Two-dimensional MXenes: recent emerging applications.

MXenes, are a rapidly growing family of two-dimensional materials exhibiting outstanding electronic, optical, mechanical, and thermal properties with versatile transition metal and surface chemistries. A wide range of transition metals and surface termination groups facilitate the properties of MXenes to be easily tuneable. Due to the physically strong and environmentally stable nature of MXenes, they have already had a strong presence in different fields, for instance energy storage, electrocatalysis, water purification, and chemical sensing. Some of the newly discovered applications of MXenes showed very promising results, however, they have not been covered in any review article. Therefore, in this review we comprehensively review the recent advancements of MXenes in various potential fields including energy conversion and storage, wearable flexible electronic devices, chemical detection, and biomedical engineering. We have also presented some of the most exciting prospects by combining MXenes with other materials and forming mixed dimensional high performance heterostructures based novel electronic devices.

A cross-sectional study of SARS-CoV-2 seroprevalence among asymptomatic healthcare workers in a tertiary healthcare centre: Assessing the impact of PPE guidelines.

PURPOSE: The present study estimates the seroprevalence of SARS-COV-2 among asymptomatic HCWs and assess the impact of various categories of PPE. METHODS: A cross-sectional study of asymptomatic HCW using different levels of PPE as per their risk profile was undertaken between 18th and 24th September 2020. Participant demographics and other relevant details including the levels of PPE used were recorded using a customized questionnaire. IgG antibodies against SARS-COV-2 were detected by chemiluminescence method & used as a surrogate marker for incomplete protection. RESULTS: Out of 1033 HCWs tested, overall SARS-COV-2 sero-prevalence was 25.8%. Univariate and multivariate analysis both demonstrated that ancillary workers including security staff (OR 5.589, P â€‹< â€‹0.001) and sanitary workers (OR 3.946, P â€‹< â€‹0.001) were at significantly higher risk of seropositivity irrespective of the PPE used as per guidelines, whereas doctors were at significantly lower risk of seropositivity (OR 0.307, P â€‹= â€‹0.005). Staff working in office areas was associated with reduced risk of seropositivity (OR 0.21, P â€‹= â€‹0.045). CONCLUSIONS: We document high seroprevalence of SARS-COV-2 antibodies in asymptomatic HCWs. Doctors who are at the highest risk had the lowest seropositivity and seroprevalence among office staff having a risk level comparable to the general community was lower than that reported in general population, supporting the efficacy of PPE practices as per guidelines in these groups. In contrast, much higher rates of seropositivity were seen among ancillary workers despite the availability of adequate PPE. Active screening, proper PPE use as per guidelines, and regular infection control trainings including Covid appropriate behaviour are therefore essential to contain COVID-19 spread among HCW & preventing them to transfer infection to the patients.

SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion.

The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era.

An infrequent etiology of Infective Endocarditis.

Abiotrophia. defectiva is an infrequent but an important cause of infectious endocarditis (IE). IE caused by A. defectiva may actually be more common than what is reported in the literature because of its failure to grown on routine media like blood agar and MacConkey agar, besides difficulty in its identification by conventional methods. IE by A. defectiva generally have more fulminant course and is associated with higher mortality and morbidity due to frequent embolic episodes and valvular tissue destruction. Ceftriaxone or vancomycin in combination with gentamicin and surgical replacement of valve is the recommended management.

Visualization of band offsets at few-layer MoS2/Ge heterojunction.

The visualization of band alignment for designing heterostructures between transition metal dichalcogenides and germanium plays a vital role in a deeper understanding of carrier dynamics at the heterointerface. Here, to study the band alignment across the MoS2/Ge heterojunction, we have deposited a wafer-scale highly crystalline few atomic layers MoS2film via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The Raman and XRD spectra of as-fabricated MoS2/Ge heterojunction expose the presence of highly crystalline few atomic layer MoS2on top of Ge substrate. Interestingly, we found a type-II band alignment at the MoS2/Ge heterointerface having valence band, and conduction band offset values of 0.88 and 0.21 eV, which can provide very efficient recombination through spatially confining charge carriers. The calculation of band offset parameters offers a promising way for device engineering across the MoS2/Ge heterojunction interface. Moreover, to demonstrate the practicability of the fabricated heterostructure, we explored the suitability of our device for broadband photodetection applications.

Group B Streptococcus in Indian pregnant women: Its prevalence and risk factors.

Purpose: To study the prevalence of group B streptococci (GBS) in Indian pregnant women and associated risk factors. Methods: Four hundred and fifty pregnant women attending antenatal outpatient/inpatient department between 35-38 weeks of gestation were enrolled in the study. All enrolled subjects were assessed by a predefined proforma for their demographics, socio-economic characteristics, education, toilet habits, obstetric history and clinical outcome. Two cotton swabs each from lower vagina and rectum were collected and plated on selective solid media CHROM agar Strept B (CHROMagarTM) and selective Enrichment Broth LIM RambaQUICK StreptB broth (CHROMagarTM). Presumptive identification of GBS was growth of 1-3 mm grayish white ß-hemolytic colonies on BAP or mauve coloured colonies on CHROM agar Strept B. All presumptively identified GBS were confirmed as group B streptococcus by automated identification system-Vitek MS (Bio Merieux). Results: The recto vaginal colonization rate of GBS in this study was observed as 3.3% (n=15). GBS colonization was significantly associated with nulliparous women (p= 0.026) and use of western style toilet (p=0.017). GBS urinary tract infections was also seen more commonly in women with GBS rectovaginal colonization (p=0.002). Conclusion: Due to the low GBS prevalence and no significant association with major risk factors, we recommend to institute universal screening of GBS in pregnant women, instead of risk based screening. Since this was a single centric study with low prevalence of GBS, its applicability may be limited, therefore further larger multi-centric prospective studies are required to understand the true GBS prevalence in Indian society.

Prevalence and Antibiogram of Urinary Tract Infections in Renal Transplant Recipients at a Tertiary Care Hospital in North India.

INTRODUCTION: Although, urinary tract infections (UTI) remain the most common cause of mortality and morbidity in renal allograft recipients, there is scarce data from India on the etiology and antibiogram of UTI post kidney transplantation. Therefore, the current study was undertaken to evaluate the prevalence, etiology and the antibiogram of pathogens causing UTI in this cohort. METHODS: Renal allograft recipients enrolled during the study period were screened for UTI by standard microscopy and routine culture on the day of admission and subsequently every 3rd day post-surgery till discharge. If UTI was present, the etiological agent and its antibiogram were recorded along with the demographic details of the patients. RESULTS: The prevalence of UTI post-transplantation at our centre was 30%. E.coli and Klebsiella pneumoniae were the most common organisms isolated in 42% and 39% cases, respectively. Majority of patients developed UTI on Day 6 (36.6%) and Day 9 (36.6%) post-transplant. Our study revealed a high percentage of resistance to commonly used 1st and 2nd line antibiotics like third generation cephalosporins (96.6%), fluoroquinolones (96.6%), and aminoglycosides (56.7%) and carbapenems (55.2%). CONCLUSION: Considering the high prevalence of UTI and antibiotic resistance rates in kidney transplant patients in our study, there is an urgent need for developing hospital based local antibiogram for appropriate management of UTI. Fosfomycin as an empirical therapy might be a useful choice for adequate coverage of potential pathogens at our centre. Further multi-centric studies on a larger sample size are recommended from India for formulating antibiotic policy.

Correction to: Pediatric Blood Cultures and Antibiotic Resistance: An Overview.

The article Pediatric Blood Cultures and Antibiotic Resistance: An Overview, written by Chand Wattal and Neeraj Goel, was originally published electronically on the publisher's internet portal (currently SpringerLink) on 21 December 2019 with open access.

Pediatric Blood Cultures and Antibiotic Resistance: An Overview.

Bloodstream infections (BSI) due to multidrug-resistant organisms, especially from pediatric intensive care units (PICU), are being increasingly reported across the world. Since BSI is associated with high mortality, it is essential to treat these infections early with appropriate antibiotics. Surveillance of etiology and emerging antimicrobial resistance (AMR) is considered an important step in the formulation of antibiotic policy for early treatment and judicious use of antibiotics. In this review on etiology and its antibiogram in community acquired BSI, S. typhi followed by S. paratyphi A were the major bacterial isolates. Quinolone resistance of more than 90% in Salmonella is now reported from all over India. Ceftriaxone remains the drug of choice for enteric fever due to its 100% susceptibility. In PICU there is an emergence of candidemia due to non-albicans candida which are now predominant isolates at few centers. BSI due to gram-negative bacteria, mostly by Klebseilla pneumoniae and gram-positive cocci (S. aureus) are the other major pathogens commonly observed in BSI from PICU. There is a high prevalence of antimicrobial resistance to commonly used antibiotics like ampicillin (94.9%-90.7%), cefotaxime (92.4%-71.4%), piperacillin-tazobactum (31.2%-27.5%) and levofloxacin (42.4%-39.8%). Resistance to carbapenems, primarily due to blaNDM is seen in all the centers and the rate varies between 1%- 79% with K. pneumoniae and A. baumannii showing the maximum resistance. This review highlights the magnitude of the AMR in the pediatric population and calls for the urgent implementation of antimicrobial stewardship programs to save the remaining antimicrobials.

Experience of Indian association of medical microbiology external quality assurance scheme centre, New Delhi: Challenges and quality assessment of clinical microbiology laboratories.

Introduction: EQAS program at New Delhi under IAMM was started in January 2014 across North and North east regions of India with 217 participants, which grew up to 540 by 2018. Materials and Methods: In 2014, 4 analytes per year were sent for 3 exercises, i.e. smear culture and serology. 2018 onwards PT analytes were increased from 4 to 12 and comparative performance of techniques analysed. Results: Out of the 22 smears sent for gram staining, ZN staining, Kinyoun staining and Albert staining, completely correct results ranged between 29.55% - 79.9%, 94.3% - 99.2%, 35.5% & 93.8%, respectively. Correct results for culture isolate identification & susceptibility testing and serology exercises varied between 70 & 92.4% and 73.1 & 98.59%, respectively. In the year 2018, 470 responses were received for bacterial culture identification & antibiotic susceptibility testing out of which manual and automated systems were used by 54% & 46% and 52.5% & 47.5% participants, respectively. Techniques used in BBV assays for HBsAg, HCV & HIV found all methods like ELISA, ELFA, CLIA and Card Test performing similarly. The major challenges in running the EQA program included requirement of large amount of specimens for PT item preparation, stability in hot and humid conditions and timely delivery of PT challenges in remote parts of the country. Conclusion: A large number of the participating laboratories (77%) had an overall score of >80% for all exercises, demonstrating acceptable baseline performance of EQAS registered laboratories. However, continued EQAS participation could further improve the quality of results.

A high-performance hydrogen sensor based on a reverse-biased MoS2/GaN heterojunction.

We report a MoS2/GaN heterojunction-based gas sensor by depositing MoS2 over a GaN substrate via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The microscopic and spectroscopic measurements expose the presence of highly crystalline and homogenous few atomic layer MoS2 on top of molecular beam epitaxially grown GaN film. Upon hydrogen exposure, the molecular adsorption tuned the barrier height at the MoS2/GaN interface under the reverse biased condition, thus resulting in high sensitivity. Our results reveal that temperature strongly affects the sensitivity of the device and it increases from 21% to 157% for 1% hydrogen with an increase in temperature (25-150 °C). For a deeper understanding of carrier dynamics at the heterointerface, we visualized the band alignment across the MoS2/GaN heterojunction having valence band and conduction band offset values of 1.75 and 0.28 eV. The sensing mechanism was demonstrated based on an energy band diagram at the MoS2/GaN interface in the presence and absence of hydrogen exposure. The proposed methodology can be readily applied to other combinations of heterostructures for sensing different gas analytes.

Performance of three commercial assays for colistin susceptibility in clinical isolates and Mcr-1 carrying reference strain.

Objective: Commercially available antibiotic susceptibility tests (cAST) for colistin are reported to shows variable performance. The current controversy on the colistin susceptibility testing and scarce data from India has left the clinical laboratories in a dilemma on the appropriate and practical approach to tackle the colistin antimicrobial susceptibility testing (AST) issue. This study was aimed to evaluate the performance of commonly used cAST for colistin against broth microdilution (BMD) as the reference method in the clinical isolates. Materials and Methods: Colistin AST was performed on 225 nonduplicate isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii by BMD as the reference method and compared with Vitek-2, Micronaut-S and E-test. The accuracy of the various cASTs was analysed by assessing categorical and essential agreement (EA). Results: We observed an overall categorical agreement of 98.2%, 99.6% and 96.4% and EA of 92%, 92.4% and 72% for Vitek-2, Micronaut-S and E-test, respectively. Unacceptable rates of major error (10.5%) and very major error (21%) were observed for P. aeruginosa with Vitek-2 and E-test, respectively. All the categorical errors (CEs) (7.7%) with Vitek-2 were seen for minimum inhibitory concentrations ranging within two-fold dilution breakpoint of 2 mg/L. Conclusion: Micronaut-S was found to be an acceptable method for colistin AST. In contrast, E-test was unreliable in terms of EA. Vitek-2 was found to be reliable for colistin AST, although it was more prone to CE near the colistin breakpoints.

A rare aetiology of spinal epidural abscess.

Spinal epidural abscess (SEA) due to Streptococcus pneumoniae is a rare entity, but it is associated with high mortality. Here, we describe a rare case of pneumococcal SEA in an immunocompetent adult who presented with fever, lower back pain and paresis. Central nervous system examination revealed a decreased power in bilateral lower limbs. Magnetic resonance imaging of the lumbosacral spine showed loculated pus collection in the epidural space at the level of L4-L5 vertebrae. Pus obtained following L4-L5 decompression along with blood cultures grew S. pneumoniae. The patient was treated with clindamycin and cefoperazone-sulbactam for 6 weeks, and no relapse was noted on 11 months follow-up.

High-performance photodetector based on hybrid of MoS2 and reduced graphene oxide.

2D materials are a promising new class of materials for next generation optoelectronic devices owing to their appealing optical and electrical properties. Pristine molybdenum disulfide (MoS2) is widely used in next generation photovoltaic and optoelectronic devices, but its low photo-dark current ratio prevents its use in highly efficient photo detection applications. Here, we decorated crumpled reduced graphene oxide (rGO) particles on a large-area vertically aligned MoS2 flake network to enhance the performance of the MoS2-based photodetector by forming multiple nanoscale p-n heterojunctions. The rGO/MoS2 device exhibited a significantly improved photoresponsivity of ∼2.10 A W-1 along with a good detectivity of ∼5 × 1011 Jones (Jones = cm Hz1/2/W) compared to that of the pristine MoS2 photodetector in ambient atmosphere. Moreover, the rGO/MoS2 photodetector showed a fast response of ∼18 ms with excellent stability and reproducibility in ambient air even after three months. The high performance of the photodetector is attributed to enhanced photoexcited carrier density and suppressed photo generated electron-hole recombination due to the strong local built-in electric field developed at the rGO/MoS2 interface. Our results showed that integration of rGO with MoS2 provides an efficient platform for photo detection applications.

UV-Activated MoS2 Based Fast and Reversible NO2 Sensor at Room Temperature.

Two-dimensional materials have gained considerable attention in chemical sensing owing to their naturally high surface-to-volume ratio. However, the poor response time and incomplete recovery at room temperature restrict their application in high-performance practical gas sensors. Herein, we demonstrate ultrafast detection and reversible MoS2 gas sensor at room temperature. The sensor's performance is investigated to NO2 at room temperature, under thermal and photo energy. Incomplete recovery and high response time of ∼249 s of sensor are observed at room temperature. Thermal energy is enough to complete recovery, but it is at the expense of sensitivity. Further, under photo excitation, MoS2 exhibits an enhancement in sensitivity with ultrafast response time of ∼29 s and excellent recovery to NO2 (100 ppm) at room temperature. This significant improvement in sensitivity (∼30%) and response time (∼88%) is attributed to the charge perturbation on the surface of the sensing layer in the context of NO2/MoS2 interaction under optical illumination. Moreover, the sensor shows reliable selectivity toward NO2 against various other gases. These unprecedented results reveal the potential of 2D MoS2 to develop a low power portable gas sensor.

Antimicrobial prescribing patterns of surgical speciality in a tertiary care hospital in India: Role of persuasive intervention for changing antibiotic prescription behaviour.

BACKGROUND: Inappropriate use of antibiotics globally has been linked to increase in antibiotic resistance. OBJECTIVES: This interventional study assessed the impact of antibiotic prescription feedback and focus group discussions (FGD) on hospital-based prescribers before and after the FGD. STUDY DESIGN: The present study was performed at a tertiary care centre in New Delhi, wherein 45 units from surgical specialities were included for FGD. Thirty-five units were assessed for the antibiotic usage during 12 months pre-intervention and 3 and 6 months post-intervention period. The outcome measured was a change in antibiotic prescription rates reflected as daily defined doses per 100 bed days as defined by the World Health Organisation. RESULTS: Reduction in the level of antibiotic consumption was observed in 15 of 35 units (42.85%) during the 3 months post-intervention period, which was significant (P < 0.05) in 3/35 (8.57%) surgical units. A significant reduction (P < 0.05) was observed for the units of endoscopic gynaecology, super-speciality and transplant surgery units B and C, and orthopaedic unit C during the 6 months period. Decreasing trend (P < 0.05) was observed in 2/35 (5.71%) units during the entire period. Overall reduction of antibiotic consumption (1.88%) was observed, with an increase in the use of low-end antibiotics and a decrease in the use of high-end antibiotics. CONCLUSION: The present study clearly demonstrates a weak impact of FGD in changing antibiotic prescribing behaviour. Further analysis of the sustainability of FGD and its long-term impact on antimicrobial resistance needs to be evaluated. The effect of continuous educational sessions and multifaceted interventions cannot be ignored.