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Biofilms that grow on implant surfaces pose a great risk and challenge for the dental implant survival. In this work, we have applied Er:YAG photoacoustic irrigation using super short pulses (Er:YAG-SSP) to remove biofilms from the titanium surfaces in the non-contact mode. Mature Enterococcus faecalis biofilms were treated with saline solution, chlorhexidine, and hydrogen peroxide, or photoacoustically with Er:YAG-SSP for 10 or 60 s. The number of total and viable bacteria as well as biofilm surface coverage was determined prior and after different treatments. Er:YAG-SSP photoacoustic treatment significantly increases the biofilm removal rate compared to saline or chemically treated biofilms. Up to 92% of biofilm-covered surface can be cleaned in non-contact mode during 10 s without the use of abrasives or chemicals. In addition, Er:YAG-SSP photoacoustic irrigation significantly decreases the number of viable bacteria that remained on the titanium surface. Within the limitations of the present in vitro model, the ER:YAG-SSP seems to constitute an efficient therapeutic option for quick debridement and decontamination of titanium implants without using abrasives or chemicals.

Benzoxonium chloride belongs to the group of quaternary ammonium salts, which have been widely used for decades as disinfectants because of their high efficacy, low toxicity, and thermal stability. In this study, we have prepared the C10-C18 set of benzoxonium-like salts to evaluate the effect of their chemical and biological decontamination capabilities. In particular, biocidal activity against a panel of bacterial strains including Staphylococcus aureus in biofilm form was screened. In addition, the most promising compounds were successfully tested against Francisella tularensis as a representative of potential biological warfare agents. From a point of view of chemical warfare protection, the efficiency of BOC-like compounds to degrade the organophosphate simulant fenitrothion was examined. Notwithstanding that no single compound with universal effectiveness was identified, a mixture of only two compounds from this group would be able to satisfactorily cover the proposed decontamination spectrum. In addition, the compounds were evaluated for their cytotoxicity as a basic safety parameter for potential use in practice. In summary, the dual effect on chemical and biological agents of benzoxonium-like salts offer attractive potential as active components of decontamination mixtures in the case of a terrorist threat or chemical or biological accidents.

Streptococcus mutans is one of the bacteria that initiates the colonization of the pellicle at the tooth surface. It forms a plaque, together with other bacteria, which gradually dissolves the pellicle and leaves the tooth surface unprotected against the acidic oral environment. Calcium phosphate ceramics are excellent synthetic materials for the study of biofilm formation in dentistry because they are comparable to teeth in chemical composition and structure. Calcium phosphates can be processed to achieve a variety of crystalline compounds with biologically relevant ionic substitutions and structures that allow study of the effect of the surface chemistry and the topography independently. In this article, we describe the preparation and characterization of three types of calcium phosphate-based materials as a suitable surface for the formation of the S. mutans biofilm: beta-tricalcium phosphate (β-TCP); sintered hydroxyapatite (SHA); and calcium-deficient hydroxyapatite (CDHA). The densest biofilms were formed on the surfaces of SHA and CDHA, with no significant differences due to the stoichiometry or microstructure. In contrast, β-TCP showed a lower susceptibility to S. mutans biofilm formation, suggesting that the crystalline structure is the controlling parameter. Subsequently, SHA was selected to develop a dental biofilm model that allowed study of S. mutans biofilm susceptibility to chlorhexidine and ethanol.

Introduction: Quaternary ammonium salts (QASs) are widely spread cationic surfactants applicable in various industrial branches. QASs manifesting antibacterial effect contain hydrophilic core and a long alkyl chain in the structure. These compounds have strong antimicrobial activity against certain bacteria strains especially non-spore forming, yeasts, or protozoa. S. Aureus is a frequent cause of nosocomial infections and plays an important role in the persistence of chronic infections, especially when it’s attached to medical implants and host tissue, and developed in mature biofilm. Either way, this pathogen represents a significant burden on the healthcare system and new antimicrobial compounds are always required in clinical practice. Hypothesis and aims: Our main research activity involves the synthesis of novel compounds based on QASs and evaluating their eradication ability against pathogenic S. Aureus in biofilm and free-floating form and subsequent effectivity comparison against these two different bacterial states. Methodology: All newly prepared compounds were prepared by the nucleophilic reaction, verified by Nuclear Magnetic Resonance (NMR) and High-Resolution Mass Spectrometry (HR-MS). The antimicrobial properties were evaluated by microdilution broth assay and by Calgary device based assay with MIC, MBC, and MBEC as outcomes. Results: Series of novel QAS were prepared and verified. The MICs, MBCs, and MBECs were measured for all substances and have shown antimicrobial potential against S. Aureus in both states, however higher concentration was needed for biofilm eradication. The activities of newly prepared compounds were comparable to QASs based disinfections already known and commonly used in practice. Conclusion: Series of synthesized compounds underwent antimicrobial evaluation and several compounds have shown antimicrobial potential against S. Aureus in planktonic and biofilm form.

Introduction: An increasing microbial resistance to known antibiotics raises the demand for new antimicrobials. New antibacterial agent should have a good activity against planktonic as well as biofilm bacteria. Quaternary ammonium compounds (QACs), are widely used in medicine, have proven antimicrobial properties, and are low toxic and low irritating. In this study new QACs were evaluated for their biofilm eradication efficiency as antibacterial compounds and as irrigants in combination with Er:YAG photoacoustic streaming. Aims: To evaluate the effectiveness of new QACs against E. faecalis biofilms and to increase the effectiveness of QACs with laser treatment. Method: The biofilm of E. faecalis were grown on titanium surface. The fraction of the dead cells and the biofilm surface coverage was determined with LIVE/DEADTM using confocal microscopy (CLSM) before and after QACs treatment. To enhance to effectiveness the biofilm samples were pretreated with QACs followed by short laser Er:YAG photoacoustic streaming treatment. Results: All tested QACs were effective against the E. faecalis biofilms. The best anti-biofilm compounds were N-Alkylimidazolinium derivatives. Compared to planktonic bacteria the bacteria in the biofilm were up to 10 fold more resistant. The fraction of the dead bacteria that were treated with QACs followed by Er:YAG photoacoustic streaming increased significantly compared to the chemical treatment alone. In addition, the biofilm surface coverage decreased after laser treatment. Conclusions: The results suggest that new QACs have a great potential as antibacterial compounds effective against biofilms of E. faecalis. The laser treatment can significantly improve the effectiveness of QACs treatment.

Quaternary ammonium salts (QASs) have been widely used for disinfection purposes because of their low price, high efficacy and low human toxicity for decades. However, precise mechanisms of action nor the powerful versatile agent against all antimicrobial species are known. In this study we have prepared 43 novel N-alkyl monoquaternary ammonium salts including 7 N,N-dialkyl monoquaternary ammonium salts differing bearing alkyl chain either of 12, 14 or 16 carbons. Together with 15 already published QASs we have studied the antimicrobial efficacy of all water-soluble compounds together with standard benzalkonium salts against Gram-positive (G+) and Gram-negative (G-) bacteria, anaerobic spore-forming Cl. difficile, yeasts, filamentous fungi and enveloped Varicella zoster virus (VZV). To address the mechanism of action, lipophilicity seems to be a key parameter which determines antimicrobial efficacy, however, exceptions are likely to occur and therefore QSAR analysis on the efficacy against G+ and G- bacteria was applied. We showed that antibacterial activity is higher when the molecule is larger, more lipophilic, less polar, and contains fewer oxygen atoms, fewer methyl groups bound to heteroatoms or fewer hydrogen atoms bound to polarized carbon atoms. In addition, from an application point of view, we have formulated mixtures, on the basis of obtained efficiency of individual compounds, in order to receive wide-spectrum agent. All formulated mixtures completely eradicated tested G+ and G- strains, including the multidrug-resistant P. aeruginosa as well as in case of yeasts. However, effect on A. fumigatus, Cl. difficile and VZV the exposition towards mixture resulted in significant reduction only. Finally, 3 out of 4 formulated mixtures were safer than reference commercial agent based on benzalkonium salts only in the skin irritation test using reconstructed human epidermidis.