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Biomedical subjects

S Kelkar

Publications and source records attributed to S Kelkar.

5 recordsLinked to original sources
PubMed2002

Broad resistance due to plasmid-mediated AmpC beta-lactamases in clinical isolates of Escherichia coli.

Escherichia coli that produce plasmid-mediated AmpC beta-lactamases are rare in the United States. The clinical features associated with infection with these organisms have not been well described. We identified 2 clinical isolates of E. coli that produced the plasmid-mediated AmpC enzyme beta-lactamase CMY-2. These organisms were recovered from urine specimens and were resistant to ceftazidime, ceftriaxone, and cefepime. One isolate was resistant to ertapenem but susceptible to imipenem and meropenem; the other was susceptible to imipenem, meropenem, and ertapenem. One of the 2 infected patients did not require specific therapy; the other required imipenem for cure. The presence of the CMY-2 beta-lactamase was confirmed by DNA sequencing. Hybridization studies confirmed that the bla(CMY-2) gene was on a plasmid in both isolates; in one of them, the probe also hybridized with chromosomal DNA. Infection with plasmid-mediated AmpC beta-lactamases in E. coli in the United States may be associated with treatment failure, and these strains may become a serious nosocomial threat.

Adult↗
PubMed2001

Infections due to vancomycin-resistant Enterococcus faecium resistant to linezolid.

Linezolid is a new oxazolidinone antibiotic used to treat infections caused by vancomycin-resistant enterococci (VRE). In early clinical trials, emergence of resistance occurred rarely. We report clinical details and antibiotic susceptibility from five patients treated with linezolid for VRE infections who had resistant organisms isolated during therapy. Four were transplant patients receiving protracted courses of the drug; three cases were associated with treatment failure. One of 45 linezolid-treated patients developed resistance during therapy. Susceptibility testing should be done in all cases on starting therapy.

Acetamides↗
PubMed2000

Ethanol enhances TNF-alpha-inducible NFkappaB activation and HIV-1-LTR transcription in CD4+ Jurkat T lymphocytes.

During the latent phase of human immunodeficiency virus type 1 (HIV-1) infection, CD4+ T cells carrying replication-competent proviral HIV-1 DNA play an important role in persistence of the virus. Several cofactors can induce and or amplify HIV-1 replication and negatively affect disease progression and pathogenesis. Ethanol consumption is an important risk factor for HIV-1 infection, and it has been implicated in increased HIV-1 replication and progression of infection. Because tumor necrosis factor-alpha (TNF-alpha) is an important modulator of HIV-1 replication, in the present study we examined the possible effects of ethanol on TNF-alpha-inducible signaling associated with HIV-1 replication in human CD4+ T cells (Jurkat E6-1). We demonstrate that clinically relevant ethanol concentrations significantly potentiate TNF-alpha-inducible NFkappaB. Although ethanol effectively collaborated with TNF-alpha, by itself it did not have a direct effect on NFkappaB activation. The ethanol-dependent potentiation of TNF-alpha-inducible NFkappaB nuclear translocation was observed to involve the enhanced degradation of IkappaBalpha. Additionally, the ethanol-mediated potentiation of TNF-alpha-inducible NFkappaB activation was abrogated by the known antioxidant pyrrolidinedithiocarbamate, suggesting an important mechanistic role for reactive oxygen species in this process. In correspondence with its effect on NFkappaB, ethanol was also observed to significantly enhance HIV-1 long terminal repeat-dependent transcription induced by TNF-alpha. Overall, the data provide a molecular basis for the possible role of ethanol as a cofactor that can adversely affect HIV-1 infection and pathogenesis.

Cycloheximide↗
PubMed1999

Neurotrophins regulate agrin-induced postsynaptic differentiation.

The precise orchestration of synaptic differentiation is critical for efficient information exchange in the nervous system. The nerve-muscle synapse forms in response to agrin, which is secreted from the motor nerve terminal and induces the clustering of acetylcholine receptors (AChRs) and other elements of the postsynaptic apparatus on the subjacent muscle cell surface. In view of the highly restricted spatial localization and the plasticity of neuromuscular junctions, it seems likely that synapse formation and maintenance are regulated by additional, as-yet-unidentified factors. Here, we tested whether neurotrophins modulate the agrin-induced differentiation of postsynaptic specializations. We show that both brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) inhibit agrin-induced AChR clustering on cultured myotubes. Nerve growth factor and NT-3 are without effect. Muscle cells express full-length TrkB, the cognate receptor for BDNF and NT-4. Direct activation of this receptor by anti-TrkB antibodies mimicked the BDNF/NT-4 inhibition of agrin-induced AChR clustering. This BDNF/NT-4 inhibition is likely to be an intrinsic mechanism for regulating AChR clustering, because neutralization of endogenous TrkB ligands resulted in elevated levels of AChR clustering even in the absence of added agrin. Finally, high concentrations of agrin can occlude the BDNF/NT-4 inhibition of AChR clustering. These results indicate that an interplay between agrin and neurotrophins can regulate the formation of postsynaptic specializations. They also suggest a mechanism for the suppression of postsynaptic specializations at nonjunctional regions.

Agrin↗