Identification of Enterococcus mundtii as a pathogenic agent involved in the "flacherie" disease in Bombyx mori L. larvae reared on artificial diet |
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Authors: | Cappellozza Silvia Saviane Alessio Tettamanti Gianluca Squadrin Marta Vendramin Elena Paolucci Paolo Franzetti Eleonora Squartini Andrea |
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Institution: | a CRA - Apiculture and Sericulture Research Unit, Padua seat, via Eulero, 6a, 35143 Padova, Italy b Department of Biotechnology and Molecular Sciences, University of Insubria, via J.H. Dunant, 3, 21100 Varese, Italy c Department of Agricultural Biotechnologies, University of Padova, via Romea, 16, 35020 Legnaro (Padova), Italy d Department of Environmental Agronomy and Crop Production, University of Padua, viale dell’Universita’, 16, 35020 Legnaro (Padova), Italy |
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Abstract: | Enterococcus mundtii was shown to be directly correlated with flacherie disease of the silkworm larvae reared on artificial diet supplemented with chloramphenicol. Its identification was carried out by means of light and electron microscopy and nucleotide sequencing of 16S gene. The bacterium is capable of rapidly multiplying in the silkworm gut and of invading other body tissues, as demonstrated by deliberate infection of germfree larvae and by subsequent TEM observations. E. mundtii can endure alkaline pH of the silkworm gut and it has been proved to adapt in vitro to commonly applied doses of chloramphenicol, whose use can further contribute to reduce competition by other bacteria in Bombyx mori alimentary canal.The modality of transmission of the infection to the larvae was among the objectives of the present research. Since contamination of the progeny by mother moths can be avoided through routine egg shell disinfection, a trans-ovarian vertical transmission can be ruled out. On the other hand the bacterium was for the first time identified on mulberry leaves, and therefore artificial diet based on leaf powder could be a source of infection. We showed that while microwaved diet could contain live E. mundtii cells, the autoclaved diet is safe in this respect. Being E. mundtii also part of the human-associated microbiota, and since B. mori is totally domestic species, a possible role of man in its epidemiology can be postulated. |
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Keywords: | Acridine ARDRA Artificial diet Bacterial disease Bombyx mori Chloramphenicol DAPI Enterococcus mundtii Germfree rearing Mulberry silkworm Pyronin TEM |
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