Biofilm stimulating activity of solanidine and Solasodine in Pseudomonas aeruginosa.

BACKGROUND: Biofilm formation has reported as an important virulence associated properties of Pseudomonas aeruginosa that is regulated by quorum-sensing associated genes. Biofilm and quorum-sensing interfering properties of steroidal alkaloids, Solanidine and Solasodine were investigated in the present study. RESULTS: Biofilm formation capacity and relative expression level of five studied genes(lasI, lasR, rhlI, rhlR and algD) were significantly increased dose-dependently after treatment with sub-inhibitory concentrations (32 and 512 µg/ml) of the both Solanidine and Solasodine. Biofilm formation capacity was more stimulated in weak biofilm formers(9 iaolates) in comparison to the strong biofilm producers(11 isolates). The lasI gene was the most induced QS-associated gene among five investigated genes. CONCLUSION: Biofilm inducing properties of the plants alkaloids and probably medicines derived from them has to be considered for revision of therapeutic guidelines. Investigating the biofilm stimulating properties of corticosteroids and other medicines that comes from plant alkaloids also strongly proposed.

The frequency of adherence, biofilm-associated, Arginine Catabolic Mobile element genes, and biofilm formation in clinical and healthcare worker coagulase-negative staphylococci isolates.

BACKGROUND: Healthcare workers may pave the way for increased infections in hospitalized patients by coagulase-negative staphylococci (CoNS). Biofilm formation and antibiotic resistance are the major problems posed by CoNS in nosocomial infections. In this study, we determined biofilm production level and the distribution of biofilm-associated and virulence genes, including icaADBC, aap, bhp, atlE, embp, and fbe, as well as IS256, IS257, mecA, and ACME clusters (arc-A, opp-3AB) among 114 clinical (n = 57) and healthcare workers (n = 57) CoNS isolates in Kerman, Iran. RESULTS: In this study, more than 80% (n = 96) of isolates were methicillin-resistant CoNS (MR-CoNS). Out of 114 isolates, 33% (n = 38) were strong biofilm producers. Strong biofilm formation was found to be significantly different between clinical and healthcare workers' isolates (P < 0.050). In addition, 28% (n = 32) of isolates were positive for icaADBC simultaneously, and all were strong biofilm producers. The prevalence of icaADBC, mecA, bhp, fbe, and IS256 in clinical isolates was higher than that in healthcare workers' isolates (P < 0.050). A significant relationship was observed between clinical isolates and the presence of icaADBC, mecA, bhp, and IS256. Although these elements were detected in healthcare workers' isolates, they were more frequent in clinical isolates compared to those of healthcare workers. CONCLUSIONS: The high prevalence of ACME clusters in healthcare workers' isolates and biofilm formation of these isolates partially confirms the bacterial colonization in the skin of healthcare workers. Isolating MR-CoNS from healthcare workers' skin through similar genetic elements to clinical isolates, such as icaADBC, mecA, and IS256, calls for appropriate strategies to control and prevent hospital infections.

Amphiphilic peptide Mastoparan-B induces conformational changes within the AdeB efflux pump, down-regulates adeB gene expression, and restores antibiotic susceptibility in an MDR strain of Acinetobacter baumannii.

Mastoparan B (MP-B) is an amphiphilic peptide with a potent antimicrobial activity against most Gram-negative bacteria. However, there is little information available on the inhibition of the Acinetobacter baumannii resistance-nodulation-cell-division (RND) efflux pump using this antimicrobial peptide. Here, we carried out a series of in-silico experiments to find the mechanisms underlying the anti-efflux activity of MP-B using a multi-drug resistant (MDR) strain of A. baumannii (AB). According to our findings, MP-B demonstrated a potent antibacterial activity against an MDR-AB (minimum inhibitory concentration [MIC] = 1 µg/mL) followed by a 20-fold reduction in the adeB gene expression in the presence of sub-MIC of this peptide. Using Groningen Machine for Chemicals Simulation (GROMACS) via PyMOL Graphical User Interface (GUI), (we observed that, the AdeB transporter had conserved helix-turn-helix regions and a tight pore rich in Phe and Ala residues. To understand how inhibition of the AdeB is achieved, we generated 20 apo-MP-B poses using the InterPep and SiteMap tools. The high-quality model was created by homology modeling and used for docking via AutoDock/Vina to identify the MP-B binding sites. We established that the most apo-MP-B formed H-bonds to the backbone of five amino acids in the Helix-5. As a result, the dihedral angles of the involved amino acids shift by 9.0-9.6 Ǻ, causing a change in the conformation of the AdeB protein. This led to helix conformation stereoisomerization and block the AdeB activity. MP-B presumably has dual mechanisms. (1) It blocks the AdeB transporter by changing its conformation. (2) MP-B influences the adeB gene expression by binding to G-protein which laterally controls efflux regulators like MarA, RamA, SoxS, and Rob proteins.

Significant association between genes encoding virulence factors with antibiotic resistance and phylogenetic groups in community acquired uropathogenic Escherichia coli isolates.

BACKGROUND: Antibiotic resistance is an increasing phenomenon in many bacterial pathogens including uropathogenic Escherichia coli. Hypothetical anti-virulent agents could be a solution, but first clear virulence associated gene-pool of antibiotic resistant isolates have to be determined. The aim of this study is to investigate the significant associations between genes encoding VFs with antibiotic resistance and phylogenetic groups in UPEC isolates. RESULTS: The majority of 248 UPEC isolates belonged to phylogenetic group B2 (67.3%). The maximum and minimum resistance was attributed to amoxicillin (90.3%) and both fosfomycin and imipenem (1.6%) respectively. 11.3% of isolates were resistant to all antibiotic agents except that of imipenem, nitrofurantoin and fosfomycin. These highly resistant isolates were placed only in group B2 and D. The most prevalent virulence gene was ompA (93.5%). The hlyA was the only virulence gene that was significantly more prevalent in the highly resistant isolates. The ompA, malX and hlyA genes were obviously more abundant in the antibiotic resistant isolates in comparison to susceptible isolates. The papC gene was associated with amoxicillin resistance (p-value = 0.006, odds ratio: 26.00). CONCLUSIONS: Increased resistance to first line drugs prescribed for UTIs were detected in CA-UPEC isolates in our study.. Minimal resistance was observed against nitrofurantoin, fosfomycin and imipenem. Therefore, they are introduced for application in empirical therapy of UTIs. Fosfomycin may be the most effective antibiotic agent against highly resistant UPEC isolates. The presence of the ompA, malX and hlyA genes were significantly associated with resistance to different antibiotic agents. We assume that the ability of UPEC isolates to upgrade their antibiotic resistance capacity may occurs in compliance with the preliminary existence of specific virulence associated genes. But, more investigation with higher number of bacterial isolates, further virulence associated genes and comparison of gene pools from CA-UPEC isolates with HA-UPEC are proposed to confirm these finding and discovering new aspects of this association.

A Novel Reduction Strategy of Clarithromycin Resistance in Helicobacter pylori.

BACKGROUND: Antibiotic resistance is a major therapeutic problem in patients infected with Helicobacter pylori. H. pylori clarithromycin resistant mutants have been evolved during antibiotic therapy, this is mainly due to 23s rRNA point mutations. OBJECTIVES: In the present study, we investigated anti-mutational features of four traditionally Iranian medicinal plants on three local isolated H. pylori strains. MATERIALS AND METHODS: In this study clarithromycin resistance was used as a mutation indicator. Frequencies of such mutations in the presence and absence of plant extracts were evaluated. Mutation incidence was evaluated by Luria Delbruck fluctuation assay. RESULTS: The mean mutation frequency in H. pylori isolates was 27 × 10(-9) which decreased at the presence of Mirtus communis, Teucrium polium, Achillea millefolium and Thymus vulgaris of plant extract, this amount was 97.4%, 95.2%, 63.7% and 19.6% respectively. Moreover, A-to-G transition at 2143 position (A2143G) was detected by PCR-sequencing as major point mutation causing clarithromycin resistant mutants. CONCLUSIONS: The efficacy of these plant extracts in prohibiting resistance showed considerable results. This finding should be considered to use plant extracts with antibiotics to develop more effective eradication regimens.

The role of different sugars, amino acids and few other substances in chemotaxis directed motility of helicobacter pylori.

OBJECTIVES: Motility plays a major role in pathogenicity of Helicobacter pylori, yet there is scarce data regarding its chemotactic behaviour. The present study was designed to investigate the chemotactic responses of local isolates of H. pylori towards various sugars, amino acids, as well as some other chemical substances. MATERIALS AND METHODS: Chemotaxis was assayed by a modified Adler's method. We used solutions of sugars, amino acids as well as urea, sodium chloride, sodium and potassium bicarbonate, sodium deoxycholate and keratin at 10 mM concentrations. RESULTS: Despite some small differences, tested H. pylori isolates generally had a positive chemotaxis towards the tested sugars (P< 0.05). Among amino acids, phenylalanine, aspartic acid, glutamic acid, isoleucine and leucine showed a positive chemotaxis (P< 0.05) ; however, tyrosine showed negative chemotaxis (repellent) (P< 0.15). Urea, sodium chloride, sodium and potassium bicarbonate showed to be attractants (P< 0.05), but sodium deoxycholate was repellent (P< 0.05). CONCLUSION: It seems that, sugars and many amino acids by their attraction for H.pylori, many amino acids, may enhance the activity of this bacterium and probably aggravate the symptoms of its infection. However, those like L-tyrosine, may possibly be employed as deterrents for H. pylori and thus can control its infections. However, we suggest that further investigations on chemotactic behaviour of many more strains of H. pylori should be carried out before a final conclusion.