Development of an NO2 Gas Sensor Based on Laser-Induced Graphene Operating at Room Temperature.

A novel, in situ, low-cost and facile method has been developed to fabricate flexible NO2 sensors capable of operating at ambient temperature, addressing the urgent need for monitoring this toxic gas. This technique involves the synthesis of highly porous structures, as well as the specific development of laser-induced graphene (LIG) and its heterostructures with SnO2, all through laser scribing. The morphology, phases, and compositions of the sensors were analyzed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The effects of SnO2 addition on structural and sensor properties were investigated. Gas-sensing measurements were conducted at room temperature with NO2 concentrations ranging from 50 to 10 ppm. LIG and LIG/SnO2 sensors exhibited distinct trends in response to NO2, and the gas-sensing mechanism was elucidated. Overall, this study demonstrates the feasibility of utilizing LIG and LIG/SnO2 heterostructures in gas-sensing applications at ambient temperatures, underscoring their broad potential across diverse fields.

[Investigation of Fosfomycin Susceptibility in Extended Spectrum Beta-Lactamase Producing Enteric Bacteria by Disk Diffusion, Automated System and Agar Dilütion Kit]. / Genislemis Spektrumlu Beta-Laktamaz Üreten Enterik Bakterilerde Fosfomisin Duyarliliginin Disk Difüzyon, Otomatize Sistem ve Agar Dilüsyon Kiti ile Arastirilmasi.

Due to the increase of bacteria that develop resistance to classical antibiotics in recent years, fosfomycin has become one of the antibiotics gaining importance again. Fosfomycin exerts its bactericidal effect on many bacteria by binding to a cytoplasmic enzyme, MurA, and inhibiting the enzyme enopurivil transferase, which is involved in peptidoglycan synthesis. Bacteria producing ESBL are common pathogens in nosocomial infections and resistance is frequently encountered in their treatment. Fosfomycin is considered as an alternative drug in these infections. With its reintroduction, it is important to establish reliable and reproducible susceptibility testing methods for fosfomycin. In this study, it was aimed to evaluate the utility of disk diffusion, agar dilution kit and automated MicroScan methods (Beckman Coulter, Brea, CA, ABD) for fosfomycin susceptibility of ESBL-producing enteric bacteria. The study included 120 ESBL positive isolates of enteric bacteria (89 Escherichia coli, 31 Klebsiella pneumoniae) cultivated from the samples sent to the Microbiology Laboratory of the Mersin University Medical Faculty of Medicine Hospital between May 2019 and November 2019. Fosfomycin susceptibilities of the isolates included in the study were tested by disk diffusion, automated MicroScan and the commercial agar dilution kit. In the study, 37 (30.8%) of 120 isolates were determined as resistant to fosfomycin by disk diffusion method and six (5%) of the isolates were found to be resistant to fosfomycin with the MicroScan automatized system. With the agar dilution kit, 11 (9.1%) of 120 isolates were found to be resistant as the minimum inhibitory concentration (MIC) values were > 32 µg/ml. Fosfomycin resistance was significantly higher in K.pneumoniae isolates than E.coli isolates by agar dilution method (p= 0.006). Ertapenem resistance was detected in seven of 120 isolates. All seven isolates that were resistant to ertapenem were susceptible to fosfomycin by agar dilution method. All three isolates, which were found resistant to colistin, were susceptible to fosfomycin by agar dilution method. In the study, the categorical agreement of the disk diffusion and MicroScan methods in E.coli isolates with the agar dilution was high and the error rates were low. For K.pneumoniae, categorical concordance was calculated as 22.5% for disk diffusion test and 74.1% for MicroScan, while major and minor error rates were found to be quite high. As a result; fosfomycin is thought to be an alternative drug option in the treatment of infections caused by especially carbapenem and colistin resistant bacteria, with its high activity on ESBL-producing enteric bacteria. It has been determined that there is a great agreement between the agar dilution, which is the reference method for the determination of fosfomycin resistance for E.coli, and the MicroScan and disk diffusion methods, and that the disk diffusion method which provides ease of use in terms of cost and labor compared to the agar dilution method, can be used as a reliable method. However, it has been demonstrated that the agar dilution method should be used in K.pneumoniae isolates. Nevertheless; It was concluded that if the automatized system is used in laboratories where agar dilution cannot be performed, the results should be interpreted carefully, since the error rates are very high.

[Comparison of Real Time PCR Cycle Threshold Values in Symptomatic and Asymptomatic COVID-19 Patients]. / Semptomatik ve Asemptomatik COVID-19 Hastalarinda Gerçek Zamanli PCR Döngü Esik Degerlerinin Karsilastirilmasi.

Patients infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) show different clinical courses ranging from asymptomatic to severe infection requiring intensive care treatment and death. Real-time reverse transcription polymerase chain reaction (rRT-PCR), used in the diagnosis, screening and surveillance of coronavirus-2019 (COVID-19), provides the viral load as a cycle threshold (Ct) value. It has been reported that the Ct value may be related to the course of the infection and the clinical condition of the patient. In this study, it was aimed to compare the Ct and C reactive-protein (CRP) results of symptomatic and asymptomatic patients who were found to be positive with rRT-PCR. Between 14 April and 29 August 2020, a total of 355 patients aged 18 years and older with positive SARS-CoV-2 rRT-PCR test were included in the study. The COVID-19 rRT-PCR test was performed with Bio-speedy SARS-CoV-2 rRT-PCR kit (Bioeksen, Turkey) versions, the kit targeting the RdRp gene region, and the dual gene kit versions targeting the N and ORF1ab gene regions were used. Patients were classified as symptomatic and asymptomatic according to their clinical findings. Ct and CRP results of the patients were analyzed statistically. Of the 355 patients included in the study, 237 (66.7%) were symptomatic and 118 (33.2%) were asymptomatic patients. The mean age of symptomatic patients (46.68 ± 18.03) was observed significantly higher than asymptomatic patients (38.27 ± 13.82) (p<0.001). When the patients are evaluated according to the age groups, the rate of asymptomatic patients was significantly higher in the 21-39 age group, while the rate of symptomatic patients was significantly higher in 65 years and older group (p<0.05). The rate of comorbidity was significantly higher in symptomatic patients (n= 69, 29.1%) than in asymptomatic patients (n= 11, 9.3%) (p<0.001). Hypertension (12.2%), diabetes mellitus (9.7%), chronic respiratory disease (9.3%) and cardiovascular diseases (5.5%) were the most common diseases in symptomatic patients. However, among these, hypertension and chronic respiratory disease were found significantly higher in symptomatic patients (p<0.05). Increased CRP rate in symptomatic patients (64.6%) was found significantly higher than asymptomatic patients (27.3%) (p<0.001). The median of Ct value was found significantly higher in asymptomatic patients (26.34, IQR= 19.78-35.48), than in symptomatic patients (21.77, IQR= 17.81-26.51) (p<0.001). Regarding the medians of Ct values obtained from target genes; RdRp gene Ct value was found significantly higher in asymptomatic patients than in symptomatic patients (p<0.001). However, no statistical difference was found between symptomatic and asymptomatic patients in the ORF1ab and N genes Ct value medians (p> 0.05). As a result, it was observed that SARS-CoV-2 PCR positive patients were symptomatic in the presence of advanced age and comorbidity. Increased CRP value at the time of admission to the hospital was found significantly higher in symptomatic patients. Ct value has been shown to be lower in symptomatic patients, as expected. Although Ct and CRP values are thought to be useful in monitoring the clinical course and prognosis of patients with COVID-19, more detailed studies are needed to prove their clinical value.