Phenotypic switching in Candida tropicalis: association with modification of putative virulence attributes and antifungal drug sensitivity.

Although Candida tropicalis has become an increasingly important human pathogen, little is known regarding its potential to cause disease. In this study we evaluated the phenotypic switching ability of C. tropicalis and analyzed the effect of switching on biological properties related to virulence factors. We demonstrated that C. tropicalis switched spontaneously, reversibly and at high frequency (10(-1) to 10(-3)) when grown on yeast extract-peptone-D-glucose (YPD) agar medium. Phenotypic switching in five clinical isolates of C. tropicalis resulted in colonies exhibiting the following morphologies: crepe, rough, crater, irregular center, mycelial and diffuse. The majority of the variant colonies were associated with higher percentages of filamentous growth relative to their parental unswitched isolates. Significant differences (P < 0.05) in the production of hemolytic factor were found between most of the switched variants and their respective parental counterparts. Variant colonies exhibiting the crepe (derived from isolates 49.07 and 100.10) and rough phenotype (derived from isolate 49.07) had higher biofilm formation than their parental counterparts exhibiting a smooth dome surface (P < 0.05). Our data revealed that switching was correlated with changes in the in vitro minimum inhibitory concentrations (MICs) of a subset of the switched variants phenotypes to itraconazole. While the MIC to itraconazole was higher for crepe variant compared with its parental isolate 49.07, the rough variant of 100.10 had a lower MIC to this antifungal agent. The presented data support the role of phenotypic switching in promoting changes in phenotypic expression of putative virulence traits and itraconazole susceptibility of clinical isolates of C. tropicalis.

Ultrastructural architecture of colonies of different morphologies produced by phenotypic switching of a clinical strain of Candida tropicalis and biofilm formation by variant phenotypes.

Candida tropicalis has been identified as one of the most prevalent pathogenic yeast species of the Candida-non-albicans (CNA) group. Study of switching in C. tropicalis has not been the subject of extensive research. Therefore, we investigated switching event and characterized the ultrastructural architecture of different phenotypes and biofilm produced in a C. tropicalis clinical strain. Cells switched heritably, reversibly, and at a high frequency between four phenotypes readily distinguishable by the shape of colonies formed on agar at 25°C. SEM analysis was used to verify the architecture of whole Candida colonies at ultrastructural level. The smooth phenotype (parental phenotype) colony showed a hemispherical shape character, while the semi-smooth was characterized by the presence of shallow marginal depressions. The ring and rough phenotypes exhibited more complex architecture and were characterized by the presence of deep central and peripheral depressions areas. The biofilm-forming ability varied among the switch phenotypes. After 12h incubation, the smooth phenotype formed less biofilm compared to the other phenotypes (P<0.05). The electron microscopy analysis revealed that filamentation (pseudohyphae) was associated with ring and rough colonies. The ultrastructural analysis allowed the observation of the arrangement of individual cells within the colonies. At the deep central and peripheral depressions areas of the ring and rough colonies extracellular material was seen in different arrangements. The data presented here open new avenues to study a possible role for extracellular material in the formation and maintenance of the architecture of switch phenotypes in C. tropicalis. It is therefore essential that more strains be investigated to determine the biological significance of extracellular material in C. tropicalis phenotypic switching phenomenon.

Correlação do doseamento do lactato liquórico com a evolução clínica de pacientes com meningites / Measurement correlation of cerebrospinal fluid (CSF) lactate from patients with meningitis

Objetivando correlacionar o doseamento do lactate liquórico com a evolução clínica de pacientes com meningite, atendidos no HURN foram estudados prospectivamente 45 amostras de LCR (Líquido Cefalorraquidiano), durante o período de setembro/94 a agosto/95. Os LCR obtidos foram analisados bioquímica e microbiologicamente, conforme metodologia já padronizada, acrescidos do doseamento de lactato e do teste de látex-aglutinação, respectivamente. Os LCR foram divididos em 3 grupos. 1º Grupo: Controle – composto por 10 pacientes não portadores de meningite, onde os valores de lacto estiveram dentro dos valores de referência, (X=15, 32mg/dl D,P=2,88) (valor de referência 10,8 a 18,9mg/dl); 2º Grupo: composto por 15 pacientes portadores de meningite linfomonocitária, onde os valores de lacto-liquórico estiveram alterados (X=22,64mg/d; D.P.=7,39); 3º Grupo: composto por 20 pacientes portadores de meningite purulenta, onde os valores de lactato estiveram muito mais elevados do que os valores de referência (X=131,36mg/dl: D.P. =46,4). Os autores verificaram que com a evolução clínica direcionada para cura, os níveis de lactato diminuíram sensivelmente, sugerindo-se assim, que o doseamento de lactato possa ser um parâmetro clínico-laboratorial para a alta dos pacientes com meningite.

Estudo da flora bacteriana nasal: estudo preliminar em equipe de enfermagem / Study of the bacteria flora nose: a nursing preliminar study

Há pouca informaçäo sobre o crescimento de microorganismos patogênicos na flora nasal em países tropicais, já que grande parte das pesquisas se realizaram em paises de clima temperado. Neste estudo, identificamos a flora nasal da equipe de enfermagem dos Hospitais universitários de Londrina, correlacionando os resultados com a literatura consultada e disponível