Multilocus Sequence Typing of Candida tropicalis Shows the Presence of Different Clonal Clusters and Fluconazole Susceptibility Profiles in Sequential Isolates from Candidemia Patients in São Paulo, Brazil

Abstract

fThe profiles of 61 Candida tropicalis isolates from 43 patients (28 adults and 15 children) diagnosed with candidemia at two teaching hospitals in São Paulo, Brazil, were characterized by multilocus sequence typing (MLST). For the 14 patients who had bloodstream infections, 32 isolates were serially collected from their blood and/or catheters. Thirty-nine diploid sequence types (DSTs) were differentiated. According to the C. tropicalis MLST database (http://pubmlst.org/ctropicalis/), 36 DSTs and 23 genotypes identified from the 61 isolates had not previously been described. This report represents the first study to characterize sequential isolates of C. tropicalis from candidemia cases in South America. Microvariation in a single gene was found in the sequential isolates from 7 patients. The main polymorphisms occurred in the alleles of the XYR1 gene, specifically at nucleotide positions 215, 242, and 344. Macrovariation in six gene fragments was detected in the isolates from 3 patients. eBURST analysis added two new groups to this study (groups 6 and 18). Additionally, susceptibility tests indicate that 3 isolates were resistant to fluconazole. No correlation was found between the DSTs and susceptibility to fluconazole and/or selective antifungal pressure. Two patients were sequentially infected with resistant and susceptible strains. MLST is an important tool for studying the genetic diversity of multiple/sequential isolates of patients with candidemia, allowing the comparison of our data with those from other regions of the world, as well as allowing an analysis of the genetic relationship among several clones in sequential isolates from the same or different candidemia patient sites (blood or catheter).

Population structure and molecular genetic characterization of clinical Candida tropicalis isolates from a tertiary-care hospital in Kuwait reveal infections with unique strains

“…Although DST168, previously reported only from Taiwan, was found in Kuwait, DST164 which was also detected in Taiwan and was previously shown to be associated with 5-flucytosine resistance [ 43 ] was not detected in our study and the single 5-flucytosine-resistant isolate (Kw45-15) from Kuwait belonged to a new DST (DST719). Furthermore, DST238, which was shared between two isolates originating from vaginal and percutaneous endoscopic gastrostomy specimens in Kuwait, has previously been described for two bloodstream isolates from Brazil [ 46 ]. Our data reinforce previous observations suggesting lack of association between different DSTs with antifungal resistance, specimen type or geographical location and support both shared and unique features among geographic populations of C .…”

Genetic diversity of medically important and emerging Candida species causing invasive infection

“…In a recent epidemiologic study conducted by Maganti and colleagues [ 25 ], nosocomial clusters have been shown to represent 33% of total isolates causing candidemia in Canadian hospitals. Using MLST analysis, the genetic relatedness of Candida isolates has been assessed in two Brazilian studies of candidemia, in which different clusters have been found among isolates of C. albicans [ 24 ] and C. tropicalis [ 65 ]. Our present study reinforces the utility of sequence polymorphism analysis for evaluating the relationships among Candida species and its application for examining the molecular epidemiology of fungal diseases.…”

Investigating Clinical Issues by Genotyping of Medically Important Fungi: Why and How?

“…Among the 14 patients with multiple isolates, seven had microvariation in a single gene from sequential isolates and three had microvariation in six gene fragments. Finally, they identified three isolates resistant to fluconazole but did not find any correlation between this resistance and the isolate clustering (195).…”

“…Jacobsen et al also found that multiple isolates from a given patient shared the same MLST profile or showed evidence of microevolution, such as loss of heterozygosity (194). Magri et al studied the genetic diversity of 61 isolates from 43 patients hospitalized in Brazil (195), reporting 39 DSTs. Among the 14 patients with multiple isolates, seven had microvariation in a single gene from sequential isolates and three had microvariation in six gene fragments.…”