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Y A Chabbert

Publications and source records attributed to Y A Chabbert.

At least 19 recordsLinked to original sources
PubMed1988

Early studies on in-vitro and experimental activity of spiramycin: a review.

This review of spiramycin activity in vitro is based mainly on early studies. The MICs of spiramycin for common pathogenic bacteria such as staphylococci, streptococci and pneumococci are higher than those of erythromycin. Conversely, in experimental models, the activity of spiramycin is equal to or greater than that of erythromycin. In addition, the activity of spiramycin on Neisseria, Legionella, Mycoplasma, Chlamydia, and Toxoplasma spp. completes its antimicrobial spectrum and shows that spiramycin covers the majority of agents responsible for respiratory tract infections. The 'spiramycin paradox'-the discrepancy between the relatively modest activity of spiramycin in vitro and its excellent activity in vivo will be explained by other papers. Its high tissue and intracellular concentrations, and the slow recovery of bacteria submitted to spiramycin are of great importance to account for its activity in vivo.

Bacteria↗
PubMed1986

[A study by the National Reference Center for Antibiotics on inocula for antibiotic sensitivity testing].

We compared the diameters of inhibition zones obtained during antibiotic sensitivity testing using two different techniques for preparing and seeding the inoculum, i.e. photometric adjustment followed by flooding, and turbidity adjustment followed by swab streaking. There was no significant difference between the results recorded following photometry-flooding of a light inoculum (2 to 3 X 10(6) CFU/ml) and following swab seeding of a bacterial suspension with a turbidity equal to 0.5 Mac Farland unit. These results indicate that both methods tested answer the NCCLS performance standards for disc antibiotic sensitivity testing and the critical values of the S.F.M. Antibiotic Sensitivity Testing Committee.

Escherichia coli↗
PubMed1985

[Effect of ceftazidime on enterobacteria and Pseudomonas producers of beta-lactamases].

The activity of cephalotin, cefoxitin, cefamandole, cefoperazone, cefotaxime, latamoxef, thienamycin, azthreonam, cefsulodine and ceftazidime against beta-lactamase producing strains of Enterobacteriaceae and Pseudomonas was compared by determination of 99% inhibitory concentrations. The isogenic strains studied differed by a single genetic event: mutation, gene amplification, acquisition of a high or low copy-number plasmid or of a transposon and were representative of the major known mechanisms of resistance toward beta-lactams. The results obtained indicate an overall excellent activity of ceftazidime, in particular against Pseudomonas.

Ceftazidime↗
PubMed1979

Reversible translocation of antibiotic resistance determinants in Salmonella ordonez.

Salmonella ordonez (BM 2000) codes for kanamycin (Km, aphA), ampicillin (Ap), streptomycin (SmSp:aadA and Sm:aphC), chloramphenicol (Cm), tetracycline (Tc) and sulfonamide (Su) resistances and for production of colicin Ib (Cib). Genetical analysis by incompatibility testing, conjugation, transformation and physical studies using electron microscopy, agarose gel electrophoresis, led us to associate the Km and Cib characters to a 98.7 kilobase (kb) IncI1 plasmid (pIP565), and the Sm (aphC) and Su determinants to a 8.3 kb plasmid (pIP605). The ApCmSmSp(aadA)SuTc determinants were not associated in BM2000 S. ordonez with a plasmid structure. Following conjugation of S. ordonez to E. coli, the ApCmSmSpSuTc determinants were found stably associated with a single plasmid structure (pIP173, 127.5 kb) belonging to IncI1 group. Agarose gel electrophoresis of plasmid DNA restriction endonuclease digests and electron microscopy heteroduplex analysis showed that the acquisition of the ApCmSmSpSuTc determinants resulted from the insertion into pIP565 of a 28.8 kb DNA sequence. This sequence coding for ApCmSmSpSuTu resistances in S. ordonez could be translocated either to pIP565 plasmid or to several IncI1 plasmids but never to plasmids belonging to IncW, IncP or IncFII, suggesting the existence of specific sequences on the IncI1 receptor plasmids. Moreover, R-determinants were translocated back "en bloc" from pIP173 to the chromosome of a susceptible S. ordanez. The results were consistent with the presence in BM2000 S. ordonez chromosomal DNA of an integrated translocatable sequence encoding ApCmSmSpSuTc resistances. Such a structural association could account for the stability of these resistances in the Salmonella ordonez serotype.

Ampicillin↗
PubMed1979

Plasmid epidemics.

Explore the source record for details and available documents.

Aminoglycosides↗
PubMed1978

Taxonomy and epidemiology of gram-negative bacterial plasmids studied by DNA-DNA filter hybridization in formamide.

Phylogenetic and epidemiological relatedness among transferable plasmids belonging to the IncC, IncM and IncH incompatibility groups has been studied by DNA-DNA filter hydridization. Hybridization was carried out on nitrocellulose microfilters, at low temperature, in formamide and under paraffin oil. The degree of hybridization among plasmids belonging to the IncC and IncM groups supported the conclusions drawn from genetic classification. Studies on relatedness among plasmids belonging to the IncH group allowed their classification into three phylogenetic sub-groups. Comparison of DNA sequences of three plasmids sharing the same genetic properties and isolated from different bacterial species suggested an epidemiological spread of the same plasmid.

Base Sequence↗
PubMed1978

Molecular studies and possible relatedness between R plasmids from groups B and D streptococci.

Resistance plasmids isolated from Streptococcus agalactiae (group B) and S. faecalis (group D) have been compared in regard to resistance markers, molecular weight, and DNA-DNA homology. Three of them (pIP501, pIP612, and pIP613) have been found to confer identical (or very similar) resistance patterns (erythromycin, lincomycin, and streptogramin B, respectively) and to have similar molecular weights (19.8 x 10(6), 22.7 x 10(6), and 17.6 x 10(6), respectively) and a high level of DNA-DNA homology in hybridization experiments (90 to 100%). These results are compatible with the view that these plasmids may derive from one common ancestor, and/or that they can be transferred between unrelated Streptococcus strains belonging to the same or different groups.

Anti-Bacterial Agents↗
PubMed1978

HR 756, the syn isomer of a new methoxyimino cephalosporin with unusual antibacterial activity.

HR 756, the syn derivative of 7-[(2-(2-amino-4-thiazolyl)-2-methoxyimino)acetamido]cephalosporanic acid, is a new semisynthetic cephalosporin. It was 80 times more active than the anti derivative against beta-lactamase-producing strains of gram-negative bacteria. The range of inhibitory concentrations of HR 756 against gram-negative bacteria, including Haemophilus influenzae, susceptible or resistant to penicillins and cephalosporins was from 0.01 to 0.1 mug/ml. This activity was consistently higher than those observed with cephalothin, cephaloridine, cephalexin, and cefazolin. Nevertheless, some strains of Enterobacter cloacae were resistant. HR 756 showed very similar activity to that of ampicillin against group A streptococci and Streptococcus pneumoniae.

Ampicillin↗
PubMed1978

Determination of the ID50 values of antibacterial agents in agar.

Microorganisms were plated on agar plates containing various concentrations of an antimicrobial drug and inhibition of growth was determined at each drug concentration. The ID50 value and the gradient of the line were calculated by the least square method. When 200 approximately 800 bacterial cells were inoculated on an agar plate, growth inhibition corresponded linearly with the log concentration of a drug within range of 5 approximately 95% inhibition. The ID50 value and the gradient obtained were reproducible and reliable using microorganisms at stationary phase of growth with all tested bacterial species and all tested antimicrobial agents. It was found that the ID50 values of drugs were more reproducible and may be more reliable than the MIC (minimum inhibitory concentration) values of the drugs.

Agar↗
PubMed1978

[Occurrence of R plasmids belonging to incompatibility group incC in Aeromonas hydrophila strains isolated from sewage water (author's transl)].

The susceptibility to antimicrobial agents of 321 strains of Aeromonas hydrophila was studied: 319 strains were found to be resistant to one or several antibiotics. Transfer of resistance markers was obtained from 24 strains. Five plasmids from these strains were classified into incompatibility group incC. Epidemiological consequences of R plasmid diffusion in water bacteria are discussed.

Aeromonas↗
PubMed1977

[Trimethoprim resistance plasmids: transferability and incompatibility groups (author's transl)].

Over a three year period, 119 strains of enterobacteria isolated from patients have been found resistant to trimethoprim (TMP) and sulfonamides (Su); 11 strains were resistant to TMP only. MIC of TMP were between 32 and 2048 microng/ml. Three groups of strains are described: (1) thymineless variants (2 strains); (2) TMP resistance non-transferable into Escherichia coli K12 (95 strains); (3) TMP resistance transferable into E. coli K12 (33 strains). TMP marker and Su marker have been transferred independantly from 13 strains; they were cotransferred from 20 strains. The incompatibility group of 31 plasmids has been determined: 10 belong to the fi+ type, group FII; 21 belong to the fi--type, group 6, group 7, group 10, group N and group I1. Epidemiological implications of such a wide range of incompatibility groups among a small number of plasmids specifying TMP resistance are discussed.

Drug Resistance, Microbial↗
PubMed1976

R plasmids in Streptococcus agalactiae (group B).

Two plasmids determining resistance to tetracycline (RIP500) and to chloramphenicol, erythromycin, lincomycin, and pristinamycin I (RIP501) were isolated from a strain of Streptococcus agalactiae. The frequency-of-resistance loss is very low for RIP500 (<3 x 10(4)) but higher for RIP501 (the efficiency was dependent upon the curing agents and incubation temperature and varied between 0.5 and 96%). Derivatives susceptible to all drugs were also obtained. RIP500 and RIP501 have similar molecular weights (17.9 x 10(6) and 20 x 10(6), respectively) and represent different percentages of total deoxyribonucleic acid (0.4 and 4%, respectively). The number of copies of RIP500 and RIP501 per cell is different, and these plasmids are likely replicated under different kinds of control (stringent and/or relaxed). No plasmid deoxyribonucleic acid was found in a derivative of strain B96 susceptible to all drugs.

Centrifugation, Density Gradient↗
PubMed1976

Chelocardin-inducible resistance in Escherichia coli bearing R plasmids.

Two plasmid-linked tetracycline resistance characters, tet A and tet B, were distinguishable in part, according to the level of resistance they conferred to minocycline (<3 mug/ml for tet A; >6 mug/ml for tet B). Escherichia coli K-12 strains that harbored the tet B character were also resistant to tetracycline but susceptible to chelocardin. In such tet B strains, subinhibitory concentrations of tetracycline could induce resistance to chelocardin as well as to otherwise inhibitory concentrations of tetracyclines. Chelocardin itself was ineffective as an inducer and therefore could be used to select constitutively resistant mutants. E. coli K-12 strains harboring the tet A character were also resistant to tetracycline and susceptible to chelocardin; tetracycline did not induce resistance to chelocardin in these strains.

Drug Antagonism↗
PubMed1976

[Instability of group FII plasmids in "Salmonella panama" (author's transl)].

Almost all Salmonella panama isolated in France only harbour R plasmids of incompatibility groups I1 (K Col Ib) and N (T). Reference R plasmids belonging to 11 incompatibility groups have been introduced into S. panama. All are stable after 50 generations except those of group FII. FII instability cannot be explained either by the presence of a group FII cryptic plasmid or by restriction enzymes in S. panama.

Conjugation, Genetic↗