Biofilm production and evaluation of antifungal susceptibility amongst clinicalCandidaspp. isolates, including strains of theCandida parapsilosiscomplex

Abstract

Candida cells can form biofilms that frequently are sources of infections and are less susceptible to antifungal drugs. Some authors have reported that Candida orthopsilosis and Candida metapsilosis isolates are not able to produce biofilms in vitro and there are no studies available on biofilm susceptibility for these species to antifungals. The aims of this study were to (i) quantify Candida spp. biofilms in vitro, and (ii) test the in vitro susceptibilities of Candida spp. biofilms to fluconazole (FLC) and amphotericin B (AMB). Isolates studied included four Candida albicans, six C. tropicalis, seven C. parapsilosis, eight C. orthopsilosis, and five C. metapsilosis. We compared two different methods to evaluate biofilm production, i.e., crystal violet (CV) staining and XTT-reduction assays (XTT). Scanning electron microscopy (SEM) was used to observe high, medium and low biofilm producing isolates screened by these two methods. To determine the minimum biofilm eradication concentration (MBEC) for FLC and AMB, XTT-reduction assay was used to measure cell metabolic activity. Biofilm quantification by CV and XTT showed that C. tropicalis isolates were the highest biofilm producer, followed by C. albicans, C. parapsilosis, C. orthopsilosis and C. metapsilosis. Examination of SEM images revealed that the extent of biofilms formed by high, medium, and low producers was highly correlated to the results generated by CV assay. Biofilm of all the isolates evaluated were resistant to FLC (MBEC(80) ≥ 256 ug/ml) but, in general, susceptible to AMB, except for six C. parapsilosis strains (MBEC(80) ≥ 8 ug/ml).

Characterization of Biofilm Formation and the Role of BCR1 in Clinical Isolates of Candida parapsilosis

“…In agreement with results in the literature, we show here that strains forming a complex spider-like biofilm displayed significantly enhanced resistance to fluconazole (128 g/ml), whereas the planktonic counterparts were susceptible. In contrast, all biofilms remain susceptible to amphotericin B and caspofungin, which is in agreement with other studies (41,44,45). However, although effective against biofilm cells, use of amphotericin B has drawbacks due to its toxicity against mam- capabilities.…”

Candida parapsilosis complex water isolates from a haemodialysis unit: biofilm production and in vitro evaluation of the use of clinical antifungals

“…The most notable of these is that sessile cells are resistant to both antimicrobial agents and host immune factors. Our results confirm that sessile C. parapsilosis complexes are highly resistant to azoles (> 512 µg/mL) as previously demonstrated by others (Ramage et al 2002, Choi et al 2007, Melo et al 2011). …”

Analysis of Inteins in the Candida parapsilosis Complex for Simple and Accurate Species Identification

“…The differentiation of the psilosis complex into C. parapsilosis, C. orthopsilosis, and C. metapsilosis species is important for epidemiological purposes and also for changes in resistance to antifungal therapy, since C. orthopsilosis and C. metapsilosis are more susceptible to some currently used antifungals (16,17,19) and may have a lower capacity for biofilm formation (19,21).…”

“…Although the prevalences, distributions, drug susceptibilities, and biofilm productions of these species remain unclear, there are several studies that demonstrate differences among them (12,(15)(16)(17)(18)(19)(20)(21)(22). For instance, the recently published genome of C. orthopsilosis shows a reduction in the gene families associated with pathogenesis compared with that of C. parapsilosis (23).…”