Microbiologically influenced corrosion of cable bolts in underground coal mines: The effect of Acidithiobacillus ferrooxidans

Reports on corrosion failure of cable bolts, used in mining and civil industries, have been increasing in the past two decades. The previous studies found that pitting corrosion on the surface of a cable bolt can initiate premature failure of the bolt. In this study, the role of Acidithiobacillus ferrooxidans (A. ferrooxidans) bacterium in the occurrence of pitting corrosion in cable bolts was studied. Stressed coupons, made from the wires of cable bolts, were immersed in testing bottles containing groundwater collected from an underground coal mine and a mixture of A. ferrooxidans and geomaterials. It was observed that A. ferrooxidans caused pitting corrosion on the surface of cable bolts in the near-neutral environment. The presence of geomaterials slightly affected the pH of the environment; however, it did not have any significant influence on the corrosion activity of A. ferrooxidans. This study suggests that the common bacterium A. ferrooxidans found in many underground environments can be a threat to cable bolts’ integrity by creating initiation points for other catastrophic failures such as stress corrosion cracking

Design and synthesis of short amphiphilic cationic peptidomimetics based on biphenyl backbone as antibacterial agents

© 2017 Elsevier Masson SAS Antimicrobial peptides (AMPs) and their synthetic mimics have received recent interest as new alternatives to traditional antibiotics in attempts to overcome the rise of antibiotic resistance in many microbes. AMPs are part of the natural defenses of most living organisms and they also have a unique mechanism of action against bacteria. Herein, a new series of short amphiphilic cationic peptidomimetics were synthesized by incorporating the 3′-amino-[1,1′-biphenyl]-3-carboxylic acid backbone to mimic the essential properties of natural AMPs. By altering hydrophobicity and charge, we identified the most potent analogue 25g that was active against both Gram-positive Staphylococcus aureus (MIC = 15.6 μM) and Gram-negative Escherichia coli (MIC = 7.8 μM) bacteria. Cytoplasmic permeability assay results revealed that 25g acts primarily by depolarization of lipids in cytoplasmic membranes. The active compounds were also investigated for their cytotoxicity to human cells, lysis of lipid bilayers using tethered bilayer lipid membranes (tBLMs) and their activity against established biofilms of S. aureus and E. coli

The presence and role of bacterial quorum sensing in activated sludge

Activated sludge used for wastewater treatment globally is composed of a high-density microbial community of great biotechnological significance. In this study the presence and purpose of quorum sensing via N-acylated-l-homoserine lactones (AHLs) in activated sludge was explored. The presence of N-heptanoyl-l-homoserine lactone in organic extracts of sludge was demonstrated along with activation of a LuxR-based AHL monitor strain deployed in sludge, indicating AHL-mediated gene expression is active in sludge flocculates but not in the bulk aqueous phase. Bacterial isolates from activated sludge were screened for AHL production and expression of phenotypes commonly but not exclusively regulated by AHL-mediated gene transcription. N-acylated-l-homoserine lactone and exoenzyme production were frequently observed among the isolates. N-acylated-l-homoserine lactone addition to sludge upregulated chitinase activity and an AHL- and chitinase-producing isolate closely related to Aeromonas hydrophila was shown to respond to AHL addition with upregulation of chitinase activity. N-acylated-l-homoserine lactones produced by this strain were identified and genes ahyI/R and chiA, encoding AHL production and response and chitinase activity respectively, were sequenced. These experiments provide insight into the relationship between AHL-mediated gene expression and exoenzyme activity in activated sludge and may ultimately create opportunities to improve sludge performance. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd

Synthesis and biological evaluation of novel acyclic and cyclic glyoxamide based derivatives as bacterial quorum sensing and biofilm inhibitors

© 2017 The Royal Society of Chemistry. Bacteria regulate the expression of various virulence factors and processes such as biofilm formation through a chemically-mediated communication mechanism called quorum sensing. Bacterial biofilms contribute to antimicrobial resistance as they can protect bacteria embedded in their matrix from the effects of antibiotics. Thus, developing novel quorum sensing inhibitors, which can inhibit biofilm formation, is a viable strategy to combat antimicrobial resistance. We report herein the synthesis of novel acyclic and cyclic glyoxamide derivatives via ring-opening reactions of N-acylisatins. These compounds were evaluated for their quorum sensing inhibition activity against P. aeruginosa MH602 and E. coli MT102. Compounds 20, 21 and 30 displayed the greatest quorum sensing inhibition activity against P. aeruginosa MH602, with 71.5%, 71.5%, and 74% inhibition, respectively, at 250 μM. Compounds 18, 20 and 21 exhibited the greatest QSI activity against E. coli MT102, with 71.5%, 72.1% and 73.5% quorum sensing inhibition activity, respectively. In addition, the biofilm inhibition activity was also investigated against P. aeruginosa and E. coli at 250 μM. The glyoxamide compounds 16, 18 and 19 exhibited 71.2%, 66.9%, and 66.5% inhibition of P. aeruginosa biofilms, respectively; whereas compounds 12, 20, and 22 showed the greatest inhibitory activity against E. coli biofilms with 87.9%, 90.8% and 89.5%, respectively. Finally, the determination of the in vitro toxicity against human MRC-5 lung fibroblast cells revealed that these novel glyoxamide compounds are non-toxic to human cells

Amphipathic guanidine-embedded glyoxamide-based peptidomimetics as novel antibacterial agents and biofilm disruptors

© The Royal Society of Chemistry. Antimicrobial resistance in bacteria is becoming increasingly prevalent, posing a critical challenge to global health. Bacterial biofilm formation is a common resistance mechanism that reduces the effectiveness of antibiotics. Thus, the development of compounds that can disrupt bacterial biofilms is a potential strategy to combat antimicrobial resistance. We report herein the synthesis of amphipathic guanidine-embedded glyoxamide-based peptidomimetics via ring-opening reactions of N-naphthoylisatins with amines and amino acids. These compounds were investigated for their antibacterial activity by the determination of minimum inhibitory concentration (MIC) against S. aureus and E. coli. Compounds 35, 36, and 66 exhibited MIC values of 6, 8 and 10 μg mL−1 against S. aureus, respectively, while compounds 55 and 56 showed MIC values of 17 and 19 μg mL−1 against E. coli, respectively. Biofilm disruption and inhibition activities were also evaluated against various Gram-positive and Gram-negative bacteria. The most active compound 65 exhibited the greatest disruption of established biofilms by 65% in S. aureus, 61% in P. aeruginosa, and 60% in S. marcescens respectively, at 250 μM concentration, while compound 52 inhibited the formation of biofilms by 72% in S. marcescens at 250 μM. We also report here the in vitro toxicity against MRC-5 human lung fibroblast cells. Finally, the pore forming capability of the three most potent compounds were tested using tethered bilayer lipid membrane (tBLM) technology

Systemic vasculitis in a patient with rhupus syndrome

Rhupus is a rare syndrome characterized by overlap of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Previous reports mentioned that rhupus patients have prominent RA associated clinical manifestations and only mild organic damage related to SLE. Progressive or life-threatening manifestations are rare in rhupus patients. Our patient diagnosed as rhupus was a young women, presented with multi-organ involvement of systemic vasculitis. Rheumatologists should be aware of possibility that rhupus may be accompanied by progressive or life-threatening conditions such as vasculitis

[Evaluation of frequency and the attacks features of patients with colchicine resistance in FMF].

INTRODUCTION: Colchicine is the mainstay for the treatment of FMF, which is an auto-inflammatory disease mainly with relapsing polyserositis. Despite daily doses of 2mg or more each day, approximately 5% to 10% of the patients continue to suffer from its attacks. In this study, we aimed to investigate the depression and attack features in patients with FMF who have colchicine resistance (CR). PATIENTS E METHODS: CR was defined for FMF patients with 2 or more attacks within the last 6 months period while using 2mg/day colchicine. Eighteen patients (9 Female/9 Male) were enrolled into the CR group and 41 patients were enrolled into the control group (12 Male/29 Female). Demographic, clinical e laboratory findings, treatment adherence, and the Beck Depression Inventory (BDI) scores were evaluated. RESULTS: The age of onset of FMF was significantly lower in the CR group (12.3 yrs vs. 16.9 yrs, P=0.03). Disease duration was longer in the CR group (P=0.01). Abdominal and leg pain due to exercise were significantly more frequent in the CR group versus controls (83% vs. 51%; P=0.02 e 88% vs. 60%; P=0.04, respectively). Patients with BDI scores over 17 points were more frequent in the CR group compared to controls (50% vs. 34.1%; P<0.001). DISCUSSION: We found that: (1) the age of disease onset was lower and (2) the disease duration was longer in CR group. Pleuritic attacks, hematuria e proteinuria were more frequent in CR patients. We propose that depression is an important factor to consider in the susceptibility to CR

Remarkable damage along with poor quality of life in Takayasu arteritis: cross-sectional results of a long-term followed-up multicentre cohort

WOS: 000402448900010PubMed ID: 27908308Objective. We aimed to assess the outcome of a large Takayasu arteritis (TAK) cohort using the vasculitis damage index (VDI) and quality of life (QoL) scale, tools which have been validated for vasculitis. Methods. Disease activity, damage and QoL were cross-sectionally evaluated in 165 TAK patients from 6 centres. SF-36 were applied to 51 age-matched healthy controls (HC). Persistent activity for months was considered as treatment resistance (r-TAK). The correlation between VDI, clinical characteristics and mental (MCS)/physical (PCS) component scores of SF-36 were analysed. SF-36 and VDI scores were compared between TAK subgroups and HC. Results. The median age, follow-up time and disease duration were 40 (17-68), 60 (6-384), and 72 (6-396) months, respectively. 35% of them were r-TAK. VDI scores (VDIs) in TAK 4 (1-12) were mainly due to the disease itself [4 (1-10)]. VDIs in r-TAK were significantly higher than nr-TAK [5 (212) vs. 3 (2-10), p<0.001)1. In the TAK patients, MCS and PCS were found as 43 10 and 38 11, respectively. A high proportion of poor MCS (70%) and PCS (80%) were demonstrated in TAK. A significantly negative but weak correlation was observed between VDI and MCS (p=0.003, r=-0.23), PCS (p<0.001, r=-0.34). Higher VDIs were detected in patients with PCS <50 [5 (.1-12) vs. 2 (1-6) p<0.001)]. SF-36 score was significantly lower in TAK than KC. Conclusion. Disease-related damage mainly caused by peripheral vascular involvement was more predominant than treatment-related damage without reaching the level of severe damage scores, but contributing to poor QoL, in the TAK cohort