The Correlation Between Candida Colonization Of Distinct Body Sites And Invasive Candidiasis

Objective: This study aimed to analyze the correlation between Candida colonization of distinct body sites and invasive candidiasis(IC),to investigate possible sources of IC,and to explore the reason why the risk of developing IC differed depending on the body sites colonized,in order to provide evidence for selecting practical body sites of Candida surveillance cultures and evaluating risk factors for IC.Methods: In section One,Candida surveillance cultures from the urine,sputum,rectum,and skin were performed on 111 patients admitted to an emergency intensive care units(EICU)of Ruijin Hospital from February 2014 to January 2015.The patients’ clinical data were collected,and Candida isolates were genotyped using polymorphic microsatellite markers(PMMs).In section two,203 isolates of Candida species(85 C.albicans,62 C.glabrata and 56 C.tropicalis)were isolated from distinct body sites of patients(urine,fecal,sterile fluid and sputum samples)in Ruijin Hospital between 2012 and 2015.Important virulence factors(biofilm formation;extracellular proteinase,phospholipase and hemolysin production;hypha formation)were examined.Results: Patients with positive urine(23.3% vs.2.5%,p =0.001)and rectal swab(13.6% vs.0%,p= 0.010)cultures were more likely to develop IC.However,the risk for IC was not significantly different among patients with and without respiratory(10.0% vs.5.8%,p=0.503)and skin(33.3% vs.6.5%,p= 0.056)colonization.Gene microevolution frequently occurred in feaces(2/8)and urine sites(4/8),and IC with possible source of infection were caused by feacal isolates(2/7),urine isolates(4/7)and sputum isolate(1/7).Both the urine(P=0.033)and fecal isolates(P=0.015)of C.tropicalis yielded greater biofilm biomass than isolates from sputum.Furthermore,non-invasive C.tropicalis isolates exhibited statistically higher hemolysin activity than their paired invasive isolates(P=0.011).Additionally,invasive C.albicans showed significantly higher phospholipase activity compared with non-invasive isolates(P=0.037).And the sputum isolates of C.albicans showed stronger proteinase activity than feaces ones(P=0.037).Conclusions: Candida colonization is a risk factor for IC.The transformation from harmless commensal yeast to pathogen is a result of complex interactions between host and Candida species,in which the virulence factors expressed by the microorganism play an important role.The expression of some virulence factors varied in Candida isolates of different sources.Gene microevolution frequently occurred in feaces and urine sites.Urinary and feacal Candida colonization were more valuable for monitoring invasive Candida infection.