[Antibacterial effect of two glycine betaine analogues against Escherichia coli]. / Activité antibactérienne de deux analogues de la glycine bétaïne vis-à-vis d'Escherichia coli.

Strains of enterobacteria that cause urinary tract infections are able to grow in urine with high tonicity. In such conditions bacterias adapt to osmotic forces by incorporation of osmoprotectant compounds including glycine betaine. Accumulation of toxic analogues in bacteria, using inducible betaine transporters, has been previously proposed for development of antibiotics. In this study we report antibacterial effect of two analogues against 82 strains of Escherichia coli isolated form urinary tract infections. Minimal inhibitory concentrations have been measured with and without osmotic stress. The betaine analogues have antibacterial effect against E. coli strains, but only in presence of an osmotic stress.

[Comparative study of the bacteriostatic and bactericidal activity of levofloxacin against Pasteurella strains isolated from man]. / Etude comparative de l'activité bactériostatique et bactéricide de la lévofloxacine vis-à-vis des souches de Pasteurella isolées chez l'homme.

The MICs of seven quinolones, nalidixic acid, pefloxacin, ofloxacin, d-ofloxacin, ciprofloxacin, sparfloxacin and levofloxacin, were determined by agar dilution method comparatively to those of amoxycillin, cefpodoxime, doxycyclin and clarithromycin against 75 clinical isolates of Pasteurella multocida, P. dagmatis and P. canis. Time-kill method was performed for three selected P. multocida isolates. Fluoroquinolones were the most active agents. At concentration of 0.016 mg/L of sparfloxacin or levofloxacin the 75 isolates were inhibited. The MICs of levofloxacin and sparfloxacin showed that the activity of these molecules was two to four times higher than that of the other quinolones studied. Time-kill studies showed a complete killing in six hours with the CMI x 2 of pefloxacin, ofloxacin, ciprofloxacin, sparfloxacin and levofloxacin. This result was obtained more rapidly with the quinolones than with amoxicillin or cefpodoxime. Doxycycline and clarithromycin were devoid of bactericidal activity.

Comparative antimicrobial resistance and genomic diversity of Escherichia coli isolated from urinary tract infections in the community and in hospitals.

Well-defined community- and nosocomially-acquired isolates of Escherichia coli responsible for urinary tract infections were studied for their resistance to beta-lactams, quinolones, and co-trimoxazole, antibiotics widely used for treatment of urinary infections. For each strain, an antibiogram was obtained using the Vitek automat, which estimates the minimal inhibitory concentrations of various drugs. Nosocomial strains were significantly more amoxycillin-resistant than community strains (P = 0.01) and were also significantly more resistant to co-trimoxazole (P = 0.025) and first generation quinolones (P = 0.02) than the latter. To determine whether this was due to transmission of strains within the hospital, DNA restriction patterns, established using XbaI enzyme and separation by pulsed-field gel electrophoresis, were compared. Extreme genomic diversity was found among both the community and nosocomial strains. The increased frequency of resistance among nosocomial strains is thus not due to transmission of resistant hospital strains but probably results from the selection of resistant strains from the endogenous flora of patients.

Increasing incidence and comparison of nalidixic acid-resistant Salmonella enterica subsp. enterica serotype typhimurium isolates from humans and animals.

We determined the resistance to quinolone of 309 Salmonella enterica subsp. enterica serotype Typhimurium strains isolated from humans and animals (cattle, pigs, or poultry) in 1995 or 1996. Nalidixic acid resistance increased from 8.5% in 1995 to 18.6% in 1996. The highest resistance levels correlated with a mutation at Ser-83 (or Asp-82). All strains remained ciprofloxacin susceptible. Human and animal isolates were compared by pulsed-field gel electrophoresis, and the banding patterns of the human isolates most closely matched those of the bovine isolates.

[Growing incidence of nalidixic acid resistance and sensitivity to quinolones in Salmonella typhimurium strains isolated from man or animal]. / Incidence croissante de la résistance à l'acide nalidixique et sensibilité aux quinolones des souches de Salmonella typhimurium isolées chez l'homme ou l'animal.

To determine the prevalence of quinolone resistance in Salmonella typhimurium strains from humans or animals (cattle, poultry, swine), the S. typhimurium strains isolated at a teaching hospital and at the central veterinary laboratory of the same district between January 1, 1995, and December 31, 1996 were studied. Susceptibility to nalidixic acid was determined using the disk diffusion method. Strains with decreased susceptibility to nalidixic acid were subjected to minimal inhibitory concentration (MIC) determination for pefloxacin, ofloxacin, ciprofloxacin, norfloxacin, levofloxacin, and grepafloxacin. Decreased susceptibility to nalidixic acid was demonstrated for 41 of the 309 strains studied and increased from 8.5% in 1995 to 18.6% in 1996. MIC90 values of fluoroquinolones for strains with decreased susceptibility to nalidixic acid were lower than 1 mg/L, which is the cutoff above which a strain is classified as susceptible, but were higher than for strains that were susceptible to nalidixic acid. These low levels of resistance may be the first step in selection of mutant strains with high levels of resistance to fluoroquinolones. This warrants continued monitoring of resistance of Salmonella to fluoroquinolones.

[Susceptibility to quinolones of Salmonella isolated from men and animals]. / Sensibilité aux quinolones des Salmonella isolées chez l'homme et l'animal.

Fluoroquinolones are efficacious antibiotics for the treatment of Salmonella infections in humans. One of these quinolones, enrofloxacin, a precursor of ciprofloxacin, is used to treat respiratory infections in calves and poultry. There is a risk of developing resistant strains of Salmonella in animals, which may then contaminate humans. To evaluate current susceptibilities of Salmonella strains to quinolones, we collected 95 strains belonging to various serotypes in a district of intensive breeding (the Ille-et-Vilaine Département): 54 human strains, 24 bovine strains, and 17 poultry strains. The technique of dilutions in agar medium was used to determine Minimal Inhibitory Concentrations (MICs) for the following antibiotics: nalidixic acid, norfloxacin, pefloxacin, ofloxacin, ciprofloxacin, levofloxacin and clinafloxacin. Our results showed that human Salmonella strains remained very susceptible to quinolones. Only 3 animal strains had nalidixic-acid MICs > 128 mg/l. For these 3 strains, pefloxacin and ciprofloxacin MICs were respectively 1 or 2 mg/l and 0.25 mg/l. For all the other human and animal strains the nalidixic-acid MICs were < 4 mg/l, and their MICs 90 were: 0.12 mg/l for ofloxacin and norfloxacin, 0.06 mg/l for pefloxacin, 0.03 mg/l for ciprofloxacin, 0.016 mg/l for levofloxacin, and 0.004 mg/l for clinafloxacin.

[Bactericidal activity of ciprofloxacin and sparfloxacin. Comparison with others active antibiotics against Pasteurella multocida]. / Activité bactéricide de la ciprofloxacine et de la sparfloxacine. Comparaison avec celle des autres antibiotiques actifs sur Pasteurella multocida.

Bactericidal activities of ciprofloxacin and sparfloxacin were compared to other antibiotics active against human isolates of Pasteurella multocida. Three human isolates of Pasteurella multocida were used for killing-curve studies with ciprofloxacin and sparfloxacin comparatively to others antibiotics. At 2x the MIC, ciprofloxacin and sparfloxacin exhibited a killing of more than 99.9% of the initial viable cells that was achieved within 6 h of incubation. These activities were faster than those of amoxycillin and cefpodoxime. No regrowth was observed after 24 h of incubation. Doxycycline and clarithromycin used at MICx2 had no bactericidal activities. It was concluded that fluoroquinolones, namely ciprofloxacin and sparfloxacin, can be considered having good bactericidal activity against P. multocida.

[Action of imipenem on Enterobacter cloacae]. / Etude de l'action de l'imipénème sur Enterobacter cloacae.

Most of Enterobacter cloacae strains produce chromosomally determined class I beta-lactamases when they are exposed to beta-lactams. Imipenem is a strong inducer of these enzymes but is poorly affected by them. We compared the effect of imipenem on inducible, non-inducible and stably derepressed strains of E. cloacae using the killing curve system. With antibiotic concentrations of 0.5 mg/l or more, an intense dose-dependent bactericidal effect was observed within 4 to 6 hours. However the bactericidal activity was incomplete. With an inoculum as low as 10(5) bacteria/ml a regrowth was observed after 24 hours. Among the surviving bacteria imipenem had the same bactericidal kinetic than on the parental strain. Similar results were observed with inducible, non-inducible and stably derepressed strains.

[Identification and rapid determination of the antibiotic resistance of enterobacteria with the automated ABAC identibiogram]. / Identification et antibiogramme rapides des entérobactéries à l'aide du système automatisé ABAC-identibiogramme.

Rapid identification and antimicrobial testing of Enterobacteriaceae by an automated system, the ABAC-Identibiogramme. The system was directly inoculated with a dilution of positive blood culture broths. The results were compared with those of API 20E and the disk method for antibiogram. The ratios of agreement of 94.5% for identification and of 93.4% for antimicrobial testing demonstrate a good accuracy of the ABAC-Identibiogramme.