Resumo: Bactérias que vencem a barreira física do organismo normal podem provocar reações inflamatórias localizadas. Essa reação é um dos componentes do sistema imunológico para conter invasão de micro-organismos ao corpo humano. Desenvolve-se um modelo matemático para descrever essa resposta do sistema imunológico, levando em consideração a patogenicidade das bactérias. Aplica-se os resultados para explicar a diferença de comportamento entre as bactérias estafilococos e estreptococos. O modelo mostra que a bactéria menos patogênica tem mais chances de superar a resposta do sistema imunológico inato Ver menos

Abstract: When bacteria overcome physical barrier (skin or mucus of digestive and intestinal tracts), they induce local inflammatory reaction due to the action of innate immune system. We develop a mathematical model to describe the bacterial infection taking into account the its pathogenicity. The results are applied to assess the invasion by two species of bacteria (staphylococcus and streptococcus) through the human skin and respiratory tract. Streptococcus and staphylococcus are bacterial pathogens that cause infections in the skin and soft tissue. They present distinct characteristics. The staphylococcus invade the tissues releasing lethal toxins. While the streptococcus don¿t cause intense local destruction. However, we observe that streptococcus has a greater disposition in spreading into the host body and cause harms, although the staphylococcus is much more destructive to the tissues.
The explanation for this phenomenon resides in the bacterium¿s capacity in provoking immune reactions. According to the mathematical model, the bacteria which managed to invade through the physical barrier of an healthy and immunecompetent individual, generally, are eliminated. The model showed that higher the lethality of toxins released by bacteria during multiplication process, stronger is the immune response. However, when the bacterium acts ¿silently¿, i.e., the bacterium can evade the local inflammatory reaction and escape to the blood vessels and spread out in the host organism causing infections in the multiple organs. This is due to the weak signalizing to attract macrophages to the infection site. The streptococcus cause relatively less destruction to the tissue cells, which induce few macrophage migration, as consequence, low per-capita rate of destruction of bacteria caused by macrophages Ver menos