Type II topoisomerase mutations in Bacillus anthracis associated with high-level fluoroquinolone resistance.

Objectives: To identify and characterize the mechanisms of high-level fluoroquinolone resistance in two strains of Bacillus anthracis following serial passage in increasing concentrations of fluoroquinolones.

Methods: Fluoroquinolone-resistant isolates of the Sterne and Russian Anthrax Vaccine STi strains were obtained following serial passage in the presence of increasing concentrations of four different fluoroquinolones. The quinolone-resistance-determining regions of the type II topoisomerase genes from the resistant strains were amplified by PCR and characterized by DNA sequence analysis.

Emergence of macrolide resistance in throat culture isolates of group a streptococci in Ontario, Canada, in 2001.

Of 500 group A streptococci isolated from pharyngeal swabs, 72 (14.4%) were macrolide resistant, compared to 2.1% in 1997.

Identification of a streptolysin S-associated gene cluster and its role in the pathogenesis of Streptococcus iniae disease.

Streptococcus iniae causes meningoencephalitis and death in cultured fish species and soft-tissue infection in humans. We recently reported that S. iniae is responsible for local tissue necrosis and bacteremia in a murine subcutaneous infection model.