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.

[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.

[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.

Different mechanisms of resistance to latamoxef (moxalactam) in Serratia marcescens.

Three pairs of latamoxef (moxalactam)-resistant and -sensitive strains of Serratia marcescens were isolated either in vivo or in vitro. Multiple mechanisms of resistance were found, and these mechanisms involved: a decrease in permeability in each case, associated with modification of the protein composition of the outer membrane in two cases; a variable increase (two-to-six-fold) in the amount of beta-lactamase; and in one case only, some modification of the penicillin binding proteins. Thus, it may be necessary for multiple mechanisms to be present to give resistance to latamoxef in this species.

[In vitro action of moxalactam on hospital bacteria. Results of a multicenter survey].

The high potency of Moxalactam on three major groups of bacteria, i.e. Enterobacteriae, Haemophilus and Bacteroïdes, predicted by previous studies, has been confirmed by the study of hospital strains in this multicenter investigation.

Selection and characterization of beta-lactam-resistant Escherichia coli K-12 mutants.

beta-Lactam-resistant mutants of Escherichia coli K-12 were selected by using 12 different beta-lactam derivatives. The mutants fell into three categories showing (i) altered permeation through reduction or loss of outer membrane porin proteins (including ompF, ompR, and envZ alleles); (ii) increase in the rate of synthesis of chromosomally mediated beta-lactamase; or (iii) defective synthesis or action of cyclic adenosine 3',5'-phosphate (cya and crp alleles).

Comparative activity of cefotetan on Escherichia coli K12 possessing plasmid-mediated beta-lactamases.

The antibacterial activity of cefotetan, a new cephamycin, was compared with that of cephalothin, cefoxitin, cefamandole, cefoperazone and cefotaxime on 12 substrains of Escherichia coli K12 BM13 harbouring single and multi-copy plasmids coding for plasmid-mediated beta-lactamases TEM, SHVI, OXA-I and OXA-III. The 99% inhibitory concentrations (IC99) for the recipient strain were increased in proportion to the enzyme activity in the case of cefamandole and cefoperazone. In contrast, the activity of cefoxitin, cefotaxime and cefotetan was not significantly modified.

Role of porin proteins OmpF and OmpC in the permeation of beta-lactams.

Mutants of Escherichia coli K-12 lacking major outer membrane proteins were obtained by selecting for resistance to the beta-lactam cefoxitin. Three classes of resistant strains were found: mutants in ompB, a regulatory locus for proteins OmpF and OmpC; mutants in ompF; and one mutant in tpo. The OmpF and OmpC proteins facilitate penetration of beta-lactams through the outer membrane.

Plasmid DNA content of multiresistant Staphylococcus aureus strains.

Multiresistant S. aureus strains (also called methicillin-resistant in clinical laboratories) share many common properties. In addition to the commonly used epidemiological markers (pattern of resistance to antibiotics and metal ions, serotype and lysotype), we considered using the molecular and genetical properties of the plasmid DNA harboured by these strains.

[Cefotaxime, syn isomer of a new methoxyimino cephalosporin with unusual activity (author's transl)].

Cefotaxime, the - syn - derivative of 7 - [(2-(2-amino-4-4-thiazolyl)-2-methoxyimino) acetamido] cephalosporanic acid, is a new semisynthetic cephalosporin. In in vitro studies, 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 cefotaxime against Gram-negative bacteria, including Haemophilus influenzae, susceptible or resistant to penicillins and cephalosporins was from 0.

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.

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.

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.

[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.

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.

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.