[Septicemia caused by beta-lactamase producing Fusobacterium nucleatum in a patient with neutropenia].
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Adult↗
Biomedical subjects
G Vedel
Publications and source records attributed to G Vedel.
[Plasmid resistance to 3d generation cephalosporins].
Beta-lactamases still play an important part in medical bacteriology, as shown by the emergence, since 1983, of plasmid-mediated beta-lactamases with an enlarged spectrum (SHV-2, CTX-1, etc.). Such enzymes are only produced by enterobacteria and, more specifically, by Klebsiella pneumoniae. This phenomenon, described in Europe and in Africa, is certainly more widespread than it would appear, as some strains are now known to be less sensitive to third generation cephalosporins (MIC 1 to 4 mg/l). Despite differences in behaviour (cefotaximase and ceftazidimase phenotypes), resistance to amino-, carboxy- and ureido-penicillins is associated with reduced sensitivity or resistance to oxyimino beta-lactams (cefotaxime, ceftriaxone, ceftazidime, aztreonam), but cefamycins and imipenem are untouched. Being sensitive to enzyme inhibitors (e.g. clavulanic acid), these beta-lactamases can easily be detected and some infections (notably urinary tract infections) can probably be treated using these inhibitors. These enzymes show modified kinetic constants (better affinity and quicker hydrolysis) against penicillins, third generation aminothiazolimino-cephalosporins and aztreonam. The producing strains are mutants, with aminoacid 1 to 2 substitutions, of those which produce the usual plasmid-borne and transposable beta-lactamases (TEM or SHV). Because these beta-lactamases are plasmid-mediated, enzyme production mechanisms are spreading among enterobacteria species in relation to other resistance markers (tobramycin, netilmicin, amikacin). Strains which produce these new enzymes are mainly isolated from patients treated in intensive care units.
Cell Membrane Permeability↗
[Titration curves (ph gradient electrophoresis) of SHV-1 and SHV-2 beta-lactamases and a new type].
The molecular structures of the SHV-1 (p 453) and SHV-2 (pBP 60-1) beta-lactamases and of a new enzyme, a SHV-2 like extended broad-spectrum beta-lactamase (86-4), were compared by analysis of their titration curves (pH gradient electrophoresis). The titration curves of SHV-1 and SHV-2, which have the same isoelectric points (pI = 7.7). were completely superimposable for the whole of the pH gradient (pH 3.5-10), indicating a close homology between the two proteins, with perhaps the substitution of several amino acids by ones having the same charge. The curves of SHV-1 (pI = 7.7) and the new SHV-2-like enzyme (pI = 6.98) indicated that a basic residue in SHV-1 has been replaced by an acidic residue in the new SHV-2-like enzyme. These results show that, like SHV-2, the new beta-lactamase is a variant of SHV-1, and that the structural differences are probably limited to a very small number of amino acid residues. Nevertheless, this new beta-lactamase (SHV-3) may have arisen directly from SHV-1, indirectly via SHV-2, or even from another beta-lactamase.
Electrophoresis, Polyacrylamide Gel↗
[Electrophoretic behavior of beta-lactamases in gram-negative bacteria].
The ongoing discoveries of new beta-lactamases, mainly penicillinases, in Gram-negative bacteria has emphasized the problem of their precise identification, and thus their phylogeny. Crude extracts, prepared by sonication, of 14 plasmid beta-lactamases, types TEM, carbenicillinases (CARB or PSE) and oxacillinases (OXA) were analysed by a simple, rapid (3.5 to 4 hours) method of electrophoresis on polyacrylamide (7%) agarose (1.4%) gels, using Tris-glycine buffer at pH 8.7. Preliminary serial dilutions were made to determine enzymic activity levels. Enzymes were then characterized by their relative electrophoretic mobilities. These mobilities had coefficients of variability between 2% and 10%, ranged from 5 to 61, and were correlated with their isoelectric points (pI). Thus, the lower the pI is, the greater the mobility is. Despite the high resolving power of the polyacrylamide-agarose gel system, enzymes with similar pI's and of similar types (PSE-1 and CARB-3, or OXA-1 and OXA-4) or different types (SHV-1 and OXA-6) could not be distinguished on the basis of their mobilities. However, this technique provides for rapid and easy identification of the major penicillinases in Gram-negative bacteria. A combination of polyacrylamide-agarose gel electrophoresis and pH gradient electrophoresis (titration curve) could provide a powerful approach to the study of the molecular structure of these enzymes.
Electrophoresis, Agar Gel↗
[Titration curves of beta-lactamases using pH gradient electrophoresis].
The molecular relationships of two types of plasmid-mediated beta-lactamases, TEM-1 (R 111), TEM-2 (RP 4) and OXA-1 (RGN 238), OXA-4 (pMG 90) were analysed by combined isoelectrofocusing-electrophoresis. Titration curves of TEM-1 (pI 5.4) and TEM-2 (pI 5.6) together were consistent with the known substitution of a glutamic acid in the former by a lysin in the latter. When OXA-1 (pI 7.4) and OXA-4 (pI 7.45) were titrated, one single mobility curve was obtained reflecting their structural homogeneity. The titration curve technique will be usefull for the study of structure of beta-lactamases.
Electrophoresis, Polyacrylamide Gel↗
[Bacterial flora in gastric juice taken at endoscopy in 93 normal subjects].
Bacteriologic examination of gastric juice samples taken during endoscopy in ninety-three subjects free of endoscopically-detectable disease was performed. Mucosal pH was determined using bromocresol green dye. Among the 17 subjects with a mucosal pH exceeding 4, 11 (64%) had more than 10(5) organisms/ml. In contrast, similar counts were found in only 10 of the 76 subjects with a normal mucosal pH. The pathogens recovered were normal hosts of the upper digestive tract and a few nitrate reductase + Enterobacteriaceae. Questions still to be resolved are whether these pathogens can induce disease and whether bacterial colonization correlates with the increased gastric nitrosamine levels and microscopic mucosal lesions previously described in patients with a gastric pH above 4.
Adult↗
[Septic arthritis caused by Campylobacter fetus].
The ten published cases of septic arthritis due to Campylobacter fetus and two more recent cases, one of which was a delayed septic complication of a total hip replacement, are discussed. In 83% of cases, febrile monoarthritis occurred which in 7 out of the 12 cases involved an already diseased joint in a subject over 70 years of age (half of the patients), who was frequently alcoholic and presented either cancer or hepatic cirrhosis and/or diabetes. Hyperleukocytosis of the blood was variable (55% of cases). The joint fluid, which contained a high level of deteriorated polynuclear cells, was routinely cultured on an enriched medium in an anaerobic or microerophilic atmosphere and in 10 out of 12 cases Campylobacter fetus was isolated within 15 days, even in the absence of previous antibiotic therapy. The arthritis, which showed little sign radiographically of destructiveness, was cured, leaving no sequellae in most cases. Treatment usually involved ampicillin or the tetracyclines, either alone or in association with the aminoglycosides.
Aged↗