CHARACTERIZATION OF AN ANTIMICROBIAL PEPTIDE PRODUCED BY A CLINICAL ISOLATE AC172 OF Shigella flexneri 2

MÓNICA F. TORREZ LAMBERTI; MARIA F BALLESTEROS; A.M. BIANCHI; LOPEZ FABIAN E; FARIZANO J. V.; MARÍA DE LAS MERCEDES PESCARETTI; DELGADO, MONICA A.

Congreso; SAMIGE 2017; 2017

This strain was isolated in the summer period 2016-2017 from a pediatric patient with enterocolitis,recovered in the Centro Provincial de Salud Infantil Eva Perón (CePSI-Santiago del Estero province).Thebiochemical and serology tests allowed us to classify this strain as a member of the Shigella flexneri 2 serotype.In this study, we analyzed the antibiotic resistance profile of this strain using the antibiotics-disctechnique. We also analyzed the AC172 plasmid profile, detecting the presences of a large number ofthese extrachromosomal elements. In addition, we determined that AC172 is able to produce a growthinhibitory substance, using the plate diffusion method and the E. coli AB1133 strain as sensitive. Thisinhibitory compound was characterized using a cell free supernatant obtained after the overnight cultureof AC172 in LB. The supernatant?s treatment with proteases showed that this inhibitory substanceis of protein nature, since it maintained its ability to inhibit bacterial growth after 2 hours of incubationat 37°C. Moreover, it compound was presented as resistant to high temperatures degradation, evenafter being incubated at 100°C for 20 min. We estimated the size of such substance by electrophoresisin a polyacrylamide gel (12%), where was compared with a molecular weight marker and developedby its growth inhibition activity. The net charge was determined by electrophoresis, running a sampleinto a 1% agarose gel, at pH 8. The results of this study allow us to characterized this compound as alike-bacteriocin peptide, of low molecular weight (3 kDa, approximately), negatively charged, stable athigh temperatures and of protein nature.