Antibiotic proteins from Apeiba tibourbou, Bixa orellana and Mucuna urens seeds actives against Rhodococcus equi

A number of animal-associated infections occur in persons infected with the human immunodeficiency virus (HIV), including those due to Rhodococcus equi. The principle of pathogenicity is the survival inside macrophages. Cavitary pneumonia is the most common manifestation of R. equi disease, but extrapulmonary infections are seen as well. Long term treatment with intracellularly active antimicrobial agents is required [1]. Actually, several antimicrobial proteins and peptides from seeds plants have been described [2]. Here, we describe the antibiotic activity of A. tibourbou, B. orellana and M. ureis proteins against R. equi. A crude extract was prepared using seeds flours and 0.1M NaCl, 0.01M HCl solution (1:2, w/v, meal to solution ratio) with continuous stirring during 2h. The material was centrifuged at 10.000 x g, 4°C for 30min and the supernatant was used to prepare an ammonium sulphate protein fraction (0–70% saturation). These fractions, after dialysis against water, were used to determine the antibacterial activity against R.equi in a disk test (disk diffusion, solid culture media, 37°C for 48h). Protein quantification was done by Bradford [3] assay and disks containing 1.0 microg/mL of proteins were used. Distilled water was utilized as a negative control. After 48h, inhibition halos zones of 9–10mm of diameter were observed around the disks containing the proteins from all fractions. SDS-PAGE [4] was done and protein bands between 10 and 60 kDa were observed in all samples. These proteins represent candidates for antibiotic production for applications in the human and veterinary medicine.

Acknowledgements: EMBRAPA Cerrados, Planaltina -DF, Brazil, Marília Santos Silva.

References: [1] – Rozsypal H, Aster V., Cas Lek Cesk. 2007;146(2):163–7. [2] – Hancock RE, Chaple DS., Antimicrob Agents Chemother. 1999 Jun;43(6):1317–23. [3] – Bradford M. M., Anal Biochem. 1976 May 7;72: 248–54. [4] – Laemmli U. K., Nature. 1970 Aug 15; 227(5259):680–5.