High Tensile Ductility and Strength in Dual-phase Bimodal Steel through Stationary Friction Stir Processing.

The combination of high strength and good ductility are very desirable for advanced structural and functional applications. However, measures to enhance strength typically lead to ductility reduction due to their inverse correlation, nano-grained structures for an instance. Bi-modal grain structure is promising in this regard, but its realization is limited by multiple complex processing steps. Here, we demonstrate a facile single-step processing route for the development of bimodal grain structure in austenitic stainless steel, SS316L. The bimodal structure comprised of fine martensite grains (<500 nm) sandwiched between coarse austenite grains (~10 µm). The dual-phase bimodal structure demonstrated higher yield strength (~620 MPa) compared to ultra-fine grain structure (~450 MPa) concurrent with high uniform tensile ductility (~35%). These exceptional properties are attributed to unique dual-phase, bimodal grain structure which delayed the onset of plastic instability resulting in higher strength as well as larger uniform elongation and work-hardening rate. Our approach may be easily extended to a wide range of material systems to engineer superior performance.

Friction Stir Processing of Stainless Steel for Ascertaining Its Superlative Performance in Bioimplant Applications.

Substrate-cell interactions for a bioimplant are driven by substrate's surface characteristics. In addition, the performance of an implant and resistance to degradation are primarily governed by its surface properties. A bioimplant typically degrades by wear and corrosion in the physiological environment, resulting in metallosis. Surface engineering strategies for limiting degradation of implants and enhancing their performance may reduce or eliminate the need for implant removal surgeries and the associated cost. In the current study, we tailored the surface properties of stainless steel using submerged friction stir processing (FSP), a severe plastic deformation technique. FSP resulted in significant microstructural refinement from 22 µm grain size for the as-received alloy to 0.8 µm grain size for the processed sample with increase in hardness by nearly 1.5 times. The wear and corrosion behavior of the processed alloy was evaluated in simulated body fluid. The processed sample demonstrated remarkable improvement in both wear and corrosion resistance, which is explained by surface strengthening and formation of a highly stable passive layer. The methylthiazol tetrazolium assay demonstrated that the processed sample is better in supporting cell attachment, proliferation with minimal toxicity, and hemolysis. The athrombogenic characteristic of the as-received and processed samples was evaluated by fibrinogen adsorption and platelet adhesion via the enzyme-linked immunosorbent assay and lactate dehydrogenase assay, respectively. The processed sample showed less platelet and fibrinogen adhesion compared with the as-received alloy, signifying its high thromboresistance. The current study suggests friction stir processing to be a versatile toolbox for enhancing the performance and reliability of currently used bioimplant materials.

Controlled growth and differentiation of MSCs on grooved films assembled from monodisperse biological nanofibers with genetically tunable surface chemistries.

The search for a cell-supporting scaffold with controlled topography and surface chemistry is a constant topic within tissue engineering. Here we have employed M13 phages, which are genetically modifiable biological nanofibers (∼ 880 nm long and ∼ 6.6 nm wide) non-toxic to human beings, to form films for supporting the growth of mesencymal stem cells (MSCs). Films were built from nearly parallel phage bundles separated by grooves. The bundles can guide the elongation and alignment of MSCs along themselves. Phage with peptides displayed on the surface exhibited different control over the fine morphologies and differentiation of the MSCs. When an osteogenic peptide was displayed on the surface of phage, the proliferation and differentiation of MSCs into osteoblasts were significantly accelerated. The use of the grooved phage films allows us to control the proliferation and differentiation of MSCs by simply controlling the concentrations of phages as well as the peptides displayed on the surface of the phages. This work will advance our understanding on the interaction between stem cells and proteins.

Progression of chronic pulmonary tuberculosis in mice intravenously infected with ethambutol resistant Mycobacterium tuberculosis.

PURPOSE: Ethambutol (EMB) is an important first line drug, however little information on its molecular mechanism of resistance and pathogenicity of resistant isolates is available. Present work was designed to study virulence of the EMB resistant M. tuberculosis strains and the host responses in-vivo on infection of EMB resistant M. tuberculosis using Balb/c mouse model of infection. METHODS: Three groups of Balb/c mice (female, age 4-6 wk; 21 mice in each group) were infected intravenously with 106 CFU of M. tuberculosis H37Rv and two EMB resistant clinical isolates. Age and sex matched control animals were mock inoculated with Middlebrook 7H9 broth alone. At 10, 20, 30, 40, 50, 60, and 70 days post-infection three animals from each group were sacrificed by cervical dislocation and lung tissue was collected for further analysis. RESULTS: Infection with EMB resistant M. tuberculosis led to progressive and chronic disease with significantly high bacillary load (p=0.02). Massive infiltration and exacerbated lung pathology with increased expression of IFN-gamma and TNF-alpha was observed in lungs of mice infected with EMB resistant strains. The present study suggests that infection with EMB resistant M. tuberculosis leads to chronic infection with subsequent loss of lung function, bacterial persistence with elevated expression of TNF-alpha resulting in increased lung pathology. CONCLUSION: These findings highlight that EMB resistant M. tuberculosis regulates host immune response differentially and its pathogenicity is different from drug sensitive strains of M. tuberculosis.

In vitro (1)H NMR studies of RD human cell infection with echovirus 11.

The effects of echovirus 11 infection on RD human cell line (derived from rhabdomyosarcoma) were studied using (1)H NMR spectroscopy and optical microscopy. Both uninfected and infected cells consumed glucose and produced lactate, acetate and formate as extracellular metabolites. In infected whole cells, phosphocholine and uridine-sugar were observed in addition to the metabolites observed in uninfected cells. Water-soluble intracellular metabolites of infected cells showed glutamine, phosphocholine and glycine which were not observed in uninfected cells. Cellular metabolites except lipid components gradually decreased and disappeared during 24-48 h of viral infection. The quantity of lipid components in infected cells was comparable with that in uninfected cells, indicating that echovirus 11 does not utilize cell lipid molecules. Unlike optical microscopy, (1)H NMR spectroscopy identified early stages of infection through metabolic changes. These results may have potential implications in probing virus-cell interactions using NMR-based metabolomics.

Nucleotide polymorphism associated with ethambutol resistance in clinical isolates of Mycobacterium tuberculosis.

Ethambutol (EMB) is a first-line drug used for antitubercular therapy in combination with other drugs as recommended by World Health Organization DOTS/DOTS-Plus regimens. EMB is also effective in the treatment of opportunistic mycobacterial infections in patients with human immunodeficiency virus. The emb locus has been considered as a drug target for EMB, and substitutions of codon 306 in Mycobacterium tuberculosis gene embB have been shown to be the most frequent and predictive mutations for EMB resistance. The aim of the present study was to detect embB and embC gene mutations in EMB-resistant clinical isolates. A total of 23 isolates of M. tuberculosis from patients with pulmonary tuberculosis were included in the study. Drug sensitivity was tested by proportion method and E-test. All 23 isolates were EMB resistant. Primers to amplify the embB and embC gene were designed, and polymerase chain reaction products were subjected for sequence analysis. H37Rv standard laboratory strain was used as control. Nucleotide sequencing showed that 16 strains had a mutation in the embB gene. The most common mutation observed in the embB gene was at codon 306, followed by mutations at codons 299 and 378 in 4 and 2 isolates, respectively. Novel mutations have been reported at codons 239, 240, 247, 282, 311, 368, 397, 446, 469, and 471. Sequence analysis of the embC gene showed mutation in 8 isolates at codon 270. Novel mutations in embC have been reported at codons 251 and 254. The most common nucleotide polymorphism in our isolates was at codons 306 and 299 in the embB gene and at codon 270 in the embC gene. A mutation at codon 306 was usually associated with high-level ethambutol resistance.

Antibiotic susceptibility of Helicobacter pylori clinical isolates: comparative evaluation of disk-diffusion and E-test methods.

Antimicrobial susceptibility of 25 Helicobacter pylori strains isolated from patients with acid peptic diseases were tested for in vitro sensitivity to commonly used antibiotics using disk-diffusion and E-test, methods. All strains tested were susceptible to tetracycline by E-test, with the minimum inhibitory concentration (MIC) values being <0.125 microg/ml for all strains except for 6 (<0.023 microg/ml). However 1 strain was resistant by disk-diffusion method. One strain was resistant to clarithromycin both by disk diffusion and E-test (MIC <48 microg/ml), and 1 strain was resistant only by disk diffusion. Only one strain was resistant to amoxicillin by disk diffusion and E-test (MIC >256 microg/ml). For ciprofloxacin, three strains were resistant by disk diffusion and two by E-test (MIC <32 microg/ml). Sixteen strains were resistant to metronidazole by disk diffusion and E-test (MIC >or= 8 microg/ml), and 1 was resistant only by E-test (MIC <48 microg/ml). Overall, 64% of the strains were resistant to metronidazole. The MIC for metronidazole was also tested by agar-dilution method, and metronidazole resistant strains had an, MIC >8 microg/ml. The disk-diffusion method showed excellent correlation with E-test results; there was 100% agreement for amoxicillin a other antibiotics showed 90% to 95% accuracy. Disk diffusion is cheaper than E-test (approximately 2.6 cents vs. 2.60 US dollars), is easy to perform, and is a reliable method for testing H. pylori susceptibility to antimicrobial agents in the clinical microbiology laboratory.

Bacterial isolates from mechanically ventilated patients with nosocomial pneumonia within intensive care unit of a tertiary care center.

Nosocomial pneumonia is a common complication in mechanically ventilated patients. A study was carried out to determine the incidence, common bacterial etiologic agents and their antimicrobial susceptibility, and outcome of such pneumonia in an Intensive Care Unit (ICU) of a tertiary care center. In Surgical ICU (SICU) 176 patients required mechanical ventilation for more than 72 hours. A total of 39 (22.1%) of these patients developed nosocomial bacterial pneumonia as determined by microbiological assays. Endotracheal aspirate cultures detected a single bacterial isolate in 22 (56.4%) patients while two and three organisms were isolated from 10 (25.6%) and 7 (17.9%) patients respectively. Fifty three (84.1%) of a total of 63 isolates were Gram negative bacilli. The most frequently encountered pathogens were Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter species among the Gram negative bacilli and Staphylococcus aureus among the Gram positives. Resistance of bacterial isolates varied from 24 to 90% against commonly used antibiotics. Amikacin had the best profile, with 14% to 55% resistance against various isolates. Twenty three (59%) of 39 patients with pneumonia expired in the ICU. P. aeruginosa (25.6%) and K. pneunmoniae (17.9%) were the predominant isolates in these patients. Nosocomial pneumonia with high mortality is a frequent occurrence in mechanically ventilated patients in our ICU setting. Gram negative organisms with high levels of antimicrobial resistance are the most common isolates. Regular surveillance and monitoring of changes in antibiotic susceptibility of bacterial pathogens and appropriate therapeutic measures are likely to reduce the mortality in these patients.

Development of a simple restriction fragment length polymorphism assay for subtyping of coxsackie B viruses.

Coxsackie B viruses (genus, Enterovirus; family, Picornaviridae) can cause aseptic meningitis, encephalitis, pleurodynia, myocarditis and are implicated in the pathogenesis of dilated cardiomyopathy. The differentiation of the group B coxsackieviruses into their subtypes has potential clinical and epidemiological implications. In the present study, a simple restriction fragment length polymorphism (RFLP) assay was developed for typing of group B coxsackieviruses into subtypes 1-6. It is a two step process, first, virus isolation and identification by virus neutralization assay, using pools of polyclonal antisera, second, the reverse transcription polymerase chain reaction (RT-PCR) using a single primer pair selected from the conserved 5'-untranslated region (5'-UTR) of enterovirus genome followed by RFLP. A 440 bp product was amplified from the reference strains of each subtype of group B coxsackievirus and 29 clinical isolates (positive for group B coxsackieviruses by neutralization assay). The amplified products were subjected to restriction endonuclease digestion by enzyme BsaJI. The assay was able to distinguish all six serotypes of coxsackie B viruses. The results were comparable to serotyping and showed that due to the relatively conserved nature of 5'-UTR in enterovirus genome, this region can be used for subgeneric molecular identification of enteroviruses.

Molecular characterization of echovirus 11 isolates from India.

BACKGROUND & OBJECTIVES: Echovirus 11 (ECV11) is one of the most frequent non-polio enteroviruses isolated from stool samples of children with acute flaccid paralysis in north India. The present work was undertaken to study the sequence variability in the 440 bp of 5'-non-translated region of ECV11 genome using heteroduplex mobility assay (HMA). METHODS: Twelve ECV11 isolates were studied for sequence variability in the 5'-non-translated region (5'NTR) using the HMA followed by nucleotide sequencing. HMA was used to determine sequence diversity between Indian ECV11 isolates and prototype Gregory strain. HMA results were confirmed by 5'NTR nucleotide sequencing of five Indian ECV11 isolates. RESULTS: HMA results showed high genomic diversity between the prototype Gregory strain and Indian ECV11 isolates. All isolates were grouped into five different types of heteroduplex mobility patterns with respect to Gregory strain. A 440 bp 5'NTR fragment of five ECV11 isolates representing different heteroduplex patterns, was sequenced. The sequence alignment showed that 5'NTR of Indian isolates was different from prototype Gregory strain and identical to the ECV11 isolates of Finland and Hungary. Phylogenetic analysis including ECV11 isolate sequences from different parts of the world showed that Indian ECV11 isolates represented a different subgroup. INTERPRETATION & CONCLUSION: The results of the present study suggested that the HMA could be successfully used as a preliminary screening method for sequence variability determination of enterovirus field isolates. The sequence data generated on ECV11 isolates from India will be useful for future studies of endemic genotypes of echovirus.

Fungal peritonitis in patients on continuous ambulatory peritoneal dialysis: a single centre Indian experience.

BACKGROUND: Fungal peritonitis (FP) is a serious complication in patients on continuous ambulatory peritoneal dialysis (CAPD). We reviewed our FP cases to analyse the causative agents and possible risk factors in relation to FP and its outcome and mortality. METHODS: Records of all FP cases were reviewed. FP was diagnosed based on effluent cell count and positive fungal culture in suitable media. RESULTS: Between October 1993 and November 2001, 261 patients underwent CAPD. FP was detected in 28 patients, one episode in each patient (14.3% of the total peritonitis episodes). Candida species and dematiaceous fungi+/-Candida species were responsible for 89.3 and 10.7% of episodes, respectively. Patients with preceding bacterial peritonitis (BP) developed FP more frequently (25.6%) than de novo cases (2.9%) (P<0.0001) and lower proportion of them continued CAPD (8.6% vs. 60%; P=0.007). Mortality in patients having abdominal pain with and without fever, and catheter in situ was significantly higher than in those patients who did not have these risk factors (9/11 vs. 6/17, P=0.01; 13/17 vs. 2/11, P=0.003; 6/6, vs. 9/22, P=0.01, respectively). CONCLUSIONS: Higher proportion of our patients had FP; preceding BP was a significant risk factor for development of FP and technique failure. Abdominal pain+/-fever in patients and catheter in situ were identified as risk factors associated with mortality.

Cryptococcal infection in patients with clinically diagnosed meningitis in a tertiary care center.

A retrospective analysis of 326 clinically diagnosed cases with meningitis over a period of five-and-a-half years was carried out to determine the prevalence of cryptococcal infection, its associated risk factors and therapeutic outcome. Fifty-four (16.6%) patients with cryptococcal meningitis were identified by smear examination, culture and/or cryptococcal antigen latex agglutination test. Records of 45 cryptococcal meningitis patients were available; 18 (40%) of them were apparently healthy immunocompetent individuals, 13 (28.9%) had human immunodeficiency virus (HIV) infection, 9 (20%) were renal transplant recipients, 4 (8.9%) were diabetic and 1 (2.2%) had systemic lupus erythematosus. Ten (22.2%) patients died and 11 (24.4%) patients (all HIV-positive) left against medical advice. The present study indicates that cryptococcal infection is associated with high mortality. Presenting symptoms being indistinguishable from other causes of central nervous system infection, all patients with a clinical diagnosis of meningitis, irrespective of their immune status should be investigated for cryptococcal infection.

Candidaemia in patients of a tertiary health care hospital from north India.

BACKGROUND & OBJECTIVES: Candidaemia is an important cause of mortality in hospital settings. Limited information is available from India on nosocomial candidaemia. The objective of the present study was to isolate and identify yeasts from patients suspected to have nosocomial bloodstream infection (BSI) and to determine the carriage rate of Candida species, risk factors for acquisition of infection and mortality in this group of patients. METHODS: Blood samples from 4871 patients suspected to have BSI at least 48 h after admission were cultured following standard protocol to isolate and identify the pathogens. Clinical details, possible risk factors and outcome of all candidaemic patients were recorded and analysed. Samples of hand washings and throat gargles from these patients were also cultured to determine the carriage rate. Candida albicans isolated from patients and their carriage sites were genotyped by randomly amplified polymorphic DNA (RAPD) analysis to study strain relatedness. RESULTS: Twenty one patients with candidaemia were detected with mortality of 55 per cent. Candidaemia per 1000 admissions was 1.61. Isolation of non-C. albicans Candida species was significantly higher than C. albicans (14/21 vs 7/21: P < 0.05). Use of broad-spectrum antibiotics (43%), gastrointestinal surgery (23%), immunosuppressive therapy (23%), protein calorie malnutrition with parenteral hyperalimentation (23%) and neutropaenia (14%) were identified as probable risk factors. The seven C. albicans strains isolated from patients with BSI were typed into 6 genotypes. Yeast carriage rate among the patients was 71.4 per cent. C. albicans isolated from the hand, throat and blood of two patients had identical genotype. INTERPRETATION & CONCLUSION: BSI due to non-C. albicans Candida species is more common than C. albicans in our patients and candidaemia is associated with high mortality. RAPD appears to be a simple method to study strain relatedness for C. albicans. There is a need for early diagnosis and systematic surveillance to meet the challenges of nosocomial candidaemia.

Use of telemedicine in evading cholera outbreak in Mahakumbh Mela, Prayag, UP, India: an encouraging experience.

Telemedicine (TM) services a process in which expert medical advice from afar is provided using electronic signals to transfer the medical data from one site to another. As a pilot project to assess the efficacy of TM in developing countries like India, a telemedicine center was set up at the main hospital of Mahakumbh mela--a grand religious fair, at Prayag, a city in north India. The daily reporting of the in-patient and outpatient cases at the fair revealed a surge of diarrhea cases among the pilgrims at the fair. This information was communicated to the referral center at Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS), which, with the help of its microbiology department, conducted microbiological examinations of stool samples and rectal swabs of patients along with various water samples. Vibrio cholerae was isolated in 22.6% (7/31) of the samples. This information was immediately relayed to the Main Hospital at the fair online, and then to the health authorities, who took strict and prompt measures to improve hygiene. Subsequently, the number of diarrhea cases decreased considerably in a matter of a few days, and thus an epidemic disaster was averted, which could have created havoc in such a large gathering.

Transmission of filarial infection through blood transfusion.

Microfilariae can be transmitted by blood transfusion and they may be circulated in the recipient's blood but they do not develop into adult worms. Mortality associated with transfusion associated filarial infection is not documented but it may give rise to morbidity in transfusion recipients in terms of allergic reaction. The present study was carried out to investigate the association of post transfusion reactions and filarial infections in an endemic area. About 11,752 transfusion recipients were followed up and in 15 months period, 47 (0.4%) post transfusion reactions (PTR) were reported. Routine investigations for post transfusion reaction were carried out in all 47 patients and their respective blood donor. Moreover, blood culture, microfilaria detection by concentration technique, filarial antibody and antigen detection (both by ELISA) were done in all subjects. Out of 47 patients showing post transfusion reaction, 29 (61.7%) patients developed allergic reaction. Eighteen (38.3%) patients having allergic reaction did not have previous history of blood transfusion and 14 (29.8%) of them received transfusion from blood donors who was either positive for microfilaria, filarial antigen or antibody. Microfilaremia was demonstrated in 4 (8.5%) patients and 5 (10.6%) blood donors. Microfilaria was concurrently present in 2 patients and their respective donors. Filarial antibody was detected in 27 (56.5%) patients and 26 (55.3%) blood donors but microfilaria was detected in 3 (6.4%) and 4 (8.5%) subjects, respectively. Antigen detection test correlated with microfileraemic state of subjects. The result shows that transfusion associated filarial infection may be a probable cause for transfusion-associated morbidity in endemic areas. In 14 (29.8%) patients having allergic reactions, the probable cause was transfusion-associated filarial infection. Filarial antigen detection test was found to be more useful in detecting infections. Blood donors with active history of filarial infection should be deferred from donating blood. Filarial antigen detection test may be employed as screening test for blood donors, if possible.

Antibiotic associated diarrhoea: infectious causes.

Nearly 25% of antibiotic associated diarrhoeas (AAD) is caused by Clostridium difficile, making it the commonest identified and treatable pathogen. Other pathogens implicated infrequently include Clostridium perfringens, Staphylococcus aureus, Klebsiella oxytoca, Candida spp. and Salmonella spp. Most mild cases of AAD are due to non-infectious causes which include reduced break down of primary bile acids and decrease metabolism of carbohydrates, allergic or toxic effects of antibiotic on intestinal mucosa and pharmacological effect on gut motility. The antibiotics most frequently associated with C. difficile associated diarrhoea are clindamycin, cephalosporin, ampicillin and amoxicillin. Clinical presentation may vary from mild diarrhoea to severe colitis and pseudomembranous colitis associated with high morbidity and mortality. The most sensitive and specific diagnostic test for C. difficile infection is tissue culture assay for cytotoxicity of toxin B. Commercial ELISA kits are available. Though less sensitive, they are easy to perform and are rapid. Withdrawal of precipitating antibiotic is all that is needed for control of mild to moderate cases. For severe cases of AAD, oral metronidazole is the first line of treatment, and oral vancomycin is the second choice. Probiotics have been used for recurrent cases.

Ralstonia mannitolilytica infection in renal transplant recipient: first report.

Ralstonia mannitolilytica is being increasingly identified as an opportunist pathogen in immunocompromised patients. We report the first case of post renal transplant infection by R. mannitolilytica, in a 14-year-old recipient. The graft and the patient were saved with prompt microbiological identification, sensitivity testing and subsequent administration of appropriate antibiotic.

UreC PCR based diagnosis of Helicobacter pylori infection and detection of cag A gene in gastric biopsies.

Polymerase chain reaction assay using ureC gene specific primers for the detection of Helicobacter pylori in gastric biopsy specimens from 116 dyspeptic patients was compared with other routine invasive diagnostic methods (culture, rapid urease test [RUT] and histology). In parallel, gastric biospy specimens from 54 patients and their corresponding Helicobacter pylori isolates were subjected to PCR with cagA targeting primers using standard protocols. Helicobacter pylori were detected in 53%, 43%, 48% and 50% of patients by PCR, RUT, culture and histological examination respectively. Based on histology and culture positive and at least three test positive result, 44 (37%), 46 (39%) and 26 (22%), and 56 (48%), 52 (44%) and 8 (6%) patients were classified as Helicobacter pylori positive, negative and indeterminate respectively. The sensitivity and specificity of PCR assay was the highest-95% and 100% when compared with both culture and histology positive, and at least any three positive results respectively. The result of cagA positivity in 54 gastric biopsy specimens and their corresponding Helicobacter pylori isolates were identical; 18 of 20 (90%) duodenal ulcer patients and 23 of 28 (82%) patients with chronic gastritis and 2 (40%) of 5 patients with portal hypertension and one gastric biopsy specimens from gastric cancer patients were found to be cagA positive. PCR-based method to detect Helicobacter pylori and the virulence gene cag A directly from gastric biopsy specimens appears to be promising and can curtail the lengthy process of culture-based approaches. The procedure proved to be rapid and reliable and could be utilized for diagnostic purposes.