Bacterial adherence to SiO2-based multifunctional bioceramics.

The bacterial adherence onto different multifunctional silica-based bioceramics has been evaluated. Staphylococcus aureus and Staphylococcus epidermidis were chosen, as they cause the majority of the implant-related infections in this field. Two SiO2 mesoporous materials (MCM-41, SBA-15), an ordered SiO2-CaO-P2O5 mesoporous glass (OMG), and a biphasic magnetic bioceramic (BMB), were incubated with S. aureus and S. epidermidis for 90 min, and subsequently sonicated to quantify the number of adhered bacteria on each material. It was found that S. aureus and S. epidermidis (10(8) CFU/mL) adhered significantly less to BMB samples when compared to MCM-41, SBA-15, or OMG. However, when the material pores accessible for bacteria in each material were taken into account, the lowest bacterial adherence was found in MCM-41, and the highest in SBA-15. The results show that bacterial adherence is higher on mesoporous bioceramics, although this higher microbial attachment is mainly due to the intergranular porosity and grain size morphology rather than to the mesoporous structure.

Adhesion of staphylococcal and Caco-2 cells on diamond-like carbon polymer hybrid coating.

Staphylococci cause the majority of the nosocomial implant-related infections initiated by adhesion of planktonic bacteria to the implant surface. It was hypothesized that plasma accelerating filtered pulsed arc discharge method enables combination of the advantageous properties of diamond with the antisoiling properties of polymers. Diamond-like carbon polytetrafluoroethylene hybrid (DLC-PTFE-h) coating was produced. The adhesion of S. aureus ATCC 25923 (10(8) colony-forming units/mL) to surfaces diminished from 2.32%, 2.35%, and 2.57% of high quality DLC, titanium, and oxidized silicon, respectively, to 1.93% of DLC-PTFE-h. For S. epidermidis ATCC 35984 the corresponding figures were 3.90%, 3.32%, 3.47%, and 2.57%. Differences in bacterial adhesion between recombinant DLC-PTFE-h and other materials were statistically significant (p < 0.05). In contrast, human Caco-2 cells adhered as well to DLC-PTFE-h as to DLC, titanium, or silicon, which were all in the MTT test found to be cytocompatible. DLC-PTFE-h coating can be used to modify the surface properties of any surgical implants and is an unfavorable substrate for staphylococcal cells, but compatible with human Caco-2 cells. DLC-PTFE-h coating may help in the combat against Staphylococcus-related implant infections which usually require both antibiotics and surgical removal of the implant for cure.

[Assessment of the invasiveness of rapidly-growing nonpigmented mycobacteria with the fibroblast microcolony assay]. / Evaluación de la capacidad invasiva de las micobacterias no pigmentadas de crecimiento rápido mediante el estudio de la morfología de las microcolonias en fibroblastos.

OBJECTIVE: The invasive capacity of rapidly-growing nonpigmented mycobacteria strains was evaluated by means of a fibroblast microcolony assay and related to the colony phenotype on Middlebrook 7H11 and to the clinical significance of the isolates. METHODS: Twenty-nine strains [Mycobacterium chelonae (8), M. fortuitum (6), M. peregrinum (5), M. abscessus (5), M. mucogenicum (4) and M. septicum (1)], proceeding from a bacterial collection and clinical isolates, were evaluated. The smooth or rough phenotype of the colonies was assessed in Middlebrook 7H11 medium. Intracellular invasiveness was determined by the fibroblast-microcolony assay described by Shepard. Quantitative culture characteristics were compared with Student's t-test, and qualitative characteristics with Fisher's exact test. RESULTS: No significant differences were found between colonies with different phenotypes or strains having a different clinical significance, except for two strains of Mycobacterium chelonae isolated from cases of catheter-related bacteremia, which showed elongated microcolonies. M. fortuitum and M. peregrinum strains showed larger microcolonies than M. chelonae, M. abscessus and M. mucogenicum, and displayed a fluffy appearance, while the latter two strains showed rounded colonies. CONCLUSION: Very few strains of mycobacteria had invasive capacity and the majority of strains isolated from human infections do not show this characteristic; hence this trait is not essential for mycobacteria to cause infection in humans.

Evaluación de la capacidad invasiva de las micobacterias no pigmentadas de crecimiento rápido mediante el estudio de la morfología de las microcolonias en fibroblastos / Assessment of the invasiveness of rapidly-growing nonpigmented mycobacteria with the fibroblast microcolony assay

Objetivos. Se evaluó la capacidad invasiva de aislamientos clínicos y de colección de varias especies de micobacterias no pigmentadas de crecimiento rápido mediante el análisis de las microcolonias en cultivo de fibroblastos diploides humanos, y se comparó la misma con el fenotipo de colonias en medio de Middlebrook 7H11 y con el significado clínico de los aislamientos. Métodos. Se analizaron 29 cepas de: Mycobacterium chelonae (8), M. fortuitum (6), M. peregrinum (5), M. abscessus (5), M. mucogenicum ( 4) y M. septicum (1), tanto clínicamente significativas como de colección. Se evaluó el fenotipo liso o rugoso de las colonias en Middlebrook 7H11. Se evaluó la capacidad de invasión intracelular mediante el ensayo de microcolonias en fibroblastos descrito por Shepard. Las características cuantitativas se compararon con el test de la t de Student y las características cualitativas con el test exacto de Fisher. Resultados. No se encontraron diferencias significativas entre colonias de fenotipos distintos o cepas con diferentes significados clínicos, excepto en dos aislamientos de M. chelonae de bacteriemia relacionados con catéteres, que presentaron microcolonias alargadas en el cultivo celular. Las cepas de M. fortuitum y M. peregrinum presentaron microcolonias más grandes y de apariencia desflecada, mientras que las de M. chelonae, M. abscessus o M. mucogenicum, presentaron unas colonias más pequeñas y de apariencia redondeada. Conclusión. La capacidad invasiva está presente solamente en unas pocas cepas de micobacterias, y esta característica no aparece en la mayoría de las cepas aisladas de infecciones en humanos y en ninguna de las que no fueron clínicamente significativas, por lo que no sería una característica esencial para que los diversos aislamientos sean causa de enfermedad en humanos (AU)

Objective. The invasive capacity of rapidly-growing nonpigmented mycobacteria strains was evaluated by means of a fibroblast microcolony assay and related to the colony phenotype on Middlebrook 7H11 and to the clinical significance of the isolates. Methods. Twenty-nine strains [Mycobacterium chelonae (8), M. fortuitum (6), M. peregrinum (5), M. abscessus (5), M. mucogenicum ( 4) and M. septicum (1)], proceeding from a bacterial collection and clinical isolates, were evaluated. The smooth or rough phenotype of the colonies was assessed in Middlebrook 7H11 medium. Intracellular invasiveness was determined by the fibroblast-microcolony assay described by Shepard. Quantitative culture characteristics were compared with Student's t-test, and qualitative characteristics with Fisher's exact test. Results. No significant differences were found between colonies with different phenotypes or strains having a different clinical significance, except for two strains of Mycobacterium chelonae isolated from cases of catheter-related bacteremia, which showed elongated microcolonies. M. fortuitum and M. peregrinum strains showed larger microcolonies than M. chelonae, M. abscessus and M. mucogenicum, and displayed a fluffy appearance, while the latter two strains showed rounded colonies. Conclusion. Very few strains of mycobacteria had invasive capacity and the majority of strains isolated from human infections do not show this characteristic; hence this trait is not essential for mycobacteria to cause infection in humans (AU)