Seleção de actinomicetos isolados de liquens da região Amazônica produtores de inibidores de β-lactamases e sua atividade antimicrobiana frente a isolados de mastite bovina

Abstract

Bovine Mastitis is one of the main diseases that affect the dairy herds in the world and is considered one of the greatest obstacles to their operation profitable. The greatest losses from mastitis are due to the decrease in milk production, depreciation in nutritional quality, treatment cost, cost of veterinary care and laboratory losses in genetic potential. Several microorganisms are cited as agents of bovine mastitis and the species most frequently isolated are Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis and Escherichia coli. The β-lactam antibiotics are important antibacterial agents, but sensitive to β-lactamase enzymes capable of cleaving the β-lactam ring, rendering them inactive. Inhibitors of β-lactamases are an alternative for diseases treatment caused by resistant-penicillin bacteria. This study evaluated the ability to produce β-lactamase inhibitors by 71 actinomycetes isolated from lichens of the Amazonian and its antimicrobial activity using Staphylococcus aureus, penicillin-resistant isolates of bovine mastitis. The selection of actinomycetes that produced β-lactamases inhibitors was performed using the agar block technique against Klebsiella pneumoniae ATCC 29665 and selected actinomycetes were tested against Staphylococcus aureus penicillin resistant. The best producers of β-lactamase inhibitors were Streptomyces sp. DPUA 1542 and Nocardia sp DPUA 1571, which were subjected to submerged cultivation in the study of the growth curve, pH and antimicrobial activity. The largest inhibition zones using S. aureus, were obtained after 96 hours of culture for both Nocardia sp (13.5 and 12.0 mm) and for Streptomyces sp. (8.0 and 14.0 mm) with diffusion-tests on the discs and wells, respectively. Nocardia sp DPUA 1571 was used in the production of inhibitors of β-lactamases by factorial design where the influence of three variables: concentrations of carbon source (0.5, 1.0 and 1.0%), concentrations of nitrogen source (1.0, 2.5 and 4.0%) and pH (6.0, 6.5 and 7.0) were evaluated. The production carried out in 250mL flasks containing 100mL of culture medium MS-2 modified according to the experimental design, the flasks were incubated in an orbital shaker (200 rpm) at 28 ° C for 120 hours and each 24 hours, aliquots of 5 mL were withdrawn and centrifuged at 5000 rpm for 20 minutes at 4 ° C for the study of biological activity and dry weight. The biological activity of the liquid assay was performed using the diffusion-tests on the discs and wells, the best cultive conditions (test 3) with concentration of carbon source of 1.0% concentration of the soy bean flour 1% and pH 6,0, were obtained from the inhibition of up to 22mm diameter test against microorganisms used. The results showed that the actinomycetes are a promising source of β-lactamase inhibitors, demonstrated the potential application to pharmaceutical industry.