Antibacterial properties of extracts from selected planktonic freshwater cyanobacteria--a comparative study of bacterial bioassays.

Aqueous and methanol extracts from five selected cyanobacteria were examined for antibacterial properties in six different bacterial bioassays. All five cyanobacteria revealed antibacterial properties. Methanol extracts made from Tychonema bourrellyi, Aphanizomenon flos-aquae and Cylindrospermopsis raciborskii showed the most pronounced inhibitory effects, Aqueous extracts made from Microcystis aeruginosa and T. bourrellyi possessed evident antibacterial properties. The bacterial bioassays were based on agar diffusion tests and included pour-plate methods commonly used to detect residues of antibacterial substances in food. In addition, a pourplate bioassay with Aeromonas hydrophila was developed and described. Antibacterial effects were observed in five of the six bacterial bioassays. No antibacterial effect was observed in the Micrococcus luteus bioassay. Bioassays based on Aer. hydrophila, Bacillus cereus and B. subtilis grown in Antibiotic Medium 8, pH5.85, seemed to be sensitive and suitable. The MIC value of diluted MeOH extracts made from C. raciborskii and T. bourrellyi against Aer. hydrophila corresponded to 38 mg freeze-dried cyanobacteria. Bacillus subtilis was more sensitive when grown in a culture medium with pH 5.85 than 7.9. The antibacterial properties of extracts from the cyanobacteria examined differed from defined cyanotoxins and antibacterial substances. The pattern of inhibition in the bacterial bioassays indicated that various antibacterial substances are involved.

Diversity of shellfish toxins of "diarrhetic" type revealed by biological and chemical assays.

Extracts of "diarrhetic" shellfish toxins from the edible mussel (Mytilus edulis) were tested with biological and chemical assays to determine toxin content. When tested with the standard mouse bioassay, a higher toxicity was detected in most samples compared to that revealed from detection of the diarrhea-causing substances okadaic acid and dinophysistoxin-1 by high-performance liquid chromatography. Routine extraction of toxins for the two assays was carried out with two different solvents, acetone versus aqueous methanol. Accordingly, we questioned whether the variation in results between the methods could be due to differences in chemical properties of these two solvents. When tested, the two solvent systems showed practically the same efficiency concerning the extraction of okadaic acid and dinophysistoxin-1. This demonstrated that toxins other than those causing diarrhea were present in the samples, and that the mouse bioassay was sensitive to these additional toxins. Subsequent testing of the samples with the mouse bioassay, employing both acetone and methanol extracts, revealed that at least two classes of toxins were present in the mussel samples in addition to okadaic acid and dinophysistoxin-1. It is unclear whether the shellfish toxins revealed in this study are partially from known, nondiarrhetic types, such as pectenotoxins or yessotoxins, or from unknown toxin groups exhibiting ichthyotoxic and hemolytic properties.

Isolation and characterization of Campylobacter jejuni and Campylobacter coli from domestic and wild mammals in Norway.

A total of 1,262 domestic and wild mammals from Norway were surveyed for fecal carriage of Campylobacter jejuni and Campylobacter coli. Of the five species of domestic mammals examined, the highest isolation rate was recorded among swine (100.0%), followed by sheep (8.1%) and cows (0.8%). No strains were recovered from horses or goats. Among wild mammals, C. jejuni was isolated from 1 of 23 hares, and no isolated were obtained from three species of cervids and three species of rodents. Of the 133 Campylobacter strains isolated, 114 were classified as C. coli, 18 were C. jejuni biotype 1, and 1 belonged to C. jejuni biotype 2. All 114 strains from swine were C. coli. Milk samples from 113 domestic animals with clinically diagnosed mastitis (106 cows, 5 sheep, 1 horse, and 1 pig) were negative for campylobacters.

[The effect of flame treatment on microflora and storage quality of chicken carcasses (author's transl)]. / Effekt av flambering på mikroorganismer og holdbarhet av fjørfeslakt

In the present investigation the effect of flame treatment on the microflora, storage time and organoleptic quality of chickens carcasses has been studied. The flame treatment had an immediate decimating effect on the surface microflora. This positive effect was observed throughout the storage period on chicken carcasses flame treated after exvisceration. The total bacterial count in this group was significantly lower both initially and in the end of the storage period compared to the bacterial counts in non treated chickens and chickens flame treated after exvisceration (F = 7.62, respectively, 7.67; df = 16). However, by organoleptic testing at the end of the storage period no significant difference could be observed between the groups.