Antimicrobial Susceptibility Studies
Molecular epidemiology and antifungal susceptibility of Candida parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis in Taiwan

https://doi.org/10.1016/j.diagmicrobio.2010.07.004Get rights and content

Abstract

Candida parapsilosis was recently reclassified into 3 closely related species, C. parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis. Variation in susceptibility characteristics and prevalence of the 3 genomic species could have therapeutic and epidemiologic implications. The aim of this study is to characterize the genetic and antifungal susceptibility profiles of 97 C. parapsilosis isolates from 71 patients. Among the 71 nonduplicate isolates, 85.9% (61/71) were identified as C. parapsilosis sensu stricto, 5.6% (4/71) as C. metapsilosis, and 8.5% (6/71) as C. orthopsilosis species based on sequences of the internal transcribed spacer (ITS) region. The delineation of these 3 species is concordant with that achieved by pulsed-field gel electrophoresis of BssHII restriction fragments at 75% similarity. Antifungal susceptibility tests showed that most isolates were susceptible to flucytosine, azoles, amphotericin B, and echinocandins, whereas 3 C. metapsilosis isolates from 1 patient showed resistance and susceptible-dose dependence to fluconazole. The C. metapsilosis isolates exhibited significantly higher MIC values to both fluconazole and voriconazole than those of C. parapsilosis sensu stricto and C. orthopsilosis. On the other hand, the C. metapsilosis isolates showed significantly lower MIC values on 24 h to caspofungin than those of C. parapsilosis sensu stricto and C. orthopsilosis. For micafungin, the isolates of C. parapsilosis sensu stricto had significantly higher MIC values on 24 h than those of C. orthopsilosis and C. metapsilosis. Compared to Candida albicans, mutations from proline to alanine were identified on the hot spot 1 of Fks1 in all these C. parapsilosis sensu lato isolates regardless of their MIC levels. Some of the C. orthopsilosis and C. metapsilosis isolates expressed the isoleucine to valine substitution on the hot spot 2 region. However, the amino acid variations in these isolates did not correlate to their MIC values of echinocandin.

Introduction

Infections caused by Candida parapsilosis species complex had dramatically increased in significance and prevalence over the past 20 years (Trofa et al., 2008). In Taiwan, survey data showed that C. parapsilosis species complex is responsible for 8% to 14 % of all the Candida infections and ranks as the third or fourth most prevalent Candida spp. (Chen et al., 2003, Hsueh et al., 2005, Yang et al., 2009).

A study in 2005 revealed that C. parapsilosis is actually composed of 3 genomic closely related species: the more prevalent C. parapsilosis sensu stricto and the 2 newly designated species, Candida orthopsilosis and Candida metapsilosis (Tavanti et al., 2005). The 3 species are physiologically and morphologically indistinguishable but may vary in resistance characteristics, as well as geographic and anatomic prevalence (Asadzadeh et al., 2009, Lockhart et al., 2008, Tay et al., 2009). However, the clinical relevance of such variation remains to be further clarified.

In this study, the 97 clinical C. parapsilosis spp. complex isolates collected from 71 patients in a Taiwan medical center during 2002 to 2003 were used to i) investigate the distribution of C. parapsilosis sensu stricto, C. orthopsilosis, and C. metapsilosis, ii) determine the antifungal resistance of each genomic species to amphotericin B, flucytosine, fluconazole, voriconazole, caspofungin, and micafungin, iii) assess the clonality of the 3 genomic species by use of pulsed-field gel electrophoresis (PFGE)-BssHII typing method, iv) ascertain whether different characteristics (e.g., antifungal resistance, patient origin, anatomic source of isolation) could be attributed to the specific genomic species or PFGE genotypes, and v) identify the mutations on the hot spot regions of Fks1 gene of isolates with various MICs to caspofungin and micafungin.

Section snippets

Organisms

A total of 97 clinical isolates obtained from 71 patients at the National Taiwan University Hospital, Taiwan, during 2002 to 2003 were originally identified as C. parapsilosis by API 20C (API; bioMérieux, Durham, NC) and Vitek II (bioMérieux). Isolates were collected from a wide range of medical services including outpatients, inpatients, and intensive care units (ICUs) in the medical center. The sources of the 97 isolates are depicted in Table 1. Between 1 and 7 isolates were collected per

Results

Based on ITS sequence data, C. metapsilosis, C. orthopsilosis, and C. parapsilosis sensu stricto constituted 5.6% (4/71), 8.5% (6/71), and 85.9% (61/71) of the nonduplicating isolates by patients and 9.3% (9/97), 7.2% (7/97), and 83.5% (81/97) by total isolates, respectively. The distribution of the 3 species in different types of anatomic sites is detailed in Table 1. The blood specimens (60.8%, 59/97) were the most frequently isolated, especially for C. parapsilosis sensu stricto (66.7%,

Discussion

C. parapsilosis is now one of the most commonly isolated non-albicans Candida spp. causing bloodstream infections in areas throughout the world, including Latin America, Europe, and Asia (Almirante et al., 2005, Miranda et al., 2009; Nakamura and TakahasNakamura and Takahashi, 2006, Pfaller et al., 2008b). Since the recognition of 3 distinct species within the C. parapsilosis complex, namely, C. parapsilosis sensu stricto, C. orthopsilosis, and C. metapsilosis in 2005, surveillance data of the

Acknowledgments

This work was supported by grants DOH98-DC-2005 and DOH99-DC-2011 from the Centers for Disease Control, Department of Health, Taiwan.

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