The Effect of Antibiotics on Planktonic Cells and Biofilm Formation Ability of Collected Arcobacter-like Strains and Strains Isolated within the Czech Republic

The purpose of this study was to test the in vitro effects of ampicillin, ciprofloxacin, clindamycin, erythromycin, gentamicin, and tetracycline on planktonic cells of Arcobacter-like microorganisms and on their biofilm formation ability. The minimum inhibitory concentrations (MICs) were determined by the microdilution method. Further, biofilm formation ability in the presence of various concentrations of antibiotics was evaluated by a modified Christensen method. Most of the 60 strains exhibited high susceptibility to gentamicin (98.3%), ciprofloxacin (95.0%), and erythromycin (100.0%). High level of resistance was observed to clindamycin and tetracycline with MIC50 and MIC90 in range of 4–32 mg/L and 32–128 mg/L, respectively. Combined resistance to both clindamycin and tetracycline was found in 38.3% of tested strains. In general, higher biofilm formation was observed especially at lower concentrations of antibiotics (0.13–2 mg/L). However, a significant decrease in biofilm formation ability of Pseudarcobacter defluvii LMG 25694 was exhibited with ampicillin and clindamycin at concentrations above 32 or 8 mg/L, respectively. Biofilm formation represents a potential danger of infection and also a risk to human health, in particular due to antimicrobial-resistant strains and the ability to form a biofilm structure at a concentration that is approximately the MIC determined for planktonic cells.

Anti-Planktonic and Anti-Biofilm Properties of Pentacyclic Triterpenes—Asiatic Acid and Ursolic Acid as Promising Antibacterial Future Pharmaceuticals

Due to the ever-increasing number of multidrug-resistant bacteria, research concerning plant-derived compounds with antimicrobial mechanisms of action has been conducted. Pentacyclic triterpenes, which have a broad spectrum of medicinal properties, are one of such groups. Asiatic acid (AA) and ursolic acid (UA), which belong to this group, exhibit diverse biological activities that include antioxidant, anti-inflammatory, diuretic, and immunostimulatory. Some of these articles usually contain only a short section describing the antibacterial effects of AA or UA. Therefore, our review article aims to provide the reader with a broader understanding of the activity of these acids against pathogenic bacteria. The bacteria in the human body can live in the planktonic form and create a biofilm structure. Therefore, we found it valuable to present the action of AA and UA on both planktonic and biofilm cultures. The article also presents mechanisms of the biological activity of these substances against microorganisms.

Insights into Background of Microbial Aggregations (Acinetobacter baumannii): A Century of Challenges

: In recent years, Acinetobacter baumannii has attracted the research community’s attention since they are turned into the leading cause of both community- and hospital-acquired infections. The emergence of MDR-Acinetobacter baumannii strains threatens hospitalized patients since antibiotics fail to withdraw the bacterial infectious agents. Despite its worldwide distribution, health settings fail to combat limitations in therapeutic regions against Acinetobacter baumannii. The capability of biofilm formation in Acinetobacter baumannii strengthens their virulence and also survival. Understanding the fundamental virulence mechanisms beyond the microbial aggregations leads to exploring alternative drug targets such as signaling molecules and Quorum sensing systems to block bacterial communication and antimicrobial resistance. The significance of examining the biofilm's structural details and the relationship between Quorum sensing networks and related signaling molecules has been explicitly highlighted. Accordingly, this review study aimed to explain the general biofilm structure, the mechanisms beyond biofilm formation, quorum sensing system, and the generation of signaling molecules in Acinetobacter baumannii.

Extracellular RNA as a potential activator of Neutrophil Extracellular Traps by Candida albicans biofilm

Neutrophils represent the first line of innate host defense. The ability to inhibit the development of infections is associated with the involvement of several fighting strategies. The still poorly understood mechanism is netosis, involving the release of Extracellular Neutrophil Traps (NETs). NETs are complexes of chromosomal DNA and granule content. Such a web-like structure inhibits the spread of invaders. Netosis plays a significant role in combating Candida albicans infections. It has been shown that several factors, composing C. albicans cell surface mediate NETs production. However, the development of difficult to eradicate fungal infection is associated with the formation of the biofilm structure, which partially protects the pathogen cells from contact with the host’s immune system. One of the reasons for the creation of a such protective environment is the production of the extracellular matrix (ECM). The major components of the C. albicans ECM layer are lipids, proteins, carbohydrates but also extracellular nucleic acids, among which we observed a significant RNA content. Considering that the ECM consisting of RNA molecules is one of the first lines of contact between biofilms and neutrophils, our current studies aimed to assess the potential role of extracellular RNA in the triggering of the netosis process by human neutrophils in vitro. We showed that RNA purified from C. albicans biofilm structure and the whole cells have the capability to induction of ROS-dependent netosis pathway. Additionally, cell migration analysis indicate that RNA molecules may also be an effective chemotactic agent. This work was supported by NCN (2019/33/B/NZ6/02284).

Imaging Flow Cytometry to Study Biofilm-Associated Microbial Aggregates

The aim of the research was to design an advanced analytical tool for the precise characterization of microbial aggregates from biofilms formed on food-processing surfaces. The approach combined imaging flow cytometry with a machine learning-based interpretation protocol. Biofilm samples were collected from three diagnostic points of the food-processing lines at two independent time points. The samples were investigated for the complexity of microbial aggregates and cellular metabolic activity. Thus, aggregates and singlets of biofilm-associated microbes were simultaneously examined for the percentages of active, mid-active, and nonactive (dead) cells to evaluate the physiology of the microbial cells forming the biofilm structures. The tested diagnostic points demonstrated significant differences in the complexity of microbial aggregates. The significant percentages of the bacterial aggregates were associated with the dominance of active microbial cells, e.g., 75.3% revealed for a mushroom crate. This confirmed the protective role of cellular aggregates for the survival of active microbial cells. Moreover, the approach enabled discriminating small and large aggregates of microbial cells. The developed tool provided more detailed characteristics of bacterial aggregates within a biofilm structure combined with high-throughput screening potential. The designed methodology showed the prospect of facilitating the detection of invasive biofilm forms in the food industry environment.

Susceptibility of Dental Caries Microcosm Biofilms to Photodynamic Therapy Mediated by Fotoenticine

Photodynamic therapy (PDT) mediated by Fotoenticine® (FTC), a new photosensitizer derived from chlorin e-6, has shown in vitro inhibitory activity against the cariogenic bacterium Streptococcus mutans. However, its antimicrobial effects must be investigated on biofilm models that represent the microbial complexity of caries. Thus, we evaluated the efficacy of FTC-mediated PDT on microcosm biofilms of dental caries. Decayed dentin samples were collected from different patients to form in vitro biofilms. Biofilms were treated with FTC associated with LED irradiation and analyzed by counting the colony forming units (log10 CFU) in selective and non-selective culture media. Furthermore, the biofilm structure and acid production by microorganisms were analyzed using microscopic and spectrophotometric analysis, respectively. The biofilms from different patients showed variations in microbial composition, being formed by streptococci, lactobacilli and yeasts. Altogether, PDT decreased up to 3.7 log10 CFU of total microorganisms, 2.8 log10 CFU of streptococci, 3.2 log10 CFU of lactobacilli and 3.2 log10 CFU of yeasts, and reached eradication of mutans streptococci. PDT was also capable of disaggregating the biofilms and reducing acid concentration in 1.1 to 1.9 mmol lactate/L. It was concluded that FTC was effective in PDT against the heterogeneous biofilms of dental caries.

Chemical composition and biological activity of Salvia officinalis essential oil

The study was aimed at analyzing chemical composition, and biological and antibiofilm activity of Salvia officinalis L. essential oil (EO) with MALDI-TOF MS Biotyper. The main compounds of S. officinalis EO were a-thujone 24.6%, camphor 20.6%, 1,8-cineole 12.1%, and a-humulene 5.8%. Free radical scavenging activity was medium high. The highest antimicrobial activity was observed against Bacillus subtilis. Changes in the biofilm structure confirmed the inhibitory action of S. officinalis and the most pronounced effect was observed in B. subtilis biofilm. The highest inhibition in situ in antimicrobial activity was 78.45% at 125 µ.L−1 on apple for B. subtilis.