Distribution Of Candidiasis Strains Isolated From Candidiasis Patients And Correlation Between Drug Resistance And Virulence Of The Strainsr

Objective: We identified the strains clinically isolated from patients with candidiasis,carried out the drug sensitivity test and analyzed its virulence in order to obtain the distributing characteristics of Candida species and drug-resistant strains,and further analyzed whether the virulence of strains had a correlation with drug resistance.Methods: Firstly,the patients suspected candidiasis clinically were collected in the Jining No.1 People’s Hospital from June 2019 to June2021.Secondly,the purified yeast colonies were identified by the method of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF MS）,meanwhile the method of DNA molecular identification was used as a gold standard to evaluate the accuracy and timeliness in species identification of clinical Candida spp.of MALDI-TOF MS.Finally,antifungal sensitivity testing in vitro was performed to identify drug-resistant Candida spp.and Galleria mellonella（G.mellonella）larvae were used to construct animal model infected with these strains to further evaluate the correlation between its virulence and antifungal drug resistance.Results: 206 patients with candidiasis were collected,and the age range was 0-96 years（68.64±16.98 years）;and the disease commonly happened in over 40-year-old patients（197/206,95.63%）,among them,over 60-year-old patients accounted for 72.82%（150/206,）and the male patients accounted for 46.12% of the total patients（95/206,46.12%）（P=0.764）.Candidiasis patients primarily hospitalized in ICU（Intensive Care Unit,ICU）（118 cases,57.28%）.The candidiasis patients always had underlying diseases,including pulmonary disease（101/206,49.03%）and brain diseases（75/206,36.41%）,cancer（45/206,21.84%）and the history of surgery and trauma（65/206,31.55%）.In addition,patients who had two or more than two other underlying diseases were susceptible to have candidiasis（136/206,66.02%）.In total,206 Candida strains were collected and the main isolated Candida species were Candida albicans（C.albicans）,Candida tropicalis（C.tropicalis）,Candida parapsilosis（C.parapsilosis）and Candida glabrata（C.glabrata）;among them,C.albicans was the most common species with the total of 159 strains（77.18%）,followed by C.tropicalis with 28 strains（13.59%）,C.parapsilosis with 13 strains（6.31%）and C.glabrata with 6 strains of（2.91%）.Compared with the gold standard method-DNA molecular identification,the accuracy of MALDI-TOF MS was 92.72%.After the strains were purified,it only took a few minutes to identify at specie level using MALDI-TOF MS,but 24-48 hours were needed by traditional methods of identification.The results showed that MALDI-TOF MS reduced the time of identification significantly.The results of antifungal drug susceptibility tests revealed that voriconazole,itraconazole,and amphotericin B were susceptive to the strains,while most Candida spp.strains were resistant to terbinafine;49drug-resistant strains were selected from the 206 Candida spp.The animal model infected with Candida spp.were constructed by G.mellonella larvae to evaluate the virulence of strains.The result showed that the mortality of G.mellonella larvae enhanced with strain concentration which indicated that the virulence of strains was in dose dependent.However,there was no significant difference in mortality rate of G.mellonella larvae among infection models of multiple-drug resistant strains,single-drug resistant strains and non-drug resistant standard strains.The data indicated that the resistance of strains had no correlation with the virulence of the strains.Conclusion: Candidiasis mainly involved elderly male patients who commonly had the underlying diseases including brain and lung diseases.There was no correlation between drug-resistance of Candida strains and their virulence.Of note,the virulence of the Candida strains was positively correlated with its dose.Thus,it was particularly important to identify species rapidly and initiate treatment with sensitive anti-Candida drugs early.MALDI-TOF MS had shown its advantages of rapidity and high accuracy,which can be used as a preferred method to fast identify Candida spp to guide the clinical diagnosis and treatment.Few Candida spp.was resistant to voriconazole,itraconazole and amphotericin B,thus and these agents can be used for the treatment of Candidiasis,while most of strains were resistant to terbinafine,so terbinafine was not recommended to treat Candidiasis.