Short communication: Lactic acid bacteria from the honeybee inhibit the in vitro growth of mastitis pathogens.

Despite the increasing knowledge of prevention and control strategies, bovine mastitis remains one of the most challenging diseases in the dairy industry. This study investigated the antimicrobial activity of 13 species of lactic acid bacteria (LAB), previously isolated from the honey crop of the honeybee, on several mastitis pathogens. The viable LAB were first reintroduced into a sterilized heather honey matrix. More than 20 different bovine mastitis isolates were tested against the mixture of the 13 LAB species in the honey medium using a dual-culture overlay assay. The mastitis isolates were identified through bacteriological culturing, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Additionally, the mastitis isolates were subjected to antimicrobial susceptibility testing through disk diffusion. Growth of all tested mastitis pathogens, including the ones displaying antimicrobial resistance to one or more antimicrobial compounds, were inhibited to some extent by the honey and LAB combination. The antibacterial effect of these LAB opens up new perspectives on alternative treatment and prevention of bovine mastitis.

Composition of the bacterial population of refrigerated beef, identified with direct 16S rRNA gene analysis and pure culture technique.

The composition of the dominating population of freshly cut beef, and beef stored at 4 degrees C for 8 d, was studied by direct analysis of the 16S rRNA gene (PCR amplification, cloning and sequencing) and compared with pure culture technique where the isolates picked from the viable plate count were identified by sequencing of the 16S rRNA gene. The composition of the bacterial population was recorded at two different time points, at the start when the viable plate count of the meat was 4 x 10(2) colony forming unit (cfu) per cm(2) and when it was 5 x 10(7) cfu per cm(2). Direct gene analysis by PCR amplification generated 30 clones, and 79 isolates were picked from the plate count, and identified by 16S rRNA gene sequencing. At the low initial bacterial load of the beef, the two sampling strategies showed variations in the composition of species. Direct 16S rRNA gene analysis revealed a domination of Bacillus-like sequences while no such sequences were found in isolates from the viable plate count. Instead the population of the plate count was dominated by Chryseobacterium spp. In contrast, the two sampling strategies matched on the multiplying beef population, where both methods indicated Pseudomonas spp. as the dominating group (99% of the population-sequences), irrespectively of sampling strategy. Pseudomonas panacis/Pseudomons brennerii was the dominating taxon (99% similarity to type strain), but sequences with highest similarity to Pseudomonas lundensis (99%), Pseudomonas beteli (99%) and Pseudomonas koreensis (100%) were also found.

The bacterial flora of vacuum-packed cold-smoked salmon stored at 7 degrees C, identified by direct 16S rRNA gene analysis and pure culture technique.

AIMS: The indigenous flora of freshly chilled cold-smoked salmon just after the vacuum packaging, and the spoilage flora after storage, in vacuum package at 7 degrees C for 19 days, were to be investigated with two different sampling strategies. METHODS AND RESULTS: Identification was performed using 16S rRNA sequencing of both isolated bacteria and bacterial DNA from tissue extract. The indigenous flora of fresh cold-smoked vacuum-packed salmon was dominated by, in order, Brochothrix thermosphacta, Yersinia ruckeri, Photobacterium and Carnobacterium, whereas the spoilage flora of the same product stored at 7 degrees C for 19 days was dominated by Lactobacillus and Photobacterium. The two sampling strategies showed similar results on the fish flora. Several new types of Photobacterium sequences, closely related to Photobacterium iliopiscarium and Photobacterium phosphoreum, were found from both the freshly processed and the stored salmon, indicating that smoked salmon harbours at least three different, as yet unknown, Photobacterium species. CONCLUSIONS: Ten per cent of the bacterial flora multiplying on chilled, vacuum-packed, cold-smoked salmon comprised unknown species. The two sampling strategies complement each other. SIGNIFICANCE AND IMPACT OF THE STUDY: As cold-smoked salmon is consumed without heat-treatment, the presence of undefined bacteria in high numbers should be considered in public health assessments.