Invasive candidiasis is the fourth leading cause of bloodstream infection in cases of nosocomial infection by fungi. Candida albicans is the most often isolated species, accounting for approximately 50% of cases1. Molecular techniques have been performed to aid epidemiological studies2,3.
This retrospective study was conducted using clinical samples obtained from the mycology collection of the laboratory of the Hospital Universitário da Universidade Federal do Mato Grosso do Sul (HU/UFMS) in Campo Grande, state of Mato Grosso do Sul, Brazil. The yeasts were previously detected in blood cultures using an automated system, BACTTECTM FX (BD, New Jersey, USA) as a routine hospital practice, and the three most frequently isolated species were selected for genotypic analysis.
The study was approved by the University Federal do Mato Grosso do Sul Ethics Committee. The molecular tests were conducted in the Laboratory of Animal Health at the Brazilian Enterprise for Agricultural Research (EMBRAPA) according to the protocol described by Valério et al.3. The dendrogram was created using GelCompar II (Applied Maths, Kortrijk, Belgium) in the Enterobacteria Laboratory of Fundação Oswaldo Cruz, RJ. Similarity was evaluated using Pearson’s coefficient. For purposes of epidemiological analysis, the strains that showed > 90% similarity or had a dendrogram showing a single insertion or inclusion were considered similar or belonging to the same clone4.
The species implicated in the infectious episodes were Candida albicans, 44 (45.8%), Candida parapsilosiscomplex 33, (34.4%), Candida tropicalis, 14 (14.6%) and Candida glabrata, 5 (5.2%).
The electrophoretic profiles of the Candida albicans and Candida parapsilosis complex strains demonstrated a predominance of profile A (Figures 1 and 2).
FIGURE 1 – (A) An example of the random amplification of polymorphic DNA patterns obtained with primer OPG-17 5´d [ACGACCGACA] – 3´ using Candida albicans isolates. Line Y: 100-pb ladder (Invitrogen); Line 1: Positive control (ATCC) 10231; and L2-L27, samples isolated from bloodstream infections. (B) Dendrograms showing the genotypic profiles of theCandida albicans isolates. Clinical samples were obtained from patients at the University Hospital in Campo Grande, state of Mato Grosso do Sul, Brazil.
FIGURE 2 – (A) Agarose gel electrophoresis (1.8%) following random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR) using the primer 5’d [ACGACCGACA] – 3 ‘indicated different genetic patterns for the Candida parapsilosis isolates that had caused bloodstream infections. Line Y: 100-pb ladder (Invitrogen); Line 1: ATCC 22019; Line 2-21: the samples isolated from bloodstream infections (B) Dendrograms showing the genotypic profile of Candida parapsilosis isolates. Clinical samples were obtained from patients at the University Hospital in Campo Grande, state of Mato Grosso do Sul, Brazil.
The frequency of systemic infections caused by Candida has increased considerably, particularly in patients hospitalized in critical areas because of the use of immunosuppressive agents, invasive medical procedures, and underlying diseases that may contribute to yeast proliferation2,5. Among infecting yeasts, C. albicans is the most common in cases of hospital-acquired infections in several countries1.
The present results demonstrate that the method was limited to detecting intra-specific polymorphisms within clones of the same species using only one primer pair2,3. The profiles obtained using random amplification of polymorphic DNA (RAPD) were able to differentiate between the Candida species, but few differences between strains of the same species were observed. Nevertheless, the dendrograms showed a genetic similarity > 90%, suggesting that the method might be useful for epidemiological studies and detection during hospital outbreaks.
