Biocomputational Prediction Approach Targeting FimH by Natural SGLT2 Inhibitors: A Possible Way to Overcome the Uropathogenic Effect of SGLT2 Inhibitor Drugs.

The Food and Drug Administration (FDA) approved a new class of anti-diabetic medication (a sodium-glucose co-transporter 2 (SGLT2) inhibitor) in 2013. However, SGLT2 inhibitor drugs are under evaluation due to their associative side effects, such as urinary tract and genital infection, urinary discomfort, diabetic ketosis, and kidney problems. Even clinicians have difficulty in recommending it to diabetic patients due to the increased probability of urinary tract infection. In our study, we selected natural SGLT2 inhibitors, namely acerogenin B, formononetin, (-)-kurarinone, (+)-pteryxin, and quinidine, to explore their potential against an emerging uropathogenic bacterial therapeutic target, i.e., FimH. FimH plays a critical role in the colonization of uropathogenic bacteria on the urinary tract surface. Thus, FimH antagonists show promising effects against uropathogenic bacterial strains via their targeting of FimH's adherence mechanism with less chance of resistance. The molecular docking results showed that, among natural SGLT2 inhibitors, formononetin, (+)-pteryxin, and quinidine have a strong interaction with FimH proteins, with binding energy (∆G) and inhibition constant (ki) values of -5.65 kcal/mol and 71.95 µM, -5.50 kcal/mol and 92.97 µM, and -5.70 kcal/mol and 66.40 µM, respectively. These interactions were better than those of the positive control heptyl α-d-mannopyranoside and far better than those of the SGLT2 inhibitor drug canagliflozin. Furthermore, a 50 ns molecular dynamics simulation was conducted to optimize the interaction, and the resulting complexes were found to be stable. Physicochemical property assessments predicted little toxicity and good drug-likeness properties for these three compounds. Therefore, formononetin, (+)-pteryxin, and quinidine can be proposed as promising SGLT2 inhibitors drugs, with add-on FimH inhibition potential that might reduce the probability of uropathogenic side effects.

Target Selectivity of FimH Antagonists.

Mannose-based FimH antagonists are considered new therapeutics for the treatment of urinary tract infections (UTIs). They prevent the adhesion of uropathogenic Escherichia coli (UPEC) to urothelial cell surfaces triggered by the lectin FimH, which is located at the tip of bacterial type 1 pili. Because all reported FimH antagonists are α-d-mannosides, they are also potential ligands of mannose receptors of the human host system. We therefore investigated the selectivity range of five FimH antagonists belonging to different compound families by comparing their affinities for FimH and eight human mannose receptors. On the basis of the detected selectivity range of approximately 5 orders of magnitude, no adverse side effects resulting from nonselective binding to the human receptors have to be expected. FimH antagonists can therefore be further considered as potential therapeutics for the treatment of UTI.

Nitazoxanide inhibits biofilm production and hemagglutination by enteroaggregative Escherichia coli strains by blocking assembly of AafA fimbriae.

Enteroaggregative Escherichia coli (EAEC) strains have emerged as common causes of persistent diarrhea and malnutrition among children and HIV-infected persons. During infection, EAEC typically adheres to the intestinal mucosa via fimbrial adhesins, which results in a characteristic aggregative pattern. In the study described here we investigated whether the broad-spectrum antiparasitic and antidiarrheal drug nitazoxanide (NTZ) might be active against EAEC in vitro. While E. coli strains were resistant to NTZ in rich Luria-Bertani medium (MIC > 64 microg/ml), the drug was slightly inhibitory in a minimal medium supplemented with glucose (MinA-G medium; MIC, approximately 32 microg/ml). NTZ also inhibited biofilm production by strain EAEC 042 in both Dulbecco's modified Eagle's medium and MinA-G medium with a 50% inhibitory concentration of approximately 12 microg/ml. Immunofluorescence and immunoblot analyses with antibody against the major fimbrial subunit AafA of aggregative adherence fimbriae vaariant II (AAF/II) established that the numbers of AAF/II filaments on bacteria grown in the presence of NTZ were dramatically reduced. Comparative quantitative reverse transcription-PCR and reporter gene fusions (aafA::phoA) indicated that aafA expression was unaffected by NTZ, while aggR transcript levels and aggR::lacZ expression were increased approximately 10- and 2.5-fold, respectively, compared with that for the untreated controls. More generally, NTZ inhibited hemagglutination (HA) of red blood cells by the non-biofilm-producing strain JM221 expressing either AAF/I or type I fimbriae. Our findings suggest that the inhibitory action of NTZ on biofilm formation and HA is likely due to inhibition of fimbrial assembly. Antimicrobial agents that inhibit the assembly or function of fimbrial filaments should be good candidates for the prevention of infection.

Inhibition of adhesion of type 1 fimbriated Escherichia coli to highly mannosylated ligands.

The inhibitory potencies of a number of mannosides, di- and trivalent mannosides, a set of mannose-terminating dendrimers, and five types of mannose-bearing neoglycoproteins were determined by using a binding assay that measures the binding of (125)I-labeled, highly mannosylated neoglycoprotein to a type 1 fimbriated Escherichia coli (K12) strain in suspension. The IC(50) values (the concentration of inhibitor that causes 50 % reduction in the bound (125)I-ligand to E. coli) obtained by this method were much lower than the equivalent values obtained by hemagglutination or in assays that involve microplate immobilization. Two important factors that strongly influence the affinity to E. coli adhesin are: 1) the presence of an alpha-oriented aglycon that has a long aliphatic chain or an aromatic group immediately next to the glycosyl oxygen, and 2) the presence of multiple mannosyl residues that can span a distance of 20 nm or longer on a relatively inflexible structure. The two best inhibitors, which are a highly mannosylated neoglycoprotein with the longest linking arm between a mannose and protein amino group and the largest mannosylated dendrimer (fourth generation), exhibited sub-nM IC(50) values.

Effect of 2,4-dichlorophenoxyacetic acid herbicide on escherichia coli growth, chemical composition, and cellular envelope.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide widely used in the world and mainly excreted by the renal route in exposed humans and animals. Herbicides can affect other nontarget organisms, such as Escherichia coli. We observed that a single exposure to 1 mM 2,4-D diminished growth and total protein content in all E. coli strains tested in vitro. In addition, successive exposures to 0.01 mM 2,4-D had a toxic effect decreasing growth up to early stationary phase. Uropathogenic E. coli adhere to epithelial cells mediated by fimbriae, adhesins, and hydrophobic properties. 2,4-D exposure of uropathogenic E. coli demonstrated altered hydrophobicity and fimbriation. Hydrophobicity index values obtained by partition in p-xylene/water were 300-420% higher in exposed cells than in control ones. Furthermore, values of hemagglutination titer, protein contents in fimbrial crude extract, and electron microscopy demonstrated a significant diminution of fimbriation in treated cells. Other envelope alterations could be detected, such as lipoperoxidation, evidenced by decreased polyunsaturated fatty acids and increased lipid degradation products (malonaldehyde), and motility diminution. These alterations decreased cell adherence to erythrocytes, indicating a diminished pathogenic capacity of the 2,4-D-exposed E. coli.

Association between antibiotic resistance and the expression of Dr adhesin among uropathogenic Escherichia coli.

BACKGROUND: Urinary tract infections (UTIs) are a significant health problem and Escherichia coli has been exported to be the primary pathogen in approximately 80% of cases. E. coli express structures called adhesins, fimbriae or pili that help them bind to specific tissue receptors. One such adhesin is Dr, which binds to the complement decay-accelerating factor (CD55) on the host cell. The purpose of the present study was to review the epidemiology and antimicrobial sensitivity spectrum of Dr adhesin-bearing E. coli isolates in women with UTI. METHODS AND RESULTS: A total of 337 uropathogenic E. coli isolates were collected, and mannose-resistant hemagglutination was observed in 43%, while 12.4% expressed Dr adhesin. All 337 uropathogenic E. coli isolates were found to be resistant to penicillin, oxacillin, bactericin and cloxacillin. None of the isolates was resistant to quinolones. The resistance to sulfamethoxazole was most common (90%), followed by nalidixic acid (51%) and ampicillin (41%). Interestingly, uropathogenic E. coli expressing Dr adhesin had a high incidence of ampicillin resistance (83%), and only 17% of the Dr-bearing isolates were found to be resistant to an ampicillin/sulbactum combination. CONCLUSION: These results indicate that UTIs may be successfully treated with ampicillin in combination with a beta-lactamase inhibitor, so that selective colonization by Dr adhesin-bearing uropathogenic E. coli is prevented, which is probably promoted by treating these patients with ampicillin alone.

Efecto modulador de antibióticos sobre la adherencia bacteriana a biomateriales / Antibiotics modulation of bacterial adherence to medical biomaterials

La colonización de polímeros origina un foco de infección de difícil erradicación, debido a que las bacterias adheridas a materiales inertes presentaban propiedades fisiológicas especiales. Las infecciones urinarias complicadas debidas a sondas vesicales son las responsables del 40 por ciento de las infecciones urinarias hospitalarias. Se analizó el efecto modular de cefotaxima y ciprofloxacina en concentraciones subinhibitorias, sobre la adherencia a sondas vesicales de cepas uropatógenas de Escherichia coli. Este estudio se efectuó con cepas con bajo y elevado grado de hidrofobicidad determinados por agregación salina. Los experimentos de adherencia a sondas vesicales, en ausencia y presencia de ambos antibióticos, se realizaron a la hora y a las 24 h de contacto con los antibacterianos mencionados. El número de UFC/ml adheridas, se determinó por espectrofotometría y recuento de colonias. Se demostró que en la mayoría de las cepas con elevado grado de hidrofobicidad, aumentó el número de UFC/ml que se adhirieron a la sonda vesical, con alguno de los tratamientos. En forma inversa se comportaron las cepas con bajo grado de hidrofobicidad. El comportamiento diferente de las cepas, tratadas en las mismas condiciones, no permite generalizar el efecto de los antibióticos en concentraciones subinhibitorias, sobre la colonización bacteriana de sondas vesicales (AU)

Efecto modulador de antibióticos sobre la adherencia bacteriana a biomateriales / Antibiotics modulation of bacterial adherence to medical biomaterials

La colonización de polímeros origina un foco de infección de difícil erradicación, debido a que las bacterias adheridas a materiales inertes presentaban propiedades fisiológicas especiales. Las infecciones urinarias complicadas debidas a sondas vesicales son las responsables del 40 por ciento de las infecciones urinarias hospitalarias. Se analizó el efecto modular de cefotaxima y ciprofloxacina en concentraciones subinhibitorias, sobre la adherencia a sondas vesicales de cepas uropatógenas de Escherichia coli. Este estudio se efectuó con cepas con bajo y elevado grado de hidrofobicidad determinados por agregación salina. Los experimentos de adherencia a sondas vesicales, en ausencia y presencia de ambos antibióticos, se realizaron a la hora y a las 24 h de contacto con los antibacterianos mencionados. El número de UFC/ml adheridas, se determinó por espectrofotometría y recuento de colonias. Se demostró que en la mayoría de las cepas con elevado grado de hidrofobicidad, aumentó el número de UFC/ml que se adhirieron a la sonda vesical, con alguno de los tratamientos. En forma inversa se comportaron las cepas con bajo grado de hidrofobicidad. El comportamiento diferente de las cepas, tratadas en las mismas condiciones, no permite generalizar el efecto de los antibióticos en concentraciones subinhibitorias, sobre la colonización bacteriana de sondas vesicales