Prevalence of ESBLs in Acinetobacter baumannii isolated from intensive care unit (ICU) of Ghaem hospital, Mashhad, Iran

Acinetobacter baumannii is an important opportunistic pathogen that mainly infects critically patients in intensive care units (ICU). The production of plasmid-mediated extended-spectrum b-lactamases (ESBLs) is one of the most important mechanisms of resistance against b-lactam antibiotics. This study aimed to evaluate the prevalence of ESBLs in A. baumannii isolated from ICU of Ghaem hospital, Mashhad, Iran. A total of 140 A. baumannii isolates recovered from hospitalized patients in ICU of Ghaem hospital in Mashhad city from December 2014 to March 2015. Identification of A. baumannii isolates carried out using biochemical laboratory methods and then confirmed by OXA-51 PCR screening. Susceptibility testing performed using disk diffusion (Kirby-Bauer) method as recommended by CLSI guidelines. A. baumannii isolates screened for production of ESBLs using combination disk test. blaPER, blaGES, blaTEM, blaSHV, blaCTX, blaVEB and blaOXA-10 beta-lactamase genes detected using conventional PCR. The most antibacterial resistance was against cefuroxime (­99.3%) and colistin was the most effective antibiotic. None of the isolates were ESBL producer by combination disk test. However, results of PCR revealed that the prevalence of blaPER, blaGES and blaTEM genes were 7.1%, 4.3% and 27.1%, respectively. blaCTX, blaVEB, and blaOXA-10 were not found in any of isolates. According to the results, the high resistance was seen against selected antibiotics and the phenotypic tests are not sufficient alone for determination of ESBLs producer of A. baumannii isolates. So, molecular tests are also necessary for detection of these enzymes

Characterization of Pseudomonas aeruginosa isolates: Occurrence rates, antimicrobial susceptibility patterns, and molecular typing in the global SENTRY Antimicrobial Surveillance Program, 1997-1999

During 1997–1999, a total of 70,067 isolates (6631 Pseudomonas aeruginosa isolates) were analyzed in the SENTRY program by geographic region and body site of infection. The respiratory tract was the most common source of P. aeruginosa. P. aeruginosa isolation rates increased during the study interval. Europe was the only region to show a significant decline in β-lactam and aminoglycoside susceptibility rates. There was a reduction in the rates of susceptibility of Canadian isolates to imipenem and of Latin American isolates to meropenem. A total of 218 multidrug-resistant P. aeruginosa isolates (MDR-PSA; resistant to piperacillin, ceftazidime, imipenem, and gentamicin) were observed; MDR-PSA occurrence rates (percentages of all isolates) ranged from 8.2% (Latin America) to 0.9% (Canada). No antimicrobial inhibited >50% of MDR-PSA strains. Molecular characterization of selected, generally resistant strains was performed. Isolates showing unique ribogroups were found in Europe, Latin America, and the United States, but clonal spread was documented in several medical centers.A. C. Gales, R. N. Jones, J. Turnidge, R. Rennie, and R. Rampha

Pentachlorophenol Induction of the Pseudomonas aeruginosa mexAB-oprM Efflux Operon: Involvement of Repressors NalC and MexR and the Antirepressor ArmR

Pentachlorophenol (PCP) induced expression of the NalC repressor-regulated PA3720-armR operon and the MexR repressor-controlled mexAB-oprM multidrug efflux operon of Pseudomonas aeruginosa. PCP's induction of PA3720-armR resulted from its direct modulation of NalC, the repressor's binding to PA3720-armR promoter-containing DNA as seen in electromobility shift assays (EMSAs) being obviated in the presence of this agent. The NalC binding site was localized to an inverted repeat (IR) sequence upstream of PA3720-armR and overlapping a promoter region whose transcription start site was mapped. While modulation of MexR by the ArmR anti-repressor explains the upregulation of mexAB-oprM in nalC mutants hyperexpressing PA3720-armR, the induction of mexAB-oprM expression by PCP is not wholly explainable by PCP induction of PA3720-armR and subsequent ArmR modulation of MexR, inasmuch as armR deletion mutants still showed PCP-inducible mexAB-oprM expression. PCP failed, however, to induce mexAB-oprM in a mexR deletion strain, indicating that MexR was required for this, although PCP did not modulate MexR binding to mexAB-oprM promoter-containing DNA in vitro. One possibility is that MexR responds to PCP-generated in vivo effector molecules in controlling mexAB-oprM expression in response to PCP. PCP is an unlikely effector and substrate for NalC and MexAB-OprM - its impact on NalC binding to the PA3720-armR promoter DNA occurred only at high µM levels - suggesting that it mimics an intended phenolic effector/substrate(s). In this regard, plants are an abundant source of phenolic antimicrobial compounds and, so, MexAB-OprM may function to protect P. aeruginosa from plant antimicrobials that it encounters in nature

Time-Resolved Microwave Photoconductivity (TRMC) Using Planar Microwave Resonators: Application to the Study of Long-Lived Charge Pairs in Photoexcited Titania Nanotube Arrays

Steady-state (SRMC) and time-resolved microwave photoconductivity (TRMC) are key techniques used to perform the contact-less determination of carrier density, transport, trapping, and recombination parameters in charge transport materials such as organic semiconductors and dyes, inorganic semiconductors, and metal–insulator composites, which find use in conductive inks, thin film transistors, light-emitting diodes, photocatalysts, and photovoltaics. We present the theory, design, simulation, and fabrication of a planar microwave ring resonator operating at 5.25 GHz with a quality factor of 224, to perform SRMC and TRMC measurements. Our method consists of measuring the resonance frequency (<i>f</i>₀) and <i>Q</i>-factor of the microwave resonator with the sample to be probed placed in a defined sensitive region of the resonator where the microwave field is highly concentrated. We also provide proof of concept measurements of the time-resolved microwave photoresponse of anatase-phase TiO₂ nanotube array membranes (TNTAMs) using the planar microstrip resonator. An unusual observation was the persistence of charged pair states in TNTAMs for several hours at room temperature under ambient conditions. Fast (120–220 s), slow (1300–2850 s), and very slow (6–26 h) components were extracted from the long-lived photoconductive decays of TNTAMs in response to 365, 250, and 405 nm illumination and assigned to various trap-mediated processes in TiO₂ nanotubes