Toxicity intraperitoneal and intragastric route of Bacillus thuringiensis and Melia azedarach in mice

Abstract

The aim of this investigation was the assessment of toxicity of two new isolates of Bacillus thuringiensis, and the aqueous extract of Melia azedarach through in vivo assays in CF1 mice. Bt 1958-2, Bt 2014-2 and the BTh Thuricide 63 standard isolates were grown in liquid usual glicosed medium, and Cry proteins were purified by centrifugation on a sucrose gradient. The supernatant was autoclaved at 121º C, 15min. to maintain the exotoxins. Dehydrated leaves of M. azedarach were used to prepare a 10% aqueous extract. Mice were treated either orally or intraperitoneally with a whole bacterial suspension (1.10 10 UFC/mL), a culture supernatant or purified crystal protein (50 µg/mL), and with the plant extract (50 µg/mL). The stomachs of the mice were collected and observed in stereomicroscopy, and the stomach contents were analyzed in 10% SDS-PAGE. Results showed that none of the oral treatments were toxic to mice, but intraperitoneal bacterial suspensions were lethal to the animals 6 -24 hours after injection. In conclusion, the Cry proteins of the new B. thuringiensis isolates must be evaluated for their use as tools in the biotechnology field, since they do not show toxicity against mammals, intragastrically or peritoneally, just like the M. azedarach aqueous extract (10%), with those being indicated for the biological control of pest insects.KEY WORDS: Bacterium, mammalian, Meliaceae, toxicology. RESUMO TOXICIDADE VIA INTRAGÁSTRICA E INTRAPERITONEAL DE BACILLUS THURINGIENSIS E MELIA AZEDARACH, EM CAMUNDONGOS. O objetivo deste estudo foi a avaliação da toxicidade de dois novos isolados deBacillus thuringiensis e o extrato aquoso de Melia azedarach, através de ensaios in vivo em camundongos CF1. Os isolados Bt 1958-2, Bt 2014-2 e o isolado padrão BTH Thuricide 63 foram cultivados em meio usual glicosado, e as proteínas Cry foram purificadas por centrifugação em gradiente de sacarose. O sobrenadante foi tratado em autoclave a 121º C, 15 min para manter as exotoxinas. As folhas desidratadas de M. azedarach foram utilizadas para preparar um extrato aquoso a 10%. Camundongos foram tratados, via oral ou por via intraperitoneal, com a suspensão bacteriana (1.10 10 UFC/mL), o sobrenadante de cultura ou a proteína do cristal purificada (50 µg/mL), e com o extrato da planta (50 µg/mL). Os estômagos dos ratos foram coletados e observados em estereomicroscópio e os conteúdos estomacais foram analisados em SDS-PAGE a 10%. Os resultados mostraram que nenhum dos tratamentos orais foram tóxicos para os camundongos, mas, via intraperitoneal, as suspensões bacterianas foram letais para os animais entre 6 e 24 horas após a injeção. Em conclusão, as proteínas Cry dos novos isolados de B. thuringiensis devem ser avaliadas para sua utilização como ferramenta no campo da biotecnologia, uma vez que elas não mostram toxicidade contra mamíferos, intragástrica ou intraperitoneal, assim como o extrato aquoso (10%) de M. azedarach, podendo ser indicado para o controle biológico de insetos-praga.

In defence of Bacillus thuringiensis, the safest and most successful microbial insecticide available to humanity—a response to EFSA

“…A concentration of 10 10 CFU ml −1 does not affect mice (Berlitz et al. 2012 ) and over 5 days human volunteers can consume 1 g per day (∼ 10 11 spores) of a formulated product (Thuricide) based on Bt without ill effects (Siegel 2001 ). Epidemiological studies confirm the results of acute toxicity tests.…”

Biological Evaluation of a New Sodium-Potassium Silico-Phosphate Glass for Bone Regeneration: In Vitro and In Vivo Studies

“…The infusion was prepared by suspending glass powder in distilled water containing potato starch (1 g starch/100 g of water). Intragastric route was applied and suspension was delivered at cumulative doses into the stomach through gavage for 0, 12 and 24 h, according to [ 32 , 33 ]. Further treatments were the same as for the intraperitoneal route toxicity assays.…”

In vitro antitumoral activity of soluble protein extracts of Bacillus thuringiensis

“…It is characterized by crystal production during sporulation, containing Cry proteins, encoded by the Cry genes, with a wide division into classes and subclasses according to their insecticide activity, and presently classified according to the percent amino acid identity between Cry protein sequences (Mezzomo et al, 2015 Palma et al, 2014a). Besides the cry proteins, known as -endotoxins, B. thuringiensis isolates can synthesize other toxins, such as -exotoxin, phospholipases, proteases, chitinases and enterotoxins (Berlitz et al, 2012).…”