Animal Studies About Gastrointestinal Infections By Geotrichum Silvicola

Purpose: Geotrichum silvicola was a rare fungi in Geotrichum isolatedfrom Brazil fly and Indian oak silkworm In2002,then we also isolated thesame fungi from a child’s kerion-like lesions and a patient suffered from toxicepidermal necrolysis, there was no reports Geotrichum silvicola infectedhuman previously[1,2]. Yin Ruirui and others builded animal models sufferedfrom systemic infection, they found this new fungi cound infect the heart, liver,spleen, lung and kidney of mice under certain condition, they also comparedthe infection status of different organs through calculating fungi residualburden of organs.In this experiment,we gived the different immune status of mice conidialsuspension by different method, and detected whether it could cause infectionof the gastrointestinal tract through observing the fungal retro-culture of thestomach, intestinal and feca. At the same time, we calculated fungi residualburden of organs,and compared the differences of infection between differentimmune status and different methods of injection, this experiments will furtherenrich the study of the systemic infection suffered by Geotrichum silvicola inmice.Method:1The establishment of a mouse systemic infection model Thepreserved fungi was revived at the room temperature and made into conidialsuspension, then injected into the mice to restore virulence. After, the conidialsuspension made by Physiological saline was injected into mice throughintradermal, intraperitoneal and intravenous pathways.2The observation of clinical symptoms and death situation Weobserved the change of the eating, drinking, reaction, activities, hair changeand the mental state in different immune status, we also recorded the death situation of each group in14days.3The morphology change of the gastrointestinal organ Under sterileconditions, we taken out of the stomach, small intestine, large intestine fromthe killed mice, then observed the morphology change of the gastrointestinalorgan after the food residue being rinsed.4Fungal retro-culture The stomach, small intestine, large intestine weregrinded and subcultivated onto the media of SDA.After culturing under37℃for one week, we observed the growth situation of the fungi and themorphology of the hyphae, spores under the microscope.5Histopathological examination The pathological stomach, smallintestine, large intestine separated from the killed mice were fixed, dehydrated,cleared, embedded, sliced, stained with HE and PAS respectively.6Observation of fungi residual burden of organs Under sterileconditions, the stomach, small intestine, large intestine were weighed, grindedand added into physiological saline according1:10(wt/vol). We picked up10ul tissue suspension onto the surface of SDA and incubated it under37°Cfor48hours, then readed the number of the colonies and calculate fungiresidual burden of organs.Results:1Clinical symptoms In the immune group, the eating and the drinkingof the mice inoculated intravenously and intraperitoneally were reduced a littlein the late. In the immunosuppressed group, the eating and the drinking of themice inoculated intravenously and intraperitoneally were reduced,the hair hadno burnish,the mental state was drooping, and the weight droped continuously.No matter what kind of immune state,there was a nodule from green beans tosoybean volume on the back of the mice inoculated subcutaneously. Thenodule of the later was bigger then the former, and bursted on the surface.2The death of the mice The mice of the immunosuppressed groupwhich was inoculated intravenously began to die at the first day after beinginjected and reached the peak of death at the seventh day, the mortality ratewas100%within9days. The mice of the immunosuppressed group which was inoculated intraperitoneally began to die at the fourth day after beinginjected and reached the peak of death at the eighth day, the mortality rate was100%within12days.3The change of organ In the immunosuppressed group,the stomach,small intestine, large intestine of the mice inoculated intravenously andintraperitoneally were red and fragile, there was a little feces in which and norotting kitchen on the surface. The organ of the mice in other groups has nomacroscopic change.4Fungal retro-culture In the different immune group inoculatedintravenously and intraperitoneally, we could see fungi growth in the culturetube at the third day, and the morphology of the fungi was same as the fungiinoculated.5Histopathological examination We could see degeneration andnecrosis in the tissue, there were also a lot of inflammatory cells between cellsfrom HE dyeing. PAS dyeing displayed purple hypha and spores.6Observation of fungi residual burden of organs The fungi residualburden of stomach, small intestine, large intestine in the immunosuppressedgroup inoculated intravenously and intraperitoneally were significantly higherthan the immune group. Between the two groups inoculated intravenously andintraperitoneally, the fungi residual burden of the former was higher than thelater. The fungi residual burden of the stomach was higher than the smallintestine and the large intestine, there was no significant difference betweenthe latter two.Conclusion:1The intravenous and the intraperitoneal injection all could lead toinfections of the stomach, small intestine and large intestine in mice, but theformer was serious. The subcutaneous injection could not lead to infections ofthe stomach, small intestine and large intestine in mice.2The mice of the immunosuppressed group were more likely to causeinfection then the mice of the immune group, and the former could also causehigher mortality rates. Geotrichum silvicola was an conditional fungi, the pathogenicity of which related with the immunity of the organism.3No matter what kind of immune state and injection, the stomach wasmore likely to cause infection then the small intestine and large intestine, therewas no obvious difference between the latter two.4The histopathological examination of the stomach and the intestinedisplayed inflammatory changes.