Evaluation of the efficacy of enrofloxacin in rainbow trout (Oncorhynchus mykiss) following experimental challenge with Yersinia ruckeri.

BACKGROUND: Use of enrofloxacin in trout farms is reported, especially for the treatment of yersiniosis, albeit various dosing regimens have been used. Therefore, optimal doses should be investigated. METHODS: Five groups of 15 fish were challenged with Y. ruckeri. Two days later, three groups received feed containing enrofloxacin (ENR) at 1, 2.5 and 5 mg/kg fish respectively, during 7 days; one group received a single intraperitoneal injection of ENR at 10 mg/kg; and one group was left untreated. On day 15, surviving fish were euthanized. RESULTS: All fish survived in the group treated by injection, compared to 53%, 60% and 40% of the fish treated with 1, 2.5 and 5 mg/kg oral ENR, respectively, and 53% in the infected untreated group. CONCLUSION: A single intraperitoneal injection of ENR at 10 mg/kg seems more relevant than repeated oral administrations. The ENR oral doses used in trout farms should be revised.

Widespread occurrence of chemical residues in beehive matrices from apiaries located in different landscapes of Western France.

BACKGROUND: The honey bee, Apis mellifera, is frequently used as a sentinel to monitor environmental pollution. In parallel, general weakening and unprecedented colony losses have been reported in Europe and the USA, and many factors are suspected to play a central role in these problems, including infection by pathogens, nutritional stress and pesticide poisoning. Honey bee, honey and pollen samples collected from eighteen apiaries of western France from four different landscape contexts during four different periods in 2008 and in 2009 were analyzed to evaluate the presence of pesticides and veterinary drug residues. METHODOLOGY/FINDINGS: A multi-residue analysis of 80 compounds was performed using a modified QuEChERS method, followed by GC-ToF and LC-MS/MS. The analysis revealed that 95.7%, 72.3% and 58.6% of the honey, honey bee and pollen samples, respectively, were contaminated by at least one compound. The frequency of detection was higher in the honey samples (n = 28) than in the pollen (n = 23) or honey bee (n = 20) samples, but the highest concentrations were found in pollen. Although most compounds were rarely found, some of the contaminants reached high concentrations that might lead to adverse effects on bee health. The three most frequent residues were the widely used fungicide carbendazim and two acaricides, amitraz and coumaphos, that are used by beekeepers to control Varroa destructor. Apiaries in rural-cultivated landscapes were more contaminated than those in other landscape contexts, but the differences were not significant. The contamination of the different matrices was shown to be higher in early spring than in all other periods. CONCLUSIONS/SIGNIFICANCE: Honey bees, honeys and pollens are appropriate sentinels for monitoring pesticide and veterinary drug environmental pollution. This study revealed the widespread occurrence of multiple residues in beehive matrices and suggests a potential issue with the effects of these residues alone or in combination on honey bee health.

Bees, honey and pollen as sentinels for lead environmental contamination.

Three beehive matrices, sampled in eighteen apiaries from West France, were analysed for the presence of lead (Pb). Samples were collected during four different periods in both 2008 and 2009. Honey was the matrix the least contaminated by Pb (min = 0.004 µg g(-1); max = 0.378 µg g(-1); mean = 0.047 µg g(-1); sd = 0.057). The contamination of bees (min = 0.001 µg g(-1); max = 1.869 µg g(-1); mean = 0.223 µg g(-1); sd = 0.217) and pollen (min = 0.004 µg g(-1); max = 0.798 µg g(-1); mean = 0.240 µg g(-1); sd = 0.200) showed similar levels and temporal variations but bees seemed to be more sensitive bringing out the peaks of Pb contamination. Apiaries in urban and hedgerow landscapes appeared more contaminated than apiaries in cultivated and island landscapes. Sampling period had a significant effect on Pb contamination with higher Pb concentrations determined in dry seasons.

Polycyclic aromatic hydrocarbons: bees, honey and pollen as sentinels for environmental chemical contaminants.

Three beehive matrices, sampled in six different apiaries from West France, were analyzed for the presence of four polycyclic aromatic hydrocarbons (PAH4: benzo[a]pyrene, benzo[a]anthracene, benzo[b]fluoranthene and chrysene). Samples were collected during four different periods in both 2008 and 2009. Honey samples showed the lowest levels of PAH4 contamination (min=0.03 µg kg(-1); max=5.80 µg kg(-1); mean=0.82 µg kg(-1); Sd=1.17). Bee samples exhibited higher levels of PAH4 contamination (min=0.32 µg kg(-1); max=73.83 µg kg(-1); mean=7.03 µg kg(-1); Sd=17.83) with a great dispersion of the concentrations due to four main events of high concentrations. Pollen samples showed only one major episode with the highest PAH4 concentration found (min=0.33 µg kg(-1); max=129.41 µg kg(-1); mean=7.10 µg kg(-1); Sd=22.28). The PAH4 concentrations found were significantly influenced by the landscape context for all beehive samples.

Survey of antibiotic resistance in an integrated marine aquaculture system under oxolinic acid treatment.

The consequences of antibiotic use in aquatic integrated systems, which are based on trophic interactions between different cultured organisms and physical continuity through water, need to be examined. In this study, fish reared in a prototype marine integrated system were given an oxolinic acid treatment, during and after which the level of resistance to this quinolone antibiotic was monitored among vibrio populations from the digestive tracts of treated fish, co-cultured bivalves and sediments that were isolated on thiosulfate-citrate-bile-sucrose. Oxolinic acid minimum inhibitory concentration distributions obtained from replica plating of thiosulfate-citrate-bile-sucrose plates indicated that a selection towards oxolinic acid resistance had occurred in the intestines of fish under treatment. In contrast, and despite oxolinic acid concentrations higher than minimum inhibitory concentrations of susceptible bacteria, no clear evolution of resistance levels was detected either in bivalves or in sediments.