Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 15

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
w słowach kluczowych:  Paenibacillus larvae
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
In recent years, microwave heating has become a common method for pasteurization and sterilization of food. Honey is a sweet substance produced by worker honeybees from nectar of flowers. The major microbial contaminants include moulds and yeasts, as well as the spore-forming bacteria, being their counts indicative of honeys' commercial quality and safety. Paenibacillus larvae is also of interest since it causes American foulbrood (AFB) in honeybee larvae. The main quality factors that are used in the honey international trade are moisture, hydroxymethylfurfural content (HMF), and enzymatic indices. Moreover, honey exhibits several thermal events, the most important being the glass transition temperature (Tg). The aim of this work was to evaluate microwave effect (800 watts during 45 and 90 seconds) on microbial content in particular over P larvae spores retained in honey, and on physicochemical and thermal properties. Microwave promoted a decrease of microbial count with time of exposure, including P larvae. Moisture content diminished after treatment, while Tg increased linearly, and acidity decremented in the majority of cases. Honeys darkened and HMF exceeded the permissible value. Diastase and glucose-oxidase enzymes were totally inactivated by microwave treatment.
The honey bee disease American foulbrood (AFB) is a serious problem since its causative agent (Paenibacillus larvae) has become increasingly resistant to conventional antibiotics. From the year 2000 the number of isolates of P. larvae resistant against oxytetracycline (OTC) has increased. Therefore, since 2000 many antibiotics, chemotherapeutic propolis and plant extracts were tested in vitro and in vivo against P. larvae. The most active in the in vitro tests appeared to be deoxycycline, minocycline, rifampicin and lincomycin. Among the 35 examined antibacterial compounds active against P. larvae were narasin, salinomycin and tylosine. In many countries tylosine, tilomycosis have been recommended for the control of AFB, while microsamicine was recommended in Japan. The studies with plain essential oils did not succeeded. The propolis extracts from the various parts of the world showed significant inhibition of P. larvae. Due to the evolution of the resistance of P. larvae to conventional antibiotic treatments, the research on normal bee microflora (Bacillus, Paenibacillus, and Brevibacillus) is an important step in identifying possible new active tools to treat AFB in honey bee colonies.
A characteristic of Paenibacillus larvae with a special reference to the current view on the systematics of this pathogen of the honey bee (Apis mellifrea L.) was presented. A great differentiation of the phenotypic and biochemical properties of the isolates often lead to errors in the diagnostics of AFB. The currently used methods of controlling AFB not only cannot eliminate the pathogen from AFB-affected colonies, but actually promote the selection of strains of higher pathogenicity to the honey bee larvae. The behavior of worker bees that quickly remove dead larvae from the sick colony may mask the symptoms of AFB. The genotyping of P. larvae should introduce PCR as a precise method for the diagnostics of AFB as soon as possible.
The paper characterizes and discusses the immune response mechanisms of the honey bee, mainly bee larvae, to infection caused by Paenibacillus larvae, the absolute pathogen of honey bee larvae. A statistically significant increase in abaecin was found in the youngest larvae during 24 h after infection that is during the germination of P. larvae endospores and the penetration of vegetative cells into the gut epithelium. Moreover, P. larvae stimulate the production of defensin - an immune protein of bee larvae. The comparative analysis of social insects and solitary model insects Drosophila melanogaster and the mosquito Anopheles gambiae revealed a significant differentiation in the number of genes and their products that play a significant role in insects’ protection against microorganisms. The comparison of the number of genes responsible for three stages of immune defense: recognition of foreignness, information transfer and effector activity showed 71 genes in the honey bee, but 209 and 196 genes in the Anopheles gambiae and Drosophila melanogaster, respectively. These tremendous differences in the number of immune genes between the discussed representatives of insects could be explained by the development of behavioral protective mechanisms in the honey bee, and probably also by the limited number of honey bee pathogens.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.