Objective To testify the virulence of extracellular phosphlipase B of Candida Albicans in experimental keratomycosis Methods Firstly, determine the activities of the phospholipase secreted by the plb1 null mutant and its isogenic parental strain of Candida albicans. Secondly,compare the differentia of the two strains in the models through observing the dynamic development in clinic and in histopathology. Finally, detect the influence of the two strains on keratocyte monolayers. Results The activities of the phospholipase secreted by the two isogenic strains were significantly different (t=3.485, P=0.009). The hyphae of the two strains present vertical growth-pattern in the corneal stroma either. The differences were found in the depth of the hyphae only inoculated for 2 days (t=4.313, P=0.002) . But in other intervals, there was no significant difference (P＞0.05) in the depth of hyphae and the severity of the inflammation in keratomycosis corneas at the any schedule between the two strains. The morphogenesis and the number of adherent germ tubes of the two isogenic strains appeared similarly (P＞0.05) , while the number of germ tubes penetrating cell monolayers was different (F=0.339, t=2.871, P=0.009) . The production of prostaglandin E2 in the culture supematants of parental strain group can be higher than that in other groups. The percentages of apoptosis and the cellular membrane damage in parental strain group were bigger than those in null strain group,while there were fewer living cells in these two groups compared with the control group. Conclusion The extracellular phosphlipase B, which makes a dominating proportion in the whole extracellular phosphlipase of Candida Albicans, has no relationship with the growth-pattern of the hyphae. It plays a virulent role in triggering fungi to invade corneas through acting on host phospholipids, inducing the necrosis, but it is not a critical virulent factor in the pathogenesis of keratomycosis.The intervention in PLB will not mitigate the damage of the pathogenic fungi in keratomycosis.Key Words: Candida Albicans, Phosphlipase B, the Null Mutant, Keratomycosis
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