The study on the effect of pH on the in vitro antifungal susceptibility test of Candida glabrata isolated from VVC

WANG Yufeng; SUN Yanxia; ZHAO Rongxin; DENG Shuwen; ZHANG Lu

doi:10.3969/j.issn.1673-3827.2025.01.002

Abstract：Objective To explore the effect of pH on the in vitro antifungal susceptibility of Candida glabrata isolated from VVC,and to provide scientific basis for clinical precision treatment of VVC.Methods All 206 Candida glabrata strains isolated from VVC patients were collected and tested against 12 commonly used clinical antifungal agents(fluconazole,voriconazole,itraconazole,posaconazole,terconazole,clotrimazole,miconazole,anidulafungin,caspofungin,micafungin,amphotericin B and nystatin),according to the CLSI M27-A4,respectively detect the in vitro antifungal susceptibility of Candida glabrata under pH7.0 and 4.5.Results Compared with those under pH 7.0,except for miconazole,the GM,MIC50 and MIC90 of other azole drugs under pH 4.5 were significantly increased.The MIC of terconazole had the most obvious impact.At pH 4.5,the value of GM(14.13 µg/mL)is 67 times higher than that at pH 7.0(0.21 µg/mL),followed by clotrimazole,voriconazole(6 times),itraconazole(5.5 times),fluconazole(3.8 times)and posaconazole(3.4 times).Similar to it,the GM of amphotericin B and nystatin increased 2.7 times at pH 4.5 compared with pH 7.0.The MIC of echinocandins are stable under this two pH.Conclusions Acidic pH can increase the MIC of Candida glabrata against most azoles,amphotericin B,and nystatin,and the degree of increase varies with different types of agengts.The most noteworthy thing is that under this two pH terconazole has a significant impact,and the proportion of sensitive or wild-type strains is also significantly reduced,while it has no effect on echinocandins.For recurrent or refractory VVC,it is recommended to conduct the antifungal susceptibility test under pH 4.5,which will guide clinical treatment more scientifically.The consistency between the results of in vitro antifungal susceptibility test and in vivo efficacy needs further research to confirm.