In vivo evaluation of antibiotic activity against Mycobacterium abscessus.

Background: The prognosis of Mycobacterium abscessus infections is poor due to the lack of effective drug treatment. The objective of this study was to set up an animal model suitable to test antibiotic activity against M. abscessus.

Target specificity of the new fluoroquinolone besifloxacin in Streptococcus pneumoniae, Staphylococcus aureus and Escherichia coli.

Objectives: Besifloxacin is a new fluoroquinolone in development for ocular use. We investigated its mode of action and resistance in two major ocular pathogens, Streptococcus pneumoniae and Staphylococcus aureus, and in the reference species Escherichia coli.

Methods: Primary and secondary targets of besifloxacin were evaluated by: (i) mutant selection experiments; (ii) MIC testing of defined topoisomerase mutants; and (iii) inhibition and cleavable complex assays with purified S.

Low selection of topoisomerase mutants from strains of Escherichia coli harbouring plasmid-borne qnr genes.

Objectives: To investigate mutations in the type II topoisomerase genes in quinolone-resistant mutants selected from bacteria harbouring plasmid-borne qnr genes.

Methods: Mutants were selected by nalidixic acid, ciprofloxacin and moxifloxacin from two Escherichia coli reference strains and corresponding transconjugants harbouring qnrA1, qnrA3, qnrB2 or qnrS1 genes.

Results: The proportion of resistant mutants selected by the three quinolones was, respectively, in the same range for qnr-positive transconjugants and reference strains.