Bacterial biofilms: a diagnostic and therapeutic challenge

Disruption of Pseudomonas aeruginosa quorum sensing influences biofilm formation without affecting antibiotic tolerance

The opportunistic bacterial pathogen Pseudomonas aeruginosa is a leading cause of antimicrobial resistance-related deaths, and novel antimicrobial therapies are urgently required. P. aeruginosa infections are difficult to treat due to the bacterium's propensity to form biofilms, whereby cells aggregate to form a cooperative, protective structure. Autolysis, the self-killing of bacterial cells, and the bacterial cell-to-cell communication system, quorum sensing (QS), play essential roles in biofilm formation. Strains of P. aeruginosa that have lost the lasI/R QS system commonly develop in patients, and previous studies have characterized distinctive autolysis phenotypes in these strains. Yet, the underlying causes and implications of these autolysis phenotypes remain unknown. This study confirmed these autolysis phenotypes in the PA14 QS mutant strains, ΔlasI and ΔlasR, and investigated the consequences of QS loss and associated autolysis on biofilm formation and antibiotic susceptibility. QS mutants exhibited delayed biofilm formation but ultimately surpassed the wild-type (WT) in biofilm mass. However, the larger biofilm mass of the QS mutants was not reflected in higher live-cell numbers, indicating an altered biofilm structure. Nevertheless, QS mutant biofilms were not more susceptible to antibiotics than the WT. Artificial supplementation of ΔlasI with a QS signal molecule (autoinducer) restored the strain's QS system without the associated costs of QS, enabling ΔlasI to achieve higher pre-treatment and post-treatment live-cell numbers. Overall, the lack of QS functioning was not detrimental to biofilm antibiotic tolerance, though the artificial disruption of QS may reduce the advantages of QS mutants within in vivo mixed-strain populations. Much remains to be understood regarding the regulation and induction of the autolysis phenotypes observed in these strains, and future research to fully elucidate the control and consequences of autolysis may offer potential for novel antimicrobial therapies.

Suppressive Mechanism of Benzalkonium Chloride-Bactericidal Activity in the Presence of Oil

Cleaning and sterilization are critical Prerequisite Programs in sanitation management based on HACCP. Most food factories clean and sanitize equipment daily after production using detergents containing benzalkonium chloride (BAC). However, in factories that produce oil and fat-rich foods, it has been discovered that microbes can persist on production equipment. Insufficient cleaning protocols may result in secondary contamination of the final products. Unfortunately, there are limited cleaning agents available that are effective in sterilizing microbes in the presence of oil. Moreover, there is a lack of research on the bactericidal mechanisms and bacterial dynamics in oily environments. In this study, we aimed to reduce bacterial contamination on equipment in such factories by hypothesizing that oil diminishes BAC's bactericidal activity. We conducted lab-scale experiments simulating actual factory conditions to examine the effects of oil on BAC's efficacy. Additionally, we investigated the effect of nonionic surfactants, which are known to enhance BAC's bactericidal activity in oil-free conditions, in the presence of oil. The results showed that BAC's bactericidal activity was significantly reduced in the presence of oil. However, the activity was restored by adding an appropriate amount of secondary alcohol ethoxylate (sec-AE). Microscopic observations revealed that bacteria tended to accumulate at the water/oil interface, suggesting that the oil interface might inhibit BAC from effectively attacking the bacteria. The addition of sec-AE appeared to disperse the bacteria into the water layer, thus restoring BAC's bactericidal activity in the presence of oil. These findings are crucial for improving daily cleaning and sterilization processes in food factories operating in high-oil environments to prevent secondary contamination and enhance food safety.

HIV-1 interaction with an O-glycan-specific bacterial lectin enhances virus infectivity and resistance to neutralizing antibodies

Bacteria dysbiosis and its accompanying inflammation or compromised mucosal integrity is associated with an increased risk of HIV-1 transmission. However, HIV-1 may also bind bacteria or bacterial products to impact infectivity and transmissibility. This study evaluated HIV-1 interactions with bacteria through glycan-binding lectins. The Streptococcal Siglec-like lectin SLBR-N, a part of the fimbriae shrouding the bacteria surface that recognizes α2,3 sialyated O-linked glycans, was noted for its ability to enhance HIV-1 infectivity in the context of cell-free infection and cell-to-cell transfer. Enhancing effects were recapitulated with O-glycan-binding plant lectins, signifying the importance of O-glycans. N-glycan-binding bacterial lectins FimH and Msl had no effect. SLBR-N was demonstrated to capture and transfer infectious HIV-1 virions, bind to O-glycans on HIV-1 Env, and increase HIV-1 resistance to neutralizing antibodies targeting different regions of Env. This study highlights the potential contribution of O-glycan-binding lectins from commensal bacteria at the mucosa in promoting HIV-1 infection.

The Antibacterial Potential of Brazilian Red Propolis against the Formation and Eradication of Biofilm of Helicobacter pylori

Helicobacter pylori is associated with gastrointestinal diseases, and its treatment is challenging due to antibiotic-resistant strains, necessitating alternative therapies. Brazilian red propolis (BRP), known for its diverse bioactive compounds with pharmaceutical properties, was investigated for its anti-H. pylori activity, focusing on biofilm formation inhibition and eradication. BRP was tested against H. pylori (ATCC 43526) using several assays: time-kill, nucleotide leakage, biofilm formation inhibition (determining the minimum inhibitory concentration of biofilm of 50%-MICB50, and cell viability), and biofilm eradication (determining the minimum eradication concentration of biofilm of 99.9%-MBEC). Standardization of H. pylori biofilm formation was also conducted. In the time-kill assay, BRP at 50 µg/mL eliminated all H. pylori cells after 24 h. The nucleotide leakage assay showed no significant differences between control groups and BRP-treated groups at 25 µg/mL and 50 µg/mL. H. pylori formed biofilms in vitro at 109 CFU/mL after 72 h. The MICB50 of BRP was 15.6 µg/mL, and at 500, 1000, and 2000 µg/mL, BRP eradicated all bacterial cells. The MBEC was 2000 µg/mL. These findings suggest that BRP has promising anti-H. pylori activity, effectively inhibiting and eradicating biofilms. Further studies are necessary to elucidate BRP's mechanisms of action against H. pylori.

The use of customized 3D-printed mandibular prostheses with pressure-reducing device: A clinical trial

BACKGROUND

Segmental bone defects of the mandible result in the complete loss of the affected region. We had incorporated the pressure-reducing device (PRD) designs into the customized mandible prostheses (CMP) and conducted a clinical trial to evaluate this approach.

METHODS

Seven patients were enrolled in this study. We examined the association among the history of radiotherapy, the number of CMP regions, the number of chin regions involved, and CMP exposure.

RESULTS

We included five men and two women with an average age of 55 years. We excised tumors with an average weight of 147.8 g and the average weight of the CMP was 68.5 g. No significant difference between the two weights was noted (p = 0.3882). Three patients received temporary dentures and the CMP remained stable in all patients.

CONCLUSION

The use of PRD in CMP may address the previous challenges associated with CMP, but further research is necessary.

Time to re-set our thinking about airways disease: lessons from history, the resurgence of chronic bronchitis / PBB and modern concepts in microbiology

In contrast to significant declines in deaths due to lung cancer and cardiac disease in Westernised countries, the mortality due to 'chronic obstructive pulmonary disease' (COPD) has minimally changed in recent decades while 'the incidence of bronchiectasis' is on the rise. The current focus on producing guidelines for these two airway 'diseases' has hindered progress in both treatment and prevention. The elephant in the room is that neither COPD nor bronchiectasis is a disease but rather a consequence of progressive untreated airway inflammation. To make this case, it is important to review the evolution of our understanding of airway disease and how a pathological appearance (bronchiectasis) and an arbitrary physiological marker of impaired airways (COPD) came to be labelled as 'diseases'. Valuable insights into the natural history of airway disease can be obtained from the pre-antibiotic era. The dramatic impacts of antibiotics on the prevalence of significant airway disease, especially in childhood and early adult life, have largely been forgotten and will be revisited as will the misinterpretation of trials undertaken in those with chronic (bacterial) bronchitis. In the past decades, paediatricians have observed a progressive increase in what is termed 'persistent bacterial bronchitis' (PBB). This condition shares all the same characteristics as 'chronic bronchitis', which is prevalent in young children during the pre-antibiotic era. Additionally, the radiological appearance of bronchiectasis is once again becoming more common in children and, more recently, in adults. Adult physicians remain sceptical about the existence of PBB; however, in one study aimed at assessing the efficacy of antibiotics in adults with persistent symptoms, researchers discovered that the majority of patients exhibiting symptoms of PBB were already on long-term macrolides. In recent decades, there has been a growing recognition of the importance of the respiratory microbiome and an understanding of the ability of bacteria to persist in potentially hostile environments through strategies such as biofilms, intracellular communities, and persister bacteria. This is a challenging field that will likely require new approaches to diagnosis and treatment; however, it needs to be embraced if real progress is to be made.

Rapid Diagnostic of Streptococcus suis in Necropsy Samples of Pigs by thrA-Based Loop-Mediated Isothermal Amplification Assay

Streptococcus (S.) suis presents a serious threat to the pig industry as well as food safety and public health. Although several LAMP assays have been developed for the identification of S. suis, no universal assay is so far available for the field-suitable examination of clinical pig specimens. Based on the thrA housekeeping gene, a new loop-mediated isothermal amplification (LAMP) assay was developed and validated for the detection of S. suis in the brain and joints of pigs. For this LAMP assay, two different methods for the extraction of DNA from brain and joint swabs were compared. Using the LPTV boiling method, the detection limit of LAMP was 1.08 CFU/reaction, while the detection limit was 53.8 CFU/reaction using a commercial DNA extraction kit. The detection limits of thrA-LAMP in combination with the LPTV boiling method were 104-105 CFU/swab in the presence of brain tissue and 103-104 CFU/swab in the presence of joint tissue. The diagnostic quality criteria of LAMP were determined by the examination of 49 brain swabs and 34 joint swabs obtained during routine diagnostic necropsies. Applying the LPTV boiling method to brain swabs, the sensitivity, specificity, and positive and negative predictive values of thrA-LAMP were 88.0, 95.8, 95.7, and 88.5% using cultural investigation as a reference method, and 76.7, 100, 100, and 73.1% using real-time PCR as a reference method. Based on these results, the thrA-LAMP assay combined with the LPTV boiling method is suitable for rapid detection of S. suis from brain swabs.

Polyalthic Acid from Copaifera lucens Demonstrates Anticariogenic and Antiparasitic Properties for Safe Use

This study aimed at evaluating the potential of Copaifera lucens, specifically its oleoresin (CLO), extract (CECL), and the compound ent-polyalthic acid (PA), in combating caries and toxoplasmosis, while also assessing its toxicity. The study involved multiple assessments, including determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against cariogenic bacteria. CLO and PA exhibited MIC and MBC values ranging from 25 to 50 μg/mL, whereas CECL showed values equal to or exceeding 400 μg/mL. PA also displayed antibiofilm activity with minimum inhibitory concentration of biofilm (MICB50) values spanning from 62.5 to 1000 μg/mL. Moreover, PA effectively hindered the intracellular proliferation of Toxoplasma gondii at 64 μg/mL, even after 24 h without treatment. Toxicological evaluations included in vitro tests on V79 cells, where concentrations ranged from 78.1 to 1250 μg/mL of PA reduced colony formation. Additionally, using the Caenorhabditis elegans model, the lethal concentration (LC50) of PA was determined as 1000 μg/mL after 48 h of incubation. Notably, no significant differences in micronucleus induction and the NDI were observed in cultures treated with 10, 20, or 40 μg/mL of CLO. These findings underscore the safety profile of CLO and PA, highlighting their potential as alternative treatments for caries and toxoplasmosis.

Oral microbiota in human health and disease: A perspective

The evolution of medical knowledge about oral microbiota has increased awareness of its important role for the entire human body health. A wide range of microbial species colonizing the oral cavity interact both with each other and with their host through complex pathways. Usually, these interactions lead to a harmonious coexistence (i.e. eubiosis). However, several factors - including diet, poor oral hygiene, tobacco smoking, and certain medications, among others - can disrupt this weak homeostatic balance (i.e. dysbiosis) with potential implications on both oral (i.e. development of caries and periodontal disease) and systemic health. This article is thus aimed at providing an overview on the importance of oral microbiota in mediating several physiological and pathological conditions affecting human health. In this context, strategies based on oral hygiene and diet as well as the role of probiotics supplementation are discussed.

The Challenge of Emerging Resistant Gram-Positive Pathogens in Hip and Knee Periprosthetic Joint Infections

➤ An increase in resistant bacterial pathogens has occurred over the last 4 decades.➤ Careful patient selection and improving or correcting risk factors for periprosthetic joint infection (PJI) before elective surgical treatment are strongly recommended. ➤ Appropriate microbiological methods, including those used to detect and grow Cutibacterium acnes, are recommended. ➤ Antimicrobial agents used in the prevention or management of infection should be selected appropriately and the duration of therapy should be carefully considered in order to mitigate the risk of developing bacterial resistance.➤ Molecular methods including rapid polymerase chain reaction (PCR) diagnostics, 16S sequencing, and/or shotgun and/or targeted whole-genome sequencing are recommended in culture-negative cases of PJI.➤ Expert consultation with an infectious diseases specialist (if available) is recommended to assist with the appropriate antimicrobial management and monitoring of patients with PJI.

Recent Advances in Antimicrobial Peptide Hydrogels

Advances in the number and type of available biomaterials have improved medical devices such as catheters, stents, pacemakers, prosthetic joints, and orthopedic devices. The introduction of a foreign material into the body comes with a risk of microbial colonization and subsequent infection. Infections of surgically implanted devices often lead to device failure, which leads to increased patient morbidity and mortality. The overuse and improper use of antimicrobials has led to an alarming rise and spread of drug-resistant infections. To overcome the problem of drug-resistant infections, novel antimicrobial biomaterials are increasingly being researched and developed. Hydrogels are a class of 3D biomaterials consisting of a hydrated polymer network with tunable functionality. As hydrogels are customizable, many different antimicrobial agents, such as inorganic molecules, metals, and antibiotics have been incorporated or tethered to them. Due to the increased prevalence of antibiotic resistance, antimicrobial peptides (AMPs) are being increasingly explored as alternative agents. AMP-tethered hydrogels are being increasingly examined for antimicrobial properties and practical applications, such as wound-healing. Here, we provide a recent update, from the last 5 years of innovations and discoveries made in the development of photopolymerizable, self-assembling, and AMP-releasing hydrogels.

Quorum sensing inhibition through site-directed mutation by deletion PCR

Quorum sensing induces biofilms and virulence factors that are adverse industrially and medically. Nowadays, quorum sensing inhibitions focus on signal analogs or signal degradation, but these methods have several downsides, which are temporal and affected by several environmental factors. In this research, we used deletion PCR to perform site-directed mutagenesis on the quorum sensing pathway gene and then analyzed its effects on quorum sensing. Serratia fonticola DSM 4576 strain was utilized as the research strain, and the gram-negative bacteria's universal quorum sensing pathway, which is conducted by acyl-homoserine lactone (AHL), was analyzed. The structure and active site of the AHL synthase enzyme encoded by S. fonticola DSM 4576's luxI-type gene were predicted. The gene's partial section solely encodes the enzyme's active site. By using sequence and ligation-independent cloning, the obtained mutagenic gene was cloned into the suicide vector pEX18Ap. The recombinant vector was used to transform wild-type S. fonticola DSM 4576 strains, and the mutants were determined through two-step selections and PCR genotyping. The gene expression level and biofilm formation were quantitatively analyzed through RT-PCR and biofilm assay, and no significant difference was noted in the gene expression between wild types and mutants. However, when mutants were compared to wildtypes, there was a significant decrease in biofilm formation as a result of quorum sensing induced bioreaction. Thus, we propose a quorum sensing inhibitory technique based on enzyme mutation on the quorum sensing pathway, and we proved the feasibility of enzyme active site's site-directed mutation through deletion PCR.

Polysaccharides' Structures and Functions in Biofilm Architecture of Antimicrobial-Resistant (AMR) Pathogens

Bacteria and fungi have developed resistance to the existing therapies such as antibiotics and antifungal drugs, and multiple mechanisms are mediating this resistance. Among these, the formation of an extracellular matrix embedding different bacterial cells, called biofilm, is an effective strategy through which bacterial and fungal cells are establishing a relationship in a unique environment. The biofilm provides them the possibility to transfer genes conferring resistance, to prevent them from desiccation and to impede the penetration of antibiotics or antifungal drugs. Biofilms are formed of several constituents including extracellular DNA, proteins and polysaccharides. Depending on the bacteria, different polysaccharides form the biofilm matrix in different microorganisms, some of them involved in the first stage of cells' attachment to surfaces and to each other, and some responsible for giving the biofilm structure resistance and stability. In this review, we describe the structure and the role of different polysaccharides in bacterial and fungal biofilms, we revise the analytical methods to characterize them quantitatively and qualitatively and finally we provide an overview of potential new antimicrobial therapies able to inhibit biofilm formation by targeting exopolysaccharides.

Measuring Niche-Associated Metabolic Activity in Planktonic and Biofilm Bacteria

Most pathobionts of the respiratory tract form biofilms during asymptomatic colonization to survive and persist in this niche. Environmental changes of the host niche, often resulting from infection with respiratory viruses, changes of the microbiota composition, or other host assaults, can result in biofilm dispersion and spread of bacteria to other host niches, resulting in infections, such as otitis media, pneumonia, sepsis, and meningitis. The niches that these bacteria encounter during colonization and infection vary markedly in nutritional availability and contain different carbon sources and levels of other essential nutrients needed for bacterial growth and survival. As these niche-related nutritional variations regulate bacterial behavior and phenotype, a better understanding of bacterial niche-associated metabolic activity is likely to provide a broader understanding of bacterial pathogenesis. In this chapter, we use Streptococcus pneumoniae as a model respiratory pathobiont. We describe methods and models used to grow bacteria planktonically or to form biofilms in vitro by incorporating crucial host environmental factors, including the various carbon sources associated with specific niches, such as the nasopharynx or bloodstream. We then present methods describing how these models can be used to study bacterial phenotypes and their association with metabolic energy production and the generation of fermentation products.

Strategies and progresses for enhancing targeted antibiotic delivery

Antibiotic resistance is a global health issue and a potential risk for society. Antibiotics administered through conventional formulations are devoid of targeting effect and often spread to various undesired body sites, leading to sub-lethal concentrations at the site of action and thus resulting in emergence of resistance, as well as side effects. Moreover, we have a very slim antibiotic pipeline. Drug-delivery systems have been designed to control the rate, time, and site of drug release, and innovative approaches for antibiotic delivery provide a glint of hope for addressing these issues. This review elaborates different delivery strategies and approaches employed to overcome the limitations of conventional antibiotic therapy. These include antibiotic conjugates, prodrugs, and nanocarriers for local and targeted antibiotic release. In addition, a wide range of stimuli-responsive nanocarriers and biological carriers for targeted antibiotic delivery are discussed. The potential advantages and limitations of targeted antibiotic delivery strategies are described along with possible solutions to avoid these limitations. A number of antibiotics successfully delivered through these approaches with attained outcomes and potentials are reviewed.

Characteristics and Biological Activity of Exopolysaccharide Produced by Lysobacter sp. MMG2 Isolated from the Roots of Tagetes patula

In the present study, exopolysaccharide (EPS) produced by Lysobacter sp. MMG2 (lyEPS) was characterized and purified. The lyEPS-producing strain Lysobacter sp. MMG2 was isolated from the roots of Tagetes patula. When lyEPS was produced in tryptic soy broth with 1% glucose and the lyophilized powder was measured, the yield was found to be 0.67 g/L. The molecular weight (Mw) of lyEPS was 1.01 × 105 Da. Its monosaccharide composition includes 84.24% mannose, 9.73% glucose, 2.55% galactose, 2.77% arabinose, 0.32% xylose, and 0.03% rhamnose. Scanning electron microscopy (SEM) revealed that lyEPS has various round and rough surfaces. Fourier-transform infrared (FTIR) analysis identified its carbohydrate polymer functional groups. Moreover, thermogravimetric analysis of lyEPS revealed two events of mass loss: the first was water loss, which resulted in 3.97% mass loss and the second event occurred at approximately 212 °C. lyEPS could inhibit biofilm-producing pathogenic bacteria without any antimicrobial activity. Furthermore, lyEPS at a concentration of 4 mg/mL could exhibit potent 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging activity (89.25%). These results indicate that lyEPS could be a promising candidate for industrial development if its biological activity is further explored.

Clinical Escherichia coli: From Biofilm Formation to New Antibiofilm Strategies

Escherichia coli is one of the species most frequently involved in biofilm-related diseases, being especially important in urinary tract infections, causing relapses or chronic infections. Compared to their planktonic analogues, biofilms confer to the bacteria the capacity to be up to 1000-fold more resistant to antibiotics and to evade the action of the host’s immune system. For this reason, biofilm-related infections are very difficult to treat. To develop new strategies against biofilms, it is important to know the mechanisms involved in their formation. In this review, the different steps of biofilm formation in E. coli, the mechanisms of tolerance to antimicrobials and new compounds and strategies to combat biofilms are discussed.

Green synthesis and characterization of silver nanoparticles using Eugenia roxburghii DC. extract and activity against biofilm-producing bacteria

The green synthesis of silver nanoparticles (AgNPs) and their applications have attracted many researchers as the AgNPs are used effectively in targeting specific tissues and pathogenic microorganisms. The purpose of this study is to synthesize and characterize silver nanoparticles from fully expanded leaves of Eugenia roxburghii DC., as well as to test their effectiveness in inhibiting biofilm production. In this study, at 0.1 mM concentration of silver nitrate (AgNO3), stable AgNPs were synthesized and authenticated by monitoring the color change of the solution from yellow to brown, which was confirmed with spectrophotometric detection of optical density. The crystalline nature of these AgNPs was detected through an X-Ray Diffraction (XRD) pattern. AgNPs were characterized through a high-resolution transmission electron microscope (HR-TEM) to study the morphology and size of the nanoparticles (NPs). A new biological approach was undertaken through the Congo Red Agar (CRA) plate assay by using the synthesized AgNPs against biofilm production. The AgNPs effectively inhibit biofilm formation and the biofilm-producing bacterial colonies. This could be a significant achievement in contending with many dynamic pathogens.

Nitric Oxide-Releasing Lock Solution for the Prevention of Catheter-Related Infection and Thrombosis

Although frequently used, venous catheters are often associated with serious complications such as infection and thrombosis. Lock solution therapies are clinically used to deter these issues but generally address only infection or thrombosis with limited success. Here, we report the development of a dual-functional lock therapy using nitric oxide (NO) donor molecule, S-nitrosoglutathione (GSNO). NO is a potent, broad-spectrum antimicrobial agent that also temporarily inhibits platelet activation, preventing thrombosis. Furthermore, NO has antibiofilm actions, an ability that traditional antibiotic lock solutions lack, thus limiting their efficacy. In this work, different concentrations of GSNO were characterized via NO analysis to determine a range of NO-releasing lock solution (NOreLS) concentrations to investigate and to demonstrate prolonged potential efficacy. Tested against clinically used vancomycin and gentamicin lock solutions, GSNO-based NOreLS repeatedly outperformed in models of different stages of catheter infections. NOreLS also prevented clot formation when exposed to whole blood, showing increased efficacy compared to a heparin lock solution. Moreover, NOreLS was demonstrated to be biocompatible via hemolysis and cytotoxicity assays. NOreLS has excellent potential for safely and effectively preventing infection and thrombosis related to catheter usage.

Periprosthetic Joint Infection (PJI)—Results of One-Stage Revision with Antibiotic-Impregnated Cancellous Allograft Bone—A Retrospective Cohort Study

Controversy exists regarding the optimal treatment of periprosthetic joint infection (PJI), considering control of infection, functional results as well as quality of life. Difficulties in treatment derive from the formation of biofilms within a few days after infection. Biofilms are tolerant to systemically applied antibiotics, requiring extreme concentrations for a prolonged period. Minimum biofilm eradicating concentrations (MBEC) are only feasible by the local application of antibiotics. One established approach is the use of allograft bone as a carrier, granting a sustained release of antibiotics in very high concentrations after appropriate impregnation. The purpose of this study was to determine the rate of reinfection after a one-stage revision of infected hip or knee prostheses, using antibiotic-impregnated allograft bone as the carrier and avoiding cement. Between 1 January 2004 and 31 January 2018, 87 patients with PJI, according to MSIS, underwent a one-stage revision with antibiotic-impregnated cancellous allograft bone. An amount of 17 patients had insufficient follow-ups. There were 70 remaining patients (34 male, 36 female) with a mean follow-up of 5.6 years (range 2–15.6) and with a mean age of 68.2 years (range 31.5–86.9). An amount of 38 hips and 11 knees were implanted without any cement; and 21 knees were implanted with moderate cementing at the articular surface with stems always being uncemented. Within 2 years after surgery, 6 out of 70 patients (8.6%, CI 2–15.1) showed reinfection and after more than 2 years, an additional 6 patients showed late-onset infection. Within 2 years after surgery, 11 out of 70 patients (15.7%, CI 7.2–24.2) had an implant failure for any reason (including infection) and after more than 2 years, an additional 7 patients had an implant failure. Using Kaplan-Meier analysis for all 87 patients, the estimated survival for reinfection was 93.9% (CI 88.8–99.1) at 1 year, 89.9% (CI 83.2–96.6) at 2 years and 81.5% (CI 72.1–90.9) at 5 years. The estimated survival for implant failure for any reason was 90.4% (CI 84.1–96.7) at 1 year, 80.9% (CI 72.2–89.7) at 2 years and 71.1% (CI 60.3–81.8) at 5 years. One-stage revision with antibiotic-impregnated cancellous allograft bone grants comparable results regarding infection control as with multiple stages, while shortening rehabilitation, improving quality of life for the patients and reducing costs for the health care system.

Overview of Candida albicans and Human Papillomavirus (HPV) Infection Agents and their Biomolecular Mechanisms in Promoting Oral Cancer in Pediatric Patients

Oral carcinoma represents one of the most common malignancies worldwide. Oral squamous cell carcinomas (OSCCs) account over 90% of all oral malignant tumors and are characterized by high mortality in the advanced stages. Early diagnosis is often a challenge for its ambiguous appearance in early stages. Mucosal infection by the human papillomavirus (HPV) is responsible for a growing number of malignancies, particularly cervical cancer and oropharyngeal carcinomas. In addition, Candida albicans (C. albicans), which is the principal fungi involved in the oral cancer development, may induce carcinogenesis through several mechanisms, mainly promoting inflammation. Medical knowledge and research on adolescent/pediatric patients' management and prevention are in continuous evolution. Besides, microbiota can play an important role in maintaining oral health and therefore all human health. The aim of this review is to evaluate epidemiological and pathophysiological characteristics of the several biochemical pathways involved during HPV and C. albicans infections in pediatric dentistry.

The Usages and Potential Uses of Alginate for Healthcare Applications

Due to their unique properties, alginate-based biomaterials have been extensively used to treat different diseases, and in the regeneration of diverse organs. A lot of research has been done by the different scientific community to develop biofilms for fulfilling the need for sustainable human health. The aim of this review is to hit upon a hydrogel enhancing the scope of utilization in biomedical applications. The presence of active sites in alginate hydrogels can be manipulated for managing various non-communicable diseases by encapsulating, with the bioactive component as a potential site for chemicals in developing drugs, or for delivering macromolecule nutrients. Gels are accepted for cell implantation in tissue regeneration, as they can transfer cells to the intended site. Thus, this review will accelerate advanced research avenues in tissue engineering and the potential of alginate biofilms in the healthcare sector.

Candida albicans and Oral Carcinogenesis. A Brief Review

Current medical knowledge and research on patients’ management are still evolving, and several protocols on minimizing risk of infection by Candida spp. among the population have developed. The aim of this work is to review the epidemiological and biomolecular characteristics and the various histopathological carcinogenesis hypothesis mechanisms that can occur during Candida albicans infections. Current evidence from the literature on the role of C. albicans during potentially malignant oral disorders and oral cancer has been sought. Thus, these biomolecular processes can give or contribute to benign lesions, also in precancerous or cancerous situations. Alongside this, the physiological microorganism oral flora (microbiota) can play a crucial role in maintaining oral health during those infections and therefore avoid carcinogenesis.

A Novel Biofilm Model System to Visualise Conjugal Transfer of Vancomycin Resistance by Environmental Enterococci

Enterococci and biofilm-associated infections are a growing problem worldwide, given the rise in antibiotic resistance in environmental and clinical settings. The increasing incidence of antibiotic resistance and its propagation potential within enterococcal biofilm is a concern. This requires a deeper understanding of how enterococcal biofilm develops, and how antibiotic resistance transfer takes place in these biofilms. Enterococcal biofilm assays, incorporating the study of antibiotic resistance transfer, require a system which can accommodate non-destructive, real-time experimentation. We adapted a Gene Frame^® combined with fluorescence microscopy as a novel non-destructive platform to study the conjugal transfer of vancomycin resistance in an established enterococcal biofilm.A multi-purpose fluorescent in situ hybridisation (FISH) probe, in a novel application, allowed the identification of low copy number mobile elements in the biofilm. Furthermore, a Hoechst stain and ENU 1470 FISH probe identified Enterococcus faecium transconjugants by excluding Enterococcus faecalis MF06036 donors. Biofilm created with a rifampicin resistant E. faecalis (MW01105^Rif) recipient had a transfer efficiency of 2.01 × 10^-3; double that of the biofilm primarily created by the donor (E. faecalis MF06036). Conjugation in the mixed enterococcal biofilm was triple the efficiency of donor biofilm. Double antibiotic treatment plus lysozyme combined with live/dead imaging provided fluorescent micrographs identifying de novo enterococcal vancomycin resistant transconjugants inside the biofilm. This is a model system for the further study of antibiotic resistance transfer events in enterococci. Biofilms promote the survival of enterococci and reduce the effectiveness of drug treatment in clinical settings, hence giving enterococci an advantage. Enterococci growing in biofilms exchange traits by means of horizontal gene transfer, but currently available models make study difficult. This work goes some way to providing a non-destructive, molecular imaging-based model system for the detection of antibiotic resistance gene transfer in enterococci.

Oleoresins and naturally occurring compounds of Copaifera genus as antibacterial and antivirulence agents against periodontal pathogens

Invasion of periodontal tissues by Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans can be associated with aggressive forms of periodontitis. Oleoresins from different copaifera species and their compounds display various pharmacological properties. The present study evaluates the antibacterial and antivirulence activity of oleoresins obtained from different copaifera species and of ten isolated compounds against two causative agents of periodontitis. The following assays were performed: determination of the minimum inhibitory concentration (MIC), determination of the minimum bactericidal concentration (MBC), and determination of the antibiofilm activity by inhibition of biofilm formation and biofilm eradication tests. The antivirulence activity was assessed by hemagglutination, P. gingivalis Arg-X and Lis-X cysteine protease inhibition assay, and A. actinomycetemcomitans leukotoxin inhibition assay. The MIC and MBC of the oleoresins and isolated compounds 1, 2, and 3 ranged from 1.59 to 50 μg/mL against P. gingivalis (ATCC 33277) and clinical isolates and from 6.25 to 400 μg/mL against A. actinomycetemcomitans (ATCC 43717) and clinical isolates. About the antibiofilm activity, the oleoresins and isolated compounds 1, 2, and 3 inhibited biofilm formation by at least 50% and eradicated pre-formed P. gingivalis and A. actinomycetemcomitans biofilms in the monospecies and multispecies modes. A promising activity concerning cysteine protease and leucotoxin inhibition was also evident. In addition, molecular docking analysis was performed. The investigated oleoresins and their compounds may play an important role in the search for novel sources of agents that can act against periodontal pathogens.

Genetic and physiological effects of subinhibitory concentrations of oral antimicrobial agents on Streptococcus mutans biofilms

Streptococcus mutans is the main etiological agent of dental caries because of its capacity to adhere to enamel structure and form biofilms. This study aimed to evaluate the effects of the anticariogenic agents - sodium fluoride (NaF) and chlorhexidine (CHX) - at levels below minimum inhibitory concentrations (sub-MICs) on the growth of planktonic cells and biofilms and on the expression of vicR and covR genes associated with the regulation of biofilm formation. MICs and minimum bactericidal concentrations (MBCs) of NaF and CHX were determined for S. mutans strains ATCC25175, UA159 and 3VF2. Growth curves were constructed for planktonic cells cultured in brain heart infusion (BHI) broth supplemented with NaF (0.125-0.75MIC) or CHX (0.25-0.75MIC). Biofilm formation assays were performed in microplates containing CHX or NaF at 0.5-1.0MIC and stained with violet crystal. Quantitative polymerase chain reaction determined the alterations in covR and vicR expression in cells exposed to antimicrobials at sub-MIC levels. NaF and CHX at sub-MIC levels affected the growth of planktonic cells of all three S. mutans strains, depending on the concentration tested. The biofilm formation in UA159 and 3VF2 was reduced by NaF at concentrations ≥0.5 MIC, while that of ATCC 25175 was reduced significantly irrespective of dose. In contrast, UA159 and 3VF2 biofilms were not affected by CHX at these levels, whereas those of ATCC 25175 were reduced significantly at all concentrations tested. Under sub-MIC conditions, CHX and (to a lesser degree) NaF increased vicR and covR expression in all three strains, although there were large differences between strains and treatment conditions employed. CHX and NaF at sub-MIC levels influence on the growth of S. mutans in planktonic and biofilm conditions and on transcript levels of biofilm-associated genes vicR and covR, in a dose-dependent manner.

Broad-spectrum treatment of bacterial biofilms using magneto-responsive liquid metal particles

The formation and proliferation of bacterial biofilms on surfaces, particularly those on biomedical devices, is a significant issue that results in substantial economic losses, presenting severe health risks to patients. Furthermore, heterogeneous biofilms consisting of different bacterial species can induce the increase in pathogenicity, and the resistance to antimicrobial agents due to the synergistic interactions between the different species. Heterogeneous bacterial biofilms are notoriously difficult to treat due to the presence of extracellular polymeric substances (EPS) and, in conjunction with the rapid rise of multi-drug resistant pathogens, this means that new solutions for anti-biofilm treatment are required. In this study, we investigate the application of magneto-responsive gallium-based liquid metal (GLM-Fe) nanomaterials against a broad range of Gram-positive and Gram-negative bacterial mono-species and multi-species biofilms. The GLM-Fe particles exhibit a magneto-responsive characteristic, causing spherical particles to undergo a shape transformation to high-aspect-ratio nanoparticles with sharp asperities in the presence of a rotating magnetic field. These shape-transformed particles are capable of physically removing bacterial biofilms and rupturing individual cells. Following treatment, both mono-species and multi-species biofilms demonstrated significant reductions in their biomass and overall cell viability, demonstrating the broad-spectrum application of this antibacterial technology. Furthermore, the loss of integrity of the bacterial cell wall and membranes was visualized using a range of microscopy techniques, and the leakage of intracellular components (such as nucleic acids and protein) was observed. Insights gained from this study will impact the design of future liquid metal-based biofilm treatments, particularly those that rely on magneto-responsive properties.

The Use of Anatomic Implants in Aesthetic Breast Surgery

Anatomic implants were introduced in the late 1980s, gaining popularity through the 1990s and beyond. The moratorium on silicone meant that the use of theses devices was less diffuse in the US and has remained so. Fifth-generation devices had improved form stability with more aggressive texturization to enhance soft tissue interaction. The ability to vary height, width and projection independently creates much versatility in their use for complex anatomical situations producing natural results. The impact of BIA-ALCL has had a significant impact on their use.

Influence of biofilm growth age, media, antibiotic concentration and exposure time on Staphylococcus aureus and Pseudomonas aeruginosa biofilm removal in vitro

BACKGROUND

Biofilm is known to be tolerant towards antibiotics and difficult to eradicate. Numerous studies have reported minimum biofilm eradication concentration (MBEC) values of antibiotics for many known biofilm pathogens. However, the experimental parameters applied in these studies differ considerably, and often the rationale behind the experimental design are not well described. This makes it difficult to compare the findings. To demonstrate the importance of experimental parameters, we investigated the influence of biofilm growth age, antibiotic concentration and treatment duration, and growth media on biofilm eradication. Additionally, OSTEOmycin™, a clinically used antibiotic containing allograft bone product, was tested for antibiofilm efficacy.

RESULTS

The commonly used Calgary biofilm device was used to grow 24 h and 72 h biofilms of Staphylococcus aureus and Pseudomonas aeruginosa, which were treated with time-dependent vancomycin (up to 3000 mg L- 1) and concentration-dependent tobramycin (up to 80 mg L- 1), respectively. Two common bacteriological growth media, tryptic soy broth (TSB) and cation-adjusted Mueller Hinton broth (CaMHB), were tested. We found for both species that biofilms were more difficult to kill in TSB than in CaMHB. Furthermore, young biofilms (24 h) were easier to eradicate than old biofilms (72 h). In agreement with vancomycin being time-dependent, extension of the vancomycin exposure increased killing of S. aureus biofilms. Tobramycin treatment of 24 h P. aeruginosa biofilms was found concentration-dependent and time-independent, however, increasing killing was indicated for 72 h P. aeruginosa biofilms. Treatment with tobramycin containing OSTEOmycin T™ removed 72 h and 168 h P. aeruginosa biofilms after 1 day treatment, while few 72 h S. aureus biofilms survived after 2 days treatment with vancomycin containing OSTEOmycin V™.

CONCLUSIONS

This study demonstrated biofilm removal efficacy was influenced by media, biofilm age and antibiotic concentration and treatment duration. It is therefore necessary to taking these parameters into consideration when designing experiments. The results of OSTEOmycin™ products indicated that simple in vitro biofilm test could be used for initial screening of antibiofilm products. For clinical application, a more clinically relevant biofilm model for the specific biofilm infection in question should be developed to guide the amount of antibiotics used for local antibiofilm treatment.

Extracellular Vesicles Influence the Growth and Adhesion of Staphylococcus epidermidis Under Antimicrobial Selective Pressure

Staphylococcus epidermidis causes infections associated with orthopedic implants due to its ability to establish persistent biofilms, making infections chronic and hard to treat. Extracellular vesicles (EVs) are part of the bacterial communication system, but the role of S. epidermidis-derived EVs in biofilm formation processes and survival is completely unknown. The aims of this study were (i) to investigate the effect of subinhibitory concentrations of antibiotics on vesiculation in S. epidermidis and evaluate the role of EVs in bacterial survival and adhesion under antimicrobial selective pressure and (ii) to evaluate whether EVs derived from a gentamicin-resistant S. epidermidis strain influence the susceptibility and adhesion of a gentamicin-susceptible strain. A gentamicin-susceptible (GEN^S) strain isolated from implant-associated osteomyelitis was cultured with EVs previously isolated from the same strain growing with subinhibitory concentrations of GEN (0, 0.03, and 0.06 μg × mL^–1) or with EVs from a gentamicin-resistant (GEN^R) strain. EVs were characterized regarding their size, number and protein content. The growth of S. epidermidis cultured with increasing concentrations of GEN (<=> MIC of 0.12 μg × mL^–1) was recorded, viability was determined by quantitative culturing and fluorescence staining, and biofilm biomass on polystyrene was quantified by crystal violet staining. Cells grown in subinhibitory concentrations of GEN produced a larger number of EVs of similar size but with greater protein content than cells grown in control (Ctrl) conditions (0 GEN). Under antimicrobial pressure, EVs promoted different mechanisms of antimicrobial tolerance depending on the EV and GEN concentrations. Cell adhesion to polystyrene decreased in the presence of 0 and 0.03 μg × mL^–1 GEN upon EV stimulation. Compared with Ctrl cells, cells treated with EVs from a GEN^R strain showed increased cell division during the exponential growth phase, faster maximal growth rate, shorter doubling time (8–33 min), and dramatically inhibited cell adhesion. These findings suggest that vesiculation in S. epidermidis is a survival response to subinhibitory concentrations of gentamicin. EVs may contribute to bacterial survival through their involvement (1) in the modulation of the growth rate, affecting cell division, and (2) in cell adhesion, decreasing cell attachment to polystyrene and glass.

Sonobactericide: An Emerging Treatment Strategy for Bacterial Infections

Ultrasound has been developed as both a diagnostic tool and a potent promoter of beneficial bio-effects for the treatment of chronic bacterial infections. Bacterial infections, especially those involving biofilm on implants, indwelling catheters and heart valves, affect millions of people each year, and many deaths occur as a consequence. Exposure of microbubbles or droplets to ultrasound can directly affect bacteria and enhance the efficacy of antibiotics or other therapeutics, which we have termed sonobactericide. This review summarizes investigations that have provided evidence for ultrasound-activated microbubble or droplet treatment of bacteria and biofilm. In particular, we review the types of bacteria and therapeutics used for treatment and the in vitro and pre-clinical experimental setups employed in sonobactericide research. Mechanisms for ultrasound enhancement of sonobactericide, with a special emphasis on acoustic cavitation and radiation force, are reviewed, and the potential for clinical translation is discussed.

Weak acids as an alternative anti-microbial therapy

Weak acids such as acetic acid and N-acetyl cysteine (NAC) at pH less than their pKa can effectively eradicate biofilms due to their ability to penetrate the biofilm matrix and the cell membrane. However, the optimum conditions for their activity against drug resistant strains, and safety, need to be understood for their application to treat infections or to inactivate biofilms on hard surfaces. Here, we investigate the efficacy and optimum conditions at which weak acids can eradicate biofilms. We compared the efficacy of various mono and triprotic weak acids such as N-acetyl cysteine (NAC), acetic acid, formic acid and citric acid, in eradicating biofilms. We found that monoprotic weak acids/acid drugs can kill mucoid P. aeruginosa mucA biofilm bacteria provided the pH is less than their pKa, demonstrating that the extracellular biofilm matrix does not protect the bacteria from the activity of the weak acids. Triprotic acids, such as citric acid, kill biofilm bacteria at pH ​< ​pKa1. However, at a pH between pKa1 and pKa2, citric acid is effective in killing the bacteria at the core of biofilm microcolonies but does not kill the bacteria on the periphery. The efficacy of a monoprotic weak acid (NAC) and triprotic weak acid (citric acid) were tested on biofilms formed by Klebsiella pneumoniae KP1, Pseudomonas putida OUS82, Staphylococcus aureus 15981, P. aeruginosa DK1-NH57388A, a mucoid cystic fibrosis isolate and P. aeruginosa PA_D25, an antibiotic resistant strain. We showed that weak acids have a broad spectrum of activity against a wide range of bacteria, including antibiotic resistant bacteria. Further, we showed that a weak acid drug, NAC, can kill bacteria without being toxic to human cells, if its pH is maintained close to its pKa. Thus weak acids/weak acid drugs target antibiotic resistant bacteria and eradicate the persister cells in biofilms which are tolerant to other conventional methods of biofilm eradication.

SEM Analysis of Enamel Abrasion after Air Polishing Treatment with Erythritol, Glycine and Sodium Bicarbonate

The aim of this in vitro study was to evaluate the enamel surface topography after treatment with three air polishing powders: Glycine (A), erythritol (B), and sodium bicarbonate (C) (Air Flow Soft, Plus and Classic powders, EMS Electro Medical Systems S.A., Nyon, Switzerland). Fifteen extracted incisors were randomly divided into three groups of five teeth each, A, B and C, respectively. The teeth were blocked in plaster bases, washed, dried and half-covered with polytetrafluoroethylene strips before treatment. In this way, each half-treated dental element became test and control of itself. Comparative statistical analysis of Rq (geometric average of the deviations occurring in roughness profile) was performed. The scanning electron microscope (SEM) analysis showed different degrees of surface roughness between the groups, decreasing after treatment. In addition, a statistically significant reduction p < 0.05 was present in group C (Rq mean non-treated 108.17 µm, 95% CI: 97.29–124.01 and Rq mean treated 86.78 µm, 95% CI: 80.63–93.70). A decrease in surface roughness post-treatment was not observed in group A and B. Therefore, it may be concluded that the air flow powders tested herein can be used on dental enamel to reduce the surface roughness due to function and the action of dental therapies.

Enzyme responsive copolymer micelles enhance the anti-biofilm efficacy of the antiseptic chlorhexidine

Staphylococcal biofilms cause many infectious diseases and are highly tolerant to the effects of antimicrobials; this is partly due to the biofilm matrix, which acts as a physical barrier retarding the penetration and reducing susceptibility to antimicrobials, thereby decreasing successful treatment outcomes. In this study, both single and mixed micellar systems based on poly vinyl caprolactam (PCL)-polyethylene glycol (PEG) copolymers were optimised for delivery of chlorhexidine (CHX) to S. aureus, MRSA and S. epidermidis biofilms and evaluated for their toxicity using Caenorhabditis elegans. The respective polyethylene glycol (PEG) and poly vinyl caprolactam (PCL) structural components promoted stealth properties and enzymatic responsive release of CHX inside biofilms, leading to significantly enhanced penetration (56%) compared with free CHX and improving the efficacy against Staphylococcus aureus biofilms grown on an artificial dermis (2.4 log reduction of CFU). Mixing Soluplus-based micelles with Solutol further enhanced the CHX penetration (71%) and promoted maximum reduction in biofilm biomass (>60%). Nematodes-based toxicity assay showed micelles with no lethal effects as indicated by their high survival rate (100%) after 72 h exposure. This study thus demonstrated that bio-responsive carriers can be designed to deliver a poorly water-soluble antimicrobial agent and advance the control of biofilm associated infections.

Disposable Patterned Electroceutical Dressing (PED-10) Is Safe for Treatment of Open Clinical Chronic Wounds

Objective: To evaluate if patterned electroceutical dressing (PED) is safe for human chronic wounds treatment as reported by wound care providers. Approach: This work reports a pilot feasibility study with the primary objective to determine physically observable effects of PED application on host tissue response from a safety evaluation point of view. For this pilot study, patients receiving a lower extremity amputation with at least one open wound on the part to be amputated were enrolled. Patients were identified through the Ohio State University Wexner Medical Center (OSUWMC) based on inclusion and exclusion criteria through prescreening through the Comprehensive Wound Center's (CWC) Limb Preservation Program and wound physicians and/or providers at OSUWMC. Wounds were treated with the PED before amputation surgery. Results: The intent of the study was to identify if PED was safe for clinical application based on visual observations of adverse or lack of adverse events on skin and wound tissue. The pilot testing performed on a small cohort (N = 8) of patients showed that with engineered voltage regulation of current flow to the open wound, the PED can be used with little to no visually observable adverse effects on chronic human skin wounds. Innovation: The PED was developed as a second-generation tunable electroceutical wound care dressing, which could potentially be used to treat wounds with deeper infections compared with current state of the art that treats wounds with treatment zone limited to the surface near topical application. Conclusion: Technology advances in design and fabrication of electroceutical dressings were leveraged to develop a tunable laboratory prototype that could be used as a disposable low-cost electroceutical wound care dressing on chronic wounds. Design revisions of PED-1 (1 kΩ ballast resistor) circumvented previously observed adverse effects on the skin in the vicinity of an open wound. PED-10 (including a 10 kΩ ballast resistor) was well tolerated in the small cohort of patients (N = 8) on whom it was tested, and the observations reported here warrant a larger study to determine the clinical impact on human wound healing and infection control.

Growing and Characterizing Biofilms Formed by Streptococcus pneumoniae

It is estimated that over 80% of bacterial infections are associated with biofilm formation. Biofilms are organized bacterial communities formed on abiotic surfaces, such as implanted or inserted medical devices, or on biological surfaces, such as epithelial linings and mucosal surfaces. Biofilm growth is advantageous for the bacterial organism as it protects the bacteria from antimicrobial host factors and allows the bacteria to reside in the host without causing excessive inflammation. Like many other opportunistic pathogens of the respiratory tract, Streptococcus pneumoniae forms biofilms during asymptomatic carriage, which promotes, among other things, persistence in the niche, intraspecies and interspecies communication, and spread of bacterial DNA. Changes within the colonizing environment resulting from host assaults, such as virus infection, can induce biofilm dispersion where bacteria leave the biofilm and disseminate to other sites with ensuing infection. In this chapter, we present methodology to form complex biofilms in the nasopharynx of mice and to evaluate the biofilm structure and function in this environment. Furthermore, we present methods that recapitulate this biofilm phenotype in vitro by incorporating crucial factors associated with the host environment and describe how these models can be used to study biofilm function, transformation, and dispersion.

Manipulation of the silkworm immune system by a metalloprotease from the pathogenic bacterium Pseudomonas aeruginosa

Antimicrobial peptide (AMP) production and melanization are two key humoral immune responses in insects. Induced synthesis of AMPs results from Toll and IMD signal transduction whereas melanization depends on prophenoloxidase (PPO) activation system. During invasion, pathogens produce toxins and other virulent factors to counteract host immune responses. Here we show that the pathways leading to PPO activation and AMP synthesis in the silkworm Bombyx mori are affected by a metalloprotease, named elastase B, secreted by Pseudomonas aeruginosa (PAO1). The metalloprotease gene (lasB) was expressed shortly after PAO1 cells had been injected into the larval silkworm hemocoel, leading to an increase of elastase activity. Injection of the purified PAO1 elastase B into silkworm hemolymph compromised PPO activation. In contrast, the protease caused a level increase of gloverin, an AMP in the hemolymph. To verify our results obtained using the purified elastase B, we infected B. mori with PAO1 ΔlasB mutant and found that PO activity in hemolymph of the PAO1 ΔlasB-infected larvae was significantly higher than that in the wild type-infected. The mutant-inhabited hemolymph had lower levels of gloverin and antimicrobial activity. PAO1 ΔlasB showed a decreased viability in the silkworm hemolymph whereas the host had a lower mortality. In addition, the effects caused by the ΔlasB mutant were restored by a complementary strain. These data collectively indicated that the elastase B produced by PAO1 is an important virulent factor that manipulates the silkworm immune system during infection.

Bacterial biofilm formation on implantable devices and approaches to its treatment and prevention

In living organisms, biofilms are defined as complex communities of bacteria residing within an exopolysaccharide matrix that adheres to a surface. In the clinic, they are typically the cause of chronic, nosocomial, and medical device-related infections. Due to the antibiotic-resistant nature of biofilms, the use of antibiotics alone is ineffective for treating biofilm-related infections. In this review, we present a brief overview of concepts of bacterial biofilm formation, and current state-of-the-art therapeutic approaches for preventing and treating biofilms. Also, we have reviewed the prevalence of such infections on medical devices and discussed the future challenges that need to be overcome in order to successfully treat biofilms using the novel technologies being developed.

The A, B and C's of Silicone Breast Implants: Anaplastic Large Cell Lymphoma, Biofilm and Capsular Contracture

Breast implantation either for cosmetic or reconstructive e purposes is one of the most common procedures performed in plastic surgery. Biofilm infection is hypothesised to be involved in the development of both capsular contracture and anaplastic large cell lymphoma (ALCL). Capsular contracture is one of the principal reasons for breast revision surgery and is characterised by the tightening and hardening of the capsule surrounding the implant, and ALCL is an indolent lymphoma found only in women with textured implants. We describe the types of breast implants available with regard to their surface characteristics of surface area and roughness and how this might contribute to capsular contracture and/or biofilm formation. The pathogenesis of capsular contracture is thought to be due to biofilm formation on the implant, which results in on-going inflammation. We describe the current research into breast implant associated ALCL and how implant properties may affect its pathogenesis, with ALCL only occurring in women with textured implants.

Development and biological evaluation of Ti6Al7Nb scaffold implants coated with gentamycin-saturated bacterial cellulose biomaterial

Herein we present an innovative method of coating the surface of Titanium-Aluminium-Niobium bone scaffold implants with bacterial cellulose (BC) polymer saturated with antibiotic. Customized Ti6Al7Nb scaffolds manufactured using Selective Laser Melting were immersed in a suspension of Komagataeibacter xylinus bacteria which displays an ability to produce a 3-dimensional structure of bio-cellulose polymer. The process of complete implant coating with BC took on average 7 days. Subsequently, the BC matrix was cleansed by means of alkaline lysis and saturated with gentamycin. Scanning electron microscopy revealed that BC adheres and penetrates into the implant scaffold structure. The viability and development of the cellular layer on BC micro-structure were visualized by means of confocal microscopy. The BC-coated implants displayed a significantly lower cytotoxicity against osteoblast and fibroblast cell cultures in vitro in comparison to non-coated implants. It was also noted that gentamycin released from BC-coated implants inhibited the growth of Staphylococcus aureus cultures in vitro, confirming the suitability of such implant modification for preventing hostile microbial colonization. As demonstrated using digital microscopy, the procedure used for implant coating and BC chemical cleansing did not flaw the biomaterial structure. The results presented herein are of high translational value with regard to future use of customized, BC-coated and antibiotic-saturated implants designed for use in orthopedic applications to speed up recovery and to reduce the risk of musculoskeletal infections.

Antibacterial, Preservative, and Mutagenic Potential of Copaifera spp. Oleoresins Against Causative Agents of Foodborne Diseases

Foodborne diseases (FBDs) are a serious public health concern worldwide. In this scenario, preservatives based on natural products, especially plants, have attracted researchers' attention because they offer potential antimicrobial action as well as reduced health impact. The genus Copaifera spp., which is native of tropical South America and West Africa, contains several species for which pharmacological activities, including antibacterial effects, have been described. On the basis of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antibiofilm activity (inhibition and eradication), preservative capacity, and Ames test, we evaluated the antibacterial, preservative, and mutagenic potential of Copaifera spp. oleoresins against the causative agents of FBDs. The Copaifera duckei, Copaifera reticulata, Copaifera paupera, and Copaifera pubiflora oleoresins displayed promising MIC/MBC values-from 12.5 to 100 μg/mL-against Staphylococcus aureus (American Type Culture Collection [ATCC] 29213), Listeria monocytogenes (ATCC 15313), and Bacillus cereus (ATCC 14579). C. duckei, C. reticulata, C. paupera, and C. pubiflora oleoresin concentrations ranging from 25 to 200 μg/mL and from 100 to 400 μg/mL inhibited biofilm formation and eradicated biofilms, respectively. The oleoresins did not exert mutagenic effects and had superior food preservative action to sodium benzoate (positive control). In conclusion, Copaifera oleoresins exhibit potential antibacterial activity and are not mutagenic, which makes them a promising source to develop novel natural food preservatives to inhibit foodborne pathogens.

What Is the Role of Diagnostic and Therapeutic Sonication in Periprosthetic Joint Infections?

BACKGROUND

Periprosthetic joint infection (PJI) is one of the most dreaded complications in joint replacement surgery. Diagnosis and treatment can be difficult and biofilms are of major concern due to their low susceptibility toward antibiotics.

METHODS

This review focuses on the use of sonication as an evolving diagnostic and adjunct treatment modality in the context of PJI. Therapeutic application of sonication is discussed separately for its (i) direct action on bacteria, (ii) synergistic effects with antibiotics, and (iii) effects on release of antibiotics from bone cement.

RESULTS

Used as a diagnostic tool, sonication shows promising results with respect to sensitivity and specificity when compared to conventional methods, notably after previous administration of antibiotics. As an adjunct treatment modality, the chemical, physical, and mechanical effects of sonication are primarily driven by cavitation and recognized as the main cause for bactericidal effects but the exact underlying mechanisms have not been identified yet. Sonication alone does not have the ability to completely eradicate biofilms but synergistic effects when used in conjunction with antibiotics have been reported. There is also evidence for enhanced antibiotic release from bone cement.

CONCLUSION

Sonication is as an evolving modality in the context of PJIs. As a diagnostic tool, it has not been introduced in routine clinical practice and sonication as a treatment modality in PJIs is still in an experimental stage. Factors such as frequency, pressure, chemical activity, intensity, and exposure time need to be evaluated for optimal application of sonication and may also improve study comparison.

Antibacterial Effect of Copaifera duckei Dwyer Oleoresin and Its Main Diterpenes against Oral Pathogens and Their Cytotoxic Effect

This study evaluates the antibacterial activity of the Copaifera duckei Dwyer oleoresin and two isolated compounds [eperu-8(20)-15,18-dioic acid and polyalthic acid] against bacteria involved in primary endodontic infections and dental caries and assesses the cytotoxic effect of these substances against a normal cell line. MIC and MBC assays pointed out the most promising metabolites for further studies on bactericidal kinetics, antibiofilm activity, and synergistic antibacterial action. The oleoresin and polyalthic acid but not eperu-8(20)-15,18-dioic provided encouraging MIC and MBC results at concentrations lower than 100 μg mL⁻¹. The oleoresin and polyalthic acid activities depended on the evaluated strain. A bactericidal effect on Lactobacillus casei (ATCC 11578 and clinical isolate) emerged before 8 h of incubation. For all the tested bacteria, the oleoresin and polyalthic acid inhibited biofilm formation by at least 50%. The oleoresin and polyalthic acid gave the best activity against Actinomyces naeslundii (ATCC 19039) and L. casei (ATCC 11578), respectively. The synergistic assays combining the oleoresin or polyalthic acid with chlorhexidine did not afford interesting results. We examined the cytotoxicity of C. duckei oleoresin, eperu-8(20)-15,18-dioic acid, and polyalthic acid against Chinese hamster lung fibroblasts. The oleoresin and polyalthic acid were cytotoxic at concentrations above 78.1 μg mL⁻¹, whereas eperu-8(20)-15,18-dioic displayed cytotoxicity at concentrations above 312.5 μg mL⁻¹. In conclusion, the oleoresin and polyalthic acid are potential sources of antibacterial agents against bacteria involved in primary endodontic infections and dental caries in both the sessile and the planktonic modes at concentrations that do not cause cytotoxicity.