Formación de biopelículas por Candida parapsilosis sensu stricto y su perfil de susceptibilidad en Venezuela / Biofilm-forming of Candida parapsilosis sensu stricto and its susceptibility profile in Venezuela

Una de las principales consecuencias del desarrollo de biopelículas es la resistencia a los antifúngicos. Se determinó la formación de biopelículas por Candida parapsilosis sensu stricto aisladas de sangre y su perfil de susceptibilidad. Se evaluaron 30 cepas de C. parapsilosis sensu stricto de la Red de Candidemias del Dpto. de Micología del Instituto Nacional de Higiene Rafael Rangel-Venezuela, por el método cuantitativo en microplaca con tinción de cristal violeta y el método cualitativo en agar Sabouraud dextrosa suplementado con rojo Congo. Se utilizó el método de microdilución según el documento M-27 del Clinical and Laboratory Standards Institute. La formación de biopelículas de C. parapsilosis sensu stricto por el método cuantitativo fue de 63% y por el método cualitativo de 50%. El método cualitativo presentó valores de sensibilidad, especificidad, valores predictivos positivo y negativo de 61,1%, 23%, 78,6%, 43,8% respectivamente frente al método cuantitativo. Los aislados en forma planctónica fueron 100% sensibles a anfotericina B y caspofungina, con susceptibilidad variable a los azoles. El método cuantitativo es una técnica confiable para determinar la formación de biopelículas. El método cualitativo puede usarse como método pantalla inicial. No se encontró relación entre la susceptibilidad de las formas planctónicas y la capacidad de producción de biopelículas

One of the main consequences of biofilm development is resistance to antifungals. Biofilmforming by Candida parapsilosis sensu stricto isolated from blood and its susceptibility profile was determined. Thirty strains of C. parapsilosis sensu stricto belonging to the Candidemia Network of the Mycology Department of the Instituto Nacional de Higiene Rafael Rangel-Venezuela, were evaluated by microplate quantitative method with violet crystal staining, and Sabouraud dextrose agar supplemented with Congo red qualitative method. The microdilution method was used to determine the susceptibility, according to the Clinical and Laboratory Standards Institute M-27 document. Biofilm formation of C. parapsilosis sensu stricto by both quantitative and qualitative method was 63% and 50%, respectively. Sensitivity, specificity, and positive and negative predictive values of the qualitative method were 61.1%, 23%, 78.6%, and 43.8% respectively, when compared with quantitative method. Planktonic isolates were 100% sensitive to amphotericin B and caspofungin, with variable susceptibility to azoles. Quantitative method is a reliable assay to determine biofilm formation, while qualitative method can be used as an initial screening assay. No relationship was found between susceptibility of planktonic isolates and the ability to biofilm-forming

Biofilm-forming capacity of two benthic microalgae, Navicula incerta and Navicula sp., on three substrates (Naviculales: Naviculaceae)

Benthic microalgae have the natural capacity to adhere to a diversity of fixed submerged substrates to form biofilms, which have important roles not only in natural ecosystems, but also in aquaculture systems. An experimental investigation was performed to assess the biofilm-forming capacity of two microalgae (Navicula incerta and Navicula sp.) on three different substrates (plastic net, fabric, and wood) under controlled temperature and light conditions. The substrates were arranged on curtains suspended from a wood stick, into plastic aquariums (45 L in capacity) filled with filtered marine water enriched with F/2 medium. The trial was carried out until the exponential growing phase of the microalgae was reached. After that, the incorporated biomass was gravimetrically calculated, and its biochemical composition was determined by standard methods. The greatest amount of incorporated dry matter was observed for Navicula sp. on fabric and the lowest was observed for wood. The highest number of cells associated with the biofilm was obtained for Navicula sp. on the plastic net (1.24 x 109 cells/m2), while the lowest was recorded for Navicula sp. on the wood (1.43 x 108 cells/m2). Significant differences in organic matter were found among the substrates, with the highest values for N. incerta on the fabric (3.22 g/m2) and the lowest for Navicula sp. on the wood (0.02 g/m2). The best biochemical profiles among the formed biofilms were observed for N. incerta on the plastic net and Navicula sp. on the fabric. The plastic net was considered the best substrate because of the stability of the biofilm and the easiness of harvesting the biomass.

Las microalgas bentónicas tienen la capacidad natural de adherirse a diversos sustratos fijos sumergidos para formar biopelículas, las cuales tienen roles importantes no solo en ecosistemas naturales sino también en sistemas de producción acuícolas. Se llevó a cabo una investigación experimental para evaluar la capacidad formadora de biopelículas de dos microalgas bentónicas (Navicula incerta y Navicula sp.) en tres diferentes sustratos (malla plástica, tela y madera), bajo condiciones controladas de temperatura y luz. Los sustratos fueron arreglados a manera de cortinas suspendidas de un tubo de PVC dentro de acuarios de plástico (45 L de capacidad) con agua marina enriquecida con el medio F/2. El experimento se llevó hasta que la fase de crecimiento exponencial de la microalga fue alcanzada. Posteriormente la biomasa incorporada fue calculada gravimétricamente, y su composición bioquímica fue determinada por métodos estándar. La mayor cantidad de materia seca se observó para N. incerta en el sustrato de tela y la menor se encontró en el de madera. El mayor número de células asociadas a la biopelícula fue registrado para Navicula sp. en malla plástica (1.24 x 109 cel/m2), mientras que el menor se encontró para Navicula sp. en madera (1.43 x 108 cels/m2). Diferencias significativas en cuanto a materia orgánica se encontraron entre los sustratos y las especies, con valores más altos para N. incerta en tela (3.22 g/m2) y más bajos para Navicula sp. en madera (0.02 ± 0.05 g/m2). Los mejores perfiles bioquímicos para las biopelículas correspondieron a las formadas por N. incerta sobre malla plástica y Navicula sp. sobre tela. La red de plástico se consideró el mejor sustrato debido a la estabilidad de la biopelícula y la facilidad para cosechar la biomasa.

An Inexpensive Microfluidic PDMS Chip for Visual Detection of Biofilm-forming Bacteria

Aims: Design and assembly of an inexpensive microfluidic PDMS chip for visual detection of cell adhesion and biofilm formation. Study Design: Three different styles of microchannels (2.6, 5.0, and 11.5 µl volumes) were designed, fabricated and tested for adhesion and biofilm formation in a microfluidic system. The pressure drop measurements system includes a bio-Ferrograph connected to the PDMS microchannel via a syringe and a pressure transducer. Methodology: Microfluidic chips were fabricated using Polydimethylsiloxane (PDMS) by means of soft lithography. Different cell densities of E.coli K12 cells were introduced to investigate adhesion and biofilm formation at different time intervals. Stabilization time and hydraulic resistance were obtained via a Bio-Ferrograph connected to a pressure transducer. Results: PDMS microfluidic volume (2.6 µl) failed to generate noticeable biofilm, while slight and greatest yield occurred with PDMS microchannels (5.0, and 11.5 µl), respectively, and could detect as low as 26 cells in 11.5 µl microchannel. As incubation time and/or initial cell density increases, cell adhesion increased, illustrated by crystal violet color intensity. High stabilization time (3 h) didn’t allow for bacterial attachment and cultivation inside the microchannel (2.6 µl) while lower stabilization time (10 min) yielded the highest capacity of cell adhesion in microchannel (11.5 µl).  Conclusions: We developed a microfluidic chip with low stabilization time and hydraulic resistance, thus offering more volume for adhesion of bacterial cells and biofilm formation. It allowed bacterial cultivation without any addition of nutrients. The microfluidic chip provides a platform to monitor biofilm growth and can be integrated in situ investigations for biological systems, food biotechnology and other industrial biotechnology applications. This would allow a non-destructive and non-invasive monitoring of the biofilm-forming bacteria inside the PDMS microfluidic chip. This work opens opportunities for further investigations of pressure drop phenomena in microchannels that would otherwise go unnoticed in macro scale measurements.

Genome sequence of Prevotella intermedia SUNY aB G8-9K-3, a biofilm forming strain with drug-resistance

Abstract Prevotella intermedia has long been known to be as the principal etiologic agent of periodontal diseases and associated with various systemic diseases. Previous studies showed that the intra-species difference exists in capacity of biofilm formation, antibiotic resistance, and serological reaction among P. intermedia strains. Here we report the genome sequence of P. intermedia SUNY aB G8-9K-3 (designated ATCC49046) that displays a relatively high antimicrobial resistant and biofilm-forming capacity. Genome sequencing information provides important clues in understanding the genetic bases of phenotypic differences among P. intermedia strains.