排序方式： 共有5条查询结果，搜索用时 15 毫秒
1
1.
2.
Staphylococcus aureus is recognized worldwide as a pathogen causing many serious diseases in humans and animals, and is the most common aetiological agent of clinical and subclinical bovine mastitis. The importance of evaluating the combination of S. aureus virulence factors has been emphasized both in human and veterinary medicine, and knowledge about the genetic variability within different S. aureus populations would help in the design of efficient treatments. The aim of the present study was to determine the genetic profiles of S. aureus strains isolated from milk of cows suffering from clinical and subclinical mastitis in Belgium. The presence of about forty virulence-associated genes was investigated by specific polymerase chain reaction (PCR) amplification. A high number of genotypic subtypes were observed, demonstrating further the large variation in the presence of virulence genes in S. aureus isolates and the considerable diversity of strains populations that are able to cause mastitis in cows. In accordance with other studies, we showed that some genes are associated with mastitis-causing S. aureus isolates, whereas others are absent or rarely present. We also further highlighted the presence of conserved gene combinations, namely the enterotoxigenic egc-cluster and the bovine pathogenicity island SaPIbov. Importantly, the presence of isolates carrying genes coding for toxins involved in important human infections makes the milk of cows with mastitis a potential reservoir for these toxins, and therefore a potential danger in human health, which strengthens the importance to consider raw milk consumption and its processing very carefully. 相似文献
3.
Aupinel P Fortini D Michaud B Marolleau F Tasei JN Odoux JF 《Pest management science》2007,63(11):1090-1094
A new in vitro method was devised to assess the effects of pesticides on honey bee brood. The method allowed the quantification of doses ingested by larvae and the assessment of larval and pupal mortality. Larval mortality in control samples was lower than 10%. Two active substances were tested: dimethoate and fenoxycarb. The LD(50) of dimethoate was 1.9 microg larva(-1) 48 h after oral exposure of larvae at day 4. Additional dose-related effects on pupal mortality were noted. After a chronic intoxication, the NOAEC (No Observed Adverse Effect Concentration) for larval mortality at day 7 was 2.5 mg kg(-1), whereas a NOAEC of 5 mg kg(-1) was found at day 22 for delayed effects on the reduction of adult emergence. Fenoxycarb applied at day 4 showed no effect on larvae, whereas emergence of adults was affected at doses higher than 6 ng larva(-1). 相似文献
4.
Atypical/Nor98 scrapie cases in sheep were diagnosed for the first time in Norway in 1998. They are now identified in small ruminants in most European countries and represent an increasingly large proportion of the scrapie cases diagnosed in Europe. Atypical/Nor98 scrapie isolates have shown to be experimentally transmissible into transgenic mice and sheep but the properties of the TSE agent involved, like its biological and biochemical features, are so clearly distinct from the agent involved in classical scrapie that they have provided a challenging diagnostic for many years. No strain diversity has yet been identified among the atypical/Nor98 scrapie sample cases. The genetic predisposition of the sheep affected by atypical/Nor98 scrapie is almost inverted compared to classical scrapie, and the exact origin of this sporadic TSE strain is still speculative, but a spontaneous, non-contagious origin, like sporadic Creutzfeldt-Jakob disease in humans, can not be excluded. Further transmission and epidemiological studies are needed to better address this hypothesis. 相似文献
5.
Awatef Trabelsi Andrzej Jaworski Ewa Kamler Jean-Noël Gardeur Fabrice Teletchea Habib Ayadi Pascal Fontaine 《Fish physiology and biochemistry》2016,42(2):593-606
Size, caloric value and chemical composition were measured separately in the progeny of two northern pike (Esox lucius) females at 3-day intervals during the endogenous feeding period from hatching to final yolk resorption. Tissue, yolk and entire larvae were analysed separately in three groups of larvae that hatched at different times (between 88 and 106 degree-days post-fertilization). An integrated approach with the Gompertz model was used to compute the yolk conversion efficiency and time to maximum tissue size in early, mid and late hatched larvae. At hatching, unresorbed yolk of early hatched larvae contained more energy (39.20 J) and more protein (0.99 mg) compared to the yolk of larvae that hatched later (38.13 J and 0.92 mg protein for late hatched larvae, p < 0.05). In contrast, a significant reduction in tissue weight (?0.7 mg DW) and protein content (?0.5 mg) was found in early hatched larvae compared to those which hatched later (p < 0.05). Between days 9 and 12 post-hatching (108 and 144 degree-days post-hatching), close to the final yolk resorption, late hatched larvae stopped growing and their tissue began to be resorbed. This tissue resorption time was delayed in early hatched larvae which presented at the end of the experiment a greater tissue weight than late hatched ones. Yolk conversion efficiency in term of energy from hatching to complete yolk resorption stage was significantly higher for early and mid hatched larvae (51 %) compared to late hatched ones (44 %) (p = 0.004). Furthermore, the time to maximum tissue size was found to be negatively related to hatching time which implies that early hatched larvae take longer time to switch from one developmental stage to the next. The maximum tissue dry weight and energy content were found to be reached at approximately the same age post-fertilization for both early hatched and late hatched larvae, suggesting that the principal steps in a fish’s lifespan are better correlated with time of fertilization than hatching time. 相似文献
1