Genetic relatedness and host specificity of Pseudomonas aeruginosa isolates from cystic fibrosis and non-cystic fibrosis patients

Background: Pseudomonas aeruginosa is one of the primary pathogens isolated more frequently in cystic fibrosis (CF) and it exhibits innate resistance to a wide range of antibiotics. Purpose: We sought to determine whether the highly prevalent genotypes of P. aeruginosa are specifically linked to CF patients and have any related multidrug antibiotic resistance. Isolates from hospitalized non-CF patients and from environmental sources were also genotypically analyzed. Methods: Collections of P. aeruginosa from lower respiratory secretions (n=45) were genotyped using pulsed-field gel electrophoresis (PFGE). Phenotypic screening for antibiotic susceptibility was performed for the common antimicrobial agents by E-test and automated Phoenix method. Results: P. aeruginosa isolates from CF (n=32), hospitalized non-CF patients (n=13), and environment sources (n=5) were analyzed. The population structure of P. aeruginosa is highly diverse and population-specific. All PFGE results of P. aeruginosa isolates fall among four major clusters. Cluster 1 contained 16 P. aeruginosa isolates from CF patients and two from environmental sources; cluster 2 contained 11 P. aeruginosa isolates from CF and one each from non-CF and environmental sources; cluster 3 contained 12 P. aeruginosa isolates from hospitalized non-CF patients and two P. aeruginosa isolates from one CF patient and one environmental source; and cluster 4 consisted of three isolates from CF patients and one from the environment. The majority of multidrug-resistant P. aeruginosa isolates were in clusters 3 and 4. P. aeruginosa isolates from CF patients were resistant to ciprofloxacin (34.4%) followed by resistance to amikacin and gentamicin (each 28%), whereas the majority of isolates from non-CF patients were resistant to meropenem (69%) and were grouped in cluster 3. Conclusion: PFGE of P. aeruginosa isolates from CF patients shows a high degree of similarity, suggesting specific adaptation of these clones to CF-affected lungs. The hospitalized non-CF cluster has a different clonal origin, indicating specific clustering in a specific location, suggesting hospital-acquired P. aeruginosa infections.The Qatar National Research Fund (UREP 14-026-3-010)

A Review of Open-Circuit Switch Fault Diagnostic Methods for Neutral Point Clamped Inverter

Due to numerous advantages, a neutral point clamped (NPC) inverter is a preferred choice for high-power applications and renewable technology. The reliability of the NPC inverter is a major concerning factor during the assessment of system performance as power semiconductor switches are vulnerable to abnormal conditions. Open-circuit (OC) switch faults are not as dangerous as short circuit (SC) faults but eventually have enough potential to cause cascaded failure to other components in the system and thus need to be supervised carefully. The OC faults result in a distortion of voltage and current signals in the NPC converter. Based on these signals, over the past few years, many efforts have been made to identify and localize the OC switch fault to the switch level in the NPC topology. In this paper, a review of different OC switch fault diagnostic methods is provided. Starting from the NPC inverter operation under healthy and faulty conditions, the various possible and unavailable switching states along with the deviation in pole voltage under different switch fault conditions is discussed. Then, based on the approach used for system-based fault detection, the OC fault detection methods are classified. The various OC methods are further discussed on the basis of signal, i.e., current, voltage or a combination of both signals used as a signature for fault detection. Emphasis is given to the principle involved, diagnostic variables utilized, the implementation approach and the diagnostic time required. Finally, the approaches are tabulated so as to provide a quick reference for NPC fault diagnostics

Host specificity of pseudomonas aeruginosa isolates from patients with cystic fibrosis and patients from different clinical backgrounds.

Background: Pseudomonas aeruginosa is one of the primary pathogens being isolated more frequently in cystic fibrosis (CF) and exhibits innate resistant to a wide range of antibiotics. Purpose: To determine whether the highly prevalent genotypes of P. aeruginosa are specifically linked to CF patients, isolates from non-CF patients and environment sources were genotypically analyzed. Methods: Collections of P. aeruginosa from lower respiratory secretions (n= 57) were genotyped using pulse-field gel electrophoresis (PFGE). Phenotypic screening for antibiotic susceptibility was performed for the common antimicrobial agents by Etest and automated Phoenix. Results: P. aeruginosa isolates from CF (n=39), non-CF patients (n=13), and environment sources (n=5) were analyzed. The population structure of P. aeruginosa is highly diverse and population specific. All the strains fall among 3 major clusters. Cluster A contained 16 isolates from CF patients and 2 environmental; cluster B contained 12 isolates from CF and one environmental while cluster C contained all the isolates from non CF patients and one environmental. The majority of P. aeruginosa strains in CF were resistant to ciprofloxacin (25.7%) followed by amikacin and gentamicin (each 23.6%). Whereas, the majority of isolates from non-CF were resistant to meropenem (69%), which grouped in cluster C. Conclusion: The fingerprints obtained with P. aeruginosa isolates from CF patients have a high degree of similarity, suggesting specific adaptation of these two clones to CF lung. The third non-CF cluster has different clonal origin, indicating specific clustering in both location and patient group