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Multiple Outbreaks of Nosocomial Salmonellosis in Russia and Belarus Caused by a Single Clone of Salmonella enterica Serovar Typhimurium Producing an Extended-Spectrum ß-Lactamase. M. Edelstein, 2004.Thirty-four cefotaxime-resistant Salmonella enterica serovar Typhimurium isolates representative of the isolates that caused outbreaks of gastroenteritis in 10 hospitals in seven regions of Russia and Belarus from 1994 to 2003 were analyzed . All isolates produced the CTX-M-5-like extended-spectrum ß-lactamase, which confers high-level resistance to cefotaxime and ceftriaxone and decreased susceptibility to ceftazidime . The blaCTX-M genes were located on small (7.4- to 12-kb) non-self-transferable plasmids approximately 20 bp downstream of the ISEcp1 insertion sequences . Some isolates carried additional conjugative plasmids mediating resistance to penicillin-inhibitor combinations and various non-ß-lactam agents, including tetracycline, chloramphenicol, gentamicin, tobramycin, and co-trimoxazole . Despite the minor differences in susceptibility patterns, all isolates were considered clonally related on the basis of arbitrarily primed PCR and pulsed-field gel electrophoresis analysis . The similarities of the restriction profiles of the CTX-M-coding plasmids further supported the clonal origin of these isolates . Environmental Response and Autoregulation of Clostridium difficile TxeR, a Sigma Factor for Toxin Gene Expression. Nagraj Mani, 2002.TxeR, a sigma factor that directs Clostridium difficile RNA polymerase to recognize the promoters of two major toxin genes, was shown to stimulate its own synthesis . Whether expressed in C . difficile, Clostridium perfringens, or Escherichia coli, TxeR stimulated transcription of fusions of the txeR promoter region to reporter genes . As is the case for the tox genes, txeR expression was responsive to the cellular growth phase and the constituents of the medium . That is, the level of expression in broth culture was low during the exponential growth phase, but rapidly increased as cells approached the stationary phase . In the presence of excess glucose, expression from the txeR promoter was repressed . The results support a model for toxin gene expression in which synthesis of TxeR is induced by specific environmental signals . The increased level of TxeR then permits high-level expression of the toxin genes . The study of txeR gene regulation in C . difficile was made possible by introduction of a mobilizable, replicative plasmid via conjugation with E . coli . Analysis of Specific Binding Involved in Genomic Packaging of the Double-Stranded-RNA Bacteriophage  6.Xueying Qiao, 2003.The genomes of bacteriophage 6 and its relatives are packaged through a mechanism that involves the recognition and translocation of the three different plus-strand transcripts of the segmented double-stranded-RNA genomes into preformed polyhedral structures called procapsids or inner cores . The packaging requires the hydrolysis of nucleoside triphosphates and takes place in the order segment S-segment M, segment L . Packaging is dependent upon unique sequences of about 200 nucleotides near the 5' ends of plus-strand transcripts of the three genomic segments . It appears that P1 is the determinant of the RNA binding sites . Directed mutation of P1 was used to locate regions that are important for genomic packaging . Specific binding of RNA to the exterior of the procapsid was dependent upon ATP, and a region that showed a high level of cross-linking to phage-specific RNA was located . Antibodies to peptide sequences were prepared, and their abilities to bind to the exterior of procapsids were determined . Sites sensitive to trypsin and to factor Xa were determined as well .
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