Caracterização de isolados clínicos de Candida albicans de estudo brasileiro multicêntrico de candidemia por metodologia de “Multilocus Sequence Typing (MLST)”

• Ano de defesa: 2009
• Autor(a) principal: Matta, Daniel Archimedes da [UNIFESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Tipagem de sequências multilocus; Candidemia; Candida albicans; Multilocus sequence typing
• Link de acesso: http://repositorio.unifesp.br/handle/11600/9170

The DNA sequence-based genotyping technique multilocus sequence typing (MLST) has emerged as an alternative typing tool for C. albicans because can characterize large numbers of isolates rapidly, and does not require the subjective interpretation of banding patterns. This methodology is a very useful tool in understanding the phylogenetics and epidemiology of C. albicans strains from invasive candidiasis. Objective: Our goal was 1) to apply MLST and ABC typing to C. albicans strains recovered from bloodstream infection from public tertiary care hospitals in Brazil and 2) determine whether indistinguishable or different strains were responsible for persistent or recurrent fungemia by performing MLST and ABC typing on sequential C. albicans isolates from the same patient. Methods: We applied MLST and ABC typing, which is based on the presence or absence of an intron in the 25S rDNA region, to C. albicans strains from 61 patients with candidemia collected during a multicenter surveillance study in 11 public tertiary care hospitals, representative of the public health system of 9 of the largest cities in Brazil. We also analyzed C. albicans strains from 8 patients with persistent or recurrent candidemia. Persistent candidemia was defined as two or more blood cultures positive for C. albicans on 2 or more separate days. Recurrent candidemia was defined as an episode of candidemia occurring at least 1 month after the apparent complete resolution of an infectious episode caused by the same Candida species. Results: A total of 48 unique profiles or diploid sequence types (DST) were observed, with 10 new sequence types (STs) and 32 new DSTs. DST 69 was the most common DST isolated. C. albicans clade 1 accounted for 56% of the collection, clade 3 and clade 8 for 10% each, clades 9 and 17 for 6.5% each, and clade 12 for 5%. Clade 2, clade 4, clade 16 and a singleton strain had 1 isolate each (1.5%). For ABC typing, 82% of the isolates were classified as type A, followed for 16.5% type B and 1.5% type C. All the patients’ strains related to persistent or recurrent candidemia but one showed the same MLST diploid sequence type (DST), ABC type and susceptibility profile to antifungals in the first and second samples. One patient with 7 samples collected sequentially over 10 days showed 3 distinct strains, well discriminated by MLST. One of the 3 strains recovered from this patient showed a single C. albicans isolate found in our total collection classified as clade 2, although clade 2 is commonly found worldwide. Conclusion: More than 50% of isolates from this study form a unique set of DSTs and clade 1 was responsible for 56% of the isolates. For ABC typing, 82% of the isolates were type A. To the best of our knowledge, this is the first study describing a blood stream infection with 3 distinct C. albicans strains in the same patient within a short period of time.