Computational evaluation of modified peptides from human neutrophil peptide 1 (HNP-1).

The development of bacterial resistance toward antibiotics has been led to pay attention to the antimicrobial peptides (AMPs). The common mechanism of AMPs is disrupting the integrity of the bacterial membrane. One of the most accessible targets for α-defensins human neutrophil peptide-1 (HNP-1) is lipid II. In the present study, we performed homology modeling and geometrical validation of human neutrophil defensin 1. Then, the conformational and physicochemical properties of HNP-1 derived peptides 2Abz14S29, 2Abz23S29, and HNP1ΔC18A, as well as their interaction with lipid II were studied computationally. The overall quality of the predicted model of full protein was -5.14, where over 90% of residues were in the most favored and allowed regions in the Ramachandran plot. Although HNP-1 and HNP1ΔC18A were classified as unstable peptides, 2Abz14S29 and 2Abz23S29 were stable, based on the instability index values. Molecular docking showed similar interaction pattern of peptides and HNP-1 to lipid II. Molecular dynamic simulations revealed the overall stability of conformations, though the fluctuations of amino acids in the modified peptides were relatively higher than HNP-1. Further, the binding affinity constant (Kd) of HNP-1 and 2Abz23S29 in complex with lipid II was 10 times stronger than 2Abz14S29 and HNP1ΔC18A. Overall, computational studies of conformational and interaction patterns have signified how derived peptides could have displayed relatively similar antimicrobial results compared to HNP-1 in the reported experimental studies. Chemical modifications not only have improved the physicochemical properties of derived peptides compared to HNP-1, but also they have retained the similar pattern and binding affinity of peptides. Communicated by Ramaswamy H. Sarma.

Relationships between Virulence Factors and Antimicrobial Resistance among Escherichia coli Isolated from Urinary Tract Infections and Commensal Isolates in Tehran, Iran.

OBJECTIVES: Uropathogenic Escherichia coli (UPEC) are the major cause of urinary tract infections (UTIs). Here, we determined whether sensitivity to antibiotics was related to the prevalence of iron scavenging genes, or to biofilm and hemolysis formation. METHODS: A total of 110 UPEC and 30 E coli isolates were collected from the urine of UTI patients and feces of healthy individuals without UTI, respectively. The presence of iron receptor genes and phenotypic properties were evaluated by polymerase chain reaction and phenotypic methods, respectively. Susceptibility to routine antibiotics was evaluated using the disc diffusion method. RESULTS: The prevalence of iron scavenging genes ranged from 21.8% (ireA) to 84.5% (chuA) in the UPEC. Resistance to ceftazidime and cefotaxime was significantly correlated with the presence of fyuA and iutA iron genes. Biofilm production was significantly associated with the prevalence of fyuA and hma iron genes. A higher degree of antibiotic resistance was exhibited by isolates that produced biofilms than by their non-biofilm producing counterparts. CONCLUSION: Our study clearly indicates that biofilm production is associated with antibiotic resistance, and that iron receptors and hemolysin production also contribute to reduced antibiotic sensitivity. These results further our understanding of the role that these virulence factors play during UPEC pathogenesis, which in turn may be valuable for the development of novel treatment strategies against UTIs.

Rapid Identification of Vancomycin Resistant Enterococcus Faecalis Clinical Isolates using a Sugar Fermentation Method.

INTRODUCTION: Vancomycin Resistant Enterococci (VRE) can be found all over the world. Thus, rapid detection of the isolates could be of high importance in the treatment or prevention of the associated disease. AIM: To measure the turanose fermentation in Enterococcus faecalis clinical isolates for rapid differentiation of VRE and Vancomycin-Susceptible E. faecalis (VSE) isolates. MATERIALS AND METHODS: Forty E. faecalis samples were isolated from 200 clinical samples in Tehran Medical Center, Iran, from October 2012 to December 2012. These isolates were detected according to the standard microbial and biochemical tests. Detection of VRE isolates was originally performed by disk diffusion using 1 µg vancomycin disk, followed by Polymerase Chain Reaction (PCR) amplification of the vanA gene. Finally, the turanose consumption in 1%, 0.7% and 0.5% dilutions was detected by a phenotypic method. RESULTS: Among the 40 E. faecalis isolates, 20 vancomycin-susceptible and 20 vancomycin-resistant E. faecalis were isolated according to the disk diffusion and PCR of the vanA gene. There was a considerable difference between VRE and VSE isolates in 0.7% dilution of turanose. However, there was no significant difference between VRE and VSE in 1% and 0.5% dilutions of turanose. CONCLUSION: Since detection of VRE isolates is of high importance, especially in nosocomial infections, phenotypic methods may be highly useful for this purpose. In conclusion, our data indicate that VRE isolated from clinical samples could be distinguished from VSE isolates by turanose fermentation at dilution 0.7%.

Genotypic Characterization of Virulence Factors in Escherichia coli Isolated from Patients with Acute Cystitis, Pyelonephritis and Asymptomatic Bacteriuria.

INTRODUCTION: Urinary Tract Infections (UTIs) caused by Uropathogenic Escherichia coli (UPEC) are among the most common infections worldwide. It is well-documented that the pathogenesis of UPEC is mediated by the production of a wide variety of Virulence Factors (VFs). Thus, detection of these VFs and evaluation of their association with different clinical types of UTIs could help to understand the role of these factors in pathogenesis of UPEC isolates. AIM: To investigate the genotypic characteristics of UPEC isolates and to examine the relationship between VFs and different clinical symptoms of UTI. MATERIALS AND METHODS: In this cross-sectional study conducted at Pasteur Institute of Iran, a total of 156 UPEC isolated from outpatients and inpatients (symptomatic and asymptomatic UTI patients) visiting general and private hospitals in Tehran, Iran between March 2014 and February 2015 were included. Among them, 49 patients experienced at least one episode of recurrent UTI. A Polymerase Chain Reaction (PCR) assay was developed to detect the presence of different VFs in the isolates. Moreover, Pulsed-Field Gel Electrophoresis (PFGE) was used to characterize clonal relationships among UPEC isolates. RESULTS: The prevalence of virulence genes ranged from 0% for cdtB to 100% for fimH. The papEF, hlyA and aer genes were found to be significantly more frequent in UPEC isolated from patients with pyelonephritis, while the afa gene, the only indicator of recurrent UTIs, was more prevalent in UPEC isolated from patients with cystitis. In the present study, 34 PFGE clonal groups were found in the UPEC genome. CONCLUSION: Our findings showed that from outpatients and patients with pyelonephritis, isolates were more virulent than those isolated from inpatients and cystitis patients, respectively. PFGE displayed a large diversity in the UPEC isolates that could be considered as an evolutionary strategy in the survival of the bacteria.

Assessment of immune responses of the flagellin (FliC) fused to FimH adhesin of Uropathogenic Escherichia coli.

Urinary tract infection (UTI) caused by Uropathogenic Escherichia coli (UPEC) is one of the most common infectious diseases in the world. Despite extensive efforts, a vaccine that protects humans against UTI is currently missing. In this study, the immunogenicity of flagellin (FliC) of UPEC strain in different vaccine combinations with FimH antigen of UPEC and conventional adjuvant Montanide ISA 206 was assessed. Finally, efficacy of the immune responses was evaluated for protection of the bladder and kidney of challenged immunized mice. Mice immunized with the fusion FimH·FliC induced significantly higher anti-FliC humoral (IgG1) and cellular (Th1 and Th2) immune responses than with FliC alone or FliC admixed with FimH. The Montanide enhanced the immune responses of FliC antigen and directed the anti-FliC responses preferentially toward Th1. The FliC vaccine combinations reduced bladder infection as compared to control mice. The fusion FimH·FliC and FliC admixed with FimH and Montanide combinations gave the best results in protection of kidney infection, compared to the control mice. The results of this study propose new promising vaccine combinations based on the FliC antigen and Montanide against UTI caused by UPEC.