Effects of the antimicrobial agent Triclosan on bacterial resistance to disinfection in wastewater treatment processes

2-(2,5-Dichlorophenoxy)-5-chlorophenol or Triclosan is a widely used antimicrobial agent included in a multitude of products, such as soap, toothpaste, and personal care products.;The objective of this research was to investigate the effects of Triclosan on the resistance of activated sludge bacteria to conventional disinfection processes applied in wastewater treatment processes, such as chlorination and UV.;Specific Aim 1. A complex bacterial community collected from an active sludge was acclimated over several sub-cultures in the presence of different concentrations of Triclosan (from 0.0 to 20 mg L-1) and then exposed to sub-lethal doses of chlorine and UV irradiation. Determination of bacterial viability by direct counting and flow-cytometry showed that microbial communities exposed to Triclosan exhibited an increased susceptibility to chlorination and UV by comparison to non-exposed bacteria.;Specific Aim 2. In order to determine the origin of the change of susceptibility observed in Specific Aim 1, we characterized the microbial communities by construction of gene library and restriction fragment length polymorphism (RFLP). Results showed that acclimation on Triclosan resulted in a significant reduction of the bacterial diversity, suggesting that the change of susceptibility to disinfection could be explained, at least partly, by a change of the bacterial community structure. To investigate whether exposure to Triclosan could select bacterial species with a lower susceptibility to chlorination, two highly resistant strains were isolated from Triclosan-acclimated cultures and identified as Pseudomonas fluorescens and Serratia marcescens, which are opportunistic pathogens previously documented as highly resistant to Triclosan. This time, flow cytometry results showed that one of the strains, S. marcescens, exhibited a significant decrease of susceptibility to chlorination after acclimation in the presence of high concentration of Triclosan.;Specific Aim 3. In order to investigate further the relative susceptibility to chlorination of different species in Triclosan-exposed activated sludge bacteria, the microbial community structure was characterized by terminal-restriction fragment length polymorphism (T-RFLP) after sorting dead and living bacteria by flow-cytometry. Our preliminary results showed again that acclimation on Triclosan resulted in a significant reduction of the bacterial diversity, and, more importantly, that several species in Triclosan-acclimated bacterial suspensions exhibited a much higher resistance to chlorination.;Our results provide the first evidence that acclimation on sub-lethal doses of the antimicrobial agent Triclosan can result in decreasing susceptibility of opportunistic pathogens, which could have potential important implication for public health. In addition, our experiments combining flow-cytometry for dead-living bacteria sorting with T-RFLP for microbial community structure characterization opens the way for further research on the effect of antimicrobial agents on the relative susceptibility of different pathogens to disinfection systems

CEG 7200-01: Information Security

This course gives a comprehensive study of security vulnerabilities· in information systems and the basic techniques for developing secure applications and practicing safe computing. Topics include: Conventional encryption; Data Encryption Standard; Advanced Encryption Standard; Hashing functions and data integrity; Basic Number Theory; Public-key encryption (RSA); Digital signature; Security standards and applications; Access Control; Management and analysis of security. After taking this course, students will have the knowledge of several well-known security standards and their applications; and the students should be able to increase system security and develop secure applications

Understanding the interfacial structures-chemistry relationships in solid oxide fuel cells (SOFC)

Issued as final reportUnited States. Dept. of Energ

CEG/EE 260 Digital Computing Hardware/Switching Circuits

We will discuss and cover basic digital, combinational and sequential logic systems. Labs will be used to gain valuable practical experience in implementing elementary circuits and logic designs

CS 400-01: Data Structures and Software Design

This is a fundamental course for students majoring in Computer Science. Students will learn: basic algorithm analysis techniques; asymptotic complexity; big-0 and big-Omega notations; efficient algorithms for discrete structures including lists, trees, stacks, and graphs; fundamental computing algorithms including sorting, searching, and hashing techniques

CEG 260: Digital Computer Hardware Switching Circuits

We will discuss and cover basic digital, combinational and sequential logic systems. Labs will be used to gain valuable practical experience in implementing elementary circuits and logic designs

CS 790-01: Information Security

This course gives a comprehensive study of security vulnerabilities in information systems and the basic techniques for developing secure applications and practicing safe computing. Topics include: Conventional encryption; Data Encryption Standard; Advanced Encryption Standard; Hashing functions and data integrity; Basic Number Theory; Public-key encryption (RSA); Digital signature; Security standards and applications; Access Control; Management and analysis of security. After taking this course, students will have the knowledge of several well-known security standards and their applications; and the students should be able to increase system security and develop secure applications

Preparation of Mesoporous Yttria-Stabilized Zirconia (YSZ) and YSZ-NiO Using a Triblock Copolymer as Surfactant

Mesoporous yttria-stabilized zirconia (YSZ) and YSZ-NiO have been prepared for the first time using Pluronic P103 as a structure-directing agent and inorganic chlorides as precursors in a nonaqueous medium. After being fired at 500°C for 2 h, mesostructured YSZ has a BET surface area of about 146 m2 g-1, with an average pore size of 3.8 nm, while mesostructured YSZ-NiO has a BET surface area of about 108 m2 g-1, with an average pore size of 4.5 nm