Agricultural Microbiology, Department of Biology, Federal University of Lavras, Central Avenue, 37200-000 Lavras, Minas Gerais, Brazil.
Department of Food Sciences, Federal University of Lavras, Central Avenue, 37200-000 Lavras, Minas Gerais, Brazil.
J Food Prot. 2021 Apr 1;84(4):579-586. doi: 10.4315/JFP-20-336.
Staphylococcus aureus causes food intoxication and can become resistant to a large number of antibacterial drugs. Thus, there is a growing interest in understanding the mechanisms involved in the adaptation of bacterial cells to environmental stresses or to antimicrobial agents. In this context, we evaluated the cinnamaldehyde (CIN) MBC for two contaminating food strains of S. aureus (GL 5674 and GL 8702) and tested the hypothesis that exposure of these strains to sublethal CIN concentrations and pH values could increase their resistance to this antimicrobial agent, to acid stress, and also to stress at high temperatures. Thus, the ability of the strains to adapt to CIN and acid stress was evaluated, as well as the cross-adaptation between acid stress and CIN. Strains GL 5674 and GL 8702 of S. aureus are sensitive to CIN in MBCs of 0.25 and 0.5% respectively, proving the antibacterial potential of this compound, but we proved the hypothesis of homologous adaptation to CIN. The strains grew in concentrations higher than the MBC after being previously exposed to sublethal concentrations of CIN. We also observed heterologous adaptation of the strains, which after exposure to the minimum pH for growth, were able to grow in concentrations of CIN greater than the MBC. GL 5674 showed greater adaptive plasticity, considerably reducing its minimum inhibitory pH and increasing its MBC after adaptation. Our results show a positive effect of adaptation to CIN on the resistance of S. aureus (P < 0.0001) to CIN at a temperature of 37°C. However, in the absence of adaptation, the presence of CIN in S. aureus cultures maintained at 37°C showed an efficient bactericidal effect associated with increased exposure time. Our results call attention to the conscious use of CIN as an antimicrobial agent and present the possibility of using CIN, in association with a temperature of 37°C and an exposure time of 35 min, as a promising measure for the elimination of pathogenic strains.
金黄色葡萄球菌会引起食物中毒，并且能够对大量抗菌药物产生耐药性。因此，人们越来越感兴趣的是了解细菌细胞适应环境压力或抗菌剂的机制。在这种情况下，我们评估了肉桂醛（CIN）对两种污染食品的金黄色葡萄球菌（GL 5674 和 GL 8702）的最小杀菌浓度（MBC），并检验了以下假设，即这些菌株在亚致死 CIN 浓度和 pH 值下的暴露会增加其对这种抗菌剂、酸应激和高温应激的抵抗力。因此，评估了菌株对 CIN 和酸应激的适应能力，以及酸应激和 CIN 之间的交叉适应。金黄色葡萄球菌的 GL 5674 和 GL 8702 菌株对 MBC 分别为 0.25%和 0.5%的 CIN 敏感，证明了该化合物的抗菌潜力，但我们证明了对 CIN 的同源适应假设。在先前暴露于亚致死浓度的 CIN 后，菌株在浓度高于 MBC 的情况下生长。我们还观察到了菌株的异源适应，在暴露于最低生长 pH 值后，它们能够在高于 MBC 的 CIN 浓度下生长。GL 5674 显示出更大的适应性可塑性，在适应后其最小抑菌 pH 值大大降低，MBC 增加。我们的结果表明，金黄色葡萄球菌对 CIN 的适应性（P < 0.0001）对 37°C 下 CIN 的抗性有积极影响。然而，在没有适应的情况下，CIN 在 37°C 下金黄色葡萄球菌培养物中的存在表现出与暴露时间增加相关的有效杀菌作用。我们的研究结果引起了对 CIN 作为抗菌剂的有意识使用的关注，并提出了在没有适应的情况下，将 CIN 与 37°C 的温度和 35 分钟的暴露时间相结合，作为消除致病菌株的有希望的措施的可能性。
