A Predominance of Clade 17 Candida albicans Isolated From Hemocultures in a Tertiary Care Hospital in Thailand

Abstract

Candida albicans is one of the most common human fungal pathogens. Candidemia has significant mortality globally. No epidemiological study of C . albicans based on multilocus sequence typing (MLST) has been conducted in Thailand. Therefore, MLST was used to study the molecular epidemiology of C . albicans blood strains in a large Thai teaching hospital. In vitro virulence phenotypes and antifungal susceptibility testing by broth microdilution were also conducted. Forty-six C . albicans blood strains from 37 patients were collected from the Department of Microbiology, Siriraj Hospital, in 2016 and 2017. Most patients (71.8%) were more than 60 years old, and the case fatality rate was 54.8%. The male-to-female ratio was 5:3. Thirty-four diploid sequence types (DSTs), including six new DSTs, were identified, with DST2514 (8.7%) and DST2876 (8.7%) as the most common DSTs. Strains were clustered into nine clades. Unlike other studies of C. albicans blood strains in Asia, clade 17 was the most common (13 strains, 28.3%). Sequential allelic changes were evident in sequential strains from one patient. All strains produced phospholipase and hemolysin, while none produced proteinase. The ability to form biofilm was found in 82.6% of the strains. Clade 17 strains showed significantly stronger hemolytic activity than non–clade 17 strains (69.2% versus 27.3%; p = 0.022). However, no significant association existed between clades and patient mortalities. All were susceptible or wild type to anidulafungin (MIC range = 0.015–0.12 and GM = 0.030), micafungin (MIC range = ≤ 0.008–0.015 and GM = 0.008), caspofungin (MIC range = 0.008–0.12 and GM = 0.036), and amphotericin B (MIC range = 0.25–0.5 and GM = 0.381). Only one strain was resistant to voriconazole (MIC range = ≤ 0.008 to ≥ 8 and GM = 0.010) and fluconazole (MIC range = 0.12–16 and GM = 0.398). In conclusion, a high prevalence of clade 17 C. albicans blood strains was found in Thailand, in contrast to other Asian countries. This unique finding might be explained by the strong hemolytic activity that is required for bloodstream infection of C. albicans.

Virulence of Clinical Candida Isolates

“…Yeast carbon base and BSA were sterilized by 0.22 µL filter. The presence of the opaque halo of degradation around the colonies indicate positive protease activity [ 61 ].…”

“…The sheep blood was added when the autoclaved reagents were cooling to 50 °C. The presence of the translucent zone around colonies indicate the positive hemolytic activity [ 61 , 62 ].…”

“…For all virulence factors the diameter of zone was measured and the activity were calculated used formula: P z (precipitation zone): the phospholipase activity value (P z ) = (colony diameter)/(colony diameter with zone of precipitation). The results were classified as non-activity (P z = 1), weak (0.64 < P z < 0.99) and strong activity (P z ≤ 0.63) [ 39 , 61 ]. The PR z index was determined as protease activity, H z index as hemolytic activity and E z index as esterase activity.…”

Invasive Fungal Infection in Children With Acute Leukemia and Severe Aplastic Anemia

“…28,29 Research has also found that the incidences of azoleresistant strains of C. tropicalis have increased, 30 and that the azole resistance of C. tropicalis is approximately ten times that of C. albicans (20.8% vs. 2.3%). 31,32 Hence, conducting a sensitivity test may play a pivotal role in determining the appropriate treatment for patients.…”

Molecular Diversity and Genetic Relatedness of Candida albicans Isolates from Birds in Hungary

“…Relationship among concatenated sequences of the seven loci of each isolate were determined using unweighted pair group method with arithmetic averages (UPGMA) algorithm with p-distance model in Mega 6 software. A bootstrap of 1000 replications was used for the construction [ 9 , 19 ]. MLST clonal complexes (CC) and their founders were predicted by goeBURST algorithm ( http://www.phyloviz.net/goeburst/ ) to analyse population structure and evolutionary relationships between isolates.…”