Biofilms: survival mechanisms of clinically relevant microorganisms

Uncovering the secrets of resistance: An introduction to computational methods in infectious disease research

Antimicrobial resistance (AMR) is a growing global concern with significant implications for infectious disease control and therapeutics development. This chapter presents a comprehensive overview of computational methods in the study of AMR. We explore the prevalence and statistics of AMR, underscoring its alarming impact on public health. The role of AMR in infectious disease outbreaks and its impact on therapeutics development are discussed, emphasizing the need for novel strategies. Resistance mutations are pivotal in AMR, enabling pathogens to evade antimicrobial treatments. We delve into their importance and contribution to the spread of AMR. Experimental methods for quantitatively evaluating resistance mutations are described, along with their limitations. To address these challenges, computational methods provide promising solutions. We highlight the advantages of computational approaches, including rapid analysis of large datasets and prediction of resistance profiles. A comprehensive overview of computational methods for studying AMR is presented, encompassing genomics, proteomics, structural bioinformatics, network analysis, and machine learning algorithms. The strengths and limitations of each method are briefly outlined. Additionally, we introduce ResScan-design, our own computational method, which employs a protein (re)design protocol to identify potential resistance mutations and adaptation signatures in pathogens. Case studies are discussed to showcase the application of ResScan in elucidating hotspot residues, understanding underlying mechanisms, and guiding the design of effective therapies. In conclusion, we emphasize the value of computational methods in understanding and combating AMR. Integration of experimental and computational approaches can expedite the discovery of innovative antimicrobial treatments and mitigate the threat posed by AMR.

Electrogenicity of microbial biofilms of medically relevant microorganisms: potentiometric, amperometric and wireless detection

Since the progression of biofilm formation is related to the success of infection treatment, detecting microbial biofilms is of great interest. Biofilms of Gram-positive Staphylococcus aureus and Streptococcus gordonii bacteria, Gram-negative Pseudomonas aeruginosa and Escherichia coli bacteria, and Candida albicans yeast were examined using potentiometric, amperometric, and wireless readout modes in this study. As a biofilm formed, the open circuit potential (OCP) of biofilm hosting electrode (bioanode) became increasingly negative. Depending on the microorganism, the OCP ranged from -70 to -250 mV. The co-culture generated the most negative OCP (-300 mV vs Ag/AgCl), while the single-species biofilm formed by E. coli developed the least negative (-70 mV). The OCP of a fungal biofilm formed by C. albicans was -100 mV. The difference in electrode currents generated by biofilms was more pronounced. The current density of the S. aureus biofilm was 0.9‧10-7 A cm-2, while the value of the P. aeruginosa biofilm was 1.3‧10-6 A cm-2. Importantly, a biofilm formed by a co-culture of S. aureus and P. aeruginosa had a slightly higher negative OCP value and current density than the most electrogenic P. aeruginosa single-species biofilm. We present evidence that bacteria can share redox mediators found in multi-species biofilms. This synergy, enabling higher current and OCP values of multi-species biofilm hosting electrodes, could be beneficial for electrochemical detection of infectious biofilms in clinics. We demonstrate that the electrogenic biofilm can provide basis to construct novel wireless, chip-free, and battery-free biofilm detection method.

Antimicrobial Activity of Trigonelline Hydrochloride Against Pseudomonas aeruginosa and Its Quorum-Sensing Regulated Molecular Mechanisms on Biofilm Formation and Virulence

Pseudomonas aeruginosa, a vivid biofilm-producing bacterium, is considered a dreadful opportunistic pathogen, and thus, management of biofilm-associated infections due to multidrug resistant strains by traditional drugs currently is of great concern. This study was aimed to assess the impact of trigonelline hydrochloride, a pyridine alkaloid, on P. aeruginosa PAO1, in search of an alternative therapeutant. The effect of trigonelline on colony morphology and motility was studied along with its role on biofilm and expression virulence factors. Trigonelline influenced the colony structure, motility, biofilm architecture, and the production of virulence factors in a dose-dependent manner. Alterations in quorum sending (QS)-regulated gene expression after treatment and molecular docking analysis for certain regulator proteins confirmed its effect on the QS-system network by affecting Las, Rhl, and Pqs signaling pathways and as possible molecular targets. Thus, trigonelline might be considered as a potential chemical lead to manage biofilm-associated pathogenesis or to develop other analogues with enhanced pharmacokinetic actions.

In Vitro Assessment of Bacterial Adhesion and Biofilm Formation on Novel Bioactive, Biodegradable Electrospun Fiber Meshes Intended to Support Tendon Rupture Repair

The surgical repair of a ruptured tendon faces two major problems: specifically increased fibrous adhesion to the surrounding tissue and inferior mechanical properties of the scar tissue compared to the native tissue. Bacterial attachment to implant materials is an additional problem as it might lead to severe infections and impaired recovery. To counteract adhesion formation, two novel implant materials were fabricated by electrospinning, namely, a random fiber mesh containing hyaluronic acid (HA) and poly(ethylene oxide) (PEO) in a ratio of 1:1 (HA/PEO 1:1) and 1:4 (HA/PEO 1:4), respectively. Electrospun DegraPol (DP) treated with silver nanoparticles (DP-Ag) was developed to counteract the bacterial attachment. The three novel materials were compared to the previously described DP and DP with incorporated insulin-like growth factor-1 (DP-IGF-1), two implant materials that were also designed to improve tendon repair. To test whether the materials are prone to bacterial adhesion and biofilm formation, we assessed 10 strains of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Enterococcus faecalis, known for causing nosocomial infections. Fiber diameter, pore size, and water contact angle, reflecting different degrees of hydrophobicity, were used to characterize all materials. Generally, we observed higher biofilm formation on the more hydrophobic DP as compared to the more hydrophilic DP-IGF-1 and a trend toward reduced biofilm formation for DP treated with silver nanoparticles. For the two HA/PEO implants, a similar biofilm formation was observed. All tested materials were highly prone to bacterial adherence and biofilm formation, pointing toward the need of further material development, including the optimized incorporation of antibacterial agents such as silver nanoparticles or antibiotics.

Clinical and microbiological features of host-bacterial interplay in chronic venous ulcers versus other types of chronic skin ulcers

Introduction

Chronic venous ulcers of the lower limbs develop in the context of advanced venous disease and have a significant impact on the patient's quality of life, being associated with depression and worrisome suicide rates, as well as with an economic burden caused by increased medical care costs and high epidemiological risks of healthcare associated infections and emergence of strains resistant to multiple classes of antibiotics and/ or antiseptics. Although numerous studies have investigated the composition of the chronic wounds microbiome, either by culture-dependent or independent methods, there are no data on the association between virulence and resistance profiles of strains isolated from venous ulcers and the clinical picture of this pathology. The elucidation of pathogenic mechanisms, at both phenotypic and molecular level, is crucial in the fight against these important human microbial agents, in order to develop novel biomarkers and discover new therapeutic targets.

Methods

In this study we aimed to characterize the phenotypic virulence profiles (including the ability to develop biofilms) of microorganisms isolated from chronic skin wounds and to correlate them with the clinical symptomatology. Considering the high incidence of Staphylococcus aureus infections in chronic ulcers, but also the ability of this species to develop multi-drug resistance, we performed an more in-depth study of the phenotypic and genotypic virulence profiles of methicillin-resistant Staphylococcus.

Results

The study revealed important differences regarding the clinical evolution and virulence profiles of microorganisms isolated from lower limb wounds, as well as between patients diagnosed with chronic venous ulcers and those with lesions of different etiology.

Progress of stimulus responsive nanosystems for targeting treatment of bacterial infectious diseases

In recent decades, due to insufficient concentration at the lesion site, low bioavailability and increasingly serious resistance, antibiotics have become less and less dominant in the treatment of bacterial infectious diseases. It promotes the development of efficient drug delivery systems, and is expected to achieve high absorption, targeted drug release and satisfactory therapy effects. A variety of endogenous stimulation-responsive nanosystems have been constructed by using special infection microenvironments (pH, enzymes, temperature, etc.). In this review, we firstly provide an extensive review of the current research progress in antibiotic treatment dilemmas and drug delivery systems. Then, the mechanism of microenvironment characteristics of bacterial infected lesions was elucidated to provide a strong theoretical basis for bacteria-targeting nanosystems design. In particular, the discussion focuses on the design principles of single-stimulus and dual-stimulus responsive nanosystems, as well as the use of endogenous stimulus-responsive nanosystems to deliver antimicrobial agents to target locations for combating bacterial infectious diseases. Finally, the challenges and prospects of endogenous stimulus-responsive nanosystems were summarized.

Chitosan-based topical formulation integrated with green-synthesized silver nanoparticles utilizing Camellia sinensis leaf extracts: A promising approach for managing infected wounds

This study explores the eco-friendly biosynthesis of silver nanoparticles (AgNPs) utilizing Camellia sinensis leaf extract. We assess their antioxidant and antibacterial properties. Furthermore, we impregnated AgNPs into 2 % chitosan (CHS) gel and assessed their wound-healing potential in Escherichia coli and Staphylococcus aureus infected wounds. Optimized AgNPs demonstrated a mean particle size of 36.90 ± 1.22 nm and a PDI of 0.049 ± 0.001. Green-synthesized AgNPs exhibited enhanced free radical inhibition (IC50: 31.45 μg/mL, 34.01 μg/mL, 27.40 μg/mL) compared to leaf extract (IC50: 52.67 μg/mL, 59.64 μg/mL, 97.50 μg/mL) in DPPH, hydrogen peroxide, and nitric oxide free radical scavenging assays, respectively. The MIC/MBC values of AgNPs against E. coli and S. aureus were 5 ppm/ 7.5 ppm and 10 ppm/ 15 ppm, respectively. Furthermore, our study showed that green-synthesized AgNPs at MIC significantly reduced the biofilm production of E. coli (70.37 %) and S. aureus (67.40 %). The CHS/AgNPs gel exhibited potent wound healing activities, comparable to a commercial cream with the re-epithelialization period of 8.16 ± 0.75. Histological analysis demonstrated enhanced skin regeneration with a thicker epidermal layer, well-defined papillary dermal structure, and organized collagen fibers. In summary, these findings hold promise for addressing bacterial infections, particularly those associated with biofilms-related wound infections.

Genomic and metabolic versatility of Pseudomonas aeruginosa contributes to its inter-kingdom transmission and survival

Pseudomonas aeruginosa is one of the most versatile bacteria with renowned pathogenicity and extensive drug resistance. The diverse habitats of this bacterium include fresh, saline and drainage waters, soil, moist surfaces, taps, showerheads, pipelines, medical implants, nematodes, insects, plants, animals, birds and humans. The arsenal of virulence factors produced by P. aeruginosa includes pyocyanin, rhamnolipids, siderophores, lytic enzymes, toxins and polysaccharides. All these virulent elements coupled with intrinsic, adaptive and acquired antibiotic resistance facilitate persistent colonization and lethal infections in different hosts. To date, treating pulmonary diseases remains complicated due to the chronic secondary infections triggered by hospital-acquired P. aeruginosa. On the contrary, this bacterium can improve plant growth by suppressing phytopathogens and insects. Notably, P. aeruginosa is one of the very few bacteria capable of trans-kingdom transmission and infection. Transfer of P. aeruginosa strains from plant materials to hospital wards, animals to humans, and humans to their pets occurs relatively often. Recently, we have identified that plant-associated P. aeruginosa strains could be pathologically similar to clinical isolates. In this review, we have highlighted the genomic and metabolic factors that facilitate the dominance of P. aeruginosa across different biological kingdoms and the varying roles of this bacterium in plant and human health.

Biofilm-forming ability, antibiotic resistance and phylogeny of Escherichia coli isolated from extra intestinal infections of humans, dogs, and chickens

Escherichia coli (E. coli) causes various infections in humans and animals. The biofilm-forming ability of E. coli has increased antimicrobial resistance and capacity to cause recurrent and chronic infections. This study determined the biofilm-forming ability of E. coli isolated from extraintestinal infections of humans, chickens, and dogs in relation to the phylogroup, type of infection, and antibiotic resistance. Isolates from chickens showed significantly higher biofilm-forming ability compared to those causing urinary tract infections in humans (p = 0.0001). Further, isolates belonging to phylogroup B1 displayed a higher likelihood to form biofilms. Resistance to ciprofloxacin and trimethoprim-sulfamethoxazole was positively correlated with biofilm-forming ability. Harbouring plasmid-mediated quinolone resistance gene, qnrS was also positively correlated with biofilm formation. This study provides insight into factors such as phylogroup and the type of infections that could enhance biofilm formation, as well as genotypic and phenotypic antibiotic resistance that could correlate with the ability to form biofilms.

Type IV pili of Enterobacteriaceae species

Type IV pili (T4Ps) are surface filaments widely distributed among bacteria and archaea. T4Ps are involved in many cellular functions and contribute to virulence in some species of bacteria. Due to the diversity of T4Ps, different properties have been observed for homologous proteins that make up T4Ps in various organisms. In this review, we highlight the essential components of T4Ps, their functions, and similarities to related systems. We emphasize the unique T4Ps of enteric pathogens within the Enterobacteriaceae family, which includes pathogenic strains of Escherichia coli and Salmonella. These include the bundle-forming pilus (BFP) of enteropathogenic E. coli (EPEC), longus (Lng) and colonization factor III (CFA/III) of enterotoxigenic E. coli (ETEC), T4P of Salmonella enterica serovar Typhi, Colonization Factor Citrobacter (CFC) of Citrobacter rodentium, T4P of Yersinia pseudotuberculosis, a ubiquitous T4P that was characterized in enterohemorrhagic E. coli (EHEC), and the R64 plasmid thin pilus. Finally, we highlight areas for further study.

Characterization of the Human Plasma Biofilm Model (hpBIOM) to Identify Potential Therapeutic Targets for Wound Management of Chronic Infections

The treatment of chronic wounds still represents a major challenge in wound management. Recent estimates suggest that 60-80% of chronic wounds are colonized by pathogenic microorganisms, which are strongly considered to have a major inhibiting influence on the healing process. By means of an innovative biofilm model based on human plasma, the time-dependent behavior of various bacterial strains under wound-milieu-like conditions were investigated, and the growth habits of different cocci species were compared. Undescribed fusion events between colonies of MRSA as well as of Staphylococcus epidermidis were detected, which were associated with the remodeling and reorganization of the glycocalyx of the wound tissue. After reaching a maximum colony size, the spreading of individual bacteria was observed. Interestingly, the combination of different cocci species with Pseudomonas aeruginosa in the human plasma biofilm revealed partial synergistic effects in these multispecies organizations. RT-qPCR analyses gave a first impression of the relevant proteins involved in the formation and maturation of biofilms, especially the role of fibrinogen-binding proteins. Knowledge of the maturation and growth behavior of persistent biofilms investigated in a translational human biofilm model reflects a starting point for the development of novel tools for the treatment of chronic wounds.

Bacteria Living in Biofilms in Fluids: Could Chemical Antibiofilm Pretreatment of Culture Represent a Paradigm Shift in Diagnostics?

Biofilms are multicellular aggregates of bacteria immersed in an extracellular matrix that forms on various surfaces, including biological tissues and artificial surfaces. However, more and more reports point out the fact that even biological fluids and semifluid, such as synovial liquid, blood, urine, or mucus and feces, harbor "non-attached" biofilm aggregates of bacteria, which represent a significant phenomenon with critical clinical implications that remain to be fully investigated. In particular, biofilm aggregates in biological fluid samples have been shown to play a relevant role in bacterial count and in the overall accuracy of microbiological diagnosis. In line with these observations, the introduction in the clinical setting of fluid sample pretreatment with an antibiofilm chemical compound called dithiothreitol (DTT), which is able to dislodge microorganisms from their intercellular matrix without killing them, would effectively improve the microbiological yield and increase the sensitivity of cultural examination, compared to the current microbiological techniques. While other ongoing research continues to unveil the complexity of biofilm formation in biological fluids and its impact on infection pathogenesis and diagnosis, we here hypothesize that the routine use of a chemical antibiofilm pretreatment of fluid and semi-solid samples may lead to a paradigm shift in the microbiological approach to the diagnosis of biofilm-related infections and should be further investigated and eventually implemented in the clinical setting.

Efficacy and Experience of Bacteriophages in Biofilm-Related Infections

Bacterial infection has always accompanied human beings, causing suffering and death while also contributing to the advancement of medical science. However, the treatment of infections has become more complex in recent times. The increasing resistance of bacterial strains to antibiotics has diminished the effectiveness of the therapeutic arsenal, making it less likely to find the appropriate empiric antibiotic option. Additionally, the development and persistence of bacterial biofilms have become more prevalent, attributed to the greater use of invasive devices that facilitate biofilm formation and the enhanced survival of chronic infection models where biofilm plays a crucial role. Bacteria within biofilms are less susceptible to antibiotics due to physical, chemical, and genetic factors. Bacteriophages, as biological weapons, can overcome both antimicrobial resistance and biofilm protection. In this review, we will analyze the scientific progress achieved in vitro to justify their clinical application. In the absence of scientific evidence, we will compile publications of clinical cases where phages have been used to treat infections related to biofilm. The scientific basis obtained in vitro and the success rate and safety observed in clinical practice should motivate the medical community to conduct clinical trials establishing a protocol for the proper use of bacteriophages.

An Overview of Biofilm-Associated Infections and the Role of Phytochemicals and Nanomaterials in Their Control and Prevention

Biofilm formation is considered one of the primary virulence mechanisms in Gram-positive and Gram-negative pathogenic species, particularly those responsible for chronic infections and promoting bacterial survival within the host. In recent years, there has been a growing interest in discovering new compounds capable of inhibiting biofilm formation. This is considered a promising antivirulence strategy that could potentially overcome antibiotic resistance issues. Effective antibiofilm agents should possess distinctive properties. They should be structurally unique, enable easy entry into cells, influence quorum sensing signaling, and synergize with other antibacterial agents. Many of these properties are found in both natural systems that are isolated from plants and in synthetic systems like nanoparticles and nanocomposites. In this review, we discuss the clinical nature of biofilm-associated infections and some of the mechanisms associated with their antibiotic tolerance. We focus on the advantages and efficacy of various natural and synthetic compounds as a new therapeutic approach to control bacterial biofilms and address multidrug resistance in bacteria.

Induction of antimicrobial, antioxidant metabolites production by co-cultivation of two red-sea-sponge-associated Aspergillus sp. CO2 and Bacillus sp. COBZ21

The growing spread of infectious diseases has become a potential global health threat to human beings. According to WHO reports, in this study, we investigated the impact of co-cultivating the isolated endophytic fungus Aspergillus sp. CO2 and Bacillus sp. COBZ21 as a method to stimulate the production of natural bioactive substances. (GC/MS)-based metabolomics profiling of two sponge-associated microbes, Aspergillus sp. CO2 and Bacillus sp. COBZ21, revealed that the co-culture of these two isolates induced the accumulation of metabolites that were not traced in their axenic cultures. By detection of different activities of extracts of Bacillus sp. COBZ21 and Aspergillus sp. CO2 and coculture between Bacillus sp. COBZ21 and Aspergillus sp. CO2. It was noted that the coculture strategy was the reason for a notable increase in some different activities, such as the antimicrobial activity, which showed potent activity against Escherichia coli ATCC 25,922, Staphylococcus aureus NRRLB-767, and Candida albicans ATCC 10,231. The antibiofilm activity showed significant biofilm inhibitory activity toward Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 10,145, and Staph aureus NRRLB-767, with activity up to 53.66, 71.17, and 47.89%, while it showed low activity against E. coli ATCC 25,922, while the antioxidant activity based on the DPPH assay showed maximum activity (75.25%). GC-MS investigations revealed the presence of variable chemical constituents belonging to different chemical categories, which reflected their chemical diversity. The main components are (+-) cis-Deethylburnamine (2.66%), Bis(3,6,9,12-tetraoxapentaethylene) crowno-N,N,N',N'-tetra methylpphanediamine (2.48%), and 11-phenyl-2,4,6,8-tetra(2-thienyl)-11-aza-5,13-dithiaeteracyclo[7.3.0.1(2,8)0.0(3,7)] trideca-3,6-diene-10,12,13-trione (3.13%), respectively, for Bacillus sp. axenic culture, Aspergillus sp. CO2, Aspergillus sp. CO2, and Bacillus sp. COBZ21 coculture. By studying the ADME-related physicochemical properties of coculture extract, the compound showed log Po/w values above 5 (8.82). The solubility of the substance was moderate. In order to provide a comprehensive definition of medicinal chemistry and leadlikness, it is important to note that the latter did not meet the criteria outlined in the rule of three (RO3). The toxicity prediction of the coculture extract was performed using the ProTox II web server, which showed that the selected compound has no pronounced toxicity.

Do Microorganisms in Bathing Water in Guadeloupe (French West Indies) Have Resistance Genes?

Waterborne faecal contamination is a major public health concern. The main objectives of this study were to investigate faecal contamination and Escherichia coli (E. coli) antibiotic resistance in recreational fresh water from Guadeloupe and to characterise the microbiome and resistome composition in biofilms from submerged rocks. Significant faecal contamination was observed at 14 freshwater sites. E. coli predominated (62%), followed by Enterobacter cloacae (11%) and Acinetobacter spp. (11%). Of 152 E. coli isolated, none produced extended-spectrum beta-lactamases (ESBLs), but 7% showed resistance to streptomycin and 4% to tetracycline. Biofilm resistome analysis revealed clinically significant antibiotic-resistance genes (ARGs), including those coding for resistance to sulfonamides (sul1), carbapenems (blaKPC), and third-generation cephalosporins (blaCTX-M). Mobile genetic elements (MGEs) (intI1, intI2, intI3) linked to resistance to aminoglycosides, beta-lactams, tetracycline, as well as heavy metal resistance determinants (copA, cusF, czcA, merA) conferring resistance to copper, silver, cadmium, and mercury were also detected. Diverse bacterial phyla were found in biofilm samples, of which Proteobacteria, Bacteroidetes, Planctonomycetes, and Cyanobacteria were predominant. Despite the frequent presence of E. coli exceeding regulatory standards, the low levels of antibiotic-resistant bacteria in freshwater and of ARGs and MGEs in associated biofilms suggest limited antibiotic resistance in Guadeloupean recreational waters.

The role of human extracellular matrix proteins in defining Staphylococcus aureus biofilm infections

Twenty to forty one percent of the world's population is either transiently or permanently colonized by the Gram-positive bacterium, Staphylococcus aureus. In 2017, the CDC designated methicillin-resistant S. aureus (MRSA) as a serious threat, reporting ∼300 000 cases of MRSA-associated hospitalizations annually, resulting in over 19 000 deaths, surpassing that of HIV in the USA. S. aureus is a proficient biofilm-forming organism that rapidly acquires resistance to antibiotics, most commonly methicillin (MRSA). This review focuses on a large group of (>30) S. aureus adhesins, either surface-associated or secreted that are designed to specifically bind to 15 or more of the proteins that form key components of the human extracellular matrix (hECM). Importantly, this includes hECM proteins that are pivotal to the homeostasis of almost every tissue environment [collagen (skin), proteoglycans (lung), hemoglobin (blood), elastin, laminin, fibrinogen, fibronectin, and fibrin (multiple organs)]. These adhesins offer S. aureus the potential to establish an infection in every sterile tissue niche. These infections often endure repeated immune onslaught, developing into chronic, biofilm-associated conditions that are tolerant to ∼1000 times the clinically prescribed dose of antibiotics. Depending on the infection and the immune response, this allows S. aureus to seamlessly transition from colonizer to pathogen by subtly manipulating the host against itself while providing the time and stealth that it requires to establish and persist as a biofilm. This is a comprehensive discussion of the interaction between S. aureus biofilms and the hECM. We provide particular focus on the role of these interactions in pathogenesis and, consequently, the clinical implications for the prevention and treatment of S. aureus biofilm infections.

The Binding of Pseudomonas aeruginosa to Cystic Fibrosis Bronchial Epithelial Model Cells Alters the Composition of the Exosomes They Produce Compared to Healthy Control Cells

Cystic fibrosis (CF) is a genetic disease that causes dehydration of the surface of the airways, increasing lung infections, most frequently caused by Pseudomonas aeruginosa. Exosomes are nanovesicles released by cells that play an essential role in intercellular communication, although their role during bacterial infections is not well understood. In this article, we analyze the alterations in exosomes produced by healthy bronchial epithelial and cystic fibrosis cell lines caused by the interaction with P. aeruginosa. The proteomic study detected alterations in 30% of the species analyzed. In healthy cells, they mainly involve proteins related to the extracellular matrix, cytoskeleton, and various catabolic enzymes. In CF, proteins related to the cytoskeleton and matrix, in addition to the proteasome. These differences could be related to the inflammatory response. A study of miRNAs detected alterations in 18% of the species analyzed. The prediction of their potential biological targets identified 7149 genes, regulated by up to 7 different miRNAs. The identification of their functions showed that they preferentially affected molecules involved in binding and catalytic activities, although with differences between cell types. In conclusion, this study shows differences in exosomes between CF and healthy cells that could be involved in the response to infection.

Shifting from Ammonium to Phosphonium Salts: A Promising Strategy to Develop Next-Generation Weapons against Biofilms

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics' ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria.

Investigating the effects of ultrafine bubbles on bacterial growth

Several previous studies have considered ultrafine bubbles as a potential research target because their properties can be applied in many different research areas. In particular, the interaction between UFBs and microorganisms has always been one of the aspects that receives much attention due to the high difficulty in controlling a living system. The properties of UFBs, as mobile air-water interfaces, are greatly determined by their gas cores which play a critical role in regulating microbial growth. This study aims to investigate the effects of ultrafine bubbles on bacterial growth. Two well-studied organisms were chosen as models - Escherichia coli and Staphylococcus aureus. Their growing behavior was examined based on the growth rate, phenotype and biomass. Three types of Luria-Bertani cultures were tested, including a standard culture containing distilled water, an air ultrafine bubble culture, and a hydrogen ultrafine bubble culture. The UFBs were generated via ultrasonic cavitation and stabilized by 50 μM SDS, which was proven to have negligible effects on bacterial growth. By comparing among the three cultivation conditions, the bacterial growth rates were observed to be the highest in exposure to HUFBs. The results also signified that UFBs had an enhancement on cell proliferation. On the other hand, while proposing an increase in cell density, bacteria cultured in HUFB media have their sizes decreased uniformly and significantly (p-value < 0.05). This study confirmed that bacterial growth was promoted by UFBs; and better effects recorded were due to the HUFB present in the culture media. However, the average morphological size of bacteria was in negative correlation with their population size.

Screening of antibiogram, virulence factors, and biofilm production of Staphylococcus aureus and the bio-control role of some probiotics as alternative antibiotics

Background

Food safety is a serious challenge in the face of increasing population and diminishing resources. Staphylococcus aureus is a critical foodborne pathogen characterized by its capability to secret a diverse range of heat-resistant enterotoxins. Antibiotic usage in dairy herds resulted in the occurrence of antimicrobial resistance (AMR) patterns among bacterial species, which were consequently transmitted to humans via dairy products. Lactic acid bacteria (LAB) produce bacteriocins, which provide an excellent source of natural antimicrobials with the further advantage of being environmentally friendly and safe.

Aim

Detection of multidrug resistance (MDR) S. aureus isolates in concerned samples, molecular characteristics, biofilm production, and the inhibitory role of LAB against it.

Methods

Random samples of raw milk and other dairy products were analyzed for S. aureus isolation. Phenotypic and genotypic assessment of AMR was performed, in addition to detection of classical enterotoxin genes of S. aureus. Finally, evaluation of the antimicrobial action of some Lactobacillus strains against S. aureus.

Results

Incidence rates of presumptive S. aureus in raw milk, Kariesh cheese, and yogurt samples were 50%, 40%, and 60%, respectively. The highest resistance of S. aureus was to Kanamycin (100%) and Nalidixic acid (89.3%), respectively. (78.66%) of S. aureus were MDR. 11.1% of S. aureus carried mecA gene. In concern with enterotoxins genes, PCR showed that examined isolates harbored sea with a percentage of (22.2%), while sed was found in (11.1%) of isolates. Regarding biofilm production, (88.88%) of S. aureus were biofilm producers. Finally, agar well diffusion showed that Lactobacillus acidophilus had the strongest antimicrobial action against S. aureus with inhibition zone diameter ranging from 18 to 22 mm.

Conclusion

There is a widespread prevalence of MDR S. aureus in raw milk and dairy products. Production of staphylococcal enterotoxins, as well as biofilm production are responsible for public health risks. Therefore, installing proper hygienic routines and harsh food safety policies at food chain levels is substantial.

Antimicrobial Tolerance in Cross-Kingdom Dual-Species Biofilms Formed by Fungi and Bacteria

Candida albicans, the most common pathogenic fungus, can form biofilms on the surface of medical devices and often causes bloodstream infections. Biofilms have a complex structure composed of microorganisms and a surrounding extracellular matrix. Biofilms are difficult to treat because they are resistant to antifungal drugs and the host environment. Nearly one in four patients with candidemia have a polymicrobial infection. These polymicrobial biofilms, especially those comprising cross-kingdom species of fungi and bacteria, can lead to long hospital stays and high mortality rates. This review outlines the unique interactions of dual-species biofilms with Candida albicans and the clinically important bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli.

Efficacy of Lysostaphin functionalized silicon catheter for the prevention of Staphylococcus aureus biofilm

Staphylococcus aureus readily forms biofilms on tissue and indwelling catheter surfaces. These biofilms are resistant to antibiotics. Consequently, effective prevention and treatment strategies against staphylococcal biofilms are actively being pursued over the past two decades. One of the proposed strategies involve the incorporation of antibiotics and antiseptics into catheters, however, a persistent concern regarding the possible emergence of antimicrobial resistance is associated with these medical devices. In this study, we developed two types of silicone catheters: one with Lysostaphin (Lst) adsorbed onto the surface, and the other with Lst functionalized on the surface. To confirm the presence of Lst protein on the catheter surface, we conducted FTIR-ATR and SEM-EDS analysis. Both catheters exhibited hemocompatibility, biocompatibility, and demonstrated antimicrobial and biofilm prevention activities against both methicillin-sensitive and resistant strains of S. aureus. Furthermore, the silicone catheters that were surface-functionalized with Lst showed substantially better and more persistent anti-biofilm effects when compared to the catheters where Lst was surface-adsorbed, both under in vitro static and flow conditions, as well as in vivo in BALB/c mice. These results indicate that surface-functionalized Lst catheters have the potential to serve as a promising new medical device for preventing S. aureus biofilm infections in humans.

Sucralfate Prevents Pin Site Infections of External Fixators in Open Tibia Fractures

Pin site infections are the main complication of external fixators. The most common pathogens are Staphylococcus epidermidis and Staphylococcus aureus. The incidence of pin site infections ranges from 2% to 30%. Until now, no satisfactory prevention strategy exists. Therefore, we performed this study to assess the effect of a sucralfate gel 25% applied around the pins of external fixation systems in trauma patients with open tibia fractures. We prospectively studied two groups of patients with open tibia fractures treated with external fixators. In group A patients, pin site care was performed with the use of normal saline and plain dressings once a day. In group B patients, pin site care was performed with the use of sucralfate gel 25%. The incidence of pin site infections was 33.33% for patients of group A and 16.67% for patients of group B. Patients of group B showed significantly lower rate of pin site infections compared to patients of group A (p-value = 0.032). No patient experienced any complications related to the local application of the drug. Sucralfate significantly prevents pin site infections of external fixators in open tibia fractures. Therefore, it can be used as a preventive antimicrobial agent for pin site infections in patients with external fixators.

Effect of Salicylic Acid on the gene expression of FnbA and FnbB genes in Staphylococcus hominis

BACKGROUND

Staphylococcus hominis is an opportunistic pathogen that expresses surface proteins, which are adhesive proteins that play a major role in biofilm formation. Biofilm is a protective layer that provides S. hominis bacteria with greater antibiotic resistance and promotes its adherence to biomedical surfaces, facilitating its entry into the bloodstream.

OBJECTIVE

This research aimed to investigate the activity of Salicylic Acid (SA) and its effect on the gene expression of biofilm genes (FnbA and FnbB genes).

METHODS

A total of 150 blood specimens were collected from patients. The specimens were cultured in broth media of the BacT/ALERT® system and subcultured on blood and chocolate agar. Bacteria were detected using the VITEK2 system. FnbA and FnbB genes were detected using PCR. The broth microdilution method performed the minimum inhibitory concentration (MIC) of Salicylic acid (SA) on S. hominis isolates with both genes. Detection of the gene expression levels of FnbA and FnbB genes was assessed using Real-Time PCR(RT-PCR).

RESULTS

The results showed that out of the 150 specimens collected, 35 were S. hominis. The detection of S. hominis bacteria was performed by PCR amplification of two genes FnbA and FnbB and showed 100% and 17.14% of isolates were positive for genes FnbA and FnbB, respectively. The expression of FnbA and FnbB genes was decreased in samples treated with SA compared with untreated ones.

CONCLUSION

In conclusion, there is a significant impact of SA on the prevention of biofilm formation of S. hominis through the suppression of gene expression, specifically FnbA and FnbB. This could enhance susceptibility to antimicrobial treatments. However, more research is required to determine whether SA leads to the selection of resistant bacteria.

Stress in the microbiome-immune crosstalk

The gut microbiota exerts a mutualistic interaction with the host in a fragile ecosystem and the host intestinal, neural, and immune cells. Perturbations of the gastrointestinal track composition after stress have profound consequences on the central nervous system and the immune system. Reciprocally, brain signals after stress affect the gut microbiota highlighting the bidirectional communication between the brain and the gut. Here, we focus on the potential role of inflammation in mediating stress-induced gut-brain changes and discuss the impact of several immune cells and inflammatory molecules of the gut-brain dialogue after stress. Understanding the impact of microbial changes on the immune system after stress might provide new avenues for therapy.

Antibacterial properties and abrasion-stability: Development of a novel silver-compound material for orthodontic bracket application

PURPOSE

Bacteria-induced white spot lesions are a common side effect of modern orthodontic treatment. Therefore, there is a need for novel orthodontic bracket materials with antibacterial properties that also resist long-term abrasion. The aim of this study was to investigate the abrasion-stable antibacterial properties of a newly developed, thoroughly silver-infiltrated material for orthodontic bracket application in an in situ experiment.

METHODS

To generate the novel material, silver was vacuum-infiltrated into a sintered porous tungsten matrix. A tooth brushing simulation machine was used to perform abrasion equal to 2 years of tooth brushing. The material was characterized by energy dispersive X‑ray (EDX) analysis and roughness measurement. To test for antibacterial properties in situ, individual occlusal splints equipped with specimens were worn intraorally by 12 periodontal healthy patients for 48 h. After fluorescence staining, the quantitative biofilm volume and live/dead distribution of the initial biofilm formation were analyzed by confocal laser scanning microscopy (CLSM).

RESULTS

Silver was infiltrated homogeneously throughout the tungsten matrix. Toothbrush abrasion only slightly reduced the material's thickness similar to conventional stainless steel bracket material and did not alter surface roughness. The new silver-modified material showed significantly reduced biofilm accumulation in situ. The effect was maintained even after abrasion.

CONCLUSION

A promising, novel silver-infiltrated abrasion-stable material for use as orthodontic brackets, which also exhibit strong antibacterial properties on in situ grown oral biofilms, was developed. The strong antibacterial properties were maintained even after surface abrasion simulated with long-term toothbrushing.

Different concentrations of vancomycin with gentamicin loaded PMMA to inhibit biofilm formation of Staphylococcus aureus and their implications

BACKGROUND

This study aimed to evaluate different concentrations of vancomycin and/or gentamicin loaded polymethylmethacrylate (PMMA) against biofilm formation of Staphylococcus aureus.

METHODS

Biofilm production of S. aureus in PMMA loaded with different concentrations of vancomycin and gentamicin were evaluated by quantitative analysis of biofilm cells, scanning electronic microscopy, viability assay, Fourier transform infrared spectroscopy, and checkerboard. Statistical analysis was performed by Mann Whitney test. The difference in colony forming units per mL was significant when p < 0.05.

RESULTS

All loaded PMMA presented a reduction in the number of colony forming units per mL (p < 0.05). The gentamicin-loaded PMMA could inhibits the grown of sessile cells (p < 0.05), where the group vancomycin 4 g + gentamicin 500 mg presented a better result. The Fourier transform infrared spectra showed no significant differences, and checkerboard of vancomycin and gentamicin showed synergism.

CONCLUSION

Effects against adherence and bacterial development in PMMA loaded with antibiotics were mainly seen in the group vancomycin 4 g + gentamicin 500 mg, and synergic effect can be applied in antibiotic-loaded cement.

Formation and Analysis of Biofilms in Vivo

Establishing a biofilm infection model in vivo allows a better understanding of the underlying infection mechanisms of bacteria. Here we describe a method for constructing an in vivo biofilm model of Streptococcus suis. The animal modeled is a piglet, which is the natural reservoir of S. suis, and the mode of clinical infection is simulated by intranasal inoculation of S. suis. This model is in line with clinical practice, easy to operate, and has good repeated stability.

Vulnerabilities of Prostate Glandular Concretions Considered as Artefacts: A Cross-sectional Biopsy Slide Study

Objective

There is no clear consensus regarding the contour of prostatic glandular intraluminal concretions. This study enlightens the rational approach toward deciphering the true nature of these concretions and evaluates their role in normal routine histology of the prostate gland.

Methods

Fifty hematoxylin and eosin slides that were prepared from procured transrectal biopsy specimens of normal prostate glands from asymptomatic patients suspected of having a prostatic disease but later found to be normal were retrospectively observed for the staining, contour, and positioning of the aggregated masses or concretions within their prostatic lumina and were then compared with the blood prostate specific antigen (PSA) levels.

Results

Although significant associations highlighting the utility of these masses in presumed pathological states of the gland were drawn by comparing their staining parameters and contours to those of their respective PSA levels, their interluminal contour variations and vivid staining appearances did not necessarily rule out the possibility of some of them being artefacts, provided they were assessed in totality with the surrounding acini. Intensely eosinophilic concretions were found in patients with a high mean age and those with high PSA levels.

Conclusions

Prostatic intraluminal masses that were rounded tended to indicate pathological shifts within the gland; however, the possibility of them changing to artefacts during slide preparations could not be ruled out.

Recent Progress in antibacterial hydrogel coatings for targeting biofilm to prevent orthopedic implant-associated infections

The application of orthopedic implants for bone tissue reconstruction and functional restoration is crucial for patients with severe bone fractures and defects. However, the abiotic nature of orthopedic implants allows bacterial adhesion and colonization, leading to the formation of bacterial biofilms on the implant surface. This can result in implant failure and severe complications such as osteomyelitis and septic arthritis. The emergence of antibiotic-resistant bacteria and the limited efficacy of drugs against biofilms have increased the risk of orthopedic implant-associated infections (OIAI), necessitating the development of alternative therapeutics. In this regard, antibacterial hydrogels based on bacteria repelling, contact killing, drug delivery, or external assistance strategies have been extensively investigated for coating orthopedic implants through surface modification, offering a promising approach to target biofilm formation and prevent OIAI. This review provides an overview of recent advancements in the application of antibacterial hydrogel coatings for preventing OIAI by targeting biofilm formation. The topics covered include: (1) the mechanisms underlying OIAI occurrence and the role of biofilms in exacerbating OIAI development; (2) current strategies to impart anti-biofilm properties to hydrogel coatings and the mechanisms involved in treating OIAI. This article aims to summarize the progress in antibacterial hydrogel coatings for OIAI prevention, providing valuable insights and facilitating the development of prognostic markers for the design of effective antibacterial orthopedic implants.

Assessment of biofilm, enzyme production and antibiotic susceptibility of bacteria from milk pre- and post-pasteurization pipelines in Algeria

Bacterial biofilm is a major concern of dairy industry due to its association with milk contamination and its derived products. Algerian pasteurized milk shelf-life does not exceed one day, which may reflect the high level of contamination of this product and presence of extracellular enzymes such as lipases and proteases. This work aimed to investigate the microbial biodiversity in milk-processing surfaces of a dairy plant in Algeria. Therefore, stainless steel cylinders were placed in piping system of the dairy system before and after pasteurization of the milk, being removed after 7 days, for biofilm maturation and microorganism isolation and identification by mass spectrometry. Fifty-nine Gram-positive isolates were identified, namely Bacillus altitudinis, Bacillus cereus, Bacillus pumilus, Bacillus subtilis, Bacillus weithenstephanensis, Enterococcus casseliflavus, Enterococcus faecium, and Staphylococcus epidermidis. In addition, twenty-four Gram-negative isolates were identified, namely Acinetobacter schindleri Enterobacter cloacae, Enterobacter xiangfangensis, Leclercia adecarboxylata, and Raoultella ornithinolytica. Bacterial isolates showed ability for production of extracellular enzymes, being 49 % capable of both proteolytic and lipolytic activities. Milk isolates were tested for the ability to form biofilms on stainless steel. The cell numbers recovered on plate count agar plates from stainless steel biofilms ranged from 3.52 to 6.92 log10 CFU/cm2, being the maximum number detected for Enterococcus casseliflavus. Bacterial isolates showed intermediate and/or resistant profiles to multiple antibiotics. Resistance to amoxicillin, cefoxitin and/or erythromycin was commonly found among the bacterial isolates.

Development and validation of a large animal ovine model for implant-associated spine infection using biofilm based inocula

Postoperative implant-associated spine infection remains poorly understood. Currently there is no large animal model using biofilm as initial inocula to study this challenging clinical entity. The purpose of the present study was to develop a sheep model for implant-associated spine infection using clinically relevant biofilm inocula and to assess the in vivo utility of methylene blue (MB) for visualizing infected tissues and guiding debridement. This 28-day study used five adult female Rambouillet sheep, each with two non-contiguous surgical sites- in the lumbar and thoracic regions- comprising randomized positive and negative infection control sites. A standard mini-open approach to the spine was performed to place sterile pedicle screws and Staphylococcus aureus biofilm-covered (positive control), or sterile (negative control) spinal fusion rods. Surgical site bioburden was quantified at the terminal procedure. Negative and positive control sites were stained with MB and staining intensity quantified from photographs. Specimens were analyzed with x-ray, micro-CT and histologically. Inoculation rods contained ∼10.44 log10 colony forming units per rod (CFU/rod). Biofilm inocula persisted on positive-control rod explants with ∼6.16 log10 CFU/rod. There was ∼6.35 log10 CFU/g of tissue in the positive controls versus no identifiable bioburden in the negative controls. Positive controls displayed hallmarks of deep spine infection and osteomyelitis, with robust local tissue response, bone resorption, and demineralization. MB staining was more intense in infected, positive control sites. This work presents an animal-efficient sheep model displaying clinically relevant implant-associated deep spine infection.

Phage-Based Biosanitation Strategies for Minimizing Persistent Salmonella and Campylobacter Bacteria in Poultry

Control strategies to minimize pathogenic bacteria in food animal production are one of the key components in ensuring safer food for consumers. The most significant challenges confronting the food industry, particularly in the major poultry and swine sectors, are antibiotic resistance and resistance to cleaning and disinfection in zoonotic bacteria. In this context, bacteriophages have emerged as a promising tool for zoonotic bacteria control in the food industry, from animals and farm facilities to the final product. Phages are viruses that infect bacteria, with several advantages as a biocontrol agent such as high specificity, self-replication, self-limitation, continuous adaptation, low inherent toxicity and easy isolation. Their development as a biocontrol agent is of particular interest, as it would allow the application of a promising and even necessary "green" technology to combat pathogenic bacteria in the environment. However, bacteriophage applications have limitations, including selecting appropriate phages, legal restrictions, purification, dosage determination and bacterial resistance. Overcoming these limitations is crucial to enhance phage therapy's effectiveness against zoonotic bacteria in poultry. Thus, this review aims to provide a comprehensive view of the phage-biosanitation strategies for minimizing persistent Salmonella and Campylobacter bacteria in poultry.

Restoring Colistin Sensitivity and Combating Biofilm Formation: Synergistic Effects of Colistin and Usnic Acid against Colistin-Resistant Enterobacteriaceae

Colistin (COL), the last line of defense in clinical medicine, is an important therapeutic option against multidrug-resistant Gram-negative bacteria. In this context, the emergence of colistin-resistant (COL-R) bacteria mediated by broad-spectrum efflux pumps, mobile genetic elements, and biofilm formation poses a significant public health concern. In response to this challenge, a novel approach of combining COL with usnic acid (UA) has been proposed in this study. UA is a secondary metabolite derived from lichens and is well-known for its anti-inflammatory properties. This study aimed to investigate the synergistic effects of UA and COL against COL-R Enterobacteriaceae both in vitro and in vivo. The exceptional synergistic antibacterial activity exhibited by the combination of COL and UA was demonstrated by performing a comprehensive set of assays, including the checkerboard assay, time-dependent killing assay, and Live/Dead bacterial cell viability assay. Furthermore, crystal violet staining and scanning electron microscopy assays revealed the inhibitory effect of this combination on the biofilm formation. Mechanistically, the combination of UA and COL exacerbated cell membrane rupture, induced DNA damage, and generated a significant amount of reactive oxygen species, which ultimately resulted in bacterial cell death. In addition, erythrocyte hemolysis and cell viability tests confirmed the biocompatibility of the combination. The evaluation of the COL/UA combination in vivo using Galleria mellonella larvae and a mouse infection model showed a significant improvement in the survival rate of the infected larvae as well as a reduction in the bacterial load in the mouse thigh muscle. These findings, for the first time, provide strong evidence for the potential application of COL/UA as an effective alternative therapeutic option to combat infections caused by COL-R Enterobacteriaceae strains.

Identification and characterization of a Reeler domain containing protein in Procambarus clarkii provides new insights into antibacterial immunity in crustacean

Crayfish, as an invertebrate, relies only on the innate immune system to resist external pathogens. In this study, a molecule containing a single Reeler domain was identified from red swamp crayfish Procambarus clarkii (named as PcReeler). Tissue distribution analysis showed that PcReeler was highly expressed in gills and its expression was induced by bacterial stimulation. Inhibiting the expression of PcReeler by RNA interference led to a significant increase in the bacterial abundance in the gills of crayfish, and a significant increase in the crayfish mortality. Silencing of PcReeler influenced the stability of the microbiota in the gills revealed by 16S rDNA high-throughput sequencing. Recombinant PcReeler showed the ability to bind microbial polysaccharide and bacteria and to inhibit the formation of bacterial biofilms. These results provided direct evidence for the involvement of PcReeler in the antibacterial immune mechanism of P. clarkii.

Biofilm and Hospital-Acquired Infections in Older Adults

Biofilm infections are a serious threat to public health, resistant to traditional treatments and host immune defenses. Biofilm infections are often polymicrobial, related to chronic wounds, medical devices (eg, knee replacements, catheters, tubes, contact lenses, or prosthetic valves) and chronic recurring diseases. Biofilms are more complex than nonadhered planktonic bacteria and produce a structure that prevents damage to the bacteria within the biofilm structure. The structure provides a hidden route to feed and nurture the bacteria allowing for ongoing spread of the bacteria.

Co-regulation of biofilm formation and antimicrobial resistance in Acinetobacter baumannii: from mechanisms to therapeutic strategies

In recent years, multidrug-resistant Acinetobacter baumannii has emerged globally as a major threat to the healthcare system. It is now listed by the World Health Organization as a priority one for the need of new therapeutic agents. A. baumannii has the capacity to develop robust biofilms on biotic and abiotic surfaces. Biofilm development allows these bacteria to resist various environmental stressors, including antibiotics and lack of nutrients or water, which in turn allows the persistence of A. baumannii in the hospital environment and further outbreaks. Investigation into therapeutic alternatives that will act on both biofilm formation and antimicrobial resistance (AMR) is sorely needed. The aim of the present review is to critically discuss the various mechanisms by which AMR and biofilm formation may be co-regulated in A. baumannii in an attempt to shed light on paths towards novel therapeutic opportunities. After discussing the clinical importance of A. baumannii, this critical review highlights biofilm-formation genes that may be associated with the co-regulation of AMR. Particularly worthy of consideration are genes regulating the quorum sensing system AbaI/AbaR, AbOmpA (OmpA protein), Bap (biofilm-associated protein), the two-component regulatory system BfmRS, the PER-1 β-lactamase, EpsA, and PTK. Finally, this review discusses ongoing experimental therapeutic strategies to fight A. baumannii infections, namely vaccine development, quorum sensing interference, nanoparticles, metal ions, natural products, antimicrobial peptides, and phage therapy. A better understanding of the mechanisms that co-regulate biofilm formation and AMR will help identify new therapeutic targets, as combined approaches may confer synergistic benefits for effective and safer treatments.

The Inhibitory Effects of Amylase and Streptokinase on Minimum Inhibitory Concentration of Antibiotics Used to Treat Gram Negative Bacteria Biofilm Infection on Indwelling Devices

The study evaluated and compared the effect of adding streptokinase and amylase to antibiotics that are already used in clinical practice to treat Gram negative bacteria biofilm infection on indwelling devices on the antibiotics' minimum inhibitory concentration (MIC). 24 h-old biofilms were developed on 96-well plate with eight clinical isolates. MIC of amikacin, cefepime, ceftazidime, colistin, meropenem, and piperacillin-tazobactam, on biofilms were measured before and after the addition of 25 U/ml streptokinase and 25 μg/ml amylase with microplate reader. The addition of streptokinase reduces the MICs of cefepime, ceftazidime, colistin, meropenem from (16, 16, 8, 4 μg/ml) to (8, 1, 1, 0.5 μg/ml) in Escherichia coli (isolate 1). While the addition of amylase reduces the MICs of only cefepime, ceftazidime from (16, 16 μg/ml) to (2, 4 μg/ml) in E. coli (isolate 1). In Pseudomonas aeruginosa (isolate 4), the MICs of amikacin, cefepime, ceftazidime, colistin and meropenem (64, 16, 32, 4, 32 μg/ml) reduced to (2, 1, 0.5, 0.25, 0.5 μg/ml) with streptokinase and (4, 4, 4, 2, 0.5 μg/ml) with amylase respectively. Similar inhibitions were seen in Pseudomonas putida, Proteus mirabilis. We can conclude that the addition of streptokinase and amylase were effective in reducing the MICs of antibiotics that are commonly used to treat Gram negative bacteria biofilm infection on indwelling devices, thereby increasing susceptibility of bacteria to antibiotics. Streptokinase obviously had a greater effect than amylase, implying that it should be prioritized in future in vivo and clinical studies to obtain successful therapy with antibiotics on biofilm infections.

Concordance of bone culture and deep tissue culture during the operation of diabetic foot osteomyelitis and clinical characteristics of patients

PURPOSE

To retrospectively analyze the concordance of bacterial culture between bone tissue and deep soft tissue in diabetic foot osteomyelitis (DFO) patients and clinical characteristics of patients.

METHODS

This study collected samples from 155 patients with suspected DFO (who required amputation after clinical evaluation). Bacterial culture and drug susceptibility tests were performed on the patients' deep soft tissue and bone tissue, and the consistency between the two was compared. In addition, the differences among DFO patients with different degrees of infection were compared classified by the PEDIS classifications.

RESULTS

Among the 155 patients diagnosed with DFO, the positive rate of bone culture was 78.7% (122/155). This study cultured 162 strains, including 73 Gram-positive bacteria, 83 Gram-negative bacteria, and 6 fungi. Staphylococcus aureus (33 strains) was the most common bacteria. The overall agreement between bone culture and tissue culture was 42.8%, with Staphylococcus aureus and Enterobacteria having the best (64.3%) and least agreements (27.3%), respectively. The drug sensitivity results in bone culture showed that Staphylococcus aureus was the main Gram-positive bacteria. The bacteria were sensitive to linezolid and vancomycin. Proteus mirabilis was the main Gram-negative bacteria. These were more sensitive than biapenem and piperacillin/tazobactam. Fungi were more sensitive to voriconazole and itraconazole.

CONCLUSION

The culture results of deep soft tissues near the bone cannot accurately represent the true pathogen of DFO. For DFO patients, bone culture should be taken as much as possible, and appropriate antibiotics should be selected according to the drug susceptibility results.

Biofilm Inhibition of Inula viscosa (L.) Aiton and Globularia alypum L. Extracts Against Candida Infectious Pathogens and In Vivo Action on Galleria mellonella Model

The increasing importance of fungal infections has fueled the search for new beneficial alternatives substance from plant extracts. The current study investigates the antifungal and antibiofilm activity of Inula viscosa (L.) Aiton and Globularia alypum (L.) leaves extracts against Candida both in vitro and in vivo. The inhibition of planktonic and sessile Candida albicans and Candida glabrata growth using both leaf extracts are evaluated. Moreover; an in vivo infection model using Galleria mellonella larvae; infected and treated with the extracts are performed. All extracts show fungicidal activity; with a minimum fungicidal concentration (MFC) ranging from 128 to 512 µg mL-1 against the two selected strains of Candida. In particular, the best results are obtained with methanolic extract of I. viscosa and G. alypum with an MFC value of 128 µg mL-1 . The extracts are capable to prevent 90% of biofilm development at minor concentrations ranging from 100.71 ± 2.49 µg mL-1 to 380.4 ± 0.92 µg mL-1 . In vivo, tests on Galleria mellonella larvae show that the extracts increase the survival of the larvae infected with Candida. The attained results reveal that I. viscosa and G. alypum extracts may be considered as new antifungal agents and biofilm inhibiting agents for the pharmaceutical and agro-food field.

Boolean model of the gene regulatory network of Pseudomonas aeruginosa CCBH4851

Introduction

Pseudomonas aeruginosa infections are one of the leading causes of death in immunocompromised patients with cystic fibrosis, diabetes, and lung diseases such as pneumonia and bronchiectasis. Furthermore, P. aeruginosa is one of the main multidrug-resistant bacteria responsible for nosocomial infections worldwide, including the multidrug-resistant CCBH4851 strain isolated in Brazil.

Methods

One way to analyze their dynamic cellular behavior is through computational modeling of the gene regulatory network, which represents interactions between regulatory genes and their targets. For this purpose, Boolean models are important predictive tools to analyze these interactions. They are one of the most commonly used methods for studying complex dynamic behavior in biological systems.

Results and discussion

Therefore, this research consists of building a Boolean model of the gene regulatory network of P. aeruginosa CCBH4851 using data from RNA-seq experiments. Next, the basins of attraction are estimated, as these regions and the transitions between them can help identify the attractors, representing long-term behavior in the Boolean model. The essential genes of the basins were associated with the phenotypes of the bacteria for two conditions: biofilm formation and polymyxin B treatment. Overall, the Boolean model and the analysis method proposed in this work can identify promising control actions and indicate potential therapeutic targets, which can help pinpoint new drugs and intervention strategies.

Surface Conditioning Effects on Submerged Optical Sensors: A Comparative Study of Fused Silica, Titanium Dioxide, Aluminum Oxide, and Parylene C

Optical sensors excel in performance but face efficacy challenges when submerged due to potential surface colonization, leading to signal deviation. This necessitates robust solutions for sustained accuracy. Protein and microorganism adsorption on solid surfaces is crucial in antibiofilm studies, contributing to conditioning film and biofilm formation. Most studies focus on surface characteristics (hydrophilicity, roughness, charge, and composition) individually for their adhesion impact. In this work, we tested four materials: silica, titanium dioxide, aluminum oxide, and parylene C. Bovine Serum Albumin (BSA) served as the biofouling conditioning model, assessed with X-ray photoelectron spectroscopy (XPS). Its effect on microorganism adhesion (modeled with functionalized microbeads) was quantified using a shear stress flow chamber. Surface features and adhesion properties were correlated via Principal Component Analysis (PCA). Protein adsorption is influenced by nanoscale roughness, hydrophilicity, and likely correlated with superficial electron distribution and bond nature. Conditioning films alter the surface interaction with microbeads, affecting hydrophilicity and local charge distribution. Silica shows a significant increase in microbead adhesion, while parylene C exhibits a moderate increase, and titanium dioxide shows reduced adhesion. Alumina demonstrates notable stability, with the conditioning film minimally impacting adhesion, which remains low.

The Anti-Virulence Activities of the Antihypertensive Drug Propranolol in Light of Its Anti-Quorum Sensing Effects against Pseudomonas aeruginosa and Serratia marcescens

The development of bacterial resistance is an increasing global concern that requires discovering new antibacterial agents and strategies. Bacterial quorum sensing (QS) systems play important roles in controlling bacterial virulence, and their targeting could lead to diminishing bacterial pathogenesis. In this context, targeting QS systems without significant influence on bacterial growth is assumed as a promising strategy to overcome resistance development. This study aimed at evaluating the anti-QS and anti-virulence activities of the β-adrenoreceptor antagonist propranolol at sub-minimal inhibitory concentrations (sub-MIC) against two Gram-negative bacterial models Pseudomonas aeruginosa and Serratia marcescens. The effect of propranolol on the expression of QS-encoding genes was evaluated. Additionally, the affinity of propranolol to QS receptors was virtually attested. The influence of propranolol at sub-MIC on biofilm formation, motility, and production of virulent factors was conducted. The outcomes of the propranolol combination with different antibiotics were assessed. Finally, the in vivo protection assay in mice was performed to assess propranolol's effect on lessening the bacterial pathogenesis. The current findings emphasized the significant ability of propranolol at sub-MIC to reduce the formation of biofilms, motility, and production of virulence factors. In addition, propranolol at sub-MIC decreased the capacity of tested bacteria to induce pathogenesis in mice. Furthermore, propranolol significantly downregulated the QS-encoding genes and showed significant affinity to QS receptors. Finally, propranolol at sub-MIC synergistically decreased the MICs of different antibiotics against tested bacteria. In conclusion, propranolol might serve as a plausible adjuvant therapy with antibiotics for the treatment of serious bacterial infections after further pharmacological and pharmaceutical studies.

Biofilms in Periprosthetic Orthopedic Infections Seen through the Eyes of Neutrophils: How Can We Help Neutrophils?

Despite advancements in our knowledge of neutrophil responses to planktonic bacteria during acute inflammation, much remains to be elucidated on how neutrophils deal with bacterial biofilms in implant infections. Further complexity transpires from the emerging findings on the role that biomaterials play in conditioning bacterial adhesion, the variety of biofilm matrices, and the insidious measures that biofilm bacteria devise against neutrophils. Thus, grasping the entirety of neutrophil-biofilm interactions occurring in periprosthetic tissues is a difficult goal. The bactericidal weapons of neutrophils consist of the following: ready-to-use antibacterial proteins and enzymes stored in granules; NADPH oxidase-derived reactive oxygen species (ROS); and net-like structures of DNA, histones, and granule proteins, which neutrophils extrude to extracellularly trap pathogens (the so-called NETs: an allusive acronym for "neutrophil extracellular traps"). Neutrophils are bactericidal (and therefore defensive) cells endowed with a rich offensive armamentarium through which, if frustrated in their attempts to engulf and phagocytose biofilms, they can trigger the destruction of periprosthetic bone. This study speculates on how neutrophils interact with biofilms in the dramatic scenario of implant infections, also considering the implications of this interaction in view of the design of new therapeutic strategies and functionalized biomaterials, to help neutrophils in their arduous task of managing biofilms.

Inhibition and Reduction of Biofilm Production along with Their Antibiogram Pattern among Gram-Negative Clinical Isolates

Background

Bacterial biofilm is a significant virulence factor threatening patients, leading to chronic infections and economic burdens. Therefore, it is crucial to identify biofilm production, its inhibition, and reduction. In this study, we investigated biofilm production among Gram-negative isolates and assessed the inhibitory and reduction potential of ethylene diamine tetra acetic acid (EDTA) and dimethyl sulfoxide (DMSO) towards them. In addition, we studied the antimicrobial resistance pattern of the Gram-negative isolates.

Methods

Bacterial isolation and identification was done using standard microbiological techniques, following the Clinical and Laboratory Standards Institute (CLSI) guideline, 28th edition. The Kirby-Bauer disk diffusion method was used to determine the antibiotic susceptibility pattern of the isolates, and β-lactamase production was tested via the combination disk method. Biofilm formation was detected through the tissue culture plate (TCP) method. Different concentrations of EDTA and DMSO were used to determine their inhibitory and reduction properties against the biofilm. Both inhibition and reduction by the various concentrations of EDTA and DMSO were analyzed using paired t-tests.

Results

Among the 110 clinical isolates, 61.8% (68) were found to be multidrug resistant (MDR). 30% (33/110) of the isolates were extended-spectrum β-lactamase (ESBL) producers, 14.5% (16/110) were metallo-β-lactamase (MBL), and 8% (9/110) were Klebsiella pneumoniae carbapenemase (KPC) producers. Biofilm formation was detected in 35.4% of the isolates. Biofilm-producing organisms showed the highest resistance to antibiotics such as cephalosporins, chloramphenicol, gentamicin, and carbapenem. The inhibition and reduction of biofilm were significantly lower (p < 0.05) for 1 mM of EDTA and 2% of DMSO.

Conclusion

Isolates forming biofilm had a higher resistance rate and β-lactamase production compared to biofilm nonproducers. EDTA and DMSO were found to be potential antibiofilm agents. Hence, EDTA and DMSO might be an effective antibiofilm agent to control biofilm-associated infections.

Preparation and Characterization of Mono- and Biphasic Ca1-xAgxHPO4·nH2O Compounds for Biomedical Applications

This study aimed to explore the effects of the full-scale replacement (up to 100%) of Ca2+ ions with Ag1+ ions in the structure of brushite (CaHPO4·2H2O). This substitution has potential benefits for producing monophasic and biphasic Ca1-xAgxHPO4·nH2O compounds. To prepare the starting solutions, (NH4)2HPO4, Ca(NO3)2·4H2O, and AgNO3 at different concentrations were used. The results showed that when the Ag/Ca molar ratio was below 0.25, partial substitution of Ca with Ag reduced the size of the unit cell of brushite. As the Ag/Ca molar ratio increased to 4, a compound with both monoclinic CaHPO4·2H2O and cubic nanostructured Ag3PO4 phases formed. There was a nearly linear relationship between the Ag ion ratio in the starting solutions and the wt% precipitation of the Ag3PO4 phase in the resulting compound. Moreover, when the Ag/Ca molar ratio exceeded 4, a single-phase Ag3PO4 compound formed. Hence, adjusting the Ag/Ca ratio in the starting solution allows the production of biomaterials with customized properties. In summary, this study introduces a novel synthesis method for the mono- and biphasic Ca1-xAgxHPO4·nH2O compounds brushite and silver phosphate. The preparation of these phases in a one-pot synthesis with controlled phase composition resulted in the enhancement of existing bone cement formulations by allowing better mixing of the starting ingredients.

In Vitro Antibiofilm Effect of N-Acetyl-L-cysteine/Dry Propolis Extract Combination on Bacterial Pathogens Isolated from Upper Respiratory Tract Infections

Bacterial biofilms play an important role in the pathogenesis of chronic upper respiratory tract infections. In addition to conventional antimicrobial therapy, N-acetyl-L-cysteine (NAC) and propolis are dietary supplements that are often recommended as supportive therapy for upper respiratory tract infections. However, no data on the beneficial effect of their combination against bacterial biofilms can be found in the scientific literature. Therefore, the aim of our study was to investigate the in vitro effect of N-acetyl-L-cysteine (NAC) and dry propolis extract in fixed combinations (NAC/dry propolis extract fixed combination) on biofilm formation by bacterial species isolated from patients with chronic rhinosinusitis, chronic otitis media, and chronic adenoiditis. The prospective study included 48 adults with chronic rhinosinusitis, 29 adults with chronic otitis media, and 33 children with chronic adenoiditis. Bacteria were isolated from tissue samples obtained intraoperatively and identified using the MALDI-TOF Vitek MS System. The antimicrobial activity, synergism, and antibiofilm effect of NAC/dry propolis extract fixed combination were studied in vitro. A total of 116 different strains were isolated from the tissue samples, with staphylococci being the most frequently isolated in all patients (57.8%). MICs of the NAC/dry propolis extract fixed combination ranged from 1.25/0.125 to 20/2 mg NAC/mg propolis. A synergistic effect (FICI ≤ 0.5) was observed in 51.7% of strains. The majority of isolates from patients with chronic otitis media were moderate biofilm producers and in chronic adenoiditis they were weak biofilm producers, while the same number of isolates in patients with chronic rhinosinusitis were weak and moderate biofilm producers. Subinhibitory concentrations of the NAC/propolis combination ranging from 0.625-0.156 mg/mL to 10-2.5 mg/mL of NAC combined with 0.062-0.016 mg/mL to 1-0.25 mg/mL of propolis inhibited biofilm formation in all bacterial strains. Suprainhibitory concentrations ranging from 2.5-10 mg/mL to 40-160 mg/mL of NAC in combination with 0.25-1 mg/mL to 4-16 mg/mL of propolis completely eradicated the biofilm. In conclusion, the fixed combination of NAC and dry propolis extract has a synergistic effect on all stages of biofilm formation and eradication of the formed biofilm in bacteria isolated from upper respiratory tract infections.

Iodine-doped TiO2 nanotube coatings: a technique for enhancing the antimicrobial properties of titanium surfaces against Staphylococcus aureus

BACKGROUND

Implant-related infections are a challenging complication of orthopedic surgery, primarily due to the formation of bacterial biofilms on the implant surface. An antibacterial coating for titanium implants was developed to provide novel insights into the prevention and treatment of implant-related infections.

METHODS

Titanium plates were coated with TiO2 nanotubes by anodization, and iodine was doped onto the coating via electrophoretic deposition. The obtained plates were characterized using a range of analytical techniques. Subsequently, Staphylococcus aureus was inoculated onto the surfaces of untreated titanium plates (control group), TiO2-nanocoated titanium plates (TiO2 group), and iodine-doped TiO2-nanocoated titanium plates (I-TiO2 group) to compare their antibacterial properties.

RESULTS

Twenty-four hour in vitro antimicrobial activity test of the I-TiO2 group against Staphylococcus aureus was superior to those of the other groups, and this difference was statistically significant (P < 0.05).

CONCLUSIONS

This coating technology provides a new theoretical basis for the development of anti-infective implants against Staphylococcus aureus in orthopedics.

Aqueous Extracts from Hemp Seeds as a New Weapon against Staphylococcus epidermidis Biofilms

This study investigated the antibiofilm activity of water-soluble extracts obtained under different pH conditions from Cannabis sativa seeds and from previously defatted seeds. The chemical composition of the extracts, determined through GC-MS and NMR, revealed complex mixtures of fatty acids, monosaccharides, amino acids and glycerol in ratios depending on extraction pH. In particular, the extract obtained at pH 7 from defatted seeds (Ex7d) contained a larger variety of sugars compared to the others. Saturated and unsaturated fatty acids were found in all of the analysed extracts, but linoleic acid (C18:2) was detected only in the extracts obtained at pH 7 and pH 10. The extracts did not show cytotoxicity to HaCaT cells and significantly inhibited the formation of Staphylococcus epidermidis biofilms. The exception was the extract obtained at pH 10, which appeared to be less active. Ex7d showed the highest antibiofilm activity, i.e., around 90%. Ex7d was further fractionated by HPLC, and the antibiofilm activity of all fractions was evaluated. The 2D-NMR analysis highlighted that the most active fraction was largely composed of glycerolipids. This evidence suggested that these molecules are probably responsible for the observed antibiofilm effect but does not exclude a possible synergistic contribution by the other components.