Evaluation of the role of substrate and albumin on Pseudomonas aeruginosa biofilm morphology through FESEM and FTIR studies on polymeric biomaterials

Cyclic olefin copolymer (COC) as a promising biomaterial for affecting bacterial colonization: investigation on Vibrio campbellii

Cyclic olefin copolymer (COC) has emerged as an interesting biocompatible material for Organ-on-a-Chip (OoC) devices monitoring growth, viability, and metabolism of cells. Despite ISO 10993 approval, systematic investigation of bacteria grown onto COC is a still not documented issue. This study discusses biofilm formations of the canonical wild type BB120 Vibrio campbellii strain on a native COC substrate and addresses the impact of the physico-chemical properties of COC compared to conventional hydroxyapatite (HA) and poly(dimethylsiloxane) (PDMS) surfaces. An interdisciplinary approach combining bacterial colony counting, light microscopy imaging and advanced digital image processing remarks interesting results. First, COC can reduce biomass adhesion with respect to common biopolymers, that is suitable for tuning biofilm formations in the biological and medical areas. Second, remarkably different biofilm morphology (dendritic complex patterns only in the case of COC) was observed among the examined substrates. Third, the observed biofilm morphogenesis was related to the interaction of COC with the conditioning layer of the planktonic biological medium. Fourth, Level Co-occurrence Matrix (CGLM)-based analysis enabled quantitative assessment of the biomass textural fractal development under different coverage conditions. All of this is of key practical relevance in searching innovative biocompatible materials for pharmaceutical, implantable and medical products.

Insights into the microbiological and virulence characteristics of bacteria in orthopaedic implant infections: A study from Pakistan

The exponential increase in the prevalence of multidrug resistant bacteria has resulted in limiting surgical treatment options globally, potentially causing biofilm-related complications, implant failure, and severe consequences. This study aims to isolate and characterize bacteria from post-surgical orthopaedic implant infections and screening for multiple antibiotic resistance. A cross-sectional study was conducted, involving isolation of forty-four dominant pathogenic bacterial isolates from 16 infected implant samples from across Islamabad and Rawalpindi. Out of forty-four, 38% cocci and 61% bacilli were obtained. Approximately 90% of isolates showed multiple antibiotic resistance (MAR) index of more than 0.2. Eleven strains were identified via 16S rRNA gene sequencing as Pseudomonas aeruginosa, Bacillus spp., Planococcus chinensis, Staphylococcus, Escherichia coli and Enterobacter cloacae. The bacterial strain E. coli MB641 showed sensitivity to Polymyxin only, and was resistant to all other antibiotics used. Maximum biofilm forming ability 0.532 ± 0.06, 0.55 ± 0.01 and 0.557 ± 0.07 was observed in Pseudomonas aeruginosa MB663, Pseudomonas aeruginosa MB664 and Bacillus spp. MB647 respectively after 24 hours of incubation. EPS production of bacterial strains was assessed, the polysaccharides and protein content of EPS were found to be in the range of 11-32 μg/ml and 2-10 μg/ml, respectively. Fourier transform infrared spectroscopic analysis of EPS showed the presence of carbohydrates, proteins, alkyl halides, and nucleic acids. X-ray diffraction analysis revealed crystalline structure of EPS extracted from biofilm forming bacteria. These findings suggest a high prevalence of antibiotic-resistant bacteria in orthopaedic implant-associated surgeries, highlighting the urgent need for ongoing monitoring and microorganism testing in infected implants.

Attachment and optimization of Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa biofilms to a 3D printed lattice

A lattice was designed and fabricated using three-dimensional (3D) printing that allows for the facile transfer of biofilms formed from either Staphylococcus aureus, Staphylococcus epidermidis, or Pseudomonas aeruginosa into a fresh cell culture flask. To enhance biofilm production onto the filaments, three protein-based treatments were compared: fetal bovine serum (FBS), bovine serum albumin (BSA), and fibrinogen (Fb). Protein treatments included either supplementing the growth broths or pre-coating the lattice prior to immersion into the broth. S. aureus and P. aeruginosa biofilms were observed on all tested filaments that contained the supplement Fb. S. epidermidis required BSA to form biofilm. Ultimately, polycarbonate (PC) was chosen as the optimal material for lattice creation since it can be autoclaved without warping key design features. In addition, this 3D printed design may facilitate biofilm transfer from the bacterial culture to different cell culture platforms.

Decisive Role of Polymer-Bovine Serum Albumin Interactions in Biofilm Substrates on "Philicity" and Extracellular Polymeric Substances Composition

Formation of extracellular polymeric substances (EPS) is a crucial step for bacterial biofilm growth. The dependence of EPS composition on growth substrate and conditioning of the latter is thus of primary importance. We present results of studies on the growth of biofilms of two different strains each, of the Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae, on four polymers used commonly in indwelling medical devices ─polyethene, polypropylene, polycarbonate, and polytetrafluoroethylene─immersed in bovine serum albumin (BSA) for 24 h. The polymer substrates are studied before and after immersing in BSA for 9 and 24 h, using contact angle measurement (CAM) and field emission scanning electron microscopy (FE-SEM) to extract, respectively, the "philicity" φ (defined as -cos θ, where θ is the contact angle of the liquid on the solid at a particular temperature and ambient pressure) and spatial Hirsch parameter H (defined from the relation F(r) ∼ r^2H, where F(r) is the mean squared density fluctuation at the sample surface). H = 0.5, <0.5, or >0.5 signifies no correlation, anticorrelation, and correlation, respectively. The substrates are seen to transform from large hydrophobicity to near amphiphilicity with the formation of a BSA conditioning surface layer, and the H-values distinguish the length scales of 100, 500, and 2000 nm, with the anticorrelation increasing with length scale. Biofilms of E. coli did not grow on bare PTFE and HDPE substrates. Biofilms grown on BSA-covered surfaces are studied with CAM, FE-SEM, Fourier transform infrared (FTIR), and surface-enhanced Raman spectroscopy (SERS). Both spectra and φ-values were independent of bacterial species but dependent on the polymer, while H-values show some bacterial variation. Thus, EPS composition and wetting properties of the corresponding bacterial biofilms seem to be decided by the interaction of the conditioning BSA layer with the specific polymer substrate.

Exploration of the Pharmacodynamics for Pseudomonas aeruginosa Biofilm Eradication by Tobramycin

Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen which is involved in numerous infections. It is of growing concern within the field of antibiotic resistant and tolerance and often exhibits multi-drug resistance. Previous studies have shown the emergence of antibiotic resistant and tolerant variants within the zone of clearance of a biofilm lawn after exposure to aminoglycosides. As concerning as the tolerant variant emergence is, there was also a zone of killing (ZOK) immediately surrounding the antibiotic source from which no detectable bacteria emerged or were cultured. In this study, the ZOK was analyzed using both in vitro and in silico methods to determine if there was a consistent antibiotic concentration versus time constraint (area under the curve, (AUC)) which is able to completely kill all bacteria in the lawn biofilms in our in vitro model. Our studies revealed that by achieving an average AUC of 4,372.5 μg*hr/mL, complete eradication of biofilms grown on both agar and hydroxyapatite was possible. These findings show that appropriate antibiotic concentrations and treatment duration may be able to treat antibiotic resistant and tolerant biofilm infections.

Microscopic techniques to evaluate the biofilm formation ability of a marine bacterium Pseudomonas aeruginosa PFL-P1 on different substrata

Biofilm formation in bacteria is strongly affected by the nature of substrata. Different substrata such as glass, polystyrene, steel, ceramic, and rubber were used to assess the biofilm forming ability of a marine bacterium Pseudomonas aeruginosa PFL-P1 using a scanning electron microscope (SEM), atomic force microscope (AFM), and confocal laser scanning microscope (CLSM). The bacterium formed dense biofilms with varied aggregation on different substrata. SEM study revealed small rod-shaped cells with diverse arrangements within the biofilms on all the substrata under study. The AFM study revealed the highest roughness of 545 nm on the ceramic substratum. The biofilms formed on ceramic substratum were characterized with maximum roughness (742 nm), maximum peak height (1,480 nm), and maximum arithmetic mean height (611 nm), significantly higher than all the other substrata (p < .05). AFM studies confirmed that P. aeruginosa PFL-P1 exhibited biofilm heterogeneity on all the substrata. The CLSM study indicated a higher fraction of nucleic acids to α-polysaccharides ratio in the biofilms. COMSTAT analysis revealed the highest biofilm biomass of ~18 μm³ /μm² on the ceramic substratum. The maximum biofilm thickness of ~50 μm in the native state on the ceramic substratum was significantly higher than glass (p = .0015), polystyrene (p = .0001), steel (p = .0035), and rubber substrata (p = .0001). The higher surface roughness of ceramic substratum is accountable for more area for colonization, as evident from higher biomass and thickness of the biofilm. This study provides insight into the substratum properties, which modulate the biofilm forming ability in bacteria.

Periodicities in the roughness and biofilm growth on glass substrate with etching time: Hydrofluoric acid etchant

Adherence of the microorganism to submerged solid surfaces leads to biofilm formation. Biofilm formation modifies the surfaces in favor of bacteria facilitating the survival of the bacteria under different stressed conditions. On the other hand, the formation of biofilm has a direct adverse economic impact in various industries and more importantly in medical practices. This adherence is the reason for the failure of many indwelling medical devices. Surface biofilm adhesion is the key to biofilm growth and stability. Hence this adhesion needs to be substantially lowered to inhibit biofilm stability. Both chemical and physical properties of the surface influence biofilm formation and modulating these properties can control this formation. In this study, we have investigated the effect of Hydrofluoric acid (HF), at a specific concentration as an etchant, on the surface morphology of substrates and the growth of biofilms of Pseudomonas aeruginosa. and Staphylococcus aureus. We find that the bacterial counts on the etched surfaces undergo a periodic increase and decrease. This, on one hand, shows the close correlation between the biofilm growth and the particular roughness scale, and on the other hand, explains the existing contradictory results regarding the effects of etching on substrate roughness and biofilm growth. We propose a simple model of a sequence of hole formation, hole expansion and etching away of the hole walls to form a new, comparatively smooth surface, coupled with the preferential accumulation of bacteria at the hole edges, to explain these periodicities.

Influence of exposure time on the release of bacteria from a biofilm on Ti6Al4V discs using sonication: An in vitro model

Implant sonication is considered a useful method for the diagnosis of implant-related infections. We designed an in vitro study using Ti6Al4V discs and 5 different bacteria to determine the optimal sonication time for recovery of most bacteria tested to enable use of sonication in clinical practice for microbiological diagnosis of implant-related infections. We carried out a specific protocol for the adherence and subsequent biofilm formation on the materials used. The discs were then sonicated and the retrieved bacteria were quantified. From minute 1 to 5, the amount of recovered organisms grew progressively for all bacteria. Between minute 6 and minute 10, the number was irregular for all strains except E. coli, though no pattern was evidenced. E. coli was the only microorganism with a progressive increase in liberation throughout the process. Significant differences were observed in each of the 10minutes analyzed as concerns the release of the 5 strains (P<0.021) as well as in the mean dislodgement (of the 10minutes) of all tested strains (P<0.00001). Considering that infections in which biofilms are involved could be polymicrobial, we concluded that 5minutes is the optimal time of sonication in order to recover the maximum amount of most bacteria attached to Ti6Al4V discs.