Microbial Biofilms, Second Edition

Improvement of a low-cost protocol for a simultaneous comparative evaluation of hydrolytic activity between sessile and planktonic cells: Candida albicans as a study model

Candida albicans is often implicated in nosocomial infections with fatal consequences. Its virulence is contributed to hydrolytic enzymes and biofilm formation. Previous research focused on studying these virulence factors individually. Therefore, this study aimed to investigate the impact of biofilm formation on the hydrolytic activity using an adapted low-cost method. Eleven strains of C. albicans were used. The biofilms were formed on pre-treated silicone discs using 24-well plates and then deposited on the appropriate agar to test each enzyme, while the planktonic cells were conventionally seeded. Biofilms were analysed using Raman spectroscopy, fluorescent and scanning electron microscopy. The adapted method provided an evaluation of hydrolytic enzymes activity in C. albicans biofilm and showed that sessile cells had a higher phospholipase and proteinase activities compared with planktonic cells. These findings were supported by spectroscopic and microscopic analyses, which provided valuable insights into the virulence mechanisms of C. albicans during biofilm formation.

Stopping the Unstoppable: Unconventional Methods to Prevent the Biofilm Growth

Biofilms are consortia of microorganisms encased in extracellular matrix that protect cells from adverse conditions. A biofilm matrix is typically composed of extracellular DNA, cellulose and proteinaceous amyloid fibers. The matrix aids in adhesion to abiotic and biotic surface including medical devices and host tissues. The presence of biofilm makes bacteria more resilient and non-responsive to most current treatment regimes at disposal. Therefore, biofilm-associated infections are serious threat in hospital settings and pose a huge burden on economy. Inhibition of matrix components (cellulose and/or amyloid formation) has emerged as a lucrative alternative strategy to cure biofilm-related infections and combat antibiotic resistance. Here we review the current and emerging therapeutic interventions to mitigate persistent infections due to biofilms. The successful implementation of these interventions will have a huge impact on alleviating the current financial burden on healthcare services.

Mesoporous Silica-Based Materials with Bactericidal Properties

Bacterial infections are the main cause of chronic infections and even mortality. In fact, due to extensive use of antibiotics and, then, emergence of antibiotic resistance, treatment of such infections by conventional antibiotics has become a major concern worldwide. One of the promising strategies to treat infection diseases is the use of nanomaterials. Among them, mesoporous silica materials (MSMs) have attracted burgeoning attention due to high surface area, tunable pore/particle size, and easy surface functionalization. This review discusses how one can exploit capacities of MSMs to design and fabricate multifunctional/controllable drug delivery systems (DDSs) to combat bacterial infections. At first, the emergency of bacterial and biofilm resistance toward conventional antimicrobials is described and then how nanoparticles exert their toxic effects upon pathogenic cells is discussed. Next, the main aspects of MSMs (e.g., physicochemical properties, multifunctionality, and biosafety) which one should consider in the design of MSM-based DDSs against bacterial infections are introduced. Finally, a comprehensive analysis of all the papers published dealing with the use of MSMs for delivery of antibacterial chemicals (antimicrobial agents functionalized/adsorbed on mesoporous silica (MS), MS-loaded with antimicrobial agents, gated MS-loaded with antimicrobial agents, MS with metal-based nanoparticles, and MS-loaded with metal ions) is provided.

Effect of the endOclear® Device on Biofilm in Endotracheal Tubes

BACKGROUND

Organisms trapped in biofilms cause more than 80% of medical infections. Significant investments are being made to develop methods of removing these biofilms. The endOclear^® device is reported to remove biofilm from endotracheal tubes (ETTs) and to decrease pneumonia rates and ventilator time.

METHODS

This was an observational study performed at a university Level 1 trauma center intensive care unit. A series of 40 ETTs were collected at extubation, with half of the patients having been treated daily with the endOclear^® device. Biofilms were quantified from a standardized point on the distal ETT. The patients' standard and biofilm cultures were reviewed.

RESULTS

The mean hours of intubation for the control group was 135 and for the device group 138. This difference was not statistically significant (p = 0.91). Eleven patients in the device group were found to have pneumonia compared with six in the control group (p = 0.34). Ventilator data after device use showed a mean increase of 29.9 cc in tidal volume and a mean decrease in peak pressures of 0.39 cm H₂O. Comparisons between biofilm stage or hours of intubation and a diagnosis of pneumonia found no correlation. Only nine of 40 ETTs had congruence between the microbiata of the biofilm and standard bronchoalveolar lavage (BAL) fluid, a divergence rate of 78%.

CONCLUSIONS

Comparison of the endOclear^® group and controls demonstrated a trend toward a higher pneumonia rate in the former. Additionally, the device achieved very small, clinically insignificant, changes in ventilator settings, and no difference was seen in the time on the ventilator. Comparisons between biofilm and standard BAL cultures continue to show the biofilm is more diverse than previously thought. In this study, no statistical significance was found between biofilm stage and the pneumonia rate. This study provides additional evidence that there is no correlation between biofilm stage and duration of intubation.