BASALTIC SOILS OF SOUTH-WEST ICELAND. II

Data for mechanical and chemical analyses are presented with tabulated mean and median values based on fifty-five freely drained and ten poorly drained soils. The soils are relatively coarsed textured. The sand content of the mineral fraction is about 70 per cent (mean value) for freely drained and about 45 per cent (mean value) for poorly drained soils. Organic C is generally high in freely drained soils but relatively low in poorly drained soils, because of accumulating aeolian matter in the latter group, mean values are 8.2 in freely drained and 16.5 per cent in poorly drained soils. The C/N ratio is about 15 for each soil group. The cation exchange properties including pH seem to be dominated by organic matter, which may contribute to the total CEC of the soils about 165–300 me/100 g C. CEC of soils is usually 40–50 me/100 g. For some selected soils CEC of the separated mineral fractions was confirmed experimentally through ammonia retention. The pH level, especially of the freely drained soils, is relatively high (mostly 5.4–6.3) in spite of low degree of base saturation (mostly 10–30 per cent), a characteristic probably derived from the parent material. A highly significant correlation exists between pH and organic C. Proportionally exchangeable Ca seems low, while Mg and Na may be abundant. In some soils exchangeable Mg may exceed Ca.     

Comparison of the effectiveness of three different growth media for primary isolation of Renibacterium salmoninarum from Atlantic salmon, Salmo salar L., broodfish

Abstract. The effectiveness of three different growth media KDM-2, S-KDM and S-KDM-C for primary isolation of Renibacterium salmoninarum was examined over a 14-week incubation period. Kidney samples were taken from Atlantic salmon, Salmo salar L., broodfish returning to a sea ranch after 2 years at sea. Homogenized samples were inoculated onto two selective media, S-KDM supplemented with lamb serum and S-KDM-C supplemented with activated charcoal. The third medium was the non-selective serum supplemented KDM-2. Renibacterium salmoninarum was isolated from 112 samples on one or more of the media used. Of all positive samples, 91% were positive on S-KDM, 60% on S-KDM-C and 35% on KDM-2. These results demonstrate that selectivity significantly enhances the isolation capacity of the medium and that supplementing with serum is significantly more effective than supplementing with charcoal.     

Incubation time for the cultivation of Renibacterium salmoninarum from Atlantic salmon, Salmo salar L., broodfish

Abstract. Cultivation plates for the primary isolation of Renibacterium salmoninarum were incubated for 12 or more weeks over 3.5 years. The incubation time for sample of two groups of Atlantic salmon, Salmo solar L., broodfish on a selective agar medium is reported. Samples turned positive over a long time-span. but the longest incubation time recorded for growth of the bacterium was 19 week. In one group, 79% of all positive samples form fish with macroscopic signs of bacterial kidney disease were positive after 6 weeks of incubation and the highest incidence of positive samples occured during the sixth week. From covertly infected fish within the same group.42% of sample were positive after 6 weeks of incubation, and the highest incidence of positive sample occured during the sixth and the ninth weeks of incubation. The growth pattern of the bacterium at primary isolation was characterized by a prolonged lag phase followed by a relatively growth in one week from microscopic to macroscopic size of the colonies.     

Exophiala salmonis infection in Atlantic salmon Salmo salar L.

Abstract. Infection of Atlantic salmon, Salmo salar L., in seawater with Exophiala salmonis is described. Histological effects consisted principally of granuloma formation, especially in the posterior kidney and spread appeared to occur both by extension and by the liaematogenous route. The nature of the outbreak suggested that the original infection occurred via contaminated food.
A comparison is made between this condition and systemic mycoses in other species.     

Detection of Renibacterium salmoninarum in salmonid kidney samples: a comparison of results using double-sandwich ELISA and isolation on selective medium

Abstract A total of 1239 kidney samples from four species of salmonid fish, Atlantic salmon, Salmo salar L., brown trout, Salmo trutta L., Arctic charr, Salvelinus alpinus (L.), and rainbow trout, Oncorhynchus mykiss (Walbaum), were screened for Renibacterium salmoninarum using double-sandwich ELISA and bacterial isolation. For bacterial isolation, samples were homogenized, washed, plated onto S-KDM and incubated for 12 weeks. Samples for ELISA were kept frozen until tested. After thawing, 25% homogenates in PBS were heated at 100°C for 15 min in the presence (2.5% v/v) of HemoDe solvent (terpene and butylated hydroxyanisole) and then centrifuged. The supernatant was tested with polyclonal antibodies against whole bacterium in a double-sandwich ELISA. In seven out of 12 groups tested, all samples were negative in both tests. Positive ELISA results occurred in five groups. Renibacterium salmoninarum was isolated on SKDM from samples in four out of these five groups. The ELISA test gave significantly higher numbers of positive samples in three out of the four groups showing positive results in both tests.