Escherichia coli biofilm: development and therapeutic strategies

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

K1 capsule-dependent phage-driven evolution in Escherichia coli leading to phage resistance and biofilm production

AIMS

Understanding bacterial phage resistance mechanisms has implications for developing phage-based therapies. This study aimed to explore the development of phage resistance in Escherichia coli K1 isolates' to K1-ULINTec4, a K1-dependent bacteriophage.

METHODS AND RESULTS

Resistant colonies were isolated from two different strains (APEC 45 and C5), both previously exposed to K1-ULINTec4. Genome analysis and several parameters were assessed, including growth capacity, phage adsorption, phenotypic impact at capsular level, biofilm production, and virulence in the in vivo Galleria mellonella larvae model. One out of the six resistant isolates exhibited a significantly slower growth rate, suggesting the presence of a resistance mechanism altering its fitness. Comparative genomic analysis revealed insertion sequences in the region 2 of the kps gene cluster involved in the capsule biosynthesis. In addition, an immunoassay targeting the K1 capsule showed a very low positive reaction compared to the control. Nevertheless, microscopic images of resistant strains revealed the presence of capsules with a clustered organization of bacterial cells and biofilm assessment showed an increased biofilm production compared to the sensitive strains. In the G. mellonella model, larvae infected with phage-resistant isolates showed better survival rates than larvae infected with phage-sensitive strains.

CONCLUSIONS

A phage resistance mechanism was identified at the genomic level and had a negative impact on the K1 capsule production. The resistant isolates showed an increased biofilm production and a decreased virulence in vivo.

In vitro biofilm formation of Gardnerella vaginalis and Escherichia coli associated with bacterial vaginosis and aerobic vaginitis

Objective

To determine the optimum biofilm formation ratio of Gardnerella vaginalis (G. vaginalis) in a mixed culture with Escherichia coli (E. coli).

Methods

G. vaginalis ATCC14018, E. coli ATCC25922, as well as five strains of G. vaginalis were selected from the vaginal sources of patients whose biofilm forming capacity was determined by the Crystal Violet method. The biofilm forming capacity of E. coli in anaerobic and non-anaerobic environments were compared using the identical assay. The Crystal Violet method was also used to determine the biofilm forming capacity of a co-culture of G. vaginalis and E. coli in different ratios. After Live/Dead staining, biofilm thickness was measured using confocal laser scanning microscopy, and biofilm morphology was observed by scanning electron microscopy.

Results

The biofilm forming capacity of E. coli under anaerobic environment was similar to that in a 5% CO2 environment. The biofilm forming capacity of G. vaginalis and E. coli was stronger at 106:105 CFU/mL than at other ratios (P<0.05). Their thicknesses were greater at 106:105 CFU/mL than at the other ratios, with the exception of 106:102 CFU/mL (P<0.05), under laser scanning microscopy. Scanning electron microscopy revealed increased biofilm formation at 106:105 CFU/mL and 106:102 CFU/mL, but no discernible E. coli was observed at 106:102 CFU/mL.

Conclusion

G. vaginalis and E. coli showed the greatest biofilm forming capacity at a concentration of 106:105 CFU/mL at 48 hours and could be used to simulate a mixed infection of bacterial vaginosis and aerobic vaginitis in vitro.

Blunted blades: new CRISPR-derived technologies to dissect microbial multi-drug resistance and biofilm formation

The spread of multi-drug-resistant (MDR) pathogens has rapidly outpaced the development of effective treatments. Diverse resistance mechanisms further limit the effectiveness of our best treatments, including multi-drug regimens and last line-of-defense antimicrobials. Biofilm formation is a powerful component of microbial pathogenesis, providing a scaffold for efficient colonization and shielding against anti-microbials, which further complicates drug resistance studies. Early genetic knockout tools didn't allow the study of essential genes, but clustered regularly interspaced palindromic repeat inference (CRISPRi) technologies have overcome this challenge via genetic silencing. These tools rapidly evolved to meet new demands and exploit native CRISPR systems. Modern tools range from the creation of massive CRISPRi libraries to tunable modulation of gene expression with CRISPR activation (CRISPRa). This review discusses the rapid expansion of CRISPRi/a-based technologies, their use in investigating MDR and biofilm formation, and how this drives further development of a potent tool to comprehensively examine multi-drug resistance.

Competition quenching strategies reduce antibiotic tolerance in polymicrobial biofilms

Bacteria typically live in dense communities where they are surrounded by other species and compete for a limited amount of resources. These competitive interactions can induce defensive responses that also protect against antimicrobials, potentially complicating the antimicrobial treatment of pathogens residing in polymicrobial consortia. Therefore, we evaluate the potential of alternative antivirulence strategies that quench this response to competition. We test three competition quenching approaches: (i) interference with the attack mechanism of surrounding competitors, (ii) inhibition of the stress response systems that detect competition, and (iii) reduction of the overall level of competition in the community by lowering the population density. We show that either strategy can prevent the induction of antimicrobial tolerance of Salmonella Typhimurium in response to competitors. Competition quenching strategies can thus reduce tolerance of pathogens residing in polymicrobial communities and could contribute to the improved eradication of these pathogens via traditional methods.

Comparative analysis of biofilm characterization of probiotic Escherichia coli

Biofilms are thought to play a vital role in the beneficial effects of probiotic bacteria. However, the structure and function of probiotic biofilms are poorly understood. In this work, biofilms of Escherichia coli (E. coli) Nissle 1917 were investigated and compared with those of pathogenic and opportunistic strains (E. coli MG1655, O157:H7) using crystal violet assay, confocal laser scanning microscopy, scanning electron microscopy and FTIR microspectroscopy. The study revealed significant differences in the morphological structure, chemical composition, and spatial heterogeneity of the biofilm formed by the probiotic E. coli strain. In particular, the probiotic biofilm can secrete unique phospholipid components into the extracellular matrix. These findings provide new information on the morphology, architecture and chemical heterogeneity of probiotic biofilms. This information may help us to understand the beneficial effects of probiotics for various applications.

Enterobacteria in anaerobic digestion of dairy cattle wastewater: Assessing virulence and resistance for one health security

Samples from a dairy cattle waste-fed anaerobic digester were collected across seasons to assess sanitary safety for biofertilizer use. Isolated enterobacteria (suggestive of Escherichia coli) were tested for susceptibility to biocides, antimicrobials, and biofilm-forming capability. Results revealed a decrease in total bacteria, coliforms, and enterobacteria in biofertilizer compared to the effluent. Among 488 isolates, 98.12 % exhibited high biofilm formation. Biofertilizer isolates exhibited a similar biofilm formation capability as effluent isolates in summer, but greater propensity in winter. Resistance to biocides and antimicrobials varied, with tetracycline resistance reaching 19 %. Of the isolates, 25 were multidrug-resistant (MDR), with 64 % resistant to three drugs. Positive correlations were observed between MDR and increased biofilm formation capacity in both samples, while there was negative correlation between MDR and increased biocide resistance. A higher number of MDR bacteria were found in biofertilizer compared to the effluent, revealing the persistence of E. coli resistance, posing challenges to food safety and public health.

Prevalence and implications of pKs-positive Escherichia coli in colorectal cancer

Colorectal cancer (CRC) remains a significant global health concern, necessitating continuous investigation into its etiology and potential risk factors. Recent research has shed light on the potential role of pKs-positive Escherichia coli (pKs + E. coli) and colibactin in the development and progression of CRC. Therefore, this review aimed to provide an updated analysis of the prevalence and implications of pKs + E. coli in colorectal cancer. We conducted a literature review search in major scientific databases to identify relevant studies exploring the association between pKs + E. coli and CRC. The search strategy included studies published up to the present date, and articles were carefully selected based on predefined inclusion criteria. Thus, the present study encompasses scientific evidence from clinical and epidemiological studies supporting the presence of pKs + E. coli in CRC patients, demonstrating a consistent and significant association in multiple studies. Furthermore, we highlighted the potential mechanisms by which colibactin may promote tumorigenesis and cancer progression within the colorectal mucosa, including the production of genotoxic virulence factors. Additionally, we explored current diagnostic methods for detecting pKs + E. coli in clinical settings, emphasizing the importance of accurate identification. Moreover, we discussed future strategies that could utilize the presence of this strain as a biomarker for CRC diagnosis and treatment. In conclusion, this review consolidated existing evidence on the prevalence and implications of pKs + E. coli in colorectal cancer. The findings underscore the importance of further research to elucidate the precise mechanisms linking this strain to CRC pathogenesis and to explore its potential as a therapeutic target or diagnostic marker. Ultimately, a better understanding of the role of pKs + E. coli in CRC may pave the way for innovative strategies in CRC management and patient care.

Genetic insights of antibiotic resistance, pathogenicity (virulence) and phylogenetic relationship of Escherichia coli strains isolated from livestock, poultry and their handlers - a one health snapshot

BACKGROUND

Pathogenic and non-pathogenic strains of Escherichia coli harbouring antibiotic resistance genes (ARGs) from any source (clinical samples, animal settings, or environment) might be transmitted and contribute to the spread and increase of antibiotic resistance in the biosphere. The goal of this study was to investigate the genome to decipher the repertoire of ARGs, virulence genes carried by E. coli strains isolated from livestock, poultry, and their handlers (humans), and then unveil the genetic relatedness between the strains.

METHODS

Whole genome sequencing was done to investigate the genetic makeup of E. coli isolates (n = 20) [swine (n = 2), cattle (n = 2), sheep (n = 4), poultry (n = 7), and animal handlers (n = 5)] from southern India. The detection of resistome, virulome, biofilm forming genes, mobile genetic elements (MGE), followed by multilocus sequence typing (MLST) and phylogenetic analyses, were performed.

RESULTS

E. coli strains were found to be multi drug resistant, with a resistome encompassing > 20 ARGs, the virulome-17-22 genes, and > 20 key biofilm genes. MGE analysis showed four E. coli isolates (host: poultry, swine and cattle) harbouring composite transposons with ARGs/virulence genes (blaTEM, dfr, qnr/nleB, tir, eae,and esp) with the potential for horizontal transfer. MLST analyses revealed the presence of ST937 and ST3107 in both livestock/poultry and their handlers. Phylogenomic analyses with global E. coli isolates (human/livestock/poultry hosts) showed close relatedness with strains originating from different parts of the world (the United States, China, etc.).

CONCLUSION

The current study emphasizes the circulation of strains of pathogenic sequence types of clinical importance, carrying a diverse repertoire of genes associated with antibiotic resistance, biofilm formation and virulence properties in animal settings, necessitating immediate mitigation measures to reduce the risk of spread across the biosphere.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7)

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Effect of Bacteriophages against Biofilms of Escherichia coli on Food Processing Surfaces

The bacterial adhesion to food processing surfaces is a threat to human health, as these surfaces can serve as reservoirs of pathogenic bacteria. Escherichia coli is an easily biofilm-forming bacterium involved in surface contamination that can lead to the cross-contamination of food. Despite the application of disinfection protocols, contamination through food processing surfaces continues to occur. Hence, new, effective, and sustainable alternative approaches are needed. Bacteriophages (or simply phages), viruses that only infect bacteria, have proven to be effective in reducing biofilms. Here, phage phT4A was applied to prevent and reduce E. coli biofilm on plastic and stainless steel surfaces at 25 °C. The biofilm formation capacity of phage-resistant and sensitive bacteria, after treatment, was also evaluated. The inactivation effectiveness of phage phT4A was surface-dependent, showing higher inactivation on plastic surfaces. Maximum reductions in E. coli biofilm of 5.5 and 4.0 log colony-forming units (CFU)/cm2 after 6 h of incubation on plastic and stainless steel, respectively, were observed. In the prevention assays, phage prevented biofilm formation in 3.2 log CFU/cm2 after 12 h. Although the emergence of phage-resistant bacteria has been observed during phage treatment, phage-resistant bacteria had a lower biofilm formation capacity compared to phage-sensitive bacteria. Overall, the results suggest that phages may have applicability as surface disinfectants against pathogenic bacteria, but further studies are needed to validate these findings using phT4A under different environmental conditions and on different materials.

Fighting Microbial Infections from Escherichia coli O157:H7: The Combined Use of Three Essential Oils of the Cymbopogon Genus and a Derivative of Esculentin-1a Peptide

The absence of effective therapy against Escherichia coli O157:H7 infections has led to the need to develop new antimicrobial agents. As the use of synergistic combinations of natural antimicrobial compounds is growing as a new weapon in the fight against multidrug-resistant bacteria, here, we have tested new synergistic combinations of natural agents. Notably, we investigated a possible synergistic effect of combinations of essential oils and natural peptides to counteract the formation of biofilm. We chose three essential oils (i.e., Cymbopogon citratus, C. flexuosus and C. martinii) and one peptide already studied in our previous works. We determined the fractional inhibitory concentration (FIC) by analyzing the combination of the peptide derived from esculentin-1a, Esc(1-21), with the three essential oils. We also studied the effects of combinations by time-kill curves, scanning electron microscopy on biofilm and Sytox Green on cell membrane permeability. Finally, we analyzed the expression of different genes implicated in motility, biofilm formation and stress responses. The results showed a different pattern of gene expression in bacteria treated with the mixtures compared to those treated with the peptide or the single C. citratus essential oil. In conclusion, we demonstrated that the three essential oils used in combination with the peptide showed synergy against the E. coli O157:H7, proving attractive as an alternative strategy against E. coli pathogen infections.

Evaluation of bottled drinking water and occurrence of multidrug-resistance and biofilm producing bacteria in Nepal

Health consequences arising from unsafe drinking water and water insecurity lead to increased reliance on usage of bottled water. Biofilm-producing antibiotic-resistant bacteria in bottled water may pose a risk to public health. This study aims to assess the quality of bottled drinking water with a focus on biofilm-producing and drug-resistant coliform. We analyzed 60 bottled water samples of 30 different brands purchased from Kathmandu for physicochemical and microbial analysis. The parameters pH, iron, total coliform count, Escherichia coli count, and fecal coliform count exceeded National Drinking Water Quality Standards, 2022 in 30.00%, 16.67%, 66.67%, 23.33%, and 16.67% of samples, respectively. Water quality index measurement showed 36.67% and 6.67% of bottled water samples were categorized as grade A and grade B indicating excellent and good water quality, respectively. However, 56.67% of bottled water samples fall under grade E meaning unsuitable for drinking. Among 14 coliform isolates, 85.71% and 14.29% were identified as E. coli and Klebsiella spp, respectively. The antibiotic susceptibility testing revealed that 28.57% of the isolates were multidrug-resistant and Gentamicin resistant isolates comprised 71.43%. However, none of the isolates were carbapenem (meropenem) resistant. In this study, 42.87% of the isolates were found biofilm producers with 14.29% each of strong, moderate, and weak biofilm producers. The genetic potential of biofilm-producing capacity of the isolates was assessed by Polymerase Chain Reaction amplification of bcsA and csgD genes. Our results showed that 66.67% and 50.00% of the isolates harbored bcsA and csgD genes, respectively. This study highlights potential public health hazards associated with the consumption of bottled water containing biofilm-producing and drug-resistant bacteria in Nepal.

Antimicrobial and antibiofilm activities of chromone derivatives against uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a urinary tract pathogen responsible for most nosocomial urinary tract infections and can cause severe conditions like acute cystitis of the bladder or pyelonephritis. UPEC harbors a host of virulence factors like curli, hemolysin, siderophore, and motility factors and can form biofilm-like communities and quiescent reservoirs that aid its survival. This study was performed to investigate the antibiofilm, antimicrobial, and antivirulence potentials of three chromone derivatives, namely, 6-bromo 3-formylchromone, 6-chloro 3-formylchromone, and 3-formyl 6-isopropylchromone. These chromones had MICs against UPEC of 20, 20, and 50 µg/ml, respectively, inhibited biofilm formation by 72-96% at 20 µg/ml, and inhibited UPEC-associated virulence factors, that is, hemolysis, motility, curli, siderophore production, indole production, quiescent colony formation, and cell surface hydrophobicity. Gene expression analysis indicated these three derivatives downregulated virulence genes associated with toxins, biofilm production, and stress regulation and suggested they might target two-component UvrY response regulator. 3D-QSAR analysis showed that substitutions at the third and sixth positions of the chromone scaffold favor antimicrobial activity against UPEC. Furthermore, ADME profiles and C. elegans cytotoxicity assays indicated that these chromone derivatives are potent, safe drug candidates.

Escherichia coli Adhesion and Biofilm Formation on Polymeric Nanostructured Surfaces

Biofilm formation is a multistep process that requires initial contact between a bacterial cell and a surface substrate. Recent work has shown that nanoscale topologies impact bacterial cell viability; however, less is understood about how nanoscale surface properties impact other aspects of bacterial behavior. In this study, we examine the adhesive, viability, morphology, and colonization behavior of the bacterium Escherichia coli on 21 plasma-etched polymeric surfaces. Although we predicted that specific nanoscale surface structures of the surface would control specific aspects of bacterial behavior, we observed no correlation between any bacterial response or surface structures/properties. Instead, it appears that the surface composition of the polymer plays the most significant role in controlling and determining a bacterial response to a substrate, although changes to a polymeric surface via plasma etching alter initial bacteria colonization and morphology.

An effective antimicrobial strategy of colistin combined with the Chinese herbal medicine shikonin against colistin-resistant Escherichia coli

IMPORTANCE

Infections caused by multidrug-resistant Escherichia coli (MDR E. coli) have become a major global healthcare problem due to the lack of effective antibiotics today. The emergence of colistin-resistant E. coli strains makes the situation even worse. Therefore, new antimicrobial strategies are urgently needed to combat colistin-resistant E. coli. Combining traditional antibiotics with non-antibacterial drugs has proved to be an effective approach of combating MDR bacteria. This study investigated the combination of colistin and shikonin, a Chinese herbal medicine, against colistin-resistant E. coli. This combination showed good synergistic antibacterial both in vivo and in vitro experiments. Under the background of daily increasing colistin resistance in E. coli, this research points to an effective antimicrobial strategy of using colistin and shikonin in combination against colistin-resistant E. coli.

Antimicrobial Activity and Mechanisms of Walnut Green Husk Extract

Walnut green husks (WGHs), by-products of walnut production, are believed to possess antimicrobial properties, making them a potential alternative to antibiotics. In this study, the antibacterial activities of three extracts, derived from WGH, against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli were investigated, and the antibacterial mechanisms of an anhydrous ethanol extract of WGH (WGHa) were examined. The results showed that WGHa exhibited inhibitory effects on all tested bacteria. The ultrahigh-performance liquid chromatography-tandem mass spectrometry analysis revealed that the major active compounds present in WGHa were terpenoids, phenols, and flavonoids. Treatment with WGHa resulted in the leakage of intracellular ions and alkaline phosphatase; a reduction in intracellular ATP content, ATPase activity, and nucleic acid content; as well as cellular metabolic viability. The transmission electron microscopy images showed varying degrees of cell deformation and membrane damage following WGHa treatment. The transcriptome sequencing and differentially expressed gene enrichment analyses revealed an up-regulation in pathways associated with RNA degradation, translation, protein export, and oxidative phosphorylation. Conversely, pathways involved in cell movement and localization, as well as cell wall organization and carbohydrate transport, were found to be down-regulated. These findings suggest that WGHa alters cell membrane permeability and causes damage to the cell wall. Additionally, WGHa interferes with cellular energy metabolism, compromises RNA integrity, and induces DNA replication stress, consequently inhibiting the normal growth and proliferation of bacteria. These findings unveiled the antimicrobial mechanisms of WGHa, highlighting its potential application as an antibiotic alternative.

Synthesis and evaluation of aromatic BDSF bioisosteres on biofilm formation and colistin sensitivity in pathogenic bacteria

The diffusible signal factor family (DSF) of molecules play an important role in regulating intercellular communication, or quorum sensing, in several disease-causing bacteria. These messenger molecules, which are comprised of cis-unsaturated fatty acids, are involved in the regulation of biofilm formation, antibiotic tolerance, virulence and the control of bacterial resistance. We have previously demonstrated how olefinic N-acyl sulfonamide bioisosteric analogues of diffusible signal factor can reduce biofilm formation or enhance antibiotic sensitivity in a number of bacterial strains. This work describes the design and synthesis of a second generation of aromatic N-acyl sulfonamide bioisosteres. The impact of these compounds on biofilm production in Acinetobacter baumannii, Escherichia coli, Burkholderia multivorans, Burkholderia cepacia, Burkholderia cenocepacia, Pseudomonas aeruginosa and Stenotrophomonas maltophilia is evaluated, in addition to their effects on antibiotic tolerance. The ability of these molecules to increase survival rates on co-administration with colistin is also investigated using the Galleria infection model.

Antimicrobial Potency and E. coli β-Carbonic Anhydrase Inhibition Efficacy of Phenazone-Based Molecules

In this investigation, 4-antipyrinecarboxaldhyde was reacted with methyl hydrazinecarbodithioate to afford the carbodithioate derivative 3. The as-prepared carbodithioate derivative 3 is considered to be a key molecule for the preparation of new antipyrine-1,3,4-thiadiazole-based molecules (4-9) through its reaction with the appropriate hydrazonoyl halides. Furthermore, a typical Biginelli three-component cyclocondensation reaction involving ethyl acetoacetate, 4-antipyrinecarboxaldhyde, and thiourea under the standard conditions is carried out in the presence of sulfuric acid to afford the corresponding antipyrine-pyrimidine hybrid molecule (10). The latter was submitted to react with hydrazine monohydrate to provide the corresponding hydrazide derivative (11) which, under reaction with ethyl acetoacetate in refluxing ethanol containing catalytic amount of acetic acid, afforded the corresponding derivative (12). The structure of the newly synthesized compounds was affirmed by their spectral and microanalytical data. We also screened for their antimicrobial potential (ZOI and MIC) and conducted a kinetic study. Additionally, the mechanism of biological action was assessed by a membrane leakage assay and SEM imaging technique. Moreover, the biological activities and the binding modes of these compounds were further supplemented by an in silico docking study against E. coli β-carbonic anhydrase. The amount of cellular protein released by E. coli is directly correlated to the concentration of compound 9, which was found to be 177.99 µg/mL following treatment with 1.0 mg/mL of compound 9. This finding supports compound 9's antibacterial properties and explains how the formation of holes in the E. coli cell membrane results in the release of proteins from the cytoplasm. The newly synthesized compounds represent acceptable antimicrobial activities with potential action against E. coli β-carbonic anhydrase. The docking studies and antimicrobial activity test proved that compound (9) declared a greater activity than the other synthesized compounds.

Quorum sensing N-acyl homoserine lactones-SdiA enhances the biofilm formation of E. coli by regulating sRNA CsrB expression

As an important virulence phenotype of Escherichia coli, the regulation mechanism of biofilm by non-coding RNA and quorum sensing system has not been clarified. Here, by transcriptome sequencing and RT-PCR analysis, we found CsrB, a non-coding RNA of the carbon storage regulation system, was positively regulated by the LuxR protein SdiA. Furthermore, β-galactosidase reporter assays showed that SdiA enhanced promoter transcriptional activity of csrB. The consistent dynamic expression levels of SdiA and CsrB during Escherichia coli growth were also detected. Moreover, curli assays and biofilm assays showed sdiA deficiency in Escherichia coli SM10λπ or BW25113 led to a decreased formation of biofilm, and was significantly restored by over-expression of CsrB. Interestingly, the regulations of SdiA on CsrB in biofilm formation were enhanced by quorum sensing signal molecules AHLs. In conclusion, SdiA plays a crucial role in Escherichia coli biofilm formation by regulating the expression of non-coding RNA CsrB. Our study provides new insights into SdiA-non-coding RNA regulatory network involved in Escherichia coli biofilm formation.

Multidrug-resistant Escherichia coli isolated from patients and surrounding hospital environments in Bangladesh: A molecular approach for the determination of pathogenicity and resistance

Extended spectrum β-lactamase producing Escherichia coli (ESBL E. coli) is a primary concern for hospital and community healthcare settings, often linked to an increased incidence of nosocomial infections. This study investigated the characteristics of ESBL E. coli isolated from hospital environments and clinical samples. In total, 117 ESBL E. coli isolates were obtained. The isolates were subjected to molecular analysis for the presence of resistance and virulence genes, antibiotic susceptibility testing, quantitative adherence assay, ERIC-PCR for phylogenetic analysis and whole genome sequencing of four highly drug resistant isolates. Out of the 117 isolates, 68.4% were positive for blaCTX-M, 39.3% for blaTEM, 30.8% for blaNDM-1, 13.7% for blaOXA and 1.7% for blaSHV gene. Upon screening for diarrheagenic genes, no isolates were found to harbour any of the tested genes. In the case of extraintestinal pathogenic E. coli (ExPEC) virulence factors, 7.6%, 11%, 5.9%, 4.3% and 21.2% of isolates harbored the focG, kpsMII, sfaS, afa and iutA genes, respectively. At a temperature of 25°C, 14.5% of isolates exhibited strong biofilm formation with 21.4% and 28.2% exhibiting moderate and weak biofilm formation respectively, whereas 35.9% were non-biofilm formers. On the other hand at 37°C, 2.6% of isolates showed strong biofilm formation with 3.4% and 31.6% showing moderate and weak biofilm formation respectively, whereas, 62.4% were non-biofilm formers. Regarding antibiotic susceptibility testing, all isolates were found to be multidrug-resistant (MDR), with 30 isolates being highly drug resistant. ERIC-PCR resulted in 12 clusters, with cluster E-10 containing the maximum number of isolates. Hierarchical clustering and correlation analysis revealed associations between environmental and clinical isolates, indicating likely transmission and dissemination from the hospital environment to the patients. The whole genome sequencing of four highly drug resistant ExPEC isolates showed the presence of various antimicrobial resistance genes, virulence factors and mobile genetic elements, with isolates harbouring the plasmid incompatibility group IncF (FII, FIB, FIA). The sequenced isolates were identified as human pathogens with a 93.3% average score. This study suggests that ESBL producing E. coli are prevalent in the healthcare settings of Bangladesh, acting as a potential reservoir for AMR bacteria. This information may have a profound effect on treatment, and improvements in public healthcare policies are a necessity to combat the increased incidences of hospital-acquired infections in the country.

Evaluation of Gold Complexes to Address Bacterial Resistance, Quorum Sensing, Biofilm Formation, and Their Antiviral Properties against Bacteriophages

The worldwide increase in antibiotic resistance poses a significant challenge, and researchers are diligently seeking new drugs to combat infections and prevent bacterial pathogens from developing resistance. Gold (I and III) complexes are suitable for this purpose. In this study, we tested four gold (I and III) complexes, (1) chlorotrimethylphosphine gold(I); (2) chlorotriphenylphosphine gold(I); (3) dichloro(2-pyridinecarboxylate) gold (III); and (4) 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene gold(I) chloride, for their antibacterial, antibiofilm, antiviral, and anti-quorum sensing activities. Results reveal that 1 significantly inhibits Escherichia coli DSM 1077 and Staphylococcus aureus ATCC 6538, while 2, 3, and 4 only inhibit S. aureus ATCC 6538. The minimum inhibitory concentration (MIC) of 1 for S. aureus ATCC 6538 is 0.59 μg/mL (1.91 μM), and for methicillin-resistant S. aureus strains MRSA 12 and MRSA 15, it is 1.16 μg/mL (3.75 μM). For E. coli DSM 1077 (Gram-negative), the MIC is 4.63 μg/mL (15 μM), and for multi-resistant E. coli I731940778-1, it is 9.25 μg/mL (30 μM). Complex 1 also disrupts biofilm formation in E. coli and S. aureus after 6 h or 24 h exposure. Moreover, 1 and 2 inhibit the replication of two enterobacteria phages. Anti-quorum sensing potential still requires further clarification. These findings highlight the potential of gold complexes as effective agents to combat bacterial and viral infections.

Aptitude of Uropathogenic Escherichia coli in Renal Transplant Recipients: A Comprehensive Review on Characteristic Features, and Production of Extended Spectrum β-Lactamase

Urinary tract infection is the most common infection in almost half of the renal transplant patients. The development of UTI in these patients may progress to bacteremia, acute T cell-mediated rejection, impaired allograft function, or allograft loss, along with the increased risk of hospitalization and death. Among various pathogens implicated, Uropathogenic E. coli (UPEC), especially sequence type 131 (ST131), is the most virulent and multidrug-resistant pathogen. High antimicrobial resistance to most β-lactam antibiotics, mediated by extended spectrum β-lactamases (ESBLs) produced by UPEC, is a challenge in the clinical management of UTIs in kidney transplant recipients. Indeed, multidrug resistance to β-lactam antibiotics is a direct consequence of ESBL production. Resistance to other antibiotics such as aminoglycosides, fluoroquinolones, and trimethoprim-sulphamethoxazole has also been reported in ESBLs-producing UPEC, which reduces the therapeutic options, rising healthcare-associated costs and subsequently leads to renal failure or even graft loss. In this review, we aimed to discuss the post-transplant risk factors of UTI, UPEC virulence factors (VF), and the related factors including quorum sensing, and stress resistance genes. Furthermore, we searched for the current treatment strategies and some of the alternate approaches proposed as therapeutic options that may affirm the treatment of ESBL-producing UPEC.

Cupferron impairs the growth and virulence of Escherichia coli clinical isolates

AIMS

Multidrug resistance is a worrying problem worldwide. The lack of readily available drugs to counter nosocomial infections requires the need for new interventional strategies. Drug repurposing represents a valid alternative to using commercial molecules as antimicrobial agents in a short time and with low costs. Contextually, the present study focused on the antibacterial potential of the ammonium salt N-nitroso-N-phenylhydroxylamine (Cupferron), evaluating the ability to inhibit microbial growth and influence the main virulence factors.

METHODS AND RESULTS

Cupferron cytotoxicity was checked via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and hemolysis assays. The antimicrobial activity was assessed through the Kirby-Bauer disk diffusion test, broth microdilution method, and time-killing kinetics. Furthermore, the impact on different stages of the biofilm life cycle, catalase, swimming, and swarming motility was estimated via MTT and crystal violet (CV) assay, H2O2 sensitivity, and motility tests, respectively. Cupferron exhibited <15% cytotoxicity at 200 µg/mL concentration. The 90% bacterial growth inhibitory concentrations (MIC90) values recorded after 24 hours of exposure were 200 and 100 µg/mL for multidrug-resistant (MDR) and sensitive strains, respectively, exerting a bacteriostatic action. Cupferron-treated bacteria showed increased susceptibility to biofilm production, oxidative stress, and impaired bacterial motility in a dose-dependent manner.

CONCLUSIONS

In the new antimicrobial compounds active research scenario, the results indicated that Cupferron could be an interesting candidate for tackling Escherichia coli infections.

Evolving biofilm inhibition and eradication in clinical settings through plant-based antibiofilm agents

BACKGROUND

After almost 100 years since evidence of biofilm mode of growth and decades of intensive investigation about their formation, regulatory pathways and mechanisms of antimicrobial tolerance, nowadays there are still no therapeutic solutions to eradicate bacterial biofilms and their biomedical related issues.

PURPOSE

This review intends to provide a comprehensive summary of the recent and most relevant published studies on plant-based products, or their isolated compounds with antibiofilm activity mechanisms of action or identified molecular targets against bacterial biofilms. The objective is to offer a new perspective of most recent data for clinical researchers aiming to prevent or eliminate biofilm-associated infections caused by bacterial pathogens.

METHODS

The search was performed considering original research articles published on PubMed, Web of Science and Scopus from 2015 to April 2023, using keywords such as "antibiofilm", "antivirulence", "phytochemicals" and "plant extracts".

RESULTS

Over 180 articles were considered for this review with a focus on the priority human pathogens listed by World Health Organization, including Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. Inhibition and detachment or dismantling of biofilms formed by these pathogens were found using plant-based extract/products or derivative compounds. Although combination of plant-based products and antibiotics were recorded and discussed, this topic is currently poorly explored and only for a reduced number of bacterial species.

CONCLUSIONS

This review clearly demonstrates that plant-based products or derivative compounds may be a promising therapeutic strategy to eliminate bacterial biofilms and their associated infections. After thoroughly reviewing the vast amount of research carried out over years, it was concluded that plant-based products are mostly able to prevent biofilm formation through inhibition of quorum sensing signals, but also to disrupt mature biofilms developed by multidrug resistant bacteria targeting the biofilm extracellular polymeric substance. Flavonoids and phenolic compounds seemed the most effective against bacterial biofilms.

A novel method using a differential staining fluorescence microscopy (DSFM) to track the location of enteric pathogens within mixed-species biofilms

This study developed a new tool, differential staining fluorescence microscopy (DSFM), to measure the biovolume and track the location of enteric pathogens in mixed-species biofilms which can pose a risk to food safety in beef processing facilities. DSFM was employed to examine the impact of pathogenic bacteria, Escherichia coli O157:H7 and three different Salmonella enterica strains on mixed-species biofilms of beef processing facilities. Fourteen floor drain biofilm samples from three beef processing plants were incubated with overnight BacLight stained enteric pathogens at 7 °C for 5 days on stainless steel surface then counter-stained with FM-1-43 biofilm stain and analyzed using fluorescence microscopy. Notable variations in biovolume of biofilms were observed across the fourteen samples. The introduction of E. coli O157:H7 and S. enterica strains resulted in diverse alterations of biofilm biovolume, suggesting distinct impacts on mixed-species biofilms by different enteric pathogens which were revealed to be located in the upper layer of the mixed-species biofilms. Pathogen strain growth curve comparisons and verification of BacLight Red Stain staining effectiveness were validated. The findings of this study show that the DSFM method is a promising approach to studying the location of enteric pathogens within mixed-species biofilms recovered from processing facilities. Understanding how foodborne pathogens interact with biofilms will allow for improved targeted antimicrobial interventions.

Modification of halloysite lumen with dopamine derivatives as filler for antibiofilm coating

HYPOTHESIS

Development of nanocomposite coating with antibiofilm properties is of fundamental importance to efficient fight biofilm formation preventing infections in biomedical area. In this context, halloysite nanotubes (HNTs), biocompatible and low-cost clay mineral, have been efficiently used as filler for different polymeric matrices affording several nanocomposites with appealing antimicrobial properties. The modification of HNTs surfaces represents a valuable strategy to improve the utilization of the clay for biological purposes.

EXPERIMENTS

Herein, the covalent modification of the HNTs lumen with properly designed dopamine derivatives with different perfluoroalkyl chain length is reported. The obtained nanomaterials are thoroughly characterized by several techniques. As proof of concept the antibiofilm properties on E. coli strain of the nanomaterials are assayed as well. Finally, the HNTs fillers were introduced into a polydopamine matrix allowing for the preparation of functional coatings, resistant to formation of microbial biofilms.

FINDINGS

All characterization methods proved the selectivity of the modification and the increased hydrophobicity of the lumen. In particular 27Al solid state nuclear magnetic resonance (NMR) spectra showed a upfield shift of the Al signal. Studies on the antibiofilm properties highlighted different activities according to the length of perfluoroalkyl chains of organic molecules as proved by 19F solid state NMR spectra. The synthetized materials were promising for future application as coatings on medical implants.

Benzoic acid derivatives as potent antibiofilm agents against Klebsiella pneumoniae biofilm

Klebsiella pneumoniae is responsible for a significant proportion of human urinary tract infections, and its biofilm is a major virulence. One potential approach to controlling biofilm-associated infections is targeting the adhesin MrkD1P to disrupt biofilm formation. We employed Schrodinger's Maestro tool with the OPLS 2005 force field to dock compounds with the target protein. Two benzoic acid derivatives, 3-hydroxy benzoic acid and 2,5-dihydroxybenzoic acid, had strong binding free energies (-55.57 and -18.68 kcal/mol) and were the most potent compounds. The in-vitro experiments were conducted to validate the in-silico results. The results showed that both compounds effectively inhibited biofilm formation at low concentrations (4 and 8 mg/mL, respectively) and had antibiofilm activity, restricting cell attachment. Both compounds demonstrated a strong biofilm inhibitory effect, with 97% and 89% reduction in biofilm by 3-hydroxy benzoic acid and 2,5-dihydroxybenzoic acid, respectively. These findings suggest that natural compounds can be a potential source of new drugs to combat biofilm-associated infections. The study highlights the potential of targeting adhesin MrkD1P as an effective approach to controlling biofilm-associated infections caused by K. pneumoniae. The results may have implications for the development of new therapies for biofilm-associated infections and pave the way for future research in this area.

Resistance-driven innovations in the discovery of bactericides: novel triclosan derivatives decorating isopropanolamine moiety as promising anti-biofilm agents against destructive plant bacterial diseases

BACKGROUND

Controlling bacterial infections in plants is a major challenge owing to the appearance of resistant strains. As a physical barrier, the bacterial biofilm helps bacterial infections acquire drug resistance by enabling bacteria to accommodate complex and volatile environmental conditions and avoid bactericidal effects. Thus, developing new antibacterial agents with antibiofilm potency is imperative.

RESULTS

A series of simple triclosan derivatives containing isopropanolamine moiety were elaborately designed and assessed for their antibacterial behavior. Bioassay results showed that some title compounds had excellent bioactivity against three destructive bacteria Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac) and Pseudomonas syringae pv. actinidiae (Psa). Notably, compound C₈ displayed high bioactivities toward Xoo and Xac, with EC₅₀ values were 0.34 and 2.11 μg mL^-1 , respectively. In vivo trials revealed that compound C₈ exhibited excellent protective activities against rice bacterial blight and citrus bacterial canker at 200 μg mL^-1 , with control effectivenesses of 49.57% and 85.60%, respectively. Compound A₄ had remarkably inhibitory activity toward Psa, with an EC₅₀ value of 2.63 μg mL^-1 , and demonstrated outstanding protective activity with a value of 77.23% against Psa in vivo. Antibacterial mechanisms indicated that compound C₈ dose-dependently prevented biofilm formation and extracellular polysaccharide production. C₈ also significantly weakened the motility and pathogenicity of Xoo.

CONCLUSION

This study contributes to the development and excavation of novel bactericidal candidates with broad-spectrum antibacterial activity by targeting bacterial biofilm to control refractory plant bacterial diseases. © 2023 Society of Chemical Industry.

RNA in situ hybridization of Escherichia coli in equine endometrial biopsies

Endometritis is one of the major causes of infertility in mares. Escherichia coli and β-haemolytic streptococci are among the bacterial species most frequently isolated from the equine uterus. Some bacteria such as β-hemolytic streptococci, can persist in dormant forms and cause prolonged, latent or recurrent infections. Dormant bacteria may be present despite negative bacterial cultures, and they are resistant to antimicrobial treatment due to their resting metabolic state. The purpose of this study was to study formalin-fixed paraffin-embedded equine endometrial biopsies for the presence and localization of E. coli-bacteria, with a chromogenic RNAscope^®-method for detection of E. coli-related 16S ribosomal RNA. Hematoxylin-eosin-stained endometrial biopsies were evaluated to determine the level of inflammation and degeneration. During estrus, samples were taken for endometrial culture and cytology with a double-guarded uterine swab. The samples included eight samples with moderate to severe endometrial inflammation detected in endometrial histopathology, and growth of E. coli in bacterial culture, six samples with moderate to severe endometrial inflammation but negative bacterial culture, and five samples with no endometrial pathology (grade I endometrial biopsy, negative endometrial culture and cytology) serving as controls. Positive and negative control probes were included in the RNA in situ hybridization, and results were confirmed with a fluorescence detection method (fluorescence in situ hybridization). Only unspecific signals of limited size and frequency of occurrence were detected in all samples, with random localization in the endometrium. No samples contained rod-shaped signals corresponding to bacterial findings. In conclusion, there was no evidence of bacterial invasion in the endometrium regardless of the inflammatory status of the biopsy or previous bacterial culture results. According to these findings on a small number of samples, invasion of E. coli is not a common finding in the lamina propria of mares, but these bacteria may also evade detection due to localized foci of infections, or supra-epithelial localization under the cover of biofilm. These bacteria and biofilm covering the epithelium may also be lost during formalin-fixation and processing.

Pseudomonas aeruginosa's greenish-blue pigment pyocyanin: its production and biological activities

A subject of great interest is the bioprospecting of microorganisms and their bioactive byproducts, such as pigments. Microbial pigments have various benefits, including being safe to use due to their natural makeup, having therapeutic effects, and being produced all year round, regardless of the weather or location. Pseudomonas aeruginosa produces phenazine pigments that are crucial for interactions between Pseudomonas species and other living things. Pyocyanin pigment, which is synthesized by 90-95% of P. aeruginosa, has potent antibacterial, antioxidant, and anticancer properties. Herein, we will concentrate on the production and extraction of pyocyanin pigment and its biological use in different areas of biotechnology, engineering, and biology.

Heat-resistant and biofilm-forming Escherichia coli in pasteurized milk from Brazil

Escherichia coli harboring a transmissible locus of stress tolerance (tLST) and the ability to form biofilms represent a serious risk in dairy production. Thus, we aimed to evaluate the microbiological quality of pasteurized milk from two dairy producers in Mato Grosso, Brazil, with a focus on determining the possible presence of E. coli with heat resistance (60 °C/6 min), biofilm-forming potential phenotypes and genotypes, and antimicrobial susceptibility. For this, fifty pasteurized milk samples from producers named A and B were obtained for 5 weeks to investigate the presence of Enterobacteriaceae members, coliforms, and E. coli. For heat resistance, E. coli isolates were exposed to a water bath at 60 °C for 0 and 6 min. In antibiogram analysis, eight antibiotics belonging to six antimicrobial classes were analyzed. The potential to form biofilms was quantified at 570 nm, and curli expression by Congo Red was analyzed. To determine the genotypic profile, we performed PCR for the tLST and rpoS genes, and pulsed-field gel electrophoresis (PFGE) was used to investigate the clonal profile of the isolates. Thus, producer A presented unsatisfactory microbiological conditions regarding Enterobacteriaceae and coliforms for weeks 4 and 5, while all samples analyzed for producer B were contaminated at above-the-limit levels established by national and international legislation. These unsatisfactory conditions enabled us to isolate 31 E. coli from both producers (7 isolates from producer A and 24 isolates from producer B). In this way, 6 E. coli isolates (5 from producer A and 1 from producer B) were highly heat resistant. However, although only 6 E. coli showed a highly heat-resistant profile, 97% (30/31) of all E. coli were tLST-positive. In contrast, all isolates were sensitive to all antimicrobials tested. In addition, moderate or weak biofilm potential was verified in 51.6% (16/31), and the expression of curli and presence of rpoS was not always related to this biofilm potential. Therefore, the results emphasize the spreading of heat-resistant E. coli with tLST in both producers and indicate the biofilm as a possible source of contamination during milk pasteurization. However, the possibility of E. coli producing biofilm and surviving pasteurization temperatures cannot be ruled out, and this should be investigated.

Genomics, biofilm formation and infection of bladder epithelial cells in potentially uropathogenic Escherichia coli (UPEC) from animal sources and human urinary tract infections (UTIs) further support food-borne transmission

Escherichia coli is the main cause of urinary tract infections (UTI). While genomic comparison of specific clones recovered from animals, and human extraintestinal infections show high identity, studies demonstrating the uropathogenicity are lacking. In this study, comparative genomics combined with bladder-cell and biofilm formation assays, were performed for 31 E. coli of different origins: 7 from meat (poultry, beef, and pork); 2 from avian-farm environment; 12 from human uncomplicated UTI, uUTI; and 10 from human complicated UTI, cUTI. These isolates were selected based on their genetic uropathogenic (UPEC) status and phylogenetic background. In silico analysis revealed similar virulence-gene profiles, with flagella, type 1 and curli fimbriae, outer-membrane proteins (agn43, ompT, iha), and iron-uptake (iutA, entA, and fyuA) associated-traits as the most prevalent (>65%). In bladder-cell assays, moderate to strong values of association (83%, 60%, 77.8%) and invasion (0%, 70%, 55.5%) were exhibited by uUTI, cUTI, and animal-derived isolates, respectively. Of interest, uUTI isolates exhibited a significantly lower invasive capacity than cUTI isolates (p < 0.05). All isolates but one produced measurable biofilm. Notably, 1 turkey meat isolate O11:H6-F-ST457, and 2 cUTI isolates of the pandemic lineages O83:H42-F-ST1485-CC648 and O25b:H4-B2-ST131, showed strong association, invasion and biofilm formation. These isolates showed common carriage of type 1 fimbriae and csg operons, toxins (hlyF, tsh), iron uptake systems (iutA, entA, iroN), colicins, protectins (cvaC, iss, kpsM, traT), ompT, and malX. In summary, the similar in vitro behaviour found here for certain E. coli clones of animal origin would further reinforce the role of food-producing animals as a potential source of UPEC. Bladder-cell infection assays, combined with genomics, might be an alternative to in vivo virulence models to assess uropathogenicity.

A rapid-crosslinking antimicrobial hydrogel with enhanced antibacterial capabilities for improving wound healing

One of the main reasons impeding wound healing is wound infection caused by bacterial colonization with a continuous stage of inflammation. Traditional wound treatments like gauze are being replaced by tissue adhesives with strong wet tissue adhesion and biocompatibility. Herein, a fast-crosslinking hydrogel is developed to achieve both strong antimicrobial properties and excellent biocompatibility. In this study, a simple and non-toxic composite hydrogel was prepared by the Schiff base reaction between the aldehyde group of 2,3,4-trihydroxybenzaldehyde (TBA) and the amino group of ε-Poly-_L-lysine (EPL). Subsequently, a succession of experiments toward this new hydrogel including structure characterization, antimicrobial properties, cell experiment and wound healing were applied. The results of the experiments show that the EPL-TBA hydrogel not only exhibited excellent contact-active antimicrobial activities against Gram-negative bacteria Escherichia coli (E. coil) and Gram-positive Bacteria Staphylococcus aureus (S. aureus), but also inhibited the biofilm formation. More importantly, the EPL-TBA hydrogel promoted the wound healing with low cytotoxicity in vivo. These findings indicate that the EPL-TBA hydrogel has a promising use as a wound dressing in the bacterial infection prevention and wounds healing acceleration.

Reduction of biofilm formation of Escherichia coli by targeting quorum sensing and adhesion genes using the CRISPR/Cas9-HDR approach, and its clinical application on urinary catheter

BACKGROUND

Escherichia coli is a common cause of biofilm-associated urinary tract infections (UTIs). Biofilm formation in E. coli is responsible for various indwelling medical device-associated infections, including catheter-associated urinary tract infections (CAUTIs). This study aimed to reduce biofilm formation of E. coli ATCC 25922 by knocking out genes involved in quorum sensing (QS) (luxS) and adhesion (fimH and bolA) using the CRISPR/Cas9-HDR approach.

METHOD

Single-guide RNAs (sgRNAs) were designed to target luxS, fimH and bolA genes. Donor DNA for homologous recombination was constructed to provide accurate repairs of double-strand breaks (DSBs). A biofilm quantification assay (crystal violet assay) was performed to quantify the biofilm formation of mutant and wild-type strains. Morphological changes in biofilm architecture were confirmed by scanning electron microscopy (SEM). Further application of the biofilm formation of mutant and wild-type strains on urinary catheter was tested.

RESULTS

Crystal violet assay showed that the biofilm formation of ΔfimH, ΔluxS, and ΔbolA strains was significantly reduced compared to the wild-type strain (P value < 0.001). The percentage of biofilm reduction of mutant strains was as follows: ΔluxS1 77.51 %, ΔfimH1 78.37 %, ΔfimH2 84.17 %, ΔbolA1 78.24 %, and ΔbolA2 75.39 %. Microscopic analysis showed that all mutant strains lack extracellular polymeric substances (EPS) production compared to the wild-type strain, which was embedded in its EPS matrix. The adherence, cell aggregation, and biofilm formation of wild-type strain on urinary catheters were significantly higher compared to ΔfimH, ΔluxS and ΔbolA strains.

CONCLUSION

Altogether, our results demonstrated that the knockout of luxS, fimH, and bolA genes reduced EPS matrix production, which is considered the main factor in the development, maturation, and maintenance of the integrity of biofilm. This pathway could be a potential strategy to disrupt E. coli biofilm-associated UTIs. This study suggests that CRISPR/Cas9-HDR system may provide an efficient and site-specific gene editing approach that exhibits a possible antibiofilm strategy through intervention with the QS mechanism and adhesion property to suppress biofilm formation associated with UTI catheter infections.

Synthesis, Antimicrobial, and Antibiofilm Activities of Some Novel 7-Methoxyquinoline Derivatives Bearing Sulfonamide Moiety against Urinary Tract Infection-Causing Pathogenic Microbes

A new series of 4-((7-methoxyquinolin-4-yl) amino)-N-(substituted) benzenesulfonamide 3(a-s) was synthesized via the reaction of 4-chloro-7-methoxyquinoline 1 with various sulfa drugs. The structural elucidation was verified based on spectroscopic data analysis. All the target compounds were screened for their antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, and unicellular fungi. The results revealed that compound 3l has the highest effect on most tested bacterial and unicellular fungal strains. The highest effect of compound 3l was observed against E. coli and C. albicans with MIC = 7.812 and 31.125 µg/mL, respectively. Compounds 3c and 3d showed broad-spectrum antimicrobial activity, but the activity was lower than that of 3l. The antibiofilm activity of compound 3l was measured against different pathogenic microbes isolated from the urinary tract. Compound 3l could achieve biofilm extension at its adhesion strength. After adding 10.0 µg/mL of compound 3l, the highest percentage was 94.60% for E. coli, 91.74% for P. aeruginosa, and 98.03% for C. neoformans. Moreover, in the protein leakage assay, the quantity of cellular protein discharged from E. coli was 180.25 µg/mL after treatment with 1.0 mg/mL of compound 3l, which explains the creation of holes in the cell membrane of E. coli and proves compound 3l's antibacterial and antibiofilm properties. Additionally, in silico ADME prediction analyses of compounds 3c, 3d, and 3l revealed promising results, indicating the presence of drug-like properties.

Elucidating the Mechanism of Action of the Gram-Negative-Pathogen-Selective Cyclic Antimicrobial Lipopeptide Brevicidine

Due to the accelerated appearance of antimicrobial-resistant (AMR) pathogens in clinical infections, new first-in-class antibiotics, operating via novel modes of action, are desperately needed. Brevicidine, a bacterial nonribosomally produced cyclic lipopeptide, has shown potent and selective antimicrobial activity against Gram-negative pathogens. However, before our investigations, little was known about how brevicidine exerts its potent bactericidal effect against Gram-negative pathogens. In this study, we find that brevicidine has potent antimicrobial activity against AMR Enterobacteriaceae pathogens, with MIC values ranging between 0.5 μM (0.8 mg/L) and 2 μM (3.0 mg/L). In addition, brevicidine showed potent antibiofilm activity against the Enterobacteriaceae pathogens, with the same 100% inhibition and 100% eradication concentration of 4 μM (6.1 mg/L). Further mechanistic studies showed that brevicidine exerts its potent bactericidal activity by interacting with lipopolysaccharide in the outer membrane, targeting phosphatidylglycerol and cardiolipin in the inner membrane, and dissipating the proton motive force of bacteria. This results in metabolic perturbation, including the inhibition of ATP synthesis; the inhibition of the dehydrogenation of NADH; the accumulation of reactive oxygen species in bacteria; and the inhibition of protein synthesis. Finally, brevicidine showed a good therapeutic effect in a mouse peritonitis-sepsis model. Our findings pave the way for further research on the clinical applications of brevicidine to combat prevalent infections caused by AMR Gram-negative pathogens worldwide.

Untargeted Metabolomics for Unraveling the Metabolic Changes in Planktonic and Sessile Cells of Salmonella Enteritidis ATCC 13076 after Treatment with Lippia origanoides Essential Oil

Nontyphoidal Salmonella species are one of the main bacterial causes of foodborne diseases, causing a public health problem. In addition, the ability to form biofilms, multiresistance to traditional drugs, and the absence of effective therapies against these microorganisms are some of the principal reasons for the increase in bacterial diseases. In this study, the anti-biofilm activity of twenty essential oils (EOs) on Salmonella enterica serovar Enteritidis ATCC 13076 was evaluated, as well as the metabolic changes caused by Lippia origanoides thymol chemotype EO (LOT-II) on planktonic and sessile cells. The anti-biofilm effect was evaluated by the crystal violet staining method, and cell viability was evaluated through the XTT method. The effect of EOs was observed by scanning electron microscopy (SEM) analysis. Untargeted metabolomics analyses were conducted to determine the effect of LOT-II EO on the cellular metabolome. LOT-II EO inhibited S. Enteritidis biofilm formation by more than 60%, without decreasing metabolic activity. Metabolic profile analysis identified changes in the modulation of metabolites in planktonic and sessile cells after LOT-II EO treatment. These changes showed alterations in different metabolic pathways, mainly in central carbon metabolism and nucleotide and amino acid metabolism. Finally, the possible mechanism of action of L. origanoides EO is proposed based on a metabolomics approach. Further studies are required to advance at the molecular level on the cellular targets affected by EOs, which are promising natural products for developing new therapeutic agents against Salmonella sp. strains.

Characterization and genomic study of EJP2, a novel jumbo phage targeting antimicrobial resistant Escherichia coli

The emergence of antimicrobial resistance (AMR) Escherichia coli has noticeably increased in recent years worldwide and causes serious public health concerns. As alternatives to antibiotics, bacteriophages are regarded as promising antimicrobial agents. In this study, we isolated and characterized a novel jumbo phage EJP2 that specifically targets AMR E. coli strains. EJP2 belonged to the Myoviridae family with an icosahedral head (120.9 ± 2.9 nm) and a non-contractile tail (111.1 ± 0.6 nm), and contained 349,185 bp double-stranded DNA genome with 540 putative ORFs, suggesting that EJP2 could be classified as jumbo phage. The functions of genes identified in EJP2 genome were mainly related to nucleotide metabolism, DNA replication, and recombination. Comparative genomic analysis revealed that EJP2 was categorized in the group of Rak2-related virus and presented low sequence similarity at the nucleotide and amino acid level compared to other E. coli jumbo phages. EJP2 had a broad host spectrum against AMR E. coli as well as pathogenic E. coli and recognized LPS as a receptor for infection. Moreover, EJP2 treatment could remove over 80% of AMR E. coli biofilms on 96-well polystyrene, and exhibit synergistic antimicrobial activity with cefotaxime against AMR E. coli. These results suggest that jumbo phage EJP2 could be used as a potential biocontrol agent to combat the AMR issue in food processing and clinical environments.

TargIDe: a machine-learning workflow for target identification of molecules with antibiofilm activity against Pseudomonas aeruginosa

Bacterial biofilms are a source of infectious human diseases and are heavily linked to antibiotic resistance. Pseudomonas aeruginosa is a multidrug-resistant bacterium widely present and implicated in several hospital-acquired infections. Over the last years, the development of new drugs able to inhibit Pseudomonas aeruginosa by interfering with its ability to form biofilms has become a promising strategy in drug discovery. Identifying molecules able to interfere with biofilm formation is difficult, but further developing these molecules by rationally improving their activity is particularly challenging, as it requires knowledge of the specific protein target that is inhibited. This work describes the development of a machine learning multitechnique consensus workflow to predict the protein targets of molecules with confirmed inhibitory activity against biofilm formation by Pseudomonas aeruginosa. It uses a specialized database containing all the known targets implicated in biofilm formation by Pseudomonas aeruginosa. The experimentally confirmed inhibitors available on ChEMBL, together with chemical descriptors, were used as the input features for a combination of nine different classification models, yielding a consensus method to predict the most likely target of a ligand. The implemented algorithm is freely available at https://github.com/BioSIM-Research-Group/TargIDe under licence GNU General Public Licence (GPL) version 3 and can easily be improved as more data become available.

Antibiofilm Effect of Biogenic Silver Nanoparticles Combined with Oregano Derivatives against Carbapenem-Resistant Klebsiella pneumoniae

Resistant bacteria may kill more people than COVID-19, so the development of new antibacterials is essential, especially against microbial biofilms that are reservoirs of resistant cells. Silver nanoparticles (bioAgNP), biogenically synthesized using Fusarium oxysporum, combined with oregano derivatives, present a strategic antibacterial mechanism and prevent the emergence of resistance against planktonic microorganisms. Antibiofilm activity of four binary combinations was tested against enteroaggregative Escherichia coli (EAEC) and Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC): oregano essential oil (OEO) plus bioAgNP, carvacrol (Car) plus bioAgNP, thymol (Thy) plus bioAgNP, and Car plus Thy. The antibiofilm effect was accessed using crystal violet, MTT, scanning electron microscopy, and Chromobacterium violaceum anti-quorum-sensing assays. All binary combinations acted against preformed biofilm and prevented its formation; they showed improved antibiofilm activity compared to antimicrobials individually by reducing sessile minimal inhibitory concentration up to 87.5% or further decreasing biofilm metabolic activity and total biomass. Thy plus bioAgNP extensively inhibited the growth of biofilm in polystyrene and glass surfaces, disrupted three-dimensional biofilm structure, and quorum-sensing inhibition may be involved in its antibiofilm activity. For the first time, it is shown that bioAgNP combined with oregano has antibiofilm effect against bacteria for which antimicrobials are urgently needed, such as KPC.

Emerging Non-Antibiotic Options Targeting Uropathogenic Mechanisms for Recurrent Uncomplicated Urinary Tract Infection

Urinary tract infections (UTIs) are the most frequent bacterial infections in the clinical setting. Even without underlying anatomic or functional abnormalities, more than 40% of women experience at least one UTI in their lifetime, of which 30% develop recurrent UTIs (rUTIs) within 6 months. Conventional management with antibiotics for rUTIs may eventually lead to the development of multidrug-resistant uropathogens. Targeting of the pathogenicity of rUTIs, the evolution of uropathogenic Escherichia coli (UPEC), and inadequate host defenses by immune responses should be explored to provide non-antibiotic solutions for the management of rUTIs. The adaptive evolution of UPEC has been observed in several aspects, including colonization, attachment, invasion, and intracellular replication to invade the urothelium and survive intracellularly. Focusing on the antivirulence of UPEC and modulating the immunity of susceptible persons, researchers have provided potential alternative solutions in four categories: antiadhesive treatments (i.e., cranberries and D-mannose), immunomodulation therapies, vaccines, and prophylaxis with topical estrogen therapy and probiotics (e.g., Lactobacillus species). Combination therapies targeting multiple pathogenic mechanisms are expected to be a future trend in UTI management, although some of these treatment options have not been well established in terms of their long-term efficacy. Additional clinical trials are warranted to validate the therapeutic efficacy and durability of these techniques.

Investigation of the biofilm formation in extra-intestinal pathogenic Escherichia coli ST131 strains and its correlation with the presence of fimH, afa, and kpsMSTII genes

Escherichia coli sequence type 131 (ST131) is a multidrug-resistant strain with the global dissemination. Biofilm formation-related factors include the most important virulence factors in extra-intestinal pathogenic E. coli (ExPEC) ST131 strains causing infections with treatment-limited subjects. This study aims to investigate the biofilm formation ability and its correlation with the presence of fimH, afa, and kpsMSTII genes in clinical isolates of ExPEC ST131. In this regard, the prevalence and characteristics of these strains collected and evaluated. The results revealed strong, moderate, and weak attachment abilities related to biofilm formation attributes in 45%, 20%, and 35% of strains, respectively. In the meantime, the frequency of the fimH, afa, and kpsMSTII genes among the isolates was observed as follows: fimH positive: 65%; afa positive: 55%; and kpsMSTII positive: 85%. The results convey a significant different of biofilm formation ability between clinical E. coli ST131 and non-ST131 isolates. Furthermore, while 45% of ST131 isolates produced strong biofilms, only 2% of non-ST131 isolates showed the ability to form strong biofilms. The attending of fimH, afa, and kpsMSTII genes in the majority of ST131 strains demonstrated a key role leading to biofilm formation. These findings suggested the application of fimH, afa, and kpsMSTII gene suppressors for treating biofilm infections caused by drug-resistant ST131 strains.

Antibacterial Activity of Epigallocatechin Gallate (EGCG) against Shigella flexneri

Shigella flexneri (S. flexneri), a major intestinal pathogen, is a global public health concern. The biofilms formed by S. flexneri threaten environmental safety, since they could promote the danger of environmental contamination and strengthen the disease-causing properties of bacteria. Epigallocatechin gallate (EGCG) is an important catechin in tea, which has a high antibacterial activity. However, its antibacterial mechanism is still unclear. This research aims to quantify the antibacterial function and investigate the possible mechanism of EGCG inhibition of S. flexneri. The minimum inhibitory concentration (MIC) of EGCG against planktonic S. flexneri in the investigation was measured to be 400 μg/mL. Besides, SDS-PAGE and field emission scanning electron microscopy showed that EGCG interfered with protein synthesis and changed bacteria morphology. Through controlling the expression of the mdoH gene, EGCG was found to be able to prevent an S. flexneri biofilm extracellular polysaccharide from forming, according to experiments utilizing the real-time PCR test. Additional research revealed that EGCG might stimulate the response of S. flexneri to oxidative stress and prevent bacterial growth. These findings suggest that EGCG, a natural compound, may play a substantial role in S. flexneri growth inhibition.

Antibacterial and anti-biofilm properties of carvacrol alone and in combination with cefixime against Escherichia coli

BACKGROUND

Plant-derived compounds can be used as antimicrobial agents in medicines and as food preservatives. These compounds can be applied along with other antimicrobial agents to strengthen the effect and/or reduce the required treatment dose.

RESULTS

In the present study, the antibacterial, anti-biofilm and quorum sensing inhibitory activity of carvacrol alone and in combination with the antibiotic cefixime against Escherichia coli was investigated. The MIC and MBC values for carvacrol were 250 μg/mL. In the checkerboard test, carvacrol showed a synergistic interaction with cefixime against E. coli (FIC index = 0.5). Carvacrol and cefixime significantly inhibited biofilm formation at MIC/2 (125 and 62.5 μg/mL), MIC/4 (62.5 and 31.25 μg/mL) and MIC/8 (31.25 and 15.625 μg/mL) for carvacrol and cefixime, respectively. The antibacterial and anti-biofilm potential effect of carvacrol confirmed by the scanning electron microscopy. Real-time quantitative reverse transcription PCR revealed significant down-regulation of the luxS and pfs genes following treatment with a MIC/2 (125 μg/mL) concentration of carvacrol alone and of only pfs gene following treatment with MIC/2 of carvacrol in combination with MIC/2 of cefixime (p < 0.05).

CONCLUSIONS

Because of the significant antibacterial and anti-biofilm activity of carvacrol, the present study examines this agent as an antibacterial drug of natural origin. The results indicate that in this study the best antibacterial and anti-biofilm properties are for the combined use of cefixime and carvacrol.

The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli

Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.

Virtual Screening and In Vitro Experimental Verification of LuxS Inhibitors for Escherichia coli O157:H7

Enterohemorrhagic Escherichia coli O157:H7 is an important foodborne pathogen that forms biofilms. In this study, three quorum-sensing (QS) inhibitors (M414-3326, 3254-3286, and L413-0180) were obtained through virtual screening, and their in vitro antibiofilm activities were validated. Briefly, the three-dimensional structure model of LuxS was constructed and characterized using the SWISS-MODEL. High-affinity inhibitors were screened from the ChemDiv database (1,535,478 compounds) using LuxS as a ligand. Five compounds (L449-1159, L368-0079, M414-3326, 3254-3286, and L413-0180) with a good inhibitory effect (50% inhibitory concentration <10 μM) on type II QS signal molecule autoinducer-2 (AI-2) were obtained using a AI-2 bioluminescence assay. The absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties predicated that the five compounds had high intestinal absorption levels (high) and plasma protein binding (absorbent strong) and did not inhibit the metabolism of CYP2D6 metabolic enzymes. In addition, molecular dynamics simulation showed that compounds L449-1159 and L368-0079 could not stably bind with LuxS. Thus, these compounds were excluded. Furthermore, surface plasmon resonance results showed that the three compounds could specifically bind to LuxS. IN addition, the three compounds could effectively inhibit the biofilm formation without affecting the growth and metabolism of the bacteria. Finally, the reverse transcription-quantitative PCR results showed that the three compounds downregulated the expression of the LuxS gene. Overall, these results revealed that the three compounds obtained through virtual screening could inhibit biofilm formation of E. coli O157:H7 and are potential LuxS inhibitors that can be used to treat E. coli O157:H7 infections. IMPORTANCE E. coli O157:H7 is a foodborne pathogen of public health importance. Quorum sensing (QS) is a form of bacterial communication that can regulate various group behaviors, including biofilm formation. Here, we identified three QS AI-2 inhibitors (M414-3326, 3254-3286, and L413-0180) that can stably and specifically bind to LuxS protein. The three QS AI-2 inhibitors inhibited biofilm formation without affecting the growth and metabolic activity of E. coli O157:H7. The three QS AI-2 inhibitors are promising agents for treating E. coli O157:H7 infections. Further studies to identify the mechanism of the three QS AI-2 inhibitors are needed to develop new drugs to overcome antibiotic resistance.

Multiple rare organisms causing ventriculoperitoneal shunt infection and brain abscess

Ventriculoperitoneal shunts (VPS) are inserted to treat issues with CSF flow dynamics, such as obstructions causing CSF build up which raises the intracranial pressure. A major complication of this procedure is VPS infections. Vast majority of VPS infections are monomicrobial and may occur in the first two years of insertion due to contiguous or hematogenous spread. Here, we report a rare case of polymicrobial VPS infection with 5 pathogens. One of these organisms (Citrobacter werkmanii) has been reported as a cause of meningitis for the first time in this report. The other organism (Enterococcus casseliflavus) has been reported as a cause only one other time. Hence, we recommend considering these newly emerging organisms when dealing with meningitis.