Study On The Mechanism Of Immune Inhibitor - Mediated Intestinal Infection Of Invasive Candida Albicans

Objective:It is proved that immunosuppression, broad-spectrum antibiotics and/or stress can cause intestinal flora disturbance, and make small amount of the normal flora of bacteria or fungal (e.g., Candida albicans) and the passing flora multiply growth. It is confirmed that the intestinal flora disorder can cause Candidemia.Methods:This study was carried out in an animal experiment:, and the experimental subjects were SD rats. Eighty SD rats were divided (regardless of male and female) into 4 groups(n=20 per group). The 1st group was the immunosupression group; the 2nd group was immunosuppression+antibiotics group; the 3rd group was immunosuppression+acute pancreatitis(AP) group; the 4th group was immunosuppression+antibiotics+acute pancreatitis(AP) group. The rats in the immunosuppressive model were given 200mg/kg of cyclophosphamide(CTX) by intraperitoneal injection on the first day of the experiment. The rats in antibiotics group were intravenously injected 100 mg/kg of ceftriaxone daily. In the acute pancreatitis (AP) group, the rats were given 20% L-Arginine (L-ARG) intraperitoneal injection (2.0g/kg) twice with the interval of one hour to cause acute hemorrhagic pancreatitis. All rats of the four groups were provided the same food, water and living condition. We divided each group of rats into two subgroups according to the different time:the 5 days group and the 10 days group, which were took 10 rats of each subgroup. All rats were put to death by breaking the cervical vertebra, and the samples were got out rapidly under aseptic condition. The samples included intracardiac blood, intestinal content, the tissue of jejunum, colon, pancreas and mesenteric lymph nodes. We sent blood, intestinal contents and others tissues homogenate for fungal culture, and make pathological section with the tissue of jejunum, colon and pancreas. If the cultures were positive, method of Candida coloar culture medium was employed for identication of the samples. If the screening results showed Candida albicans, Polymerase Chain Reaction (PCR) was used to amplify the intron area of the 25S rDNA of Candida albicans. Sequence analysis technology was used to make sure whether the fungi breakthrough the intestinal mucosa barrier.Results:1. On the 5th day of the study, the intestinal content culture from the immunosuppression+antibiotics group were significantly different from the immunosupression group. It was implied that there were already intestinal flora disturbance in the 5th day, and the fungi had already multiplied.2. On the 10th day of the study, the intestinal content culture from the immunosuppression+antibiotics group and immunosuppression+antibiotics+AP group were significantly different from the immunosupression group. It was implied that there were still intestinal flora disturbance in the 10th day, and the fungi multiplied.3. No matter on the 5th day or the 10th day of the study, there were no statistical differences between intestinal content culture from the immunosuppression+ antibiotics group and immunosuppression+antibiotics+AP group. It suggested that acute stress may not aggravate the intestinal flora disturbance with antibiotics used for enough time.4. On the 5th day of the study, the intracardiac blood culture from the immunosuppression+antibiotics group were significantly different from the immunosupression group. It was implied that there can cause Candidemia.5. Both on the 5th day and the 10th day of the study, there were evidences of intestinal barrier disruption and fungal invasion in the immunosuppression+ antibiotics group and immunosuppression+antibiotics+AP group with the immunosupression group in pathology and genomics.Conclusions:Using broad-spectrum antibiotics continuously for a long time can cause intestinal flora disturbance and fungi proliferation in the condition of immunosuppression. And with the time of antibiotics use grows, stress factors may aggravate intestinal flora disturbance. In this study, from pathology and genomics, there are obvious evidences of the intestinal barrier disruption, which cause invasive fungal infections and Candidemia.