Inhibition of Acinetobacter baumannii Biofilm Formation by Terpenes from Oregano (Lippia graveolens) Essential Oil.

Acinetobacter baumannii is a nosocomial pathogen known for its ability to form biofilms, leading to persistent infections and antibiotic resistance. The limited effective antibiotics have encouraged the development of innovative strategies such as using essential oils and their constituents. This study evaluated the efficacy of oregano (Lippia graveolens) essential oil (OEO) and its terpene compounds, carvacrol and thymol, in inhibiting A. baumannii biofilms. These treatments showed a minimum inhibitory concentration of 0.6, 0.3, and 2.5 mg/mL and a minimum bactericidal concentration of 1.2, 0.6, and 5 mg/mL, respectively. Sub-inhibitory doses of each treatment and the OEO significantly reduced biofilm biomass and the covered area of A. baumannii biofilms as measured by fluorescence microscopy. Carvacrol at 0.15 mg/mL exhibited the most potent efficacy, achieving a remarkable 95% reduction. Sub-inhibitory concentrations of carvacrol significantly reduced the biofilm formation of A. baumannii in stainless steel surfaces by up to 1.15 log CFU/cm2 compared to untreated bacteria. The OEO and thymol exhibited reductions of 0.6 log CFU/cm2 and 0.4 log CFU/cm2, respectively, without affecting cell viability. Moreover, the terpenes inhibited twitching motility, a crucial step in biofilm establishment, with carvacrol exhibiting the highest inhibition, followed by OEO and thymol. The study provides valuable insights into the potential of terpenes as effective agents against A. baumannii biofilms, offering promising avenues for developing novel strategies to prevent persistent infections and overcome antibiotic resistance.

Assessing Different Ways of Bacillus subtilis Spreading over Abiotic Surfaces.

Surface-associate motility on biotic and abiotic environments is a key mechanism used by the model bacterium Bacillus subtilis and its closest relatives (i.e., B. amyloliquefaciens, B. thuringiensis, B. cereus, B. pumilus) for surface colonization and spreading across surfaces. The study of this mechanism in a research, industrial or clinic laboratory is essential; however, precautions should be taken for the reproducibility of the results, for example, the procedure to inoculate the bacteria on the testing plate, the humidity of the plate and the agar concentration. In this protocol, we describe, using Bacillus subtilis, how to perform these assays and, in addition, we show how by varying the agar concentration in the plate, you can make a first approximation of what type of motility has other bacterial species.

Influence of twitching and swarming motilities on biofilm formation in Pseudomonas strains.

The genus Pseudomonas mainly includes opportunistic pathogens that rely on type IV pili as an important virulence factor, which is associated with adherence and biofilm formation. Pseudomonas infections are well known to be persistent and resilient in nature largely because of the tendency of the species to form biofilms. This study aimed at analyzing environmental strains of Pseudomonas genus with respect to their ability to execute twitching and swarming motilities as well as with respect to their ability to form biofilms both in the presence as well as in the absence of furanone, a substance that has the potential to prevent the formation of biofilms. Strains of Pseudomonas aeruginosa and strains belonging to other species of the genus were analyzed. Twitching and swarming motility assays and biofilm-formation assays, both in the presence as well as in the absence of furanone, were performed. In twitching assay strains belonging to P. aeruginosa outperformed those belonging to other species. Interestingly, it was seen that the presence of furanone had a negative impact on formation of twitching and swarming motility zones. In the case of biofilm assays, it was observed that the presence of furanone resulted in an observable decrease in the degree of adhesion in 30% of the analyzed strains. Thus, from our results, it can be concluded that, as compared to other species, the strains belonging to P. aeruginosa exhibit a higher potential for twitching motility and similar performance in swarming motility and biofilm formation. It can also be concluded that furanone has the potential to interfere with both motilities as well as with biofilm formation.

Iron-depletion prevents biofilm formation in Pseudomonas aeruginosa through twitching motility and quorum sensing

Influence of iron-depletion on twitching motility and quorum sensing (QS) system in P. aeruginosa was evaluated. The results demonstrated iron-depletion can retard biofilm formation and increase the twitching motility and expression of QS-related genes, suggesting a potential interaction between twitching motility and QS system in P. aeruginosa biofilm formation.

Iron-depletion prevents biofilm formation in Pseudomonas aeruginosa through twitching motility and quorum sensing

Influence of iron-depletion on twitching motility and quorum sensing (QS) system in P. aeruginosa was evaluated. The results demonstrated iron-depletion can retard biofilm formation and increase the twitching motility and expression of QS-related genes, suggesting a potential interaction between twitching motility and QS system in P. aeruginosa biofilm formation.

Iron-Depletion prevents biofilm formation in Pseudomonas Aeruginosa through twitching mobility and quorum sensing.

Influence of iron-depletion on twitching motility and quorum sensing (QS) system in P. aeruginosa was evaluated. The results demonstrated iron-depletion can retard biofilm formation and increase the twitching motility and expression of QS-related genes, suggesting a potential interaction between twitching motility and QS system in P. aeruginosa biofilm formation.

Iron-depletion prevents biofilm formation in Pseudomonas aeruginosa through twitching motility and quorum sensing

Influence of iron-depletion on twitching motility and quorum sensing (QS) system in P. aeruginosa was evaluated. The results demonstrated iron-depletion can retard biofilm formation and increase the twitching motility and expression of QS-related genes, suggesting a potential interaction between twitching motility and QS system in P. aeruginosa biofilm formation.

Biofilm formation by Stenotrophomonas maltophilia isolates from device-associated nosocomial infections / Formación de biopelículas por aislamientos de Stenotrophomonas maltophilia recuperados de infecciones nosocomiales asociadas al uso de dispositivos médicos

Medical devices are often colonized by bacteria which may cause severe infections. The aim of this work was to evaluate biofilm formation by S. maltophilia isolates from device-associated nosocomial infections. The 13 local isolates exhibited different capacities of biofilm formation on hydrophilic and hydrophobic surfaces. All isolates formed strong biofilms in polystyrene microplates, while strong, moderate or weak biofilms were detected in borosilicate (BS) or polypropylene (PP) tubes. The proficiency of biofilm formation was better evaluated by the level of crystal violet staining expressed relative to the final culture density. The microscopic analysis of biofilms formed on glass coverslips revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Isolates with increased adhesion to BS showed larger microcolonies. According to our results, twitching correlated well with attachment to the three abiotic surfaces tested, while swimming only showed a slight correlation with biofilm formation on PP. Poor correlation was observed between cell surface hydrophobicity and biofilm formation. One of the highest biofilm-producing isolates adhered to urethral catheters of different materials, and exhibited an increased resistance to oxidative stress, one of the common stresses encountered by bacteria during the infection process due to the immune response.

El objetivo de este trabajo fue evaluar la formación de biopelículas por parte de aislamientos de Stenotrophomonas maltophilia. Los 13 aislamientos locales evaluados mostraron diferente capacidad de formar biopelículas en superficies hidrofílicas e hidrofóbicas. Todos ellos formaron biopelículas fuertes en microplacas de poliestireno (PS), mientras que se observaron biopelículas fuertes, moderadas o débiles en tubos de borosilicato (BS) o polipropileno (PP). La medida del cristal violeta unido a la biopelícula expresada en función de la densidad final de los cultivos permitió una mejor evaluación de la eficiencia de formación de biopelículas. El análisis microscópico de biopelículas formadas sobre cubreobjetos mostró la presencia de una matriz de exopolisacáridos y microcolonias típicas de la arquitectura de las biopelículas. Los aislamientos con mayor adhesión a BS mostraron microcolonias de mayor tamaño. La motilidad asociada a superficies ( twitching) presentó buena correlación con la adhesión a BS, PP y PS, mientras que la motilidad asociada a flagelos solo correlacionó ligeramente con la adhesión a PP. La correlación entre la hidrofobicidad de la superficie bacteriana y la formación de biopelículas fue escasa. Uno de los aislamientos productores de biopelículas fuertes evidenció capacidad de adhesión a catéteres uretrales de diferentes materiales y mayor resistencia al estrés oxidativo.