PubMed Health⌕ Search

Biomedical subjects

D Sirot

Publications and source records attributed to D Sirot.

103 records · Page 6Linked to original sources
PubMed1983

[Effect of trimethoprim at a subinhibitory concentration on the appearance of mutants resistant to rifampicin].

Experiments have been performed to establish the effect of trimethoprim (Tmp) on the emergence of Staphylococcus aureus (S. aureus) mutants to rifampicin (Ramp). Four S. aureus strains were used: two strains with low MIC of Ramp (0,01 microgram/ml), two strains with enhanced MIC of Ramp (2 micrograms/ml). For each of them the frequency of mutants and the mutation rates to Ramp were determined when various concentrations of Tmp were added. Results showed that subinhibitory concentrations of Tmp reduced 10 to 100 folds the frequency of mutants and the rates of mutation to Ramp alone. The more the Tmp concentrations were near the MIC, the more this effect was important.

Drug Resistance, Microbial↗
PubMed1982

[Statistical regression analysis for four new cephalosporins (author's transl)].

The MIC (agar dilution method) and the zone diameter (disk diffusion) were determined for two hundred and sixteen of the most frequently bacterial strains found in hospitals in order to establish the regression curves for four new cephalosporins : cefotaxime, cefoperazone, cefotiam, moxalactam. The dta (MIC, zone size) were represented by a series of points (Mi (Xi Yi) in semilogarithmic rectangular co-ordinates expressed as : Xi = log2 MIC + 7 ; Yi = zone diameter. Firstly, we tried to fit a regression polynomial to this series of points progressing from degree 1, simple equation (standard regression line) 2, 3, etc. in order to reduce if need be, the deviation between the model (polynomial) and the empirical data. For these four cephalosporins a regression polynomial was obtained. Secondly, the global series was divided into three series of points Mi corresponding to three ranges of MIC : MIC less than or equal to 4 microgram/ml ; 4 less than or equal to 16 micrograms/ml; MIC greater than or equal to 16 microgram/ml. A regression line was obtained for each series and compared with each other and each one with the global regression line (they do not coincide statistically). Concerning these antibiotics, it is better to use a regression polynomial rather than apply a standard regression line.

Bacteria↗
PubMed1982

[Antibacterial activity of netilmicin in combination with other antibiotics. Comparison with other aminoglycosides (author's transl)].

We studied in vitro bactericidal effects of netilmicin combined with other antibiotics, comparing with that obtained with other aminoglycosides combinations. We used strains of Streptococci and Gram negative rods tested versus 11 antibiotics : penicillin (P), ampicillin (Am), carbenicillin (Cb), cefalotin (Cth), cefazolin (Cfz), cefradin (Cfa), cefoxitin (Cxt), cefotaxime (CTX), erythromycin (E), pristinamycin (Pr), vancomycin (V). These were combined with streptomycin (Sm), tobramycin (To), amikacin (Ak), gentamicin (G) and netilmicin (Nl). First of all, we noted the high bactericidal power of Nl, whatever the strains tested. Against Streptococci, the activity of P + Nl and Am + Nl were equivalent or superior to that of P + G and Am + G. Among cephalosporins, we noted a synergistic effect of Ctx + Nl which did not exist with Ctx + G. In the same way, E + Nl showed synergism whereas E + G didn't. V + Nl combinations, as active upon Streptococci as V + G, are more active than V + G upon Enterococci. Against Gram negative bacilli, we observed good effects with Cb + Nl. Cephalosporins combinations were also interesting : Cfz + Nl were as active Cfz + G but Czt + Nl showed higher synergistic effect than Cxt + G. Ctx + Nl combinations were effective upon E. coli.

Aminoglycosides↗
PubMed1979

[Bactericidal activity "in vitro" of sulfamethoxazol-tri-methoprime (SMZ-TMP) alone and in combination with various antibiotics on bacterial strains isolated from urinary tract infections (author's transl)].

The authors study "in vitro" effects of sulfamethoxazol-trimethroprime (SMZ-TMP) on 1 078 bacterial strains isolated from urinary-tract infections during january 1974, the second trimester 1974 and january 1975. Study involves two parts : comparison between bacteriostatic activity of SMZ-TMP, ampicillin and nalidixic acid; evaluation of bactericidal activity of antibiotic associations including SMZ-TMP. MIC study included all strains. On Gram- negative bacilli the bacteriostatic activity of SMZ-TMP (74,6 percent of sensitive strains) was comparable with nalidixic acid (79,6 percent of sensitive strains) and better than ampicillin 31,4 percent of sensitive strains). On staphylococcus strains the bacteriostatic activity of SMZ-TMP (84,6 percent of sensitive strains) is better than ampicillin (36,4 percent of sensitive strains); on streptococcus strains the bacteriostatic activity of ampicillin (71 percent of sensitive strains) is better than SMZ-TMP (5l percent of sensitive strains). 473 associations including SMZ-TMP were studied upon 44 strains of Gram- negative bacilli by bactericidal test. ("Cross disposition" method, derive from "cellophane transfer method".

Ampicillin↗
PubMed1977

[Comparative study of 7 cephalosporins on "Staphylococcus aureus" by the method of population analysis (author's transl)].

Miscellaneous Staphylococcus aureus populations were tested with seven commercialized cephalosporins. The strains were divided in five groups according to the following criteria: penicillinase production or not: sensitivity to methicillin and cephalosporins; RB type resistance to methicillin; RH and RO type resistance to every beta-lactamine (according to Chabbert and Baudens). For each cephalosporin studied, the population cell analysis performed with these different groups showed the constant heterogeneous arrangement of the individual MIC. However, whatever the staphylococcus group, cephaloridine remains the antibiotic that inhibits the largest number of cells at lower concentration than other cephalosporins. In vitro results were compared with pharmacokinetic data of the different cephalosporins.

Cefazolin↗
PubMed1975

[Should resistance to methicillin of RH mutant staphylococci be necessarily attributed to cephalosporins?].

The resistance to cephalosporins of 48 heterogeneous methicillin-resistant strains ("RH" mutants) of Staphylococcus pyogenes var. aureus is studied in vitro with various methods: sensitivity discs test on Mueller-Hinton medium with 5 per cent NaCl at 37 degrees C; M.I.C. in solid medium by spots medium with two inocula: a light inoculum (10(7) bacterial/ml) and a heavy inoculum (10(9) bacteria/ml). With light inoculum all strains have M.I.C. to cephaloridin less than 2 meg/ml and seem sensitive. With heavy inoculum 45 sc. equal or superior to 64 meg/ml and then are resistant. These resistances occur after 3 degrees C. The varied methods of detection of mutants to cephalosporins are discussed in this paper.

Cephalosporins↗
PubMedDate not supplied

Treatment of a meningitis due to an Enterobacter aerogenes producing a derepressed cephalosporinase and a Klebsiella pneumoniae producing an extended-spectrum beta-lactamase.

A case of nosocomial meningitis due to a Klebsiella pneumoniae producing a CAZ-5 extended-spectrum beta-lactamase and an Enterobacter aerogenes producing a derepressed cephalosporinase is reported. The intrathecal catheter incriminated was removed and a treatment with ceftazidime (4 g/24 h) and amikacin (1.5 g/24 h) was started. After 24 h ceftazidime was replaced by imipenem (2 then 4 g/24 h). This treatment failed to obtain cerebrospinal fluid sterilization; therefore the imipenem dosage was increased to 8 g/24 h and two intrathecal infusions of amikacin (50 mg) were carried out. Thereafter the patient recovered.

Adult↗
PubMedDate not supplied

Susceptibility of new beta-lactams to the expanded-spectrum beta-lactamase CTX-1.

Forty-three clinical isolates of enterobacteria were selected for the production of the new plasmid-mediated expanded-spectrum beta-lactamase CTX-1. The geometric means of MICs were ranged as follows: ticarcillin, greater than 4096 mg/l; ticarcillin + clavulanic acid (2 mg/l), 64-87 mg/l; LY 163892, 8.0-69.1 mg/l; cefotaxime, 5.7-26.4 mg/l; temocillin, 8.0-21.8 mg/l; Ro 158074, 4.0-18.7 mg/l aztreonam, 1.0-14.4 mg/l and BMY 28142, 1.4-2.8 mg/l. Moxalactam, imipenem and CM 40876 were resistant to hydrolysis and MICs were lower than 2.0 mg/l. A high protective effect on cefotaxime (MIC less than or equal to 0.5 mg/l) was obtained by sulbactam (4 mg/l). Escherichia coli transconjugants from each species showed similar levels of MICs.

Anti-Bacterial Agents↗
PubMedDate not supplied

Characterization of a beta-lactamase from Pasteurella multocida.

A bovine strain of Pasteurella multocida was found to produce a beta-lactamase. The minimal inhibitory concentrations of amoxicillin (128 mg/l) and ticarcillin (512 mg/l) were high for this strain. The enzyme was periplasmic and produced constitutively, and there was no obvious permeability barrier. This enzyme had a TEM-substrate profile, and no inhibition was detected with antisera (anti-TEM-1, anti-TEM-2). The apparent isoelectric point was estimated at 8.8.

Amoxicillin↗
PubMedDate not supplied

Klebsiella pneumoniae and other Enterobacteriaceae producing novel plasmid-mediated beta-lactamases markedly active against third-generation cephalosporins: epidemiologic studies.

Analysis of the enzymes produced by clinical isolates of multiresistant Klebsiella pneumoniae from hospitals in France revealed two novel broad-spectrum beta-lactamases. The first, characterized by an isoelectric point of 6.3 and a high hydrolytic activity on cefotaxime, is designated CTX-1. This beta-lactamase was encoded by a 95-kilobase plasmid (incompatibility group 7M) and cotransferred with resistance to tetracyclines, sulfonamides, and aminoglycosides (AAC [6']-IV). From 1984 to June 1987, 490 CTX-1-producing strains of Enterobacteriaceae were isolated. The second plasmid-mediated beta-lactamase (CAZ-1) was isolated in 1987 from three K. pneumoniae strains more resistant to ceftazidime than to other third-generation cephalosporins. This broad-spectrum beta-lactamase differed from CTX-1 by its isoelectric point--close to 5.6--and its high hydrolytic activity on ceftazidime and was encoded by a 150-kilobase plasmid. It was demonstrated that these expanded-spectrum beta-lactamases are TEM derivatives.

Cephalosporins↗
PubMedDate not supplied

Interactions of new plasmid-mediated beta-lactamases with third-generation cephalosporins.

The kinetic constants of three recently identified plasmid-mediated beta-lactamases--SHV-2, CTX-1, and CAZ-1--markedly active against third-generation cephalosporins were analyzed in comparison with three better-characterized beta-lactamases--two plasmid-mediated enzymes, TEM-2 and PIT-2/SHV-1, and R-30, a beta-lactamase from Klebsiella oxytoca that has few similarities to the newer enzymes. All of these enzymes are synthesized constitutively, demonstrate efficient hydrolysis of penicillins, are highly susceptible to the action of clavulanic acid and sulbactam, and have no detectable activity against the cephamycins and imipenem. With the methoxyimino cephalosporins, including those of the third generation, the rates of hydrolysis observed for the SHV-2, CTX-1, and CAZ-1 enzymes are high and show no relation to those observed for the other presently known beta-lactamases. Structure-activity relations suggest that the oxime substituent of these cephalosporins is a major structural factor in the catalytic process observed with the three new beta-lactamases.

Cephalosporins↗
PubMedDate not supplied

[Changes in the activity of antibiotics by fatty acids in bone tissue].

The C14 to C18 fatty acid content of spongious bone was measured by gas-liquid chromatography. Palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) represented 20 to 40% of the total free fatty acid concentration (30 mM/l). Linoleic acid was found to have the greatest bacteriostatic activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa strains. The effect of linoleic acid-gentamicin combination was synergistic against S. aureus. In contrast, both gentamicin and colistin activities were highly antagonized by linoleic and oleic acids against E. coli and P. aeruginosa strains. These different effects of free fatty acids on antibiotic activity could be explained, in part, by a change in permeability of bacterial cells. The clinical implications of these results in bone infections are discussed.

Anti-Bacterial Agents↗