Detection, characterization, and antibiogram of extended-spectrum beta-lactamase Escherichia coli isolated from bovine milk samples in West Bengal, India.

BACKGROUND: Milk is considered as complete food and an important part of human diet throughout the world including India. Bacterial contamination of milk such as Escherichia coli due to unhygienic condition and poor udder health can cause infections, especially in infants and elders or in immunocompromised persons. Possession of antimicrobial resistance genes by commensal bacteria present in milk makes the issue more serious. AIM: The study was aimed to isolate and characterize extended-spectrum beta-lactamase (ESBL)-producing E. coli from milk samples collected from different parts of West Bengal, India, to assess the potential risk associated with the food. MATERIALS AND METHODS: Around 182 milk samples were collected from apparently healthy cows reared by organized dairy farms in West Bengal. E. coli was isolated from collected samples as per standard methods followed by serotyping. The detection of ESBL-producing E. coli was done both phenotypically and genotypically by detecting the presence of bla CTX-M gene. Antibiogram of the ESBL-positive isolates was done using common 12 antibiotics by disc diffusion method. RESULTS: A total of 22 (12.1%) samples were found to be positive for E. coli in this study. Different serotypes such as O11, O20, O22, O34, O35, O128, O149, and UT were isolated from the collected samples. 12 (54.5%) E. coli strains showed the capability of producing ESBL, both phenotypically and genotypically with the presence of bla CTX-M gene. Antibiogram of these ESBL-positive isolates revealed the drugs such as colistin (100%), levofloxacin (83.33%), and imipenem (66.67%) to be highly sensitive against this pathogen but drugs such as cefotaxime (100%), ceftazidime (91.67%), amoxicillin/clavulanic acid (83.33%), tetracycline (75.00%), and gentamicin (58.33%) to be very much resistant. CONCLUSION: More than 50% of the E. coli strains prevalent in the bovine milk samples were positive for ESBL production and are resistant to most of the common antimicrobials which may be alarming for human health.

Characterization of Salmonella Gallinarum isolates from backyard poultry by polymerase chain reaction detection of invasion (invA) and Salmonella plasmid virulence (spvC) genes.

AIM: The aim was to characterize Salmonella enterica serovar Gallinarum isolated from backyard poultry by polymerase chain reaction (PCR) detection of virulence genes invasion (invA) and Salmonella plasmid virulence C (spvC). MATERIALS AND METHODS: Two strains of Salmonella serovar Gallinarum isolates used in this study were obtained from an outbreak of fowl typhoid in backyard Vanaraja fowl. PCR technique was used for detection of invA and spvC genes using standard methodology. The invA PCR product from one representative isolate was sequenced and compared with other related Salmonella serovars in GenBank data. RESULTS: Salmonella Gallinarum produced expected amplicons of invA and spvC gene products. Nucleotide sequence of 285 bp invA gene was deposited in GenBank with accession no. KX788214. Sequence analysis of invA gene was found conserved in Salmonella serovars and demonstrated 100% homology with closely related serovars of Salmonella. CONCLUSION: Invasion gene (invA) was found to be highly conserved in Salmonella Gallinarum and highly similar with closely related serovars. The isolates also contained plasmid-mediated spvC gene indicating possession of virulence plasmid.

Carbon nanostraws: nanotubes filled with superparamagnetic nanoparticles.

A two-step magnetically assisted capillary action method is demonstrated as a facile technique to produce hollow carbon nanotubes filled with uniformly dispersed Fe3O4 nanoparticles (NPs). Template-assisted chemical vapor deposition (CVD) grown CNTs with average diameter 200-300 nm and length 5-6 microm were effectively used as 'nanostraws' to suck in chemically synthesized Fe3O4 nanoparticles (mean size approximately 6 nm) in a ferrofluid suspension. Temperature and magnetic field-dependent DC magnetization measurements indicate that these functionalized nanotubes are superparamagnetic at room temperature with enhanced interparticle interactions due to the close packing of the nanoparticles within the tubes. Magnetic relaxation phenomena in these filled nanotubes are probed using frequency-dependent AC susceptibility. The reasonably large saturation magnetization (M(s) = 65 emu g(-1)) attained in these nanostructures makes them very promising for a diverse set of applications that utilize both the magnetic and dielectric functionalities of these composite nanotube materials.

Morphology controllable nanostructured chitosan matrix and its cytocompatibility.

It is becoming clear that surface nanotopography of underlying substrates can influence cell behavior such as adhesion, proliferation, and orientation of mammalian cells. Nanofabrication methods such as electron beam lithography are, however, expensive and time consuming. In this study, a simple and cost-effective approach, heterogeneous seeded growth, was developed to create nanostructured chitosan matrix (CSM) from amorphous chitosan nanoparticles (CNPs). The physiochemical properties of CSM were characterized followed by an evaluation of CSM cytocompatibility. Shape-controllable morphology of CSM from nanoparticles to three-dimensional urchin-like architectures was achieved by using varying amounts of seeds. CSM was found to be cytocompatible with human foreskin fibroblasts suggesting that the nanofibrous surface morphology and crystalline structure of CSM could favor cell spread and growth.

Thermodynamic behavior of poly(3-alkyl thiophene) blends: Equilibrium cocrystal formation and phase segregation.

The equilibrium cocrystal formation of poly(3-alkyl thiophene) (P3AT) blends has been studied by isothermal cocrystallization in a differential scanning calorimeter (DSC-7). The equilibrium melting points (T(m)0) of the cocrystals are measured using the Hoffman-Weeks extrapolation procedure. The equilibrium phase diagrams are of three different types: (a) concave upward, (b) linear, and (c) linear with phase separation at higher content of lower melting component. The phase diagram nature depends on the regioregularity difference and also on the difference in the number of carbon atoms in the pendent alkyl group of the components. The origin of biphasic nature of type "c" phase diagram has been explored from the glass transition temperature (Tg) measurement using a dynamic mechanical analyzer. The biphasic compositions show two glass transition temperatures (Tg) as well as two beta transition temperatures (T beta). The T(g)s of phase-separated regions correspond to almost the component values but the T(beta)s correspond to that of a lower (T beta) component value, and the other is higher than that of the higher (T beta) component value. Possible reasons are discussed from the interchain lamella thickness in the P3AT blends and molecular modeling using molecular mechanics program.

Temperature variation of DC conductivity of poly(3-alkyl thiophenes) and their cocrystals.

The dc conductivity of poly(3-alkyl thiophenes) (P3ATs) and their cocrystals are measured in the temperature range of -130 to 150 degrees C. Both solvent-cast films and the melt-cooled films are used. The former exhibit a sharp increase followed by a decrease in conductivity, whereas the latter show only a sigmoidal increase in conductivity with temperature. The sigmoidal increase of the melt-cooled samples is dependent on the regioregularity and alkyl chain length of the samples and is explained from the solid-state transformation of the interdigited type-II crystal to a noninterdigited type-I crystal. The type-I crystal itself has lower conductivity than type-II crystals, and the samples exhibit a blue shift in UV-vis absorption spectra with an increase in temperature. So the sigmoidal increase of conductivity is attributed to the increase in carrier mobility with temperature in the type-I crystals. The X-ray and DSC results suggest that during the transformation of type-II to type-I crystals with increasing temperature, localized crystallites of smaller dimensions separated by narrower amorphous portions are produced throughout the whole matrix. But in the type-II polymorph, the crystallites are large with a wider gap in between. The sigmoidal increase is attributed to the easier hopping of the charge carrier among the localized crystallites of the type-I crystal with increasing temperature. In the cocrystals, the smaller sigmoidal increase with increasing irregular sample concentration is valid for a lower concentration of such localized crystallites. The same is true for cocrystals with longer alkyl chain lengths. The interfibrillar contribution of conductivity through the network junctions together with the carrier hopping between the localized crystallites might be a possible reason for the metallic-type behavior of solvent-cast samples after a certain temperature. The melt-cooled films do not exhibit metallic-type behavior because of the absence of a fibrillar network morphology.