Bruguiera gymnorhiza (L.) Lam. at the Forefront of Pharma to Confront Zika Virus and Microbial Infections-An In Vitro and In Silico Perspective.

The recent emergence of Zika virus (ZIKV) in Brazil and the increasing resistance developed by pathogenic bacteria to nearly all existing antibiotics should be taken as a wakeup call for the international authority as this represents a risk for global public health. The lack of antiviral drugs and effective antibiotics on the market triggers the need to search for safe therapeutics from medicinal plants to fight viral and microbial infections. In the present study, we investigated whether a mangrove plant, Bruguiera gymnorhiza (L.) Lam. (B. gymnorhiza) collected in Mauritius, possesses antimicrobial and antibiotic potentiating abilities and exerts anti-ZIKV activity at non-cytotoxic doses. Microorganisms Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 70603, methicillin-resistant Staphylococcus aureus ATCC 43300 (MRSA), Salmonella enteritidis ATCC 13076, Sarcina lutea ATCC 9341, Proteus mirabilis ATCC 25933, Bacillus cereus ATCC 11778 and Candida albicans ATCC 26555 were used to evaluate the antimicrobial properties. Ciprofloxacin, chloramphenicol and streptomycin antibiotics were used for assessing antibiotic potentiating activity. ZIKVMC-MR766NIID (ZIKVGFP) was used for assessing anti-ZIKV activity. In silico docking (Autodock 4) and ADME (SwissADME) analyses were performed on collected data. Antimicrobial results revealed that Bruguiera twig ethyl acetate (BTE) was the most potent extract inhibiting the growth of all nine microbes tested, with minimum inhibitory concentrations ranging from 0.19-0.39 mg/mL. BTE showed partial synergy effects against MRSA and Pseudomonas aeruginosa when applied in combination with streptomycin and ciprofloxacin, respectively. By using a recombinant ZIKV-expressing reporter GFP protein, we identified both Bruguiera root aqueous and Bruguiera fruit aqueous extracts as potent inhibitors of ZIKV infection in human epithelial A549 cells. The mechanisms by which such extracts prevented ZIKV infection are linked to the inability of the virus to bind to the host cell surface. In silico docking showed that ZIKV E protein, which is involved in cell receptor binding, could be a target for cryptochlorogenic acid, a chemical compound identified in B. gymnorhiza. From ADME results, cryptochlorogenic acid is predicted to be not orally bioavailable because it is too polar. Scientific data collected in this present work can open a new avenue for the development of potential inhibitors from B. gymnorhiza to fight ZIKV and microbial infections in the future.

Biofilm Development on Urinary Catheters Promotes the Appearance of Viable but Nonculturable Bacteria.

Catheter-associated urinary tract infections have serious consequences, for both patients and health care resources. Much work has been carried out to develop an antimicrobial catheter. Although such developments have shown promise under laboratory conditions, none have demonstrated a clear advantage in clinical trials. Using a range of microbiological and advanced microscopy techniques, a detailed laboratory study comparing biofilm development on silicone, hydrogel latex, and silver alloy-coated hydrogel latex catheters was carried out. Biofilm development by Escherichia coli, Pseudomonas aeruginosa, and Proteus mirabilis on three commercially available catheters was tracked over time. Samples were examined with episcopic differential interference contrast (EDIC) microscopy, culture analysis, and staining techniques to quantify viable but nonculturable (VBNC) bacteria. Both qualitative and quantitative assessments found biofilms to develop rapidly on all three materials. EDIC microscopy revealed the rough surface topography of the materials. Differences between culture counts and quantification of total and dead cells demonstrated the presence of VBNC populations, where bacteria retain viability but are not metabolically active. The use of nonculture-based techniques showed the development of widespread VBNC populations. These VBNC populations were more evident on silver alloy-coated hydrogel latex catheters, indicating a bacteriostatic effect at best. The laboratory tests reported here, which detect VBNC bacteria, allow more rigorous assessment of antimicrobial catheters, explaining why there is often minimal benefit to patients.IMPORTANCE Several antimicrobial urinary catheter materials have been developed, but, although laboratory studies may show a benefit, none have significantly improved clinical outcomes. The use of poorly designed laboratory testing and lack of consideration of the impact of VBNC populations may be responsible. While the presence of VBNC populations is becoming more widely reported, there remains a lack of understanding of the clinical impact or influence of exposure to antimicrobial products. This is the first study to investigate the impact of antimicrobial surface materials and the appearance of VBNC populations. This demonstrates how improved testing is needed before clinical trials are initiated.

Does washing medical devices before and after use decrease bacterial contamination?: An in vitro study.

ABSTRACT: Surface treatment of medical devices may be a way of avoiding the need for replacement of these devices and the comorbidities associated with infection. The aim of this study was to evaluate whether pre- and postcontamination washing of 2 prostheses with different textures can decrease bacterial contamination.The following microorganisms were evaluated: Staphylococcus aureus, Staphylococcus epidermidis, Proteus mirabilis and Enterococcus faecalis. Silicone and expanded polytetrafluoroethylene vascular prostheses were used and divided into 3 groups: prostheses contaminated; prostheses contaminated and treated before contamination; and prostheses contaminated and treated after contamination. Treatments were performed with antibiotic solution, chlorhexidine and lidocaine. After one week of incubation, the prostheses were sown in culture medium, which was incubated for 48 hours. The area of colony formation was evaluated by fractal dimension, an image analysis tool.The antibiotic solution inhibited the growth of S epidermidis and chlorhexidine decrease in 53% the colonization density for S aureus in for both prostheses in the pre-washing. In postcontamination washing, the antibiotic solution inhibited the growth of all bacteria evaluated; there was a 60% decrease in the colonization density of S aureus and absence of colonization for E faecalis with chlorhexidine; and lidocaine inhibited the growth of S aureus in both prostheses.Antibiotic solution showed the highest efficiency in inhibiting bacterial growth, especially for S epidermidis, in both washings. Lidocaine was able to reduce colonization by S aureus in post-contamination washing, showing that it can be used as an alternative adjuvant treatment in these cases.

Deacidification by FhlA-dependent hydrogenase is involved in urease activity and urinary stone formation in uropathogenic Proteus mirabilis.

Proteus mirabilis is an important uropathogen, featured with urinary stone formation. Formate hydrogenlyase (FHL), consisting of formate dehydrogenase H and hydrogenase for converting proton to hydrogen, has been implicated in virulence. In this study, we investigated the role of P. mirabilis FHL hydrogenase and the FHL activator, FhlA. fhlA and hyfG (encoding hydrogenase large subunit) displayed a defect in acid resistance. fhlA and hyfG mutants displayed a delay in medium deacidification compared to wild-type and ureC mutant failed to deacidify the medium. In addition, loss of fhlA or hyfG decreased urease activity in the pH range of 5-8. The reduction of urease activities in fhlA and hyfG mutants subsided gradually over the pH range and disappeared at pH 9. Furthermore, mutation of fhlA or hyfG resulted in a decrease in urinary stone formation in synthetic urine. These indicate fhlA- and hyf-mediated deacidification affected urease activity and stone formation. Finally, fhlA and hyfG mutants exhibited attenuated colonization in mice. Altogether, we found expression of fhlA and hyf confers medium deacidification via facilitating urease activity, thereby urinary stone formation and mouse colonization. The link of acid resistance to urease activity provides a potential strategy for counteracting urinary tract infections by P. mirabilis.

Evaluation of inhibitory activity of domestic probiotics for against invasion and infection by Proteus mirabilis in the urinary tract.

INTRODUCTION: Approximately 5% of men and 40%-50% of women have experienced urinary tract infections (UTI), which are the most common infectious diseases and nosocomial infections in humans. Proteus mirabilis is susceptible to most antibiotics, but antibiotic treatment usually causes side effects. In this research, lactic acid bacteria (LAB) was assessed for its inhibitory activity against a urinary tract pathogen. METHODOLOGY: We studied the effect of pH adjustment, heat, and enzyme treatments on the inhibitory activity of LAB strains and their supernatants, using well-diffusion and co-culture assays. In the cell culture assay, anti-adhesion and anti-invasion activities against P. mirabilis were tested with SV-HUC-1 urothelial cells. RESULTS: LAB were able to adhere to the urothelial cells and inhibited P. mirabilis growth. LAB were also able to inhibit P. mirabilis adhesion to or invasion of SV-HUC-1 urothelial cells. Finally, in the competition assay, LAB showed inhibitory effects against P. mirabilis. LAB could also inhibit the invasion of P. mirabilis into urothelial cells. CONCLUSIONS: Two LAB strains (PM206 and 229) exhibited antagonistic activity against P. mirabilis adhesion or invasion of urothelial cells in culture. In the future, probiotics may be used in food or urinary tract cleansing and could replace antibiotic treatments.

Impact of Antibiotic-Resistant Bacteria on Immune Activation and Clostridioides difficile Infection in the Mouse Intestine.

Antibiotic treatment of patients undergoing complex medical treatments can deplete commensal bacterial strains from the intestinal microbiota, thereby reducing colonization resistance against a wide range of antibiotic-resistant pathogens. Loss of colonization resistance can lead to marked expansion of vancomycin-resistant Enterococcus faecium (VRE), Klebsiella pneumoniae, and Escherichia coli in the intestinal lumen, predisposing patients to bloodstream invasion and sepsis. The impact of intestinal domination by these antibiotic-resistant pathogens on mucosal immune defenses and epithelial and mucin-mediated barrier integrity is unclear. We used a mouse model to study the impact of intestinal domination by antibiotic-resistant bacterial species and strains on the colonic mucosa. Intestinal colonization with K. pneumoniae, Proteus mirabilis, or Enterobacter cloacae promoted greater recruitment of neutrophils to the colonic mucosa. To test the hypothesis that the residual microbiota influences the severity of colitis caused by infection with Clostridioides difficile, we coinfected mice that were colonized with ampicillin-resistant bacteria with a virulent strain of C. difficile and monitored colonization and pathogenesis. Despite the compositional differences in the gut microbiota, the severity of C. difficile infection (CDI) and mortality did not differ significantly between mice colonized with different ampicillin-resistant bacterial species. Our results suggest that the virulence mechanisms enabling CDI and epithelial destruction outweigh the relatively minor impact of less-virulent antibiotic-resistant intestinal bacteria on the outcome of CDI.

Proteus mirabilis Targets Atherosclerosis Plaques in Human Coronary Arteries via DC-SIGN (CD209).

Bacterial DNAs are constantly detected in atherosclerotic plaques (APs), suggesting that a combination of chronic infection and inflammation may have roles in AP formation. A series of studies suggested that certain Gram-negative bacteria were able to interact with dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin [DC-SIGN; cluster of differentiation (CD) 209] or langerin (CD207), thereby resulting in deposition of CD209s at infection sites. We wondered if Proteus mirabilis (a member of Proteobacteria family) could interact with APs through CD209/CD207. In this study, we first demonstrated that CD209/CD207 were also receptors for P. mirabilis that mediated adherence and phagocytosis by macrophages. P. mirabilis interacted with fresh and CD209s/CD207-expressing APs cut from human coronary arteries, rather than in healthy and smooth arteries. These interactions were inhibited by addition of a ligand-mimic oligosaccharide and the coverage of the ligand, as well as by anti-CD209 antibody. Finally, the hearts from an atherosclerotic mouse model contained higher numbers of P. mirabilis than that of control mice during infection-challenging. We therefore concluded that the P. mirabilis interacts with APs in human coronary arteries via CD209s/CD207. It may be possible to slow down the progress of atherosclerosis by blocking the interactions between CD209s/CD207 and certain atherosclerosis-involved bacteria with ligand-mimic oligosaccharides.

Phytochemical, antimicrobial and time-kill kinetics potentials of Euphorbia nivulia Buch.-Ham.: A Cholistan desert medicinal plant.

Euphorbia nivulia a locally occurring plant species possesses antiseptic, analgesic and anti-inflammatory properties and is ethnopharmacologically used in various ailments like skin, ear disorders, boils, and worm infestation. Preliminary phytochemical screening showed presence of flavonoids, polyphenolics, glycosides, alkaloids, tannins and triterpenoids in (70% aqueous-ethanolic) Euphorbia nivulia crude extract (En cr) and its four fractions, i.e., hexane fraction (En hex), butanol fraction (En bt), chloroform fraction (En ch), and aqueous fraction (En aq). In current study, Agar well diffusion and time-kill kinetic assays were performed for antimicrobial activity. 300 mg/ml concentration showed maximum inhibitory zone. Highest zone of inhibition (15.5mm) was demonstrated by En ch fraction against Proteus mirabilis. Staphyllococcus aureus was the most sensitive bacteria against whom all fractions except En aq fraction were active. Maximum MIC (15.3 mg/ml) was shown by En ch fraction against Proteus mirabilis. Similarly, En ch fraction showed (15.1 mg/ml) remarkable MIC against Candida albicans. Significant higher antibacterial and antifungal activity was revealed in high concentration. Time-kill kinetics studies revealed bacteriostatic action. Noteworthy antimicrobial activity may be due to bioactive compounds of extract which may be a potential antibacterial and antifungal agent.

Altered metabolomic profile of dual-species biofilm: Interactions between Proteus mirabilis and Candida albicans.

In this study, we aimed to determine the interspecies interactions between Proteus mirabilis and Candida albicans. Mono and dual-species biofilms were grown in a microtiter plate and metabolomic analysis of the biofilms was performed. The effects of togetherness of two species on the expression levels of candidal virulence genes and urease and swarming activities of P.mirabilis were investigated. The growth of C.albicans was inhibited by P.mirabilis whereas the growth and swarming activity of P.mirabilis were increased by C.albicans. The inhibition of Candida cell growth was found to be biofilm specific. The alteration was not detected in urease activity. The expressions of EFG1, HWP1 and SAP2 genes were significantly down-regulated, however, LIP1 was upregulated by P.mirabilis. In the presence of P.mirabilis carbonhydrates, amino acids, polyamine and lipid metabolisms were altered in C.albicans. Interestingly, the putrescine level was increased up to 230 fold in dual-species biofilm compared to monospecies C.albicans biofilm. To our knowledge, this is the first study to investigate the impact of each microbial pathogen on the dual microbial environment by integration of metabolomic data.

Inhibition of urease activity in the urinary tract pathogens Staphylococcus saprophyticus and Proteus mirabilis by dimethylsulfoxide (DMSO).

AIMS: Urease is a virulence factor for the urinary tract pathogens Staphylococcus saprophyticus and Proteus mirabilis. Dimethylsulfoxide (DMSO) is structurally similar to urea, used as a solvent for urease inhibitors, and an effective treatment for interstitial cystitis/bladder pain syndrome (IC/BPS). The aims of this study were to test DMSO as a urease inhibitor and determine its physiological effects on S. saprophyticus and P. mirabilis. METHODS AND RESULTS: Urease activity in extracts and whole cells was measured by the formation of ammonium ions. Urease was highly sensitive to noncompetitive inhibition by DMSO (Ki about 6 mmol l-1 ). DMSO inhibited urease activity in whole cells, limited bacterial growth in media containing urea, and slowed the increase in pH which occurred in artificial urine medium. CONCLUSIONS: DMSO should be used with caution as a solvent when testing plant extracts or other potential urease inhibitors. Because it can inhibit bacterial growth and delay an increase in pH, it may be an effective treatment for urinary tract infections. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first detailed study of the inhibition of urease by DMSO. Dimethylsulfoxide may be used to treat urinary tract infections that are resistant to antibiotics or herbal remedies.

A Rare Opportunist, Morganella morganii, Decreases Severity of Polymicrobial Catheter-Associated Urinary Tract Infection.

Catheter-associated urinary tract infections (CAUTIs) are common hospital-acquired infections and frequently polymicrobial, which complicates effective treatment. However, few studies experimentally address the consequences of polymicrobial interactions within the urinary tract, and the clinical significance of polymicrobial bacteriuria is not fully understood. Proteus mirabilis is one of the most common causes of monomicrobial and polymicrobial CAUTI and frequently cocolonizes with Enterococcus faecalis, Escherichia coli, Providencia stuartii, and Morganella morganiiP. mirabilis infections are particularly challenging due to its potent urease enzyme, which facilitates formation of struvite crystals, catheter encrustation, blockage, and formation of urinary stones. We previously determined that interactions between P. mirabilis and other uropathogens can enhance P. mirabilis urease activity, resulting in greater disease severity during experimental polymicrobial infection. Our present work reveals that M. morganii acts on P. mirabilis in a contact-independent manner to decrease urease activity. Furthermore, M. morganii actively prevents urease enhancement by E. faecalis, P. stuartii, and E. coli Importantly, these interactions translate to modulation of disease severity during experimental CAUTI, predominantly through a urease-dependent mechanism. Thus, products secreted by multiple bacterial species in the milieu of the catheterized urinary tract can directly impact prognosis.

Chlorpromazine-impregnated catheters as a potential strategy to control biofilm-associated urinary tract infections.

Aim: This study proposes the impregnation of Foley catheters with chlorpromazine (CPZ) to control biofilm formation by Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae. Materials & methods: The minimum inhibitory concentrations (MICs) for CPZ and the effect of CPZ on biofilm formation were assessed. Afterward, biofilm formation and the effect of ciprofloxacin and meropenem (at MIC) on mature biofilms grown on CPZ-impregnated catheters were evaluated. Results: CPZ MIC range was 39.06-625 mg/l. CPZ significantly reduced (p < 0.05) biofilm formation in vitro and on impregnated catheters. In addition, CPZ-impregnation potentiated the antibiofilm activity of ciprofloxacin and meropenem. Conclusion: These findings bring perspectives for the use of CPZ as an adjuvant for preventing and treating catheter-associated urinary tract infections.

Culture Methods for Proteus mirabilis.

Proteus mirabilis is generally easy to culture, but its tendency to swarm on a wide variety of media can interfere with isolation of single colonies or identification of other species in a sample. Therefore, specialized media may be needed to control swarming or to study the bacteria under chemically defined conditions. Here, methods are described for routine culture of P. mirabilis, isolation of P. mirabilis from mixed cultures, and culture of P. mirabilis on physiologically relevant media.

Isolation and Purification of Proteus mirabilis Bacteriophage.

Bacteriophages specifically targeting different strains of bacteria can be isolated from urban sewage using properly modified enrichment techniques. This chapter provides a detailed protocol for isolation of Proteus mirabilis-specific bacteriophages. Briefly, prefiltered sewage is mixed with double-concentrated tryptic soy broth containing the target strain and incubated. Subsequently, the suspension is spread on phage nutrient agar, and if needed, supplemented with swarming motility inhibitor, for the induction of bacterial growth and phage multiplication. Phages infecting bacteria are identified by plaques (patches of dead bacteria) in the confluent bacterial lawn. A pure phage preparation is obtained by cutting out a single plaque from a double-layer agar plate and subsequent virus propagation five times on a given P. mirabilis strain.

Magnesium-doped zinc oxide nanoparticles alter biofilm formation of Proteus mirabilis.

Aim:Proteus mirabilis biofilms colonize medical devices, and their role in microbial pathogenesis is well established. Magnesium-doped zinc oxide nanoparticles (ZnO:MgO NPs) have potential antimicrobial properties; thus, we aimed at evaluating the antibiofilm activity of ZnO:MgO NPs against P. mirabilis biofilm. Materials & methods: After synthesis and characterization of ZnO:MgO NPs and their addition to a polymer film, we evaluated the stages of P. mirabilis biofilm development over glass coverslip covered by different concentrations of ZnO:MgO NPs. Results: Low concentrations of ZnO:MgO NPs affect the development of P. mirabilis biofilm. Descriptors showed reduced values in bacterial number, bacterial volume and extracellular material. Conclusion: Our results highlight this new application of ZnO:MgO NPs as a potential antibiofilm strategy in medical devices.

Allicin prevents the formation of Proteus-induced urinary crystals and the blockage of catheter in a bladder model in vitro.

Stone formation and catheter blockage are major complications of Proteus UTIs. In this study, we investigated the ability of allicin to inhibit P. mirabilis-induced struvite crystallization and catheter blockage using a synthetic bladder model. Struvite crystallization inhibition study was carried out using P. mirabilis lysate as urease enzyme source in synthetic urine (SU). Struvite productions were monitored by phase contrast light microscopy and measurements of pH, Mg2+ and Ca2+ precipitation and turbidity. A catheter blockage study was performed in a synthetic bladder model mimicking natural UTI in the presence of allicin at sub-MIC concentrations (MIC = 64 µg/ml). The results of crystallization study showed that allicin inhibited pH rise and consequently turbidity and precipitation of ions in a dose-dependent manner. The results of catheter blockage study showed that allicin at sub-MIC concentrations (2, 4, 8 µg/ml) significantly increased the time for catheter blockage to occur to 61, 74 and 92 h respectively compared to allicin-free control (48 h). In a similar way, the results showed that allicin delayed the increase of SU pH level in bladder model in a dose-dependent manner compared to allicin-free control. The results also showed that following the increase of allicin concentration, Mg2+ and Ca2+ deposition in catheters were much lower compared to allicin-free control, further confirmed by direct observation of the catheters' eyehole and cross sections. We conclude that allicin prevents the formation of Proteus-induced urinary crystals and the blockage of catheters by delaying pH increase and lowering Mg2+ and Ca2+ deposition in a dose-dependent manner.

Twin arginine translocation, ammonia incorporation, and polyamine biosynthesis are crucial for Proteus mirabilis fitness during bloodstream infection.

The Gram-negative bacterium Proteus mirabilis is a common cause of catheter-associated urinary tract infections (CAUTI), which can progress to secondary bacteremia. While numerous studies have investigated experimental infection with P. mirabilis in the urinary tract, little is known about pathogenesis in the bloodstream. This study identifies the genes that are important for survival in the bloodstream using a whole-genome transposon insertion-site sequencing (Tn-Seq) approach. A library of 50,000 transposon mutants was utilized to assess the relative contribution of each non-essential gene in the P. mirabilis HI4320 genome to fitness in the livers and spleens of mice at 24 hours following tail vein inoculation compared to growth in RPMI, heat-inactivated (HI) naïve serum, and HI acute phase serum. 138 genes were identified as ex vivo fitness factors in serum, which were primarily involved in amino acid transport and metabolism, and 143 genes were identified as infection-specific in vivo fitness factors for both spleen and liver colonization. Infection-specific fitness factors included genes involved in twin arginine translocation, ammonia incorporation, and polyamine biosynthesis. Mutants in sixteen genes were constructed to validate both the ex vivo and in vivo results of the transposon screen, and 12/16 (75%) exhibited the predicted phenotype. Our studies indicate a role for the twin arginine translocation (tatAC) system in motility, translocation of potential virulence factors, and fitness within the bloodstream. We also demonstrate the interplay between two nitrogen assimilation pathways in the bloodstream, providing evidence that the GS-GOGAT system may be preferentially utilized. Furthermore, we show that a dual-function arginine decarboxylase (speA) is important for fitness within the bloodstream due to its role in putrescine biosynthesis rather than its contribution to maintenance of membrane potential. This study therefore provides insight into pathways needed for fitness within the bloodstream, which may guide strategies to reduce bacteremia-associated mortality.

Bacterial biofilm formation on indwelling urethral catheters.

Urethral catheters are the most commonly deployed medical devices and used to manage a wide range of conditions in both hospital and community care settings. The use of long-term catheterization, where the catheter remains in place for a period >28 days remains common, and the care of these patients is often undermined by the acquisition of infections and formation of biofilms on catheter surfaces. Particular problems arise from colonization with urease-producing species such as Proteus mirabilis, which form unusual crystalline biofilms that encrust catheter surfaces and block urine flow. Encrustation and blockage often lead to a range of serious clinical complications and emergency hospital referrals in long-term catheterized patients. Here we review current understanding of bacterial biofilm formation on urethral catheters, with a focus on crystalline biofilm formation by P. mirabilis, as well as approaches that may be used to control biofilm formation on these devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Urinary catheters are the most commonly used medical devices in many healthcare systems, but their use predisposes to infection and provide ideal conditions for bacterial biofilm formation. Patients managed by long-term urethral catheterization are particularly vulnerable to biofilm-related infections, with crystalline biofilm formation by urease producing species frequently leading to catheter blockage and other serious clinical complications. This review considers current knowledge regarding biofilm formation on urethral catheters, and possible strategies for their control.

Structures of two fimbrial adhesins, AtfE and UcaD, from the uropathogen Proteus mirabilis.

The important uropathogen Proteus mirabilis encodes a record number of chaperone/usher-pathway adhesive fimbriae. Such fimbriae, which are used for adhesion to cell surfaces/tissues and for biofilm formation, are typically important virulence factors in bacterial pathogenesis. Here, the structures of the receptor-binding domains of the tip-located two-domain adhesins UcaD (1.5 Šresolution) and AtfE (1.58 Šresolution) from two P. mirabilis fimbriae (UCA/NAF and ATF) are presented. The structures of UcaD and AtfE are both similar to the F17G type of tip-located fimbrial receptor-binding domains, and the structures are very similar despite having only limited sequence similarity. These structures represent an important step towards a molecular-level understanding of P. mirabilis fimbrial adhesins and their roles in the complex pathogenesis of urinary-tract infections.

Identification of small molecule compounds active against Staphylococcus aureus and Proteus mirabilis.

Staphylococcus aureus is a human pathogen rapidly becoming a serious health problem due to ease of acquiring antibiotic resistance. To help identify potential new drug candidates effective against the pathogen, a small focused library was screened for inhibition of bacterial growth against several pathogens, including S. aureus. At least one of the compounds, Compound 10, was capable of blocking bacterial growth of S. aureus in a test tube with IC50 = 140 ±â€¯30 µM. Another inhibitor, Compound 7, was bacteriostatic against S. aureus with IC50 ranging from 33 to 150 µM against 3 different strains. However, only Compound 7 was bactericidal against P. mirabilis as examined by electron microscopy. Human cell line toxicity studies suggested that both compounds had small effect on cell growth at 100 µM concentration as examined by MTT assay. Analysis of compounds' structures showed lack of similarity to any known antibiotics and bacteriostatics, potentially offering the inhibitors as an alternative to existing solutions in controlling bacterial infections for selected pathogens.