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P Nevot

Publications and source records attributed to P Nevot.

At least 19 recordsLinked to original sources
PubMed1994

[Synergy between tobramycin and netilmicin on three strains of methicillin and gentamicin resistant staphylococci (S. epidermidis, S. aureus)].

The antibacterial effect of tobramycin-netilmicin combination on multiresistant strains of staphylococcus was performed to determine the signification of synergy images on diffusion plates. Meticillin and gentamicin resistant strains of S. epidermidis (2 strains) and S. aureus (1 strain) were examined and showed an index of combined effect < 0.05 demonstrating synergy. These values were obtained with aminoglycoside concentrations < or = 4 mg/l, levels which can be considered as pharmacologically acceptable. This synergic action can be explained by specific inhibition of the resistance enzyme in the strains, possibly in combination with a cooperative effect on the classical targets of aminoglycosides. This type of combination using tobramycin and netilmicin could define a new use of aminoglycosides based on the conception of combining antibiotic enzyme inhibition.

Drug Resistance, Microbial↗
PubMed1988

[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↗
PubMed1988

[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↗
PubMed1986

[Mechanism of enzymatic resistance to beta-lactam antibiotics].

The resistance of bacteria, particularly Gram-negative bacteria, to beta-lactam antibiotics is principally caused by enzymes. Beta-lactamases inactivate these antibiotics by opening, more or less rapidly, the beta-lactam ring. The chronology of therapeutic discoveries is governed by natural and acquired resistance. The first step was to establish the characteristics of beta-lactamases (location, biogenesis, enzymatic profile, affinity constant, inhibition profile, isoelectric point, molecular weight, genetic determination, etc.). Advances in the selection of natural or semi-synthetic compound are centred on the following points: increased stability to beta-lactamases, inhibitory effect, reduced inducibility, low affinity for the enzyme, greater speed of penetration through the bacterial wall, increased tropism for targets. Notable among the new beta-lactam antibiotics are acylureidopenicillins, beta-lactamase inhibitors and carbapenems. The antibacterial activity of third generation cephalosporins is 10 to 1000 times higher than that of previous cephalosporins; the result is a wider spectrum including, in particular, cephalosporinase-producing organisms. Concerning acquired resistance, the behaviour of new antibiotics must be examined by comparing the minimum inhibitory concentrations of isogeneic and clinical strains, and according to phenotype or mechanism: sensitive, penicillinase producer, cephalosporinase producer or producer of both penicillinases and cephalosporinases. During synthesis of a penicillinase, penicillins and some cephalosporins are more or less inactivated. With a constitutive cephalosporinase, all cephalosporins are inactivated as are, to a lesser degree, penicillins and monobactams, e.g. aztreonam. The emergence of new enzymes, including broad-spectrum beta-lactamases, and their extension to sensitive bacteria show that the enzymatic mechanism still has potentials for development.

Anti-Bacterial Agents↗
PubMed1984

[Distribution of constituent beta-lactamases in Pseudomonas aeruginosa].

Acquired resistance of Pseudomonas aeruginosa to beta-lactam antibiotics, e.g. ticarcillin, has the following characters: The incidence of ticarcillin-resistant strains is about 21% but it varies with hospitals from 10.9 to 35.1%. Resistance is predominantly due to beta-lactamases, which are produced by two-thirds of the strains (64.4% in 1982, 67.9% in 1983). The presence of beta-lactamase positive strains is dependent upon the type of patient, the hospital unit (e.g. urology or burns) and the nature of the specimen collected. Most beta-lactamase positive strains spontaneously produce one single penicillinase of the CARB (53.8%), OXA (30.5%) or TEM (8.7%) type. New types of beta-lactamases may develop and hydrolyse beta-lactam antibiotics such as ticarcillin, azlocillin, cefoperazone or cefsulodin. With beta-lactam antibiotics (cefotaxime, moxalactam, ceftazidime) that resist hydrolysis, bacterial resistance is due to production of a constitutive beta-lactamase of the cephalosporinase type. This enzyme has recently appeared and its incidence is low (6.8%). Associated beta-lactamases (e.g. penicillinase plus cephalosporinase) are exceptional.

Anti-Bacterial Agents↗
PubMed1983

[Hemoculture].

Explore the source record for details and available documents.

Blood Specimen Collection↗
PubMed1982

[Rapid bioassay of gentamicin by bioluminescence (author's transl)].

Assay of bacterial intracellular ATP levels using the firefly bioluminescence system allows a very sensitive monitoring of bacterial growth. This test has been used in some laboratories fro performing a rapid microbiological assay of the concentration of antibiotics in the serum of treated patients. Rapidity of antibiotic determination is especially important in the case of antibiotics for which therapeutic concentration are close to toxic concentration. In the present work we have used the bacterial strain Klebsiella edwardsii var. atlantae for a rapid assay of gentamicin in the serum. We show that this assay is very accurate in the range of therapeutic serum concentrations. It may be readily performed in a routine laboratory with commercially available ATP extractors and luciferine-luciferose mixtures. This assay has been shown to correlate optimally with the classical plate diffusion assay (r = 0,983) and to be independent of the presence of beta-lactams in the serum.

Adenosine Triphosphate↗
PubMed1976

[Treatment of experimental brucellosis of mice and guinea pigs by rifampicin].

The intracellular and bactericidal activity of rifampicine was observed in the treatment of experimental brucellosis in the mouse and guinea pig. Batches of mice infected by intraperitoneal route with B. melitensis, strain 53 H 38, were treated with rifampicine (20 mg/kg/day) or with tetracycline-base (200 mg/kg/day). When the treatment begins 14 days after inoculation and lasts a week, the rifampicine produces a more significant decrease of the weight of the spleen than does tetracycline. After 14 days' treatment, apart from this effect, the degree of infection of the spleen decreases at least 10(5) times with rifampicine and 10(2) times with tetracycline. After 21 days, bacteriological sterilization is obtained with rifampicine whereas 66% of the tetracycline-treated mice are still infected. However, a residual infection of weak intensity persists in 6.6% of the rifampicine-treated mice against 75% of the tetracycline-treated mice, as shown by an injection of Corynebacterium parvum and a cortisone treatment at the end of the antibiotherapy. If the antibiotic treatment begins on the day of inoculation, the greatly superior efficacity of rifampicine is in that case more rapid. Rifampicine (100 mg/kg/day) offers comparable efficacity in the guinea pig infected by intraperitoneal route with B. abortus strain 544; these efficacity is shown by the decrease in the weight of the spleen and the intensity of splenic and ganglionic infection. The rapid decrease of agglutinins and amboceptors after 7 days of treatment suggests the possible role of a suppressor of this antibiotic. Finally, the effect of rifampicine on the growth of the guinea pig was noted.

Animals↗
PubMedDate not supplied

[Beta-lactamases of ampicillin-resistant Salmonella].

One hundred and five strains of Salmonella, including 103 clinical isolates, were examined for resistance to beta-lactams (ampicillin, carbenicillin). The resistance frequency was 5.9 and 40.6%, respectively, according to the geographical source: France or Senegal. The mechanism of resistance to beta-lactam antibiotics was always related to the biosynthesis of one constitutive beta-lactamase (beta la+). By analytical isoelectric focusing on gel of all crude sonic extracts, four types of enzymes were identified: TEM-1, TEM-2, OXA-1 and SHV -1. TEM-1, the most prevalent, was observed among 17 serotypes, TEM-2 among 3 including S. poona , and OXA-1 among 2 serotypes. SHV -1 was detected in all isolates of S. ordonez (38) but only among strains of this serotype. Among others factors involved in their distribution, differences were reported according to the geographical origin of the studied strains. In France, the three types, TEM-1, TEM-2 and OXA-1, were isolated only in the north. Moreover, the resistance frequency was 4-fold higher (7.3%) than in the south (1.8%). In Africa (Senegal), three types were individualized: TEM-1, TEM-2 and SHV -1. The SHV -1 type was only detected in clinical isolates of S. ordonez from Senegal, all of which were multi-resistant to other antibiotics (chloramphenicol, sulfonamides and tetracyclines).

Ampicillin↗