Genotoxic impact of di-n-butyl phthalate on DNA: A comparative study of three generations in the neuronal tissue of Wistar rats.

Di-n-butyl phthalate (DBP), one of the plasticizers, is considered a ubiquitous environmental contaminant due to its widespread application in personal-care products and serves as a raw material in many industries for the generation of many plastic products. Several scientific investigations have shown that DBP caused embryotoxicity and cognitive impairments. However, there is less understanding of the genotoxic potential of DBP in neuronal tissue when exposure happens continuously for several generations. The present study was undertaken to investigate the impact of DBP on the nucleic acids of neuronal tissue in one-month-old rats by performing a comet assay and biochemical analyses. By oral gavage, the parental generation (F0) was administered DBP (500 mg/kg/day) during gestation (GD6-20) and lactation, and exposures were continued for three consecutive generations until the pups were grown to one-month-old. The oxidative stress assessments carried out in discrete brain regions isolated from one-month-old rats (F1-F3) following DBP exposure indicated significant inhibition in the levels of antioxidant enzymes (superoxide dismutase and catalase) while oxidant status (malondialdehyde) was elevated significantly. The extent of DNA damage using the comet assay, as measured by the olive moment, tail DNA percentage and tail length, was greater in DBP-treated rats compared with the control group, but RNA/DNA content decreased significantly. The results of this study suggested a strong link between oxidative stress and genetic integrity in the neuronal tissue of rats exposed to DBP generationally. To summarise, DBP exposure during pregnancy caused oxidative stress, which resulted in genetic instability in specific discrete brain regions of the third generation.

Direct application of an ECG-based sleep staging algorithm on reflective photoplethysmography data decreases performance.

OBJECTIVE: The maturation of neural network-based techniques in combination with the availability of large sleep datasets has increased the interest in alternative methods of sleep monitoring. For unobtrusive sleep staging, the most promising algorithms are based on heart rate variability computed from inter-beat intervals (IBIs) derived from ECG-data. The practical application of these algorithms is even more promising when alternative ways of obtaining IBIs, such as wrist-worn photoplethysmography (PPG) can be used. However, studies validating sleep staging algorithms directly on PPG-based data are limited. RESULTS: We applied an automatic sleep staging algorithm trained and validated on ECG-data directly on inter-beat intervals derived from a wrist-worn PPG sensor, in 389 polysomnographic recordings of patients with a variety of sleep disorders. While the algorithm reached moderate agreement with gold standard polysomnography, the performance was significantly lower when applied on PPG- versus ECG-derived heart rate variability data (kappa 0.56 versus 0.60, p < 0.001; accuracy 73.0% versus 75.9% p < 0.001). These results show that direct application of an algorithm on a different source of data may negatively affect performance. Algorithms need to be validated using each data source and re-training should be considered whenever possible.

Sequence Permutation Generates Peptides with Different Antimicrobial and Antibiofilm Activities.

Antibiotic resistance poses a threat to our society, and 10 million people could die by 2050. To design potent antimicrobials, we made use of the antimicrobial peptide database (APD). Using the database filtering technology, we identified a useful template and converted it into an effective peptide WW291 against methicillin-resistant Staphylococcus aureus (MRSA). Here, we compared the antibacterial activity and cytotoxicity of a family of peptides obtained from sequence permutation of WW291. The resulting eight WW peptides (WW291-WW298) gained different activities against a panel of bacteria. While WW295 inhibited the growth of Escherichia coli, WW298 was highly active against S. aureus USA300 LAC. Consistently with this, WW298 was more effective in permeating or depolarizing the S. aureus membranes, whereas WW295 potently permeated the E. coli membranes. In addition, WW298, but not WW295, inhibited the MRSA attachment and could disrupt its preformed biofilms more effectively than daptomycin. WW298 also protected wax moths Galleria mellonella from MRSA infection causing death. Thus, sequence permutation provides one useful avenue to generating antimicrobial peptides with varying activity spectra. Taken together with amino acid composition modulation, these methods may lead to narrow-spectrum peptides that are more promising to selectively eliminate invading pathogens without damaging commensal microbiota.

A study on COVID-19 transmission dynamics: stability analysis of SEIR model with Hopf bifurcation for effect of time delay.

This paper deals with a general SEIR model for the coronavirus disease 2019 (COVID-19) with the effect of time delay proposed. We get the stability theorems for the disease-free equilibrium and provide adequate situations of the COVID-19 transmission dynamics equilibrium of present and absent cases. A Hopf bifurcation parameter τ concerns the effects of time delay and we demonstrate that the locally asymptotic stability holds for the present equilibrium. The reproduction number is brief in less than or greater than one, and it effectively is controlling the COVID-19 infection outbreak and subsequently reveals insight into understanding the patterns of the flare-up. We have included eight parameters and the least square method allows us to estimate the initial values for the Indian COVID-19 pandemic from real-life data. It is one of India's current pandemic models that have been studied for the time being. This Covid19 SEIR model can apply with or without delay to all country's current pandemic region, after estimating parameter values from their data. The sensitivity of seven parameters has also been explored. The paper also examines the impact of immune response time delay and the importance of determining essential parameters such as the transmission rate using sensitivity indices analysis. The numerical experiment is calculated to illustrate the theoretical results.

Hepatotoxic evaluation of Di-n-butyl phthalate in Wistar rats upon sub-chronic exposure: A multigenerational assessment.

The extensive use of di--n-butyl phthalate (DBP) as a plasticizer in medical devices, personal care products, and industries, which is a major threat to humankind as it leaches out easily from the plastic matrix into the environment. Health risks posed to adults and children from the broad usage of DBP in cosmetics and infant toys observed predominantly due to repeated and prolonged exposure. Hence, this study was undertaken to evaluate the potential effect of DBP in the hepatic tissue of rats up to three generations. Wistar rats were induced at a dose of 500 mg DBP /kg body weight dissolved in olive oil by oral gavage throughout gestation (GD 6-21), lactation and post-weaning and reared by crossing intoxicated rats up to three generations. Results of the present study showed a significant increase in the relative weight of liver, while decreased levels of antioxidant enzymes viz., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and reduced glutathione (GSH) was evident in DBP treated rats at P < 0.05. Besides hepatic marker enzymes viz., alanine transaminase (ALT) and aspartate transaminase (AST) were elevated significantly in experimental rats compared to those of the control group. Furthermore, histological studies revealed congested central veins and dilated sinusoids in F1 progeny while mild to severe focal inflammatory infiltrations were evident in F2 & F3 rats. Negative correlation observed between the levels of antioxidant enzymes and transaminase activity. In brief, DBP exposure elicits oxidative stress and alters the transaminase activity levels causing damage in hepatic tissue. F3 progeny found to high vulnerability to the exposure of DBP than F2 & F1 rats.

Resistome of Staphylococcus aureus in Response to Human Cathelicidin LL-37 and Its Engineered Antimicrobial Peptides.

Staphylococcus aureus is notoriously known for its rapid development of resistance to conventional antibiotics. S. aureus can alter its membrane composition to reduce the killing effect of antibiotics and antimicrobial peptides (AMPs). To obtain a more complete picture, this study identified the resistance genes of S. aureus in response to human cathelicidin LL-37 peptides by screening the Nebraska Transposon Mutant Library. In total, 24 resistant genes were identified. Among them, six mutants, including the one with the known membrane-modifying gene (mprF) disabled, became more membrane permeable to the LL-37 engineered peptide 17BIPHE2 than the wild type. Mass spectrometry analysis detected minimal lysyl-phosphatidylglycerol (lysylPG) from the mprF mutant of S. aureus JE2, confirming loss-of-function of this gene. Moreover, multiple mutants showed reduced surface adhesion and biofilm formation. In addition, four S. aureus mutants were unable to infect wax moth Galleria mellonella. There appears to be a connection between the ability of bacterial attachment/biofilm formation and infection. These results underscore the multiple functional roles of the identified peptide-response genes in bacterial growth, infection, and biofilm formation. Therefore, S. aureus utilizes a set of resistant genes to weave a complex molecular network to handle the danger posed by cationic LL-37. It appears that different genes are involved depending on the nature of antimicrobials. These resistant genes may offer a novel avenue to designing more potent antibiotics that target the Achilles heels of S. aureus USA300, a community-associated pathogen of great threat.

Modulation of antimicrobial potency of human cathelicidin peptides against the ESKAPE pathogens and in vivo efficacy in a murine catheter-associated biofilm model.

Antimicrobial peptides are essential components of innate immune systems that protect hosts from infection. They are also useful candidates for developing a new generation of antibiotics to fight antibiotic-resistant pathogens. Human innate immune peptide LL-37 can inhibit biofilm formation, but suffers from high cost due to a long peptide length and rapid protease degradation. To improve the peptide, we previously identified the major active region and changed the peptide backbone structure. This study designed two families of new peptides by altering peptide side chains. Interestingly, these peptides displayed differential potency against various ESKAPE pathogens in vitro and substantially reduced hemolysis. Further potency test in vivo revealed that 17tF-W eliminated the burden of methicillin-resistant Staphylococcus aureus (MRSA) USA300 in both mouse-embedded catheters and their surrounding tissues. In addition, peptide treatment suppressed the level of chemokine TNFα, and boosted the levels of chemokines MCP-1, IL-17A and IL-10 in the surrounding tissues of the infected catheter embedded in mice. In conclusion, we have designed a set of new LL-37 peptides with varying antimicrobial activities, opening the door to potential topical treatment of infections involving different drug-resistant pathogens.

Antibacterial, antifungal, anticancer activities and structural bioinformatics analysis of six naturally occurring temporins.

Antimicrobial peptides are a special class of natural products with potential applications as novel therapeutics. This study focuses on six temporins (four with no activity data and two as positive controls). Using synthetic peptides, we report antibacterial, antifungal, and anticancer activities of temporins-CPa, CPb, 1Ga, 1Oc, 1Ola, and 1SPa. While temporin-1Ga and temporin-1OLa showed higher antifungal and anticancer activity, most of these peptides were active primarily against Gram-positive bacteria. Temporin-1OLa, with the highest cell selectivity index, could preferentially kill methicillin-resistant Staphylococcus aureus (MRSA), consistent with a reduced hemolysis in the presence of bacteria. Mechanistically, temporin-1OLa rapidly killed MRSA by damaging bacterial membranes. Using micelles as a membrane-mimetic model, we determined the three-dimensional structure of temporin-1OLa by NMR spectroscopy. The peptide adopted a two-domain structure where a hydrophobic patch is followed by a classic amphipathic helix covering residues P3-I12. Such a structure is responsible for anti-biofilm ability in vitro and in vivo protection of wax moths Galleria mellonella from staphylococcal infection. Finally, our bioinformatic analysis leads to a classification of temporins into six types and confers significance to this NMR structure since temporin-1OLa shares a sequence model with 62% of temporins. Collectively, our results indicate the potential of temporin-1OLa as a new anti-MRSA compound, which shows an even better anti-biofilm capability in combination with linezolid.

Interleukin-17 regulates matrix metalloproteinase activity in human pulmonary tuberculosis.

Tuberculosis (TB) is characterized by extensive pulmonary matrix breakdown. Interleukin-17 (IL-17) is key in host defence in TB but its role in TB-driven tissue damage is unknown. We investigated the hypothesis that respiratory stromal cell matrix metalloproteinase (MMP) production in TB is regulated by T-helper 17 (TH -17) cytokines. Biopsies of patients with pulmonary TB were analysed by immunohistochemistry (IHC), and patient bronchoalveolar lavage fluid (BALF) MMP and cytokine concentrations were measured by Luminex assays. Primary human airway epithelial cells were stimulated with conditioned medium from human monocytes infected with Mycobacterium tuberculosis (Mtb) and TH -17 cytokines. MMP secretion, activity, and gene expression were determined by ELISA, Luminex assay, zymography, RT-qPCR, and dual luciferase reporter assays. Signalling pathways were examined using phospho-western analysis and siRNA. IL-17 is expressed in TB patient granulomas and MMP-3 is expressed in adjacent pulmonary epithelial cells. IL-17 had a divergent, concentration-dependent effect on MMP secretion, increasing epithelial secretion of MMP-3 (p < 0.001) over 72 h, whilst decreasing that of MMP-9 (p < 0.0001); mRNA levels were similarly affected. Both IL-17 and IL-22 increased fibroblast Mtb-dependent MMP-3 secretion but IL-22 did not modulate epithelial MMP-3 expression. Both IL-17 and IL-22, but not IL-23, were significantly up-regulated in BALF from TB patients. IL-17-driven MMP-3 was dependent on p38 MAP kinase and the PI3K p110α subunit. In summary, IL-17 drives airway stromal cell-derived MMP-3, a mediator of tissue destruction in TB, alone and with monocyte-dependent networks in TB. This is regulated by p38 MAP kinase and PI3K pathways. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Gestational di-n-butyl phthalate exposure induced developmental and teratogenic anomalies in rats: a multigenerational assessment.

With the limited but ongoing usage of di-n-butyl phthalate (DBP) as plasticizer, the health effects of both phthalate and its alternatives are far from being understood. Multigenerational effects of phthalates were evaluated in rats upon exposure to DBP, aiming to provide some evidences about its potential in causing developmental teratogenicity. Gestational rats were exposed to DBP (500 mg/kg bw/day) and control groups with olive oil. On the 18th day of gestation, fetuses (F1) isolated from a few dams were subjected to prenatal screening, and the other rats were allowed to litter, and later postnatal screening was made. DBP-toxicated (F1) rats were crossed and reared up to three generations (F2 and F3) by adopting the same experimental design. A considerable decrease in the weight of placenta, low number of corpora lutea and increased resorptions, and pre- and postimplantation loss were observed in F1, F2, and F3 generations. Further, there was a decrease in the number of live births and fetal body weight with high mortality, the developmental indices showed reduction in litter size and sex ratio, and a considerable incidence of skeletal and malformation complex involving face and eye was observed in later generations compared to the first. The pre-weaning indices in neonates showed a considerable delay in physical growth milestones and poor scores in sensory motor development. Alterations noticed in the levels of thyroid profile and testosterone found to have a role in sensory motor, craniofacial development, and eye formation. In brief, results confirm multigenerational and fetotoxic effects of DBP; thereby, findings imply that developing tissues are the targets and endocrine disruption appears to be the underlying mechanism of phthalate action.

Small molecule mimics of DFTamP1, a database designed anti-Staphylococcal peptide.

Antimicrobial peptides (AMPs) are important templates for developing new antimicrobial agents. Previously, we developed a database filtering technology that enabled us to design a potent anti-Staphylococcal peptide DFTamP1. Using this same design approach, we now report the discovery of a new class of bis-indole diimidazolines as AMP small molecule mimics. The best compound killed multiple S. aureus clinical strains in both planktonic and biofilm forms. The compound appeared to target bacterial membranes with antimicrobial activity and membrane permeation ability similar to daptomycin.

Design and surface immobilization of short anti-biofilm peptides.

Short antimicrobial peptides are essential to keep us healthy and their lasting potency can inspire the design of new types of antibiotics. This study reports the design of a family of eight-residue tryptophan-rich peptides (TetraF2W) obtained by converting the four phenylalanines in temporin-SHf to tryptophans. The temporin-SHf template was identified from the antimicrobial peptide database (http://aps.unmc.edu/AP). Remarkably, the double arginine variant (TetraF2W-RR) was more effective in killing methicillin-resistant Staphylococcus aureus (MRSA) USA300, but less cytotoxic to human skin HaCat and kidney HEK293 cells, than the lysine-containing dibasic combinations (KR, RK and KK). Killing kinetics and fluorescence spectroscopy suggest membrane targeting of TetraF2W-RR, making it more difficult for bacteria to develop resistance. Because established biofilms on medical devices are difficult to remove, we chose to covalently immobilize TetraF2W-RR onto the polyethylene terephthalate (PET) surface to prevent biofilm formation. The successful surface coating of the peptide is supported by FT-IR and XPS spectroscopies, chemical quantification, and antibacterial assays. This peptide-coated surface indeed prevented S. aureus biofilm formation with no cytotoxicity to human cells. In conclusion, TetraF2W-RR is a short Trp-rich peptide with demonstrated antimicrobial and anti-biofilm potency against MRSA in both the free and immobilized forms. Because these short peptides can be synthesized cost effectively, they may be developed into new antimicrobial agents or used as surface coating compounds. STATEMENT OF SIGNIFICANCE: It is stunning that the total deaths due to methicillin-resistant Staphylococcus aureus (MRSA) infection are comparable to AIDS/HIV-1, making it urgent to explore new possibilities. This study deals with this problem by two strategies. First, we have designed a family of novel antimicrobial peptides with merely eight amino acids, making it cost effective for chemical synthesis. These peptides are potent against MRSA USA300. Our study uncovers that the high potency of the tryptophan-rich short peptide is coupled with arginines, whereas these Trp- and Arg-rich peptides are less toxic to select human cells than the lysine-containing analogs. Such a combination generates a more selective peptide. As a second strategy, we also demonstrate successful covalent immobilization of this short peptide to the polyethylene terephthalate (PET) surface by first using a chitosan linker, which is easy to obtain. Because biofilms on medical devices are difficult to remove by traditional antibiotics, we also show that the peptide coated surface can prevent biofilm formation. Although rarely demonstrated, we provide evidence that both the free and immobilized peptides target bacterial membranes, rendering it difficult for bacteria to develop resistance. Collectively, the significance of our study is the design of novel antimicrobial peptides provides a useful template for developing novel antimicrobials against MRSA. In addition, orientation-specific immobilization of the same short peptide can prevent biofilm formation on the PET surface, which is widely used in making prosthetic heart valves cuffs and other bio devices.

Anti-Staphylococcal Biofilm Effects of Human Cathelicidin Peptides.

Staphylococcus aureus can live together in the form of biofilms to avoid elimination by the host. Thus, a useful strategy to counteract bacterial biofilms is to re-engineer human antimicrobial peptide LL-37 so that it can be used as a remedy for preventing and removing biofilms. This study reports antibiofilm effects of four human cathelicidin LL-37 peptides against community-associated and hospital isolated methicillin-resistant Staphylococcus aureus (MRSA) strains. Although the intact molecule LL-37 inhibited biofilm formation at low concentrations, it did not inhibit bacterial attachment nor disrupt preformed biofilms. However, two 17-residue peptides, GF-17 and 17BIPHE2, inhibited bacterial attachment, biofilm growth, and disrupted established biofilms. An inactive peptide RI-10 was used as a negative control. Our results obtained using the S. aureus mutants in a static biofilm model are consistent with the literature obtained in a flow cell biofilm model. Because 17BIPHE2 is the most effective biofilm disruptor with desired stability to proteases, it is a promising lead for developing new anti-MRSA biofilm agents.

In Situ Generated Ag(II)-Catalyzed Selective Oxo-Esterification of Alkyne with Alcohol to α-Ketoester: Photophysical Study.

An expert and easy one-step catalytic method for the multi O-C coupling of alkyne is developed for the synthesis of valuable α-ketoesters and their chiral analogues, in contrast to the generation of esters by a noncatalytic method. The in situ generated powerful Ag(II) catalyst from AgOTf is the workhorse in the oxidative grafting of alkyne with PhIO and alcohol. The radical mechanism is confirmed in our controlled experiments and UV-vis study.

PdII-Catalyzed Oxidative Aldehyde-sp2C-H Functionalization and Cyclization Using NHC with Mild Oxidant DMSO for the Selective Synthesis of Esters, Sugar-Based Analogues, and ß-Hydroxy Chromanones: An 18O-Labeling Study.

We assume formation of acyl-PdII-N-heterocyclic-carbene (NHC) organometalics for diverse C-O/O-C and C-C/C-O coupling catalysis of direct functionalization and cyclization reactions. We report the first use of dimethyl sulfoxide (DMSO) as an oxidant under an inert atmosphere to O2-sensitive NHC for oxidative transformations. In situ generated imidazolium halides are utilized as a precursor of NHC and as a source of alkyl group for the sp2C-H functionalization of aldehydes to esters under mild conditions. In contrast to the reported NHC-catalyzed esterification strategies, the outstanding substrate scope of this mild catalysis approach is established through synthesis of thermally labile sugar-based chiral esters. Our competition experiments using various unsymmetrical imidazolium halides revealed an ascending rate of migratory aptitude among methyl ≪ allyl < crotyl < cinnamyl < benzyl moiety. DMSO is used as an oxidant for both esterification and cyclization reactions, and the transfer of the DMSO-oxygen to ester is confirmed using an 18O-labeling experiment. The diverse activity using DMSO-oxygen to acyl-PdII-NHC is verified by developing a unique C-C-coupled cyclization with side-chain hydroxylation of olefin to achieve valuable ß-hydroxy chromanones.

Functionalised Mn(VI)-nanoparticles: an advanced high-valent magnetic catalyst.

We discover Mn(VI)-nanoparticles (NPs) bearing functional groups, high oxidation state, strong electron affinity, unique redox and paramagnetic nature, which opens up a new avenue to catalysis, magnetism and material application. However, its synthesis is challenging and remains unexplored because of associated serious difficulties. A simple benign synthetic strategy is devised to fabricate the high-valent NPs using mild reducing agent bromide, which transformed Mn(VII) to valuable Mn(VI)-species. The EELS-imaging of individual elements, ESI-MS, XPS and other techniques established its composition as Br(Me3SiO)Mn(VI)O2. It revealed significantly improved magnetic moment (SQUID) with isotropic hyperfine splitting of six line spectrum (EPR). The high-oxidation state and incorporated-ligands of the metals present on the active surface of the NPs led to development of a general catalytic process for oxidative heterodifunctionalisation to C-C triple bond towards formation of a new O-C/N-C/S-C and C-C coupling cum cyclisation to biologically important flavones and their aza- and marcapto-analogues, and valuable enaloxy synthons.

Overexpression of insulin like growth factor binding protein 5 reduces liver fibrosis in chronic cholangiopathy.

The ATP-binding cassette, sub-family B member 4 knock-out mouse (Abcb4(-/-)) is a relevant model for chronic cholangiopathy in man. Due to the lack of this P-glycoprotein in the canalicular membrane of hepatocytes, the secretion of phospholipids into bile is absent, resulting in increased bile toxicity. Expression of insulin like growth factor binding protein 5 (Igfbp5) increases in time in the livers of these mice. It is unclear whether this induction is a consequence of or plays a role in the progression of liver pathology. The aim of this study was therefore to investigate the effect of IGFBP5 induction on the progression of liver fibrosis caused by chronic cholangiopathy. IGFBP5 and, as a control, green fluorescent protein were overexpressed in the hepatocytes of Abcb4(-/-) mice, using an adeno-associated viral vector (AAV). Progression of liver fibrosis was studied 3, 6, and 12 weeks after vector injection by analyzing serum parameters, collagen deposition, expression of pro-fibrotic genes, inflammation and oxidative stress. A single administration of the AAV vectors provided prolonged expression of IGFBP5 and GFP in the livers of Abcb4(-/-) mice. Compared to GFP control, fractional liver weight, extracellular matrix deposition and amount of activated hepatic stellate cells significantly decreased in IGFBP5 overexpressing mice even 12 weeks after treatment. This effect was not due to a change in bile composition, but driven by reduced inflammation, oxidative stress, and proliferation. Overexpression of IGFBP5 seems to have a protective effect on liver pathology in this model for chronic cholangiopathy.

Inhibition of poly(ADP-ribose) polymerase (PARP) and ataxia telangiectasia mutated (ATM) on the chemosensitivity of mantle cell lymphoma to agents that induce DNA strand breaks.

There is a high incidence of genomic aberration of ataxia telangiectasia mutated (ATM) and genes encoding proteins involved in the ATM pathway in mantle cell lymphoma (MCL). It has been shown that poly(ADP-ribose) polymerase inhibitor (PARPi) strongly enhances the cytotoxicity of agents, causing single-strand DNA breaks in cells with impaired homologous recombination repair. Here, we show that PARPi AG14361 potentiates the cytotoxicity induced by topotecan treatment in MCL cell lines, which was not dependent on either TP53 or CHEK2 status. Inhibition and/or knockdown of ATM and BRCA2 did not potentiate the cytotoxic effect of treatment with PARPi and topotecan. With loss of function of ATM, other kinases can still mediate activation of ATM substrates as demonstrated by continued phosphorylation of CHEK2 (Thr-68), although attenuated and delayed. These results suggest that PARPi may enhance the therapeutic efficacy of DNA damaging agents on MCL through TP53-independent mechanisms without requiring the inhibition of either ATM or BRCA2.

Critically ill patients with 2009 H1N1 infection in an Indian ICU.

BACKGROUND AND AIMS: The 2009 pandemic influenza A (H1N1) has taken its toll across most parts of India. We aimed to study its epidemiology, clinical characteristics and outcomes from an Indian multidisciplinary intensive care unit (ICU). MATERIALS AND METHODS: All patients admitted to our ICU with a flu-like illness and who tested positive for the 2009 H1N1 by reverse -transcriptase polymerase- chain -reaction assay during a 3 month period were prospectively studied. RESULTS: Thirty one patients were admitted to the ICU during the study period. Patients were in the younger age group with a median age of 35 years (IQR: 28.2-42.8). Obesity was the commonest risk factor. Twenty six patients (83.9%) required ventilator support; the median duration of ventilator support was 10 days (IQR: 4-22). Severe hypoxemia was the predominant feature in all patients. Circulatory failure requiring vasopressors occurred in 18 (58.1%) patients and acute kidney injury in 6 (3.2%) patients. Twenty six patients were alive at the end of 28 days; subsequently all except one were discharged. The median duration of hospital stay was 15 (IQR: 8-22.5) days. Increasing APACHE II scores were associated with an increased risk of death (Hazard Ratio: 1.1; CI: 1.08 -1.2; P = 0.04). Mean tidal volumes in non-survivors were significantly lower; this was related to poor lung compliance in this group. CONCLUSIONS: 2009 H1N1 infection caused severe disease in relatively young patients without significant co-morbidities, characterized by severe hypoxemia and the requirement for prolonged mechanical ventilation. Extra-pulmonary organ failure included circulatory and renal failure.