment in heating, ventilation, and air conditioning systems. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 1–8, 2001