Multilocus sequence typing of Candida tropicalis shows clonal cluster enrichment in azole-resistant isolates from patients in Shanghai, China.

To explore the putative correlation between the multilocus sequence types (MLST) and antifungal susceptibility of clinical Candida tropicalis isolates in Mainland China. Eighty-two clinical C. tropicalis isolates were collected from sixty-nine patients at Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, from July 2012 to February 2015, and antifungal susceptibility tests were performed. Genetic profiles of those 82 isolates (30 azole-resistant and 52 azole-susceptible) were characterised by multilocus sequence typing. Phylogenetic analysis of the data was conducted with the clustering method, using UPGMA (unweighted pair group method with arithmetic averages) and the minimal spanning tree algorithm. MLST clonal clusters were analysed using the eBURST V3 package. Of the six gene fragments identified in multilocus sequence typing, SAPT4 presented the highest typing efficiency, whereas SAPT2 was the least efficient. Of the 44 diploid sequence types (DSTs) differentiated, 32 DSTs and 12 genotypes were identified as new to the C. tropicalis DST database. Twenty (45.45%) of the 44 DSTs were assigned to seven major groups based on eBURST analysis. Of these, Group 6, which contained DST 376, DST 505, DST 506 and DST 507, accounted for 76.7% of the 30 azole-resistant isolates. However, the genetic relationships among the azole-susceptible isolates were relatively decentralised. This MLST analysis of the putative correlation between the MLST types and antifungal susceptibility of clinical C. tropicalis isolates in Mainland China shows that DSTs 376, 505, 506 and 507 are closely related azole-resistant C. tropicalis clones.