ABSTRACT
Because of an heterogeneously-expressed resistance among methicillin-resistant Staphylococcus aureus strains the conditions for antibiogram determination had rapidly to be modified so as to improve their detection. The newly recommended conditions (incubation at +30 degrees C or on hypersalted agar medium) remain widely used at the moment, although they appear to be more and more often badly adapted, particularly because of the recently-observed renewed outbreak of wild strains with a weak in vitro phenotypic expression. It is the reason why we searched for a new and more reliable phenotypic method although still accessible for any laboratory. Sixty-five strains of Staphylococcus aureus entered the study. The absence or presence of mecA gene was previously investigated by gene amplification. These strains were of various origins and had often caused difficulties for the detection of intrinsic resistance to methicillin on the antibiogram. Our results confirm the failures of the classical methods (false negative results at +30 degrees C, false negative or positive results on hypersalted agar medium incubated at +37 degrees C). They also allow to propose a new method which relies on the determination of the susceptibility to cefoxitin using the usual conditions for antibiogram determination. In our series of strains, this new method proved to widely improve both the sensitivity and the susceptibility for the detection of methicillin-resistance by diffusion on the antibiogram.
Subject(s)
Hexosyltransferases , Methicillin Resistance , Microbial Sensitivity Tests/methods , Peptidyl Transferases , Staphylococcus aureus/drug effects , Agar , Bacterial Proteins/genetics , Carrier Proteins/genetics , Cefoxitin/pharmacology , Diffusion , False Negative Reactions , False Positive Reactions , Gels , Methicillin Resistance/genetics , Muramoylpentapeptide Carboxypeptidase/genetics , Oxacillin/pharmacology , Penicillin-Binding Proteins , Phenotype , Sensitivity and Specificity , Staphylococcus aureus/geneticsABSTRACT
OBJECTIVE: To assess the impact of guidelines on drug use issued by a consensus conference on polycythemia vera held in Paris in June 1993. 32Phosphorus (32P) was recommended for patients over 70 and/or at risk, whereas pipobroman and hydroxyurea were recommended for patients under 70. METHODS: A questionnaire was sent to all 119 departments of nuclear medicine in France 1 year after the conference to find out whether and how often they measured plasma volume and red cell mass (the recommended diagnostic tests for polycythemia vera). Time-series analyses were performed on sales of 32P, pipobroman (both virtually exclusively prescribed for polycythemia), and hydroxyurea over a 4-year span (January 1992-December 1995). RESULTS: The average number of plasma volume determinations per year did not change significantly after the conference (22 +/- 26 before vs 21 +/- 25 after). 32P and pipobroman sales were stable until July 1993, when 32P sales decreased while pipobroman sales rose steadily. Hydroxyurea sales increased over the whole period with no change in trend after the guidelines were published. CONCLUSIONS: The guidelines apparently influenced clinical practice since sales of drugs that are specifically used to treat polycythemia vera showed clear changes in trend after publication of the guidelines. This type of study seems to be an effective way of assessing the impact of consensus conferences.
Subject(s)
Polycythemia Vera , Drug Utilization Review , Humans , Polycythemia Vera/complications , Polycythemia Vera/diagnosis , Polycythemia Vera/drug therapy , Practice Guidelines as TopicABSTRACT
Comparative study of twenty two strains of Escherichia coli producing a well-characterized penicillinase of the OXA type (oxacillinase) or of the IRT type (TEM resistant to inhibitors) evidenced different criteria leading to the distinction of two groups of strains, according to the type of the harboured enzyme. Applied to eleven clinical strains, these criteria were always concordant with the determination of the isoelectric point, of hybridization and of oligotyping using probes for the classification into OXA or IRT type. We therefore propose the measurement of three inhibition diameters on antibiogram (cefepime, mecillinam and ceftazidime) for the routine distinction of the two enzymes. The interest of the easy characterization of these enzymes is reinforced by our findings that, as for all OXA strains, the inoculum effect which is displayed by some third-generation cephalosporins is very important and should be taken into account in the treatment of severe infections.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/enzymology , beta-Lactamases/metabolism , Drug Resistance, Microbial , Escherichia coli/drug effects , Humans , Microbial Sensitivity Tests , beta-LactamsABSTRACT
By repeated and successive treatments of five strains of methicillin-resistant Staphylococcus aureus with sub-inhibitory concentrations of vancomycin and of teicoplanin, the authors have confirmed that selection of resistant strains could be obtained more easily with teicoplanin than with vancomycin. Moreover, we have shown that treatments with subinhibitory concentrations of teicoplanin could also influence the activity of vancomycin, although the strains have never been in contact with the latter antibiotic. This could account, at least in part, for the downhill evolution of the activity of glycopeptides against staphylococci, observed this last years. Indeed, the efficacy of these antibiotics upon which treatment of severe infections due to multiresistant staphylococci relies, is lowering. Considering the challenge, this risk is worth being not only evaluated by a reinforced epidemiologic surveillance, but also limited by more severe criteria for the prescription and the follow-up of treatments with glycopeptides.