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PubMed1983

Induction of cephalosporinase production by various penicillins in enterobacteriaceae.

The inducer activity of seven penicillins for cephalosporinase (CSase) production and their antibacterial activity against CSase-producing strains were studied using clinical isolates of Proteus morganii, P. rettgeri, P. vulgaris, Enterobacter cloacae, and Serratia marcescens. Piperacillin, apalcillin, and methicillin showed rather low inducer activity for CSase production in all strains tested. On the other hand, ampicillin, carbenicillin, and sulbenicillin showed high inducer activity for CSase production. Piperacillin, apalcillin, and ampicillin were less stable to CSases than were carbenicillin, sulbenicillin, and methicillin, but much more stable than benzylpenicillin. In the growing culture of CSase-producing strains, piperacillin and apalcillin were rather stable. Against CSase-producing strains, piperacillin and apalcillin were more active than other penicillins tested.

Cephalosporinase↗
PubMed1998

[Estimation of mean molecular weight of Enterobacteriaceae lipopolysaccharides using gas chromatography for determination of fatty acids].

In the paper, we propose a method for estimation of the mean molecular weight of lipopolysaccharide, which is important for accuracy of endotoxin activity investigation. In our study, it was assumed that lipid A portion in Enterobacterial lipopolysaccharide is substituted by four 3-hydroxytetradecanoic acid residues. Lipopolysaccharides of S, Ra, Rc and Re chemotypes being laboratory preparations as well as purchased from Sigma were investigated. Fatty acids were determined by of gas chromatography as methyl esters according to the procedure described by Wollenweber and Rietschel. Mean molecular weight was calculated by the formula: MMW = [formula: see text]. A high agreement between the estimated and the theoretical molecular weight values was demonstrated in the case of Salmonella minnesota R595 (Re) LPS preparation. As expected, LPS heterogeneity increase together with enlargement of polysaccharide chain length which is visible in electrophoregrams also. Except for LPS mean molecular weight estimation, the method allows its detection in various preparations and samples, distinguishing of R and S LPS forms as well as the determination of mean length of O-specific chain in lipopolysaccharides which structures are known.

Chromatography, Gas↗
PubMed1999

Regulation of inducible AmpC beta-lactamase expression among Enterobacteriaceae.

AmpC ss-lactamases are active-site serine enzymes that are primarily cephalosporinases. In many gram negative organisms, including Enterobacter spp.,Citrobacter freundii, Serratia marcescens, Morganella morganii and Pseudomonas aeruginosa, the expression of chromosomal ampC genes is low but inducible in response to ss-lactams and other stimuli. The current working model for AmpC induction requires exposure of bacterial cells to ss-lactam drugs or other stimuli and is linked to the cell wall recycling pathway. Induction of ampC appears to involve several gene products associated with this pathway. These gene products include AmpR, AmpD, and AmpG. In addition, anhydro forms of cell wall precursor muropeptides are believed to act as cofactors for AmpC induction. These cofactors bind to the DNA binding protein, AmpR, and define the role of AmpR as activator. Recent debate has ensued in the literature as to the identification of the precursor muropeptide involved in the activation process. Two candidate muropeptides include 1,6-anhydro-N-acetylmuramic acid L-Ala-D-Glu-meso-diaminopimelic acid (anhydro-MurNAc-tripeptide) and anhydro-MurNAc-L-Ala-D-Glu-meso-diaminopimelic acid- D-Ala-D-Ala (pentapeptide). The intent of this review is to address the general mechanism involved in AmpC induction. In doing so, the genes and gene products required for the process of AmpC induction are described. In addition, we review the data addressing cell wall recycling as it relates to AmpC induction.

Bacterial Proteins↗