[Effect of subinhibitory concentrations of antibiotics on the growth level of bacteria]. / Effet des concentrations subinhibitrices d'antibiotiques sur le taux de croissance des bactéries.

The effect of subinhibitory concentrations of 5 antibiotics on the growth rate of 2 bacteria (Staphylococcus aureus and Escherichia coli) has been studied. Chloramphenicol, dibekacin, netilmicin and nalidixic acid have a direct effect on the growth rate. Apparently, aminoglycosides and nalidixic acid have an accompanying effect on the affinity for the energizing substrate. Amoxicillin does not seem to be concerned by this 2 mechanisms. The interest of the estimation of the growth rate by an adaptative algorithm has been pointed out.

Bacterial growth measurement using an automated system: mathematical modelling and analysis of growth kinetics.

The reliability of automated systems was assessed by simultaneously using an MS2 and a methodology of data interpretation/mathematical modelling. Two experimental situations were analysed. Bacterial growth both in synthetic and in complex media could be well described by Monod's model and the logistic model. In the two cases, the fit of the models to the data was satisfactory.

[Evaluation of the Rapid-ATB system for testing the sensitivity of staphylococci to antibiotics. Comparison with the agar dilution reference method]. / Evaluation du système Rapid-ATB pour l'étude de la sensibilité aux antibiotiques des staphylocoques. Comparaison avec la méthode de référence de dilution en gélose.

Rapid ATB Staph is a new, automated, four-hour procedure for testing the susceptibility to antibiotics of staphylococci. Results obtained with this method were compared to those recorded using agar dilution. For all tested antibiotics as a group (5 on 201 strains, 8 on 100 strains), overall agreement between the two sets of results was 96%. 1,809 susceptibility tests were performed, with only 24 minor discrepancies (1.3%) mainly involving cotrimoxazole, and 50 major discrepancies (2.7%) mainly involving doxycycline and chloramphenicol. Rapid ATB Staph clearly demonstrates the heterogeneous oxacillin-resistance of staphylococci as well as their inducible resistance to erythromycin. Our results show that this new system is a very accurate means for testing the susceptibility to antibiotics of staphylococci.

[Rapid determination of staphylococcal strains resistant to novobiocin using the Autobac system]. / Reconnaissance rapide des souches de staphylocoques résistantes à la novobiocine avec le système Autobac.

Special novobiocin elution disks were prepared for testing of staphylococci in the Autobac system. The disk mass has been choosed by principal component analysis. The verification of the results showed the interest of this test for routine identification of the staphylococcal strain isolated in the urinary tract infections.