ceptible, although resistance can develop rapidly to this agent (10). MATERIALS AND METODSA total of 168 clinical isolates of Streptococcus pneumoniae were obtained from patients with pneumococcal bacteremia, pneumonia, meningitis, and otitis, and from nasopharyngeal carriers during surveys for resistant pneumococci. Pneumococci were identified by their colonial morphology on blood agar plates, optochin sensitivity, bile solubility, and capsular typing with antipneumococcal serum (Statens Seruminstitut, Copenhagen, Denmark) (2). Strains were isolated in our laboratories from blood, cerebrospinal fluid, or nasopharyngeal swabs or were referred to us from other laboratories for serotyping and susceptibility testing. All resistant strains were isolated from patients in Johannesburg and Durban, South Africa. The strains chosen were selected to represent as complete a spectrum as possible of susceptibility to the antimicrobial agents selected and to include as many intermediate resistant strains as were available.MIC determination Minimal inhibitory concentrations (MICs) were determined by the plate incorporation method (15) in 9-cm plastic petri dishes containing 19 ml of Muelier-Hinton agar (lot no. K9DFNG; BBL, Cockeysville, Md.) and 1 ml of lysed horse blood, giving a concentration of 5% blood. Anti-

The clarithromycin extended-release multisource product (Klarithran MR) does not differ significantly from the originator (Klacid XL) and the clinical cure rate of the generic formulation is non-inferior to that of the originator. The two formulations are tolerated similarly.