Biosorption efficiency of nickel by various endophytic bacterial strains for removal of nickel from electroplating industry effluents: an operational study.

Realising the hazardous effect of nickel on human health, microbes and plants are effectively used for bioremediation. The endophytic microorganisms have an important role in the phytoremediation of nickel using Vigna radiata. Therefore, in order to harness the potential of microbial strains, the present study was designed to examine the metal biosorption ability of endophytic bacterial strains isolated from plants growing in nickel-contaminated soil. A total of six endophytic nickel resistance bacteria were isolated from the plant Vigna radiata. The metal tolerant bacterial strains were identified following 16 S rRNA gene sequence analysis. Nickel biosorption estimation and plant growth-promoting (PGP) activities of isolated strains were performed and found high nickel biosorption efficiency of 91.3 ± 0.72% at 600 mg L-1 using Bacillus safensis an isolated endophytic strain from Vigna radiata. Furthermore, high indole acetic acid (IAA) and exopolysaccharide (EPS) production were obtained in all the strains as compared to without nickel-containing medium used as control. Moreover, the production of high EPS suggests improved biosorption ability of isolated endophytic strains. In addition, a kinetic study was also performed to evaluate different adsorptions isotherms and support the nickel biosorption ability of endophytic strains. The treatment of nickel electroplating industrial effluent was also demonstrated by isolated endophytic strains. Among six (6) strains, B. cereus showed maximum 57.2 ± 0.62% biosorption efficiency of nickel which resulted in the removal of 1003.50 ± 0.90 mg L-1 of nickel from the electroplating industry effluents containing initial 1791 ± 0.90 mg L-1 of nickel. All other strains were also capable of significant nickel biosorption from electroplating industry effluents as well. Thus, isolated endophytic nickel tolerant strains can be further used at large-scale biosorption of nickel from electroplating industry effluent.

Organochlorine pesticide residues in plants and their possible ecotoxicological and agri food impacts.

Scientific investigations on levels of Organochlorine Pesticide (OCP) residues in plants largely consider the edible parts (crops, vegetables, and fruit plants). Though the non-edible parts of plants are not eaten by human beings directly, these parts are consumed by livestock and other animals, thereby facilitating the flow of chemical residues through the food chain. The objective of the present investigation was to evaluate the concentration of OCP residues in non-edible plant parts to provide insights on their potential ecotoxicological impacts. Eighteen OCP residues were extracted in nine different plant species (banana Musa acuminate, brinjal Solanum melongena, Casuarina equisetifolia, Eucalyptus globulus, lotus Nelumbo nucifera, paddy Oryza sativa, sugarcane Saccharum officinarum, tapioca Manihot esculenta, tomato Lycopersicon esculentum) following QuEChERS method. The concentrations of OCP residues in plant extracts were determined using Gas Chromatography coupled with Mass Spectrometry (GC-MS). The OCP residues, namely: γ-HCH (lindane), heptachlor epoxide isomer, dieldrin, endrin, endrin aldehyde and endrin ketone were found predominantly in seven plant species. Residues of γ-HCH (lindane) were reported in different parts of plant species such as stem (581.14 ng/g in paddy and 585.82 ng/g in tapioca) and leaf (583.3 ng/g in tomato). Seven samples contained residues of heptachlor epoxide isomer (512.53 to 1173.8 ng/g). Dieldrin was found in paddy stem (489.97 ng/g), tapioca stem (490.21 ng/g) and tapioca leaf (490.32 ng/g). The detected OCPs in the present study were 10-50 times higher than the Maximum Residue Limits (MRL, 0.01-0.1 mg/Kg) as prescribed in the Codex Alimentarius of the FAO/WHO. Their elevated concentrations in the plant parts therefore pose risk of contamination to the consumers in the food chain, including human beings those are dependent on the animals as source of protein. The findings of this study are the first report on residue levels of OCPs in non-edible plant parts in the agricultural landscape of Puducherry region, India. Since, this study assumes significance for the strategic location of Oussudu Lake, an interstate lake spread over Puducherry and Tamil Nadu states, regular monitoring of OCP residues in different environmental segments in strategic locations in both the states is suggested, which will help the authorities in devising a comprehensive environmental management plan aiming at the ecosystem at large.

Potential human health hazard due to bioavailable heavy metal exposure via consumption of plants with ethnobotanical usage at the largest chromite mine of India.

Usage of native plant species for traditional medicine or nutritional supplement is a popular practice among various cultures. But consumption of plants growing on polluted soil can cause serious human health hazard due to bioaccumulation of toxic heavy metals. Present study deals with the ecological and human health impact of heavy metals, in six native plant species with ethnobotanical significance growing at the largest chromite mine of India. Exchangeable, oxidizable, reducible and residual fractions of the metals in plant rhizosphere were analyzed. Only 2-6% of total Cr (270-330 mg/kg) and Ni (150-190 mg/kg) at the mining site is bioavailable. Cd showed highest bioavailability (~ 60%) in mining site posing very high ecological risk (1055-5291) followed by Ni (1297-2124) and Cr (309-1105). The heavy metals in the shoot of the targeted plants were about 0.7 to 80 times higher than the standard limit as per Indian statutory body. The total hazard quotient (THQ) by the consumption of plants growing in mining region was very high (> 1) and varied from 2.6 to 5.9 in adult and 0.6-1.3 in children, while in non-mining region the THQ of same plants indicates low risk (< 1). This study indicates THQ (adult) in the order of, Euphorbia hirta (5.9) > Calotropis procera (4.9) > Argemone mexicana (3.6) > Vernonia cinerea (3.5) > Pteridium latiusculum (3.4) > Tridax procumbens (2.6) through consumption pathway growing in mine soil. This study concludes that consumption of plants growing in heavy metal polluted soil should be avoided due to their potential health hazard.

Chelate-assisted phytoaccumulation: growth of Helianthus annuus L., Vigna radiata (L.) R. Wilczek and Pennisetum glaucum (L.) R. Br. in soil spiked with varied concentrations of copper.

Phytoextraction is an economic, environment-friendly and growing technology for clean-up of metal-contaminated soil. Several factors play pivotal role in making phytoextraction a successful technique. Soil fraction is an important parameter that may affect phytoextraction potential. There has been an increased realization on the role of chelates in accelerating metal uptake by plants. Thus, the present study examined the influence of different soil fractions, spiked metal concentrations and chelate dosages on Cu accumulation by Helianthus annuus L. (common sunflower), Vigna radiata (L.) R. Wilczek (mung bean) and Pennisetum glaucum (L.) R. Br. (pearl millet). To mimic the mill tailings of various mined-out sites in India, five soil fractions containing different proportions of garden soil and silica were prepared (S1: 100% soil; S2: 75% soil + 25% silica; S3: 50% soil + 50% silica; S4: 25% soil + 75% silica; and S5: 100% silica) and each fraction was spiked with known Cu (100, 250, 500 and 1000 mg kg-1) concentration. Upon maturity of the plant, EDTA and NTA in different dosages (0.25, 0.5, 1.0 and 2.0 g kg-1) were applied to each pot. Bioconcentration factor (BCF), bioaccumulation coefficient (BAC) and translocation factor (TF) were estimated for each set. The accumulation of Cu by H. annuus, V. radiata and P. glaucum indicated direct relation between soil fractions and harvesting periods. Better plant growth and Cu uptake were observed in pots with silica < 50% of fraction, whereas growth was arrested in pots with silica > 75%. The Cu accumulation varied significantly (p < 0.05) among the species, spiked metal concentration, chelate dosages and plant parts. Best accumulation was reported in pots with 50% soil and 50% silica either under 1.0 g kg-1 EDTA or 2.0 g kg-1 NTA. Irrespective of the combinations of various variables, the harvesting time affected Cu accumulation considerably. Among the species, H. annuus emerged out to be the most efficient for Cu translocation. Apparently, soil amendments facilitated enhanced uptake thereby playing an active role in improving the BAC and TF. Assisted phytoextraction is still a need until full-fledged alternatives are established in the market. The future of chelate-assisted phytoextraction seems to be limited to ex situ condition.

Association of metals with geochemical phases in wetland soils of a Ramsar site in India.

Mobilization of metals in wetland ecosystems is a function of the behaviour of a specific metal species and is dependent largely on the prevailing micro-environmental conditions. Apparently, five different chemical forms of metals are known with varying affinity to binding sites, mobility, bioavailability and toxicity. Quantification of these forms of metals in the soils is imperative in predicting their biogeochemical fate and toxicity. In this context, we examined the association of Cu, Pb and Zn, with various geochemical phases in the soil profile of wetland system of Keoladeo National Park, a Ramsar site in India. The assessment covered the soil profile until 100 cm depth at every 25-cm intervals. Different operationally defined geochemical phases in the soil at different depths were examined during the study for respective metal concentrations. Hydrous oxides of Fe-Mn were the major carrier for all the three metals and the fraction associated with exchangeable phase was the least. The low organic matter content in the soil seems to be influencing the metal association with the organic matter (OM-S) phase, which was also a less preferred carrier for metals. For Cu (5.8-78.4%) and Pb (33.5-88.5%), Fe-Mn hydroxide phase was an important binding site and for Zn (31.02-79.03%), it was the silicate mineral matrix (RES phase). This suggests the importance of micro-environmental conditions in the wetland bed such as redox and pH in mobilization of metals. As metals such as Pb have high eco-toxicological potential, an assessment of fractional concentrations of metals provides insights into their mobility and bioavailability in aquatic ecosystems. This aids wetland managers to develop appropriate strategy to maintain quality of inflow water, the single most crucial factor for a wetland ecosystem, and thus controls the micro-environmental conditions.

Spatial variability and temporal changes in the trace metal content of soils: implications for mine restoration plan.

Trace metals in soils may be inherited from the parent materials or added to the system due to anthropogenic activities. In proposed mining areas, trace metals become an integral part of the soil system. Usually, researchers undertake experiments on plant species selection (for the restoration plan) only after the termination of mining activities, i.e. without any pre-mining information about the soil-plant interactions. Though not shown in studies, it is clear that several recovery plans remain unsuccessful while carrying out restoration experiments. Therefore, we hypothesize that to restore the area effectively, it is imperative to consider the pre-mining scenario of metal levels in parent material as well as the vegetation ecology of the region. With these specifics, we examined the concentrations of trace metals in parent soils at three proposed bauxite locations in the Eastern Ghats, India, and compared them at a spatio-temporal scale. Vegetation quantification and other basic soil parameters accounted for establishing the connection between soil and plants. The study recorded significant spatial heterogeneity in trace metal concentrations and the role of vegetation on metal availability. Oxidation reduction potential (ORP), pH and cation exchange capacity (CEC) directly influenced metal content, and Cu and Ni were lithogenic in origin. It implies that for effective restoration plant species varies for each geological location.

Cellular mosaicism for X-linked polymorphisms and IRAK1 expression presents a distinct phenotype and improves survival following sepsis.

ChrX cellular mosaicism for X-linked genetic polymorphisms in females versus the single ChrX representation in males denotes a genetic difference, which may contribute to gender bias in the inflammatory response. This hypothesis was tested in female F1 offspring of consomic mice (BL6J-ChrX(A/J)/NaJ) that were homokaryotic or mosaic for the active BL6 and AJ ChrXs or for IRAK1 deficiency linked to the BL6 ChrX. Sepsis was initiated by CLP. IRAK1-deficient and IRAK1-mosaic mice showed similar protection from sepsis-induced mortality and reduced IL-6 and IL-10 release compared with WT. BM cellularity and blood B cell counts were increased in naive IRAK1-mosaic mice compared with WT-mosaic or IRAK1-deficient animals. Sepsis-induced BM cell depletion was greater in IRAK1-mosaic mice compared with WT-mosaic or IRAK1-deficient subjects, whereas splenic B and T cell depletion was less in IRAK1-mosaic and IRAK1-deficient than WT-mosaic mice. Skewing toward AJ or BL6-ChrX-expressing cells was assessed by testing allele-specific expression of strain-variant Xkrx and BTK genes. In naive IRAK1-mosaic mice, BM and blood cells with the active BL6-ChrX, were greater than cells expressing the AJ-ChrX (cell ratio 2.5 in IRAK1-mosaic; 1.5 in WT-mosaic mice). Sepsis decreased cell ratios more in IRAK1-mosaic than in WT-mosaic mice. The study reveals functional variability in cellular mosaicism for IRAK1 expression and natural X-linked polymorphisms during sepsis. Mosaicism for IRAK1 expression is accompanied by skewing toward deficient immune cell populations, producing a phenotype that is preconditioned for improved sepsis outcome similar to that observed in IRAK1 deficiency.

IRAK1-dependent signaling mediates mortality in polymicrobial sepsis.

Interleukin-1 receptor-associated kinase (IRAK1) is a key regulatory protein in TLR/IL1R-mediated cell activation during inflammatory response. Studies indicated that pending on the nature of the used inflammatory model, downregulation of IRAK1 may be beneficial or detrimental. However, the role of IRAK1 in affecting outcome in polymicrobial sepsis is unknown. We tested this question using an IRAK1-deficient mouse strain and cecal ligation and puncture (CLP) procedure, which is a clinically relevant rodent septic model. Sepsis-induced mortality was markedly lower in IRAK1-deficient mice (35 %) compared to WT (85 %). Sepsis-induced increases in blood IL-6 and IL-10 levels were blunted at 6 h post-CLP in IRAK1 deficiency compared to WT, but cytokine levels were similar at 20 h post-CLP. Sepsis-induced blood granulocytosis and depletion of splenic B cells were also blunted in IRAK1-deficient mice as compared to WT. Analysis of TLR-mediated cytokine responses by IRAK1-deficient and WT macrophages ex vivo indicated a TLR4-dependent downregulation of IL-6 and IL1ß in IRAK1 deficiency, whereas TLR2-dependent responses were unaffected. TLR7/8-mediated IL-6, IL1ß, and IL-10 production was also blunted in IRAK1 macrophages as compared to WT. The study shows that IRAK1 deficiency impacts multiple TLR-dependent pathways and decreases early cytokine responses following polymicrobial sepsis. The delayed inflammatory response caused by the lack of IRAK1 expression is beneficial, as it manifests a marked increased chance of survival after polymicrobial sepsis.

Ecto-5'-nucleotidase (CD73) decreases mortality and organ injury in sepsis.

The extracellular concentrations of adenosine are increased during sepsis, and adenosine receptors regulate the host's response to sepsis. In this study, we investigated the role of the adenosine-generating ectoenzyme, ecto-5'-nucleotidase (CD73), in regulating immune and organ function during sepsis. Polymicrobial sepsis was induced by subjecting CD73 knockout (KO) and wild type (WT) mice to cecal ligation and puncture. CD73 KO mice showed increased mortality in comparison with WT mice, which was associated with increased bacterial counts and elevated inflammatory cytokine and chemokine concentrations in the blood and peritoneum. CD73 deficiency promoted lung injury, as indicated by increased myeloperoxidase activity and neutrophil infiltration, and elevated pulmonary cytokine levels. CD73 KO mice had increased apoptosis in the thymus, as evidenced by increased cleavage of caspase-3 and poly(ADP-ribose) polymerase and increased activation of NF-κB. Septic CD73 KO mice had higher blood urea nitrogen levels and increased cytokine levels in the kidney, indicating increased renal dysfunction. The increased kidney injury of CD73 KO mice was associated with augmented activation of p38 MAPK and decreased phosphorylation of Akt. Pharmacological inactivation of CD73 in WT mice using α, ß-methylene ADP augmented cytokine levels in the blood and peritoneal lavage fluid. These findings suggest that CD73-derived adenosine may be beneficial in sepsis.

Female X-chromosome mosaicism for NOX2 deficiency presents unique inflammatory phenotype and improves outcome in polymicrobial sepsis.

Cellular X-chromosome mosaicism, which is unique to females, may be advantageous during pathophysiological challenges compared with the single X-chromosome machinery of males, and it may contribute to gender dimorphism in the inflammatory response. We tested the hypothesis of whether cellular mosaicism for the X-linked gp91phox (NOX2) deficiency, the catalytic component of the superoxide anion-generating NADPH oxidase complex, is advantageous during polymicrobial sepsis. Deficient, wild-type (WT), and heterozygous/mosaic mice were compared following polymicrobial sepsis initiated by cecal ligation and puncture. Compared with WT littermates, sepsis-induced mortality was improved in deficient mice, as well as in mosaic animals carrying both deficient and WT phagocyte subpopulations. In contrast, blood bacterial counts were greatest in deficient mice. Consistent with poor survival, WT mice also showed the most severe organ damage following sepsis. In mosaic animals, the deficient neutrophil subpopulations displayed increased organ recruitment and elevated CD11b membrane expression compared with WT neutrophil subpopulations within the same animal. The dynamics of sepsis-induced blood and organ cytokine content and WBC composition changes, including lymphocyte subsets in blood and bone marrow, showed differences among WT, deficient, and mosaic subjects, indicating that mosaic mice are not simply the average of the deficient and WT responses. Upon oxidative burst, interchange of oxidants between WT and deficient neutrophil subpopulations occurred in mosaic mice. This study suggests that mice mosaic for gp91phox expression have multiple advantages compared with WT and deficient mice during the septic course.

Female X-chromosome mosaicism for gp91phox expression diversifies leukocyte responses during endotoxemia.

OBJECTIVE: To test the hypothesis, using an animal model, whether female X-chromosome mosaicism for inflammatory gene expression could contribute to the gender dimorphic response during the host response. X-chromosome-linked genetic polymorphisms present a unique biological condition because females display heterozygous cellular mosaicism, due to the fact that either the maternal or the paternal X chromosomes are inactivated in each individual cell in females. This is in contrast with the conditions in males who carry exclusively the maternal X chromosome. DESIGN: Prospective, randomized, laboratory investigation. SETTINGS: University research laboratory. SUBJECTS: Female mice deficient, heterozygous (mosaic) or WT for the X-linked gp91phox. INTERVENTIONS: We compared selected inflammatory markers among heterozygous (mosaics), WT and homozygous deficient animals in response to in vivo lipopolysaccharide (Escherichia coli, 20 mg/kg body weight). To test individual mosaic subpopulations of polymorphonuclear neutrophil responses, we also developed a flow cytometry assay that identifies the active parental X chromosomes in individual cells, using gp91phox expression as a marker. MEASUREMENTS AND MAIN RESULTS: Heterozygous mosaic mice presented white blood cell trafficking patterns similar to that observed in WT mice, despite the fact that the deficient subpopulation in mosaic animals displayed increased cell activation as reflected in elevated neutrophil CD11b expression and splenic infiltration. Mosaic animals also displayed splenic neutrophil infiltration, which was skewed toward the deficient subpopulation. Observations on splenic T-cell depletion and post lipopolysaccharide interleukin-10 responses indicated that the inflammatory response in mosaic animals does not simply display an average of the deficient and WT responses, but the mosaic subjects display a uniquely characteristic response. CONCLUSIONS: The study supports the notion that female X chromosome mosaicism for polymorphic gene expression represents a unique condition, which may contribute to the gender dimorphic character of the inflammatory response. Mosaicism for X-linked polymorphisms may have clinical significance and needs consideration in genetic association or gender-related clinical studies.

Monitoring water quality of Coimbatore wetlands, Tamil Nadu, India.

Signs of wetland-water quality degradation have been apparent for decades, especially in those wetlands situated in the vicinity of cities and human habitations. Investigation on four urban wetlands of Coimbatore have been undertaken to assess the water quality with reference to pollution from various sources. The pH and total dissolved solids (TDS) values of the lakes were found to be different from those reported almost a decade back. The concentrations of phosphate and sulphate were much lower than the earlier reported values. The present scenario states that though the biochemical oxygen demand and chemical oxygen demand values were lower for the Ukkadam wetland, the values for Perur wetland have shown a gradual increase. Alkalinity and chloride concentrations were thrice higher than the previous findings. Electrical conductivity and TDS ranged from 303.67 to 4,456.7 muS/cm and from 169 to 2,079.3 mg/l, respectively, and were positively correlated with chloride and sulphate (P < 0.05). These changes are a reflection of the environmental changes happening in the cityscape of the Coimbatore, a fast-growing city in south India.

Adenylyl cyclase type 5 protein expression during cardiac development and stress.

Adenylyl cyclase (AC) types 5 and 6 (AC5 and AC6) are the two major AC isoforms expressed in the mammalian heart that mediate signals from beta-adrenergic receptor stimulation. Because of the unavailability of isoform-specific antibodies, it is difficult to ascertain the expression levels of AC5 protein in the heart. Here we demonstrated the successful generation of an AC5 isoform-specific mouse monoclonal antibody and studied the expression of AC5 protein during cardiac development in different mammalian species. The specificity of the antibody was confirmed using heart and brain tissues from AC5 knockout mice and from transgenic mice overexpressing AC5. In mice, the AC5 protein was highest in the brain but was also detectable in all organs studied, including the heart, brain, lung, liver, stomach, kidney, skeletal muscle, and vascular tissues. Western blot analysis showed that AC5 was most abundant in the neonatal heart and declined to basal levels in the adult heart. AC5 protein increased in the heart with pressure-overload left ventricular hypertrophy. Thus this new AC5 antibody demonstrated that this AC isoform behaves similarly to fetal type genes, such as atrial natriuretic peptide; i.e., it declines with development and increases with pressure-overload hypertrophy.

Endotoxemia down-regulates bone marrow lymphopoiesis but stimulates myelopoiesis: the effect of G6PD deficiency.

Bone marrow (BM) dysfunction is an important component of immunomodulation. This study investigated alterations in cell content, apoptotic responses, and cell proliferation in BM, blood, and spleen in endotoxemic mice (LPS from Escherichia coli). As the decreased antioxidant status associated with glucose-6-phosphate dehydrogenase (G6PD) deficiency has been shown to modulate the innate immune response, we also tested whether a G6PD mutation (80% decrease in cellular enzyme activity) alters BM responses during endotoxemia. LPS decreased BM myeloid (CD45(+)CD11b(+)) and B lymphoid (CD45(+)CD19(+)CD11b(-)) cell content compared with controls. In contrast, LPS increased CD11b(+) myeloid but decreased T and B cell counts in the circulation. Endotoxemia inhibited spontaneous, heat shock, and H(2)O(2)-induced apoptosis as well as proliferative activity in BM lymphoid cells. In contrast, BM myeloid cell apoptosis was not altered, and their proliferative activity was increased during endotoxemia. Following LPS, splenic myeloid cell content was increased, and T and B cell content was unchanged; furthermore, splenocytes showed increased apoptosis compared with controls. BM cell content, including lymphoid and myeloid cells, was greater in G6PD mutant than wild-type (WT) mice, and LPS decreased BM cell counts to a greater degree in mutant than WT mice. Endotoxemia caused widespread inhibition of BM cytokine and chemokine production; however, IL-6 production was increased compared with controls. LPS-induced IL-6 production was decreased in G6PD mutant animals compared with WT. This study indicates that endotoxin inversely affects BM myeloid and lymphoid cell production. LPS-induced down-regulation of B cell production contributes to the generalized lymphopenia and lymphocyte dysfunction observed following nonspecific immune challenges.

Flavopiridol blocks integrin-mediated survival in dormant breast cancer cells.

PURPOSE: Breast cancer micrometastases in the bone marrow are resistant to chemotherapy. They can remain dormant for years before some begin to proliferate. We seek to understand survival mechanisms and develop targeted approaches to eliminating these cells. EXPERIMENTAL DESIGN: In an in vitro model of dormancy, basic fibroblast growth factor 2 (FGF-2), abundant in the bone marrow, inhibits the growth of well-differentiated cells in the 2- to 10-cell stage and up-regulates integrin alpha(5)beta(1). Through this integrin, cells bind fibronectin, spread out, and acquire a survival advantage, partly through activation of the phosphatidylinositol 3-kinase/Akt pathway. We investigated the effects of Taxotere, flavopiridol, and mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase and p38 inhibitors on survival of dormant clones and that of flavopiridol on expression of integrins, adhesion strength, and phosphorylation of Akt, ERK 1/2, and p38. RESULTS: Dormant MCF-7 and T-47D cell clones were resistant to Taxotere concentrations 10-fold higher than needed to eliminate growing clones but were almost completely eradicated by 200 nmol/L flavopiridol. Flavopiridol caused a decrease in FGF-2-induced expression of integrins, including alpha(5) and beta(1), and decreased FGF-2-induced specific adhesion to fibronectin. It diminished Akt phosphorylation, but reexpression of active Akt was not sufficient to reverse dormant clone inhibition. Flavopiridol did not affect phosphorylation of ERK 1/2 and p38 but diminished total protein levels. Chemical inhibition of these pathways partially abrogated dormant clone survival. CONCLUSIONS: Flavopiridol has pleiotropic effects on key targets involved with survival of dormant breast cancer cells and may represent a useful approach to eliminating cells dependent on multiple signal pathways for survival.

Antimicrobial resistance in Enterococcus faecalis at a tertiary care centre of northern India.

BACKGROUND & OBJECTIVES: Multiresistant enterococci are emerging as a leading nosocomial pathogen. Knowledge of the profile of antimicrobial resistance is essential to formulate treatment guidelines for infections caused by enterococci. This study reports the antimicrobial sensitivity of enterococci isolated during a one year period from clinical samples of patients admitted to a teriary care hospital of Delhi. METHODS: A total of 444 isolates of Enterococcus faecalis were screened for antimicrobial susceptibility by the disk diffusion technique as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). Screening for vancomycin resistance was done by the vancomycin screen agar method recommended by NCCLS, which was confirmed by determination of minimum inhibitory concentration (MIC) using microbroth dilution and E-test methods. Vancomycin resistance phenotypes were determined by polymerase chain reaction. RESULTS: A total of 115 (26%) isolates had high level aminoglycoside resistance, 293 (66%) were resistant to ampicillin, 391 (88%) to ciprofloxacin and 377 (85%) to erythromycin. Vancomycin resistance was found in five (1%) isolates, of which four had van A phenotype and one had van B phenotype. INTERPRETATION & CONCLUSION: Emergence of vancomycin resistant enterococci is of concern due to the limited therapeutic options. Implementation of infection control measures can contain the spread of these resistant bacteria.

Identification of Acinetobacter species isolated from clinical specimens by amplified ribosomal DNA restriction analysis.

BACKGROUND & OBJECTIVES: Taxonomy of Acinetobacter has been changing ever since it was recognized to be associated with human infections. Many biochemical schemes and molecular methods have been used for the species identification of this bacterium. Recently a simple molecular method called amplified ribosomal DNA restriction analysis (ARDRA) has been used to determine the genomospecies of ACINETOBACTER: An attempt is made in the present study to identify the Acinetobacter genomospecies isolated from clinical specimens using ARDRA and to see whether the environmental isolates are similar to those obtained from clinical specimens. METHODS: A total of 142 consecutive isolates of Acinetobacter sp. obtained from different clinical specimens (125) and environmental samples (17) of postoperative neurosurgery-intensive care unit were studied using ARDRA. Amplification was done using primers of 16S rRNA gene followed by restriction with Alu I, Cfo I and Mbo I enzymes separately to obtain a profile of patterns specific for a species. RESULTS: Of the 125 clinical isolates, 107 were Acinetobacter baumannii (genomospecies 2) and 18 were A. calcoaceticus (genomospecies 1); while 11 of the 17 environmental isolates were A. baumannii and 6 had unidentifiable patterns which were not found in the clinical isolates. INTERPRETATION & CONCLUSION: We found that ARDRA was a simple and reproducible method to be used in a clinical laboratory for identification of Acinetobacter species. A. baumannii was found to be the commonest species isolated from the patients and environment in our hospital. The presence of the same species of Acinetobacter in the environment suggests the role of environment as a source of infection to the patients in high risk units.

Phenotypic & genotypic variants of Pseudomonas aeruginosa isolated from children with cystic fibrosis in India.

BACKGROUND & OBJECTIVES: Pseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). With increase in the chronicity of the disease, there is a diversification of the organism into different colony morphological types. The antimicrobial susceptibility of the organism varies with its colony morphology. The present work was carried out to study the different morphotypes of P. aeruginosa isolated from patients of cystic fibrosis. METHODS: We studied 38 children with CF attending the Paediatric Chest Clinic at the All India Institute of Medical Sciences, New Delhi, India during October 2000-January 2001 who were regularly followed up at the clinic. Patients were divided into 2 groups, Group 1 included all patients chronically infected with P. aeruginosa and Group 2 included patients who were infrequently colonized with this organism. Different colony morphological types of P. aeruginosa on culture media were identified. They were characterized by phenotypic methods using antibiograms and genotypic methods using enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction and PCR-ribotyping. RESULTS: Fourteen of the 38 patients were colonized at least once with P. aeruginosa. Eight patients belonged to Group 1 and 42 isolates were obtained from these patients. Group 2 had 6 patients and 9 isolates were obtained from them. All patients in Group 1 harboured different colony morphotypes (Types 1-6) while all 6 patients in Group 2 showed a single type of colony morphology (Type 1). The isolates from Group 1 patients showed higher antimicrobial resistance as compared to Group 2 patients. Molecular typing of the isolates revealed 10 ERIC-PCR patterns and 2 PCR-ribotyping patterns among Group 1 and 2 ERIC-PCR and 1 PCR-ribotyping pattern among patients of Group 2. INTERPRETATION & CONCLUSION: The frequency of different morphotypes of P. aeruginosa and antibiotic resistance was higher among Group 1 patients. On molecular typing, more than one genotype was isolated from Group 1 patients while only one genotype was isolated from patients in Group 2. We conclude that at a given time, chronically infected patients can be colonized by phenotypically and genotypically distinct strains of P. aeruginosa which has an implication in the management of these patients.