Anais do Congresso Paranaense de Microbiologia
IV Congress of Microbiology in Paraná

Infectious diseases are of great concern worldwide and represent about a quarter of deaths in the world. Currently, antibiotic therapy is the main form of treatment for these diseases. Soil microorganisms have had considerable prominence in bioprospecting as they produce several active secondary metabolites. Soil bacteria in particular, have been promising in the search for antimicrobial compounds. The present work aims to fulfil the prospection of microorganisms producing antimicrobials. The search for antagonistic microorganisms occurred in soil samples collected in northern of Paraná. Serial dilutions were prepared and placed in Lúria Bertani medium and incubated at 37°C. From the second day of incubation, the presence or absence of inhibition zones was observed. Bacterial colonies recognized as producing antimicrobial compounds were selected and subsequently subjected to disk-diffusion tests against the following strains: Staphylococcus aureus (ATCC 25923); Enterococcus faecalis (ATCC 29212); Salmonella enterica (ATCC 13076); Escherichia coli (ATCC 25922); and Pseudomonas aeruginosa (ATCC 9027). Based on the halo evaluation criteria adopted by the authors, the best isolates were cultivated in a shaker at 180 rpm at 28°C for 4 days. At the end of the incubation period, the inoculum was subjected to filtration in order to remove the cells and obtain the supernatants. The agar well diffusion test was performed with 80 µl of the filtrate against the previous pathogens. Thus, the antagonist with the greatest antimicrobial potential was selected for amplification and sequencing of parts of the 16s rDNA gene. Soil was collected from 45 points of 4 cities in Northern Paraná, and after evaluating the antibiosis profile, 101 bacterial colonies were selected, purified, and stored at -20°C. In the disk-diffusion tests, performed with 101 isolates, 11.5% showed halos equal to or greater than 0.2 cm in raius against Staphylococcus aureus, 9.8% against Enterococcus faecalis, and Salmonella enterica, and 1.96% against Pseudomonas aeruginosa. The culture supernatant agar well diffusion test was performed with isolates B4, B21, and B33, in which only B33 showed a halo of 0.7 cm in raius against P. aeruginosa. Isolate B33 was selected for the sequencing step, and identified as Pseudomonas areruginosa. The isolate identified as P. aeruginosa proved to be a potential antagonist the reference strains tested, including P. aeruginosa (ATCC 9027), requiring further studies for identification and molecular characterization of the antimicrobial.