Emergence of Candida haemulonii and closely related species at five Korean hospitals has been recently described. We examined biofilm formation by these isolates and assessed their genotypic relatedness by pulsed-field gel electrophoresis (PFGE). This study is the first to show that all bloodstream isolates of Candida pseudohaemulonii can form significant biofilms in glucose-containing medium. PFGE of NotI-digested genomic DNA revealed that C. pseudohaemulonii isolates recovered from seven patients in two hospitals shared five patterns, and that 15 isolates of a proposed new species (Candida auris) obtained from patients at three hospitals shared seven patterns, suggesting that some of these isolates may be related to clonal transmission.

Multilocus sequence typing (MLST) has been successfully applied to the epidemiology of Candida albicansisolates not only within the hospital setting but also in multiple locations nationwide. We performed MLST to investigate the genetic relatedness among bloodstream infection (BSI) isolates of C. albicans recovered from 10 Korean hospitals over a 12-month period. The 156 isolates yielded 112 unique diploid sequence types (DSTs). While 95 DSTs were each derived from a single isolate, 17 DSTs were shared by 61 isolates (39.1%). Interestingly, 111 (71.1%) isolates clustered within previously known clades, and 29 (18.6%) clustered within a new clade that includes strains of Asian origin previously typed as singletons. This MLST study was complemented by restriction endonuclease analysis of genomic DNA using BssHII (REAG-B) in order to evaluate whether strains with identical DSTs and originating from the same hospital corresponded to nosocomial clusters. Importantly, only those isolates with a strong epidemiological relationship showed >95% identical REAG-B types. Our results indicate that REAG-B typing can be complementary to MLST but should be limited to the investigation of isolates of identical DSTs and when interhuman transmission is suspected.

cWe evaluated three commercial colistin susceptibility testing methods using 213 bloodstream Acinetobacter isolates identified by gene sequencing. Compared to the agar dilution reference method, excellent categorical agreements (both 99.1%) were observed using Vitek 2 and Etest, compared to 87.3% (95.7% for Acinetobacter baumannii and 80.7% for non-baumannii Acinetobacter isolates) using MicroScan.

A recent surveillance study in South Korea revealed that 14% (7/50) of Aspergillus flavus clinical isolates had a voriconazole minimum inhibitory concentration of ≥4 μg/ml. Of seven non-wild-type (non-WT) isolates, six ear isolates from four hospitals shared the same microsatellite genotype. None of the non-WT isolates showed cyp51 mutations associated with azole resistance. However, the mean expression levels of efflux pump (MDR2, atrF, and mfs1) and target (cyp51A) genes exhibited significant differences between non-WT and other isolates.

Secreted aspartic proteases (Sap), encoded by a family of 10 SAP genes, are key virulence determinants in Candida albicans. Although biofilm-associated bloodstream infections (BSIs) are frequently caused by C. albicans, SAP gene expression in C. albicans biofilms formed by BSI isolates has not been evaluated. We compared the expression of two SAP genes, SAP5 and SAP9, in C. albicans biofilms formed by BSI isolates with those formed by isolates from other body sites. Sixty-three C. albicans isolates were analyzed, comprising 35 BSI isolates and 28 from other sites. A denture-strip biofilm model was used, and expression of the two SAP genes was quantified by real-time RT-PCR during planktonic or biofilm growth. Mean SAP5 expression levels of the BSI isolates were 3.59-fold and 3.86-fold higher in 24-h and 48-h biofilms, respectively, than in planktonic cells. These results did not differ from those for isolates from other sites (2.71-fold and 2.8-fold for 24-h and 48-h biofilms, respectively). By contrast, mean SAP9 expression during biofilm formation was higher in BSI isolates (2.89-fold and 3.29-fold at 24 and 48 h, respectively) than in isolates from other sites (1.27-fold and 1.32-fold at 24 and 48 h, respectively; both, P < 0.001). These results show, for the first time, that both SAP5 and SAP9 are upregulated in C. albicans biofilms formed by BSI isolates, and that BSI isolates may have a greater capacity to express SAP9 under biofilm conditions than isolates from other sites.