Atividade antimicrobiana e antibiofilme de azo compostos frente a patógenos de importância em alimentos

Abstract

Animal production constitutes an activity of great importance for the Northeastern semiarid. Meat and its derivatives are products of great commercial importance, either for the regional consumer or as a tourism product in a rising gastronomic pole. However, as an easily contaminating product it might be a carrier of microorganisms, and the preservatives employed in meat products, the nitrite salts, have been described as of high carcinogenic potential. Consequently, several strategies have been explored as alternatives to the use of these salts. Therefore, this work aimed to evaluate the antimicrobial and antibiofilm activity of 4 azo compounds (A1, A2, A3, and A4) on microorganisms isolated from lamb and sheep meat. No reports regarding the use of the azo compounds synthesized in this research were found in other studies where their use is suggested for foods. In this study, it was also investigated if the compound presented in vitro synergistic action with the sodium nitrite, its toxic effect on Artemia salina and the mechanism used for microbial inhibition. Afterward, the shelf life of the lamb sausage was determined though treatments that differed in the preservative agent employed (azo compounds and sodium nitrite), with a treatment without preservative addition as a control group. Out of 21 meat samples, it was possible to isolate 15 S. aureus (75%) and 13 E. coli (62%). The A4 was the azo compound that presented the best activity, with a mean bactericidal concentration of 230 μg/mL on S. aureus. The isolated strains presented biofilm production, with eight (61.5%) of the S. aureus presenting a strong and seven (38.5%) with a weak production, and eight (61.5%) of the E. coli presenting a weak production. The remaining E. coli strains were not biofilm-producing. The A4 compound was able to interfere in the formation of biofilm in all the strong producers isolates of S. aureus and interfered in the stablished biofilm in 50% of these isolates. The sodium nitrite presented mean MBC of 67 μg/mL, and in the synergism test with the A4, nine (60%) S. aureus presented reduction of the MBC in synergistic action. In the shelf life test, the variables moisture and pH did not demonstrate differences in the treatments, although the colorimetry of the treatment with the A4 presented superior results to the remainder. As for the microbial counting, the test compound exhibited a reduction for the counting of S. aureus, mesophilic, and psychrotrophic microorganisms when compared to the control group (without preservative addition), although without difference in the enumeration of coliforms; however, the counting of bacteria in the tests with sodium nitrite were inferior to the treatment with the A4. Aiming to evaluate the possible action mechanism of the compound in pathogenic microorganisms, it was identified through molecular docking that the A4 presented affinity with the FtsA protein, suggesting that the inhibition of S. aureus might be related to the interference in the interaction with the FtsZ, inhibiting cell division and causing bacterial mortality. The A4 presented mortality rates of 96% for the toxicity in Artemia salina in the concentration of 10 μg/mL and 100% for upper concentrations. The study demonstrated that the azo compound presented an in vitro microbial effect, although is toxic action should be evaluated with superior organisms in order to obtain results closer to human beings, as well as synergism tests with the nitrite salt in shelf-life in order to evaluate their efficacy in reduced concentrations.