Comparative Assessment of Soil-Structure Interaction Regulations of ASCE 7-16 and ASCE 7-10

This paper evaluates the consequences of practicing soil structure interaction (SSI) regulations of ASCE 7-16 on seismic performance of building structures. The motivation for this research stems from the significant changes in the new SSI provisions of ASCE 7-16 compared to the previous 2010 edition. Generally, ASCE 7 considers SSI as a beneficial effect, and allows designer to reduce the design base shear. However, literature shows that this idea cannot properly capture the SSI effects on nonlinear systems. ASCE 7-16 is the first edition of ASCE 7 that considers the SSI effect on yielding systems. This study investigates the consequences of practicing the new provisions on a wide range of buildings with different dynamic characteristics on different soil types. Ductility demand of the structure forms the performance metric of this study, and the probability that practicing SSI provisions, in lieu of fixed-base provisions, increases the ductility demand of the structure is computed. The analyses are conducted within a probabilistic framework which considers the uncertainties in the ground motion and in the properties of the soil-structure system. It is concluded that, for structures with surface foundation on moderate to soft soils, SSI regulations of both ASCE 7-10 and ASCE 7-16 are fairly likely to result in a similar and larger structural responses than those obtained by practicing the fixed-base design regulations. However, for squat and ordinary stiff structures on soft soil or structures with embedded foundation on moderate to soft soils, the SSI provisions of ASCE 7-16 result in performance levels that are closer to those obtained by practicing the fixed-base regulations. Finally, for structures on very soft soils, the new SSI provisions of ASCE 7-16 are likely to rather conservative designs.Comment: ASCE Structures Congress, Fort Worth, TX, USA, April 19-21 (2018

Antibacterial efficacy of lytic bacteriophages against antibiotic-resistant Klebsiella species

Bacterial resistance to antibiotics is a leading and highly prevalent problem in the treatment of infectious diseases. Bacteriophages (phages) appear to be effective and safe alternatives for the treatment of resistant infections because of their specificity for bacterial species and lack of infectivity in eukaryotic cells. The present study aimed to isolate bacteriophages against Klebsiella spp. and evaluate their efficacy against antibiotic-resistant species. Seventy-two antibiotic-resistant Klebsiella spp. were isolated from samples of patients who referred to the Ghaem Hospital (Mashhad, Iran). Lytic bacteriophages against Klebsiella spp. were isolated from wastewater of the septic tank of the same hospital. Bactericidal activity of phages against resistant Klebsiella spp. was tested in both liquid (tube method; after 1 and 24 h of incubation) and solid (double-layer agar plate method; after 24 h of incubation) phases. In each method, three different concentrations of bacteriophages (low: <10 4 PFU/mL, medium: 10 4 -10 7 PFU/mL, and high: >10 7 PFU/mL) were used. Bacteriophages showed promising bactericidal activity at all assessed concentrations, regardless of the test method and duration of incubation. Overall, bactericidal effects were augmented at higher concentrations. In the tube method, higher activity was observed after 24 h of incubation compared to the 1-h incubation. The bactericidal effects were also higher in the tube method compared to the double-layer agar plate method after 24 h of incubation. The findings of the present study suggest that bacteriophages possess effective bactericidal activity against resistant Klebsiella spp. These bactericidal activities are influenced by phage concentration, duration of incubation, and test method. KEYWORDS: bacteriophage, Klebsiella, antibiotic resistance Karamoddini et al.: Bacteriophages Against Resistant Klebsiella Species TheScientificWorldJOURNAL (2011) 11, 1332-1340 1333 INTRODUCTION Bacteriophages (also called phages) are reported to be the most abundant organisms on earth Based on the replication type, phages are classified as either lytic or lysogenic. A lytic phage replicates in the bacterial host and destroys its host in a process, but a lysogenic phage inserts itself into the genome of its bacterial host and establishes a stable position in the infected bacterium After discovery, phages were the target of multiple research for the treatment of bacterial diseases, such as dysentery In spite of the great progress that has been made in the field of antimicrobial therapy, the appearance and spread of drug-resistant bacteria has caused a serious challenge in recent decades. As an example, the prevalence of resistant nosocomial infections is increasing at an alarming rate and their elimination is very difficult. This could be secondary to the wide use of antibiotics, as well as application of therapeutic measures that weaken the immune system and make subjects more susceptible to nosocomial infections. Phage therapy could be an effective alternative approach for the control of these infections, as several studies have shown their efficacy against both Gram-positive and Gram-negative bacteria The purpose of the present study was to isolate and enrich lytic bacteriophages against Klebsiella spp. and evaluate their antibacterial efficacy against antibiotic-resistant species. The impact of phage concentration, incubation duration, and method of culture (tube vs. plate) on the bactericidal effect was also investigated. MATERIALS AND METHODS Isolation of Klebsiella spp. Different samples, mainly from urine, vaginal smears, blood, wounds and their secretions, and burn lesions, were collected from patients referring to the Ghaem Hospital (Mashhad, Iran) during a course of about 1.5 years between November 2001 and March 2003. Samples were cultured on general (simple blood agar; supporting the growth of most microorganisms) as well as specific (MacConkey agar, desoxycholate agar, or eosin methylene blue agar; supporting the growth of Gram-negative bacteria) culture media. Culture media plates were incubated at 37°C for 24 h. To confirm the isolation of Klebsiella spp., Gram staining and multiple biochemical tests were performed, including glucose and lactose fermentation (Kligler iron agar medium), citrate utilization (Simmons citrate agar medium), urea (urea agar medium), hydrogen sulfide production, indole formation and motility (sulfide-indole-motility [SIM] agar medium; Kligler iron agar medium), and malonate utilization (malonate agar medium) tests. Determination of Klebsiella spp. Sensitivity to Antibiotics Mueller-Hinton agar medium was used to culture the appropriate bacteria. Colonies were first suspended in 5 mL of tripticase soy broth and kept at 37°C for several hours until the turbidity of the suspension changed, similar to that of barium sulfate solution in the 0.5 McFarland standard tube (the standard tube was shaken vigorously before usage). A sterile swab was stirred in the above suspension and the sample was cultured on Mueller-Hinton agar medium. Antibiotic disks were placed at a 15-mm distance from the Karamoddini et al.: Bacteriophages Against Resistant Klebsiella Species TheScientificWorldJOURNAL (2011) 11, 1332-1340 1334 edge of the plate. Different disks were 24 mm from the center of each nearest disk. Following a 24-h incubation at 37°C, the growth inhibition zone was measured and compared with tables provided by the National Committee for Clinical Laboratory Standards (NCCLS). The results of sensitivity were reported as sensitive, resistant, or intermediate. Antibiotics that were evaluated included ampicillin, amoxicillin, amikacin, cephalexin, chloramphenicol, nitrofurantoin (for urine samples), gentamicin, kanamycin, nalidixic acid (for urine samples), rifampin, streptomycin, tetracycline, doxycycline, tobramycin, and sulfamethoxazole. Smooth agar containing glycerin was used to keep resistant Klebsiella colonies at -20°C as follows: four to five colonies were transferred to 20 mL of triple soy broth. After 4 h of incubation at 37°C, the tube containing tryptone soy broth was centrifuged at 2500 rpm. Then, 0.5 mL of the above-cultured bacteria was transferred to a Pyrex® test tube containing 3 mL of 3% Mueller-Hinton. Test tubes were incubated at 37°C for 4-6 h in order to accelerate bacterial growth. Following that, 0.5 mL of sterile glycerin was added to test tubes and tubes were transferred to -20°C. Isolation, Enrichment, Titration, and Bacteriophages Bacteriophages utilized in this study were isolated from wastewater of the septic tank in Ghaem Hospital that had been filter sterilized. To the aforementioned wastewater (45 mL), concentrated nutrient broth medium (5 mL) and 4-h antibiotic-resistant Klebsiella culture (5 mL) were added. Also added was 1% (v/w) MgSo 4 to provide optimum attachment of bacteriophage to bacteria. The mixture was then gently shaken and kept at 37°C for 24 h. Afterwards, chloroform was added (3 mL) and the mixture was shaken for 15 min. After being kept at room temperature for 2 h, the mixture was centrifuged (30 min, 3500 rpm) and the supernatant carefully isolated. For phage enrichment, the obtained supernatant was mixed with nutrient broth (10 mL) and 4-h Klebsiella culture (2 mL). The mixture was then processed as described above. Phage suspension was maintained in the nutrient broth at 4°C in a dark place using sterile and sealed glass containers. For the titration of phages, enriched samples were diluted by 10X in tubes containing 9 mL of tryptone broth. Then, 100 µL of each diluted sample was transferred to tubes containing 3 mL of soft agar. Afterwards, 4-h Klebsiella culture (1 mL) was added to each tube. Tubes were then shaken and their contents rapidly transferred to plates containing tryptone agar medium. The plates were incubated at 37°C for 24 h. Plates containing 30-300 plaques were used to calculate the number of phages in the primary solution using the following formula: Number of phages = Number of plaques × dilution titer × volume of media Evaluation of Antibacterial Activity The antibacterial effects of phages against antibiotic-resistant Klebsiella spp. were tested by the tube method and the double-layer agar plate method at two time points: after 1 h (for the tube method) and 24 h (for both tube and plate methods) of incubation at 37°C. In each method, three different concentrations of phages were tested: low (<10 4 PFU/mL), medium (10 4 -10 7 PFU/mL), and high (>10 7 PFU/ mL). According to the intensity of growth inhibition, the results were reported as +++ (75-100% reduction of bacteria compared to control), ++ (50-75% reduction of bacteria compared to control), + (25-50% reduction of bacteria compared to control), and -(<25% reduction of bacteria compared to control). Statistical Analysis All comparisons were performed using Fisher's exact test. A two-sided p value of <0.05 was considered to be statistically significant. Karamoddini et al.: Bacteriophages Against Resistant Klebsiella Species TheScientificWorldJOURNAL (2011) 11, 1332-1340 1335 RESULTS Out of the total samples that were collected during the course of the study (a period of approximately 1.5 years), 72 antibiotic-resistant Klebsiella spp. were isolated. Most of these species were isolated from urine, wounds, and burn lesion samples Karamoddini et al.: Bacteriophages Against Resistant Klebsiella Species TheScientificWorldJOURNAL (2011) 11, 1332-1340 1336 In the tube method, different concentrations (low, medium, and high) of phages were evaluated for their inhibitory effect against the growth of isolated, resistant Klebsiella spp. after 1 and 24 h of incubation at 37°C. The results indicated that in both time points, all three assessed concentrations had antibacterial effects without even one strain being unaffected by phage treatment. There was a marked increase in the antibacterial effects after 24 h compared to 1 h of incubation, and this was observed for all three assessed phage concentrations. There was also a positive association between phage concentration and observed antibacterial effects at both assessed time points. This effect of concentration was found to be of high statistical significance when comparing the antibacterial effects of low concentration to those of medium (p < 0.001) and high (p < 0.001) concentrations. However, while there was a significant concentration effect at the 1-h incubation time point between medium and high phage concentrations (p < 0.001), no significant difference was observed after 24 h of incubation (p > 0.05) ( DISCUSSION The most obvious result to emerge from the present study was the promising antibacterial effects of phages against resistant Klebsiella spp. at all assessed (low, medium, and high) concentrations. The results also indicated that bactericidal effects of phages are augmented with increasing concentration and time of incubation. In addition, the double-layer agar plate method was associated with higher bactericidal effects compared to the tube method. Bactericidal effects of phages at low concentrations are due to their self-replication property. At low concentrations, the number of phages is exponentially increased in the presence of bacterial host 1337 Phages possess some unique properties that make them promising candidates for the treatment of bacterial infections. First, they need to bind to specific surface receptors in order to enter the bacteria and exert their effects. Hence, their bactericidal effects would be specific. Second, since eukaryotic cells lack phage receptors, phage preparations appear be harmless to human, animal, and plant cells Several reports have demonstrated the efficacy of phages in the treatment of infectious diseases caused by Gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Vibrio vulnificus, and Salmonella spp., and also Gram-positive bacteria, such as Enterococcus faecium and Staphylococcus aureus 1338 In spite of the positive findings on the therapeutic efficacy of phages, this strategy has not been introduced into routine clinical practice for the treatment of bacterial infections. This stems from several reasons, the most important of which are the advent and widespread use of antibiotics in the Western world as well as the inconsistency and unsuccessful results of early trials. The main reasons for the inconsistent findings of the early trials are (1) inadequate scientific methodology that was used; (2) not heeding the prerequisites for phage therapy, such as lack of complete knowledge on phage biology, including lysogeny phenomenon (which might have led to the employment of a wrong phage); (3) lack of placebo control and robust trial design; (4) not identifying pure phage strains; (5) not meeting safety requirements for phage preparations, such as endotoxin removal; (6) not confirming adequate phage viability in the employed preparations; and (7) rapid clearance of phages from the body. The modern generation of phage research has attempted to overcome these shortcomings and promising results have been obtained. However, there is still much work to be done in order to extrapolate positive in vitro findings into more complicated in vivo experiments In recent years, there have been relatively few studies on the efficacy of phage therapy against Klebsiella infection, particularly resistant Klebsiella spp. The promising results of this investigation add to the existing body of literature about the potential efficacy of phage therapy. As Klebsiella spp. are among the most important causes of noscomial infections As a limitation of the current study, it must be mentioned that the 24-h bacterial cultures were not tested for bacteriophage resistance. Furthermore, it would be helpful to evaluate the bactericidal efficacy of phage preparations in more detailed time points. To sum, the results of this research support the idea that phages are effective bactericidal agents that could serve as potential alternatives for antibiotics in the treatment of resistant bacterial infections. In addition, the present findings provide evidence with respect to the impact of concentration, incubation duration, and method of culture on the bactericidal effects of phages. ACKNOWLEDGMENT

A microfluidics-based method for measuring neuronal activity in Drosophila chemosensory neurons

Monitoring neuronal responses to defined sensory stimuli is a powerful and widely used approach for understanding sensory coding in the nervous system. However, providing precise, stereotypic and reproducible cues while concomitantly recording neuronal activity remains technically challenging. Here we describe the fabrication and use of a microfluidics system that allows precise temporally restricted stimulation of Drosophila chemosensory neurons with an array of different chemical cues. The system can easily be combined with genetically encoded calcium sensors, and it can measure neuronal activity at single-cell resolution in larval sense organs and in the proboscis or leg of the adult fly. We describe the design of the master mold, the production of the microfluidic chip and live imaging using the calcium sensor GCaMP, expressed in distinct types of Drosophila chemosensory neurons. Fabrication of the master mold and microfluidic chips requires basic skills in photolithography and takes ~2 weeks; the same devices can be used repeatedly over several months. Flies can be prepared for measurements in minutes and imaged for up to 1 h

Comparison of Canal Transportation and Centering Ability of Wave One and SafeSider in Curved Root Canals Using Cone-Beam Computed Tomography

Background and Aim: Maintaining the original central canal path during cleaning and shaping of the root canal system plays an important role in the success of endodontic treatment. This study sought to compare canal transportation and centering ability of WaveOne and SafeSider rotary files using cone-beam computed tomography (CBCT). Materials and Methods: This in-vitro, experimental study was conducted on 40 mesiobuccal canals of extracted human mandibular first molars with 20° to 40° of curvature. The teeth were randomly divided into two groups (n=20) and mounted in putty. Next, preoperative CBCT scans were obtained. Root canals were prepared using primary file of WaveOne in group A and SafeSider system up to file #25/0.04 taper in group B. Postoperative CBCT scans were taken and cross-sectional images at 1, 3, and 7 mm distances from the anatomic apex were compared. Data were analyzed using t-test and two-way analysis of variance (ANOVA). Results: WaveOne was significantly superior to SafeSider regarding the canal centering ability and caused significantly less canal transportation (P<0.001). The canal centering ability of both systems was higher at the coronal and middle thirds of the root compared to the apical region (P<0.05). Conclusion: WaveOne, in contrast to SafeSider, has optimal canal centering ability and less transportation in curved root canals

Antibacterial Efficacy of Lytic Bacteriophages against Antibiotic-Resistant Klebsiella

Bacterial resistance to antibiotics is a leading and highly prevalent problem in the treatment of infectious diseases. Bacteriophages (phages) appear to be effective and safe alternatives for the treatment of resistant infections because of their specificity for bacterial species and lack of infectivity in eukaryotic cells. The present study aimed to isolate bacteriophages against Klebsiella spp. and evaluate their efficacy against antibiotic-resistant species. Seventy-two antibiotic-resistant Klebsiella spp. were isolated from samples of patients who referred to the Ghaem Hospital (Mashhad, Iran). Lytic bacteriophages against Klebsiella spp. were isolated from wastewater of the septic tank of the same hospital. Bactericidal activity of phages against resistant Klebsiella spp. was tested in both liquid (tube method; after 1 and 24 h of incubation) and solid (double-layer agar plate method; after 24 h of incubation) phases. In each method, three different concentrations of bacteriophages (low: 107 PFU/mL) were used. Bacteriophages showed promising bactericidal activity at all assessed concentrations, regardless of the test method and duration of incubation. Overall, bactericidal effects were augmented at higher concentrations. In the tube method, higher activity was observed after 24 h of incubation compared to the 1-h incubation. The bactericidal effects were also higher in the tube method compared to the double-layer agar plate method after 24 h of incubation. The findings of the present study suggest that bacteriophages possess effective bactericidal activity against resistant Klebsiella spp. These bactericidal activities are influenced by phage concentration, duration of incubation, and test method