The in-vitro susceptibilities of 326 Streptococcus pneumoniae isolates to nine antimicrobial agents including penicillin and newer quinolones

Streptococcus pneumoniae is an important cause of both upper and lower respiratory tract infections for which penicillin has long been the treatment of choice. Since 1967, however, there have been increasing numbers of reports of penicillin-resistant isolates from many countries throughout the world, particularly Spain and South Africa (Jacobs et al., 1978; Fenoll et al., 1991). In the United States, the overall incidence of reduced susceptibility to penicillin amongst strains of pneumococci is approximately 15%, although there has been considerable geographical variation (Thornsberry, Marler & Rich, 1992). To date, Canada has been spared the Spanish and American trends towards increasing resistance, with rates of reduced susceptibility of between 1.3% and 1.5% (Dixon, Lipinski & Graham, 1977; Jette, Lamothe & the Pneumococcus Study Group, 1989; Mazzulli et al., 1990). Recently, several novel fluoroquinolones have become available for clinical and investigational use. These agents are well-absorbed after oral administration and possess broad spectra of antibacterial activity. Their usefulness as treatment for patients with pneumococcal infection, however, may be limited by their comparatively modest in-vitro activities against streptococci, especially S. pneumoniae (Mazzulli et al., 1990; Spangler, Jacobs & Appelbaum, 1992). In this study, we report the serotype prevalence of S. pneumoniae isolates in an adult tertiary care hospital in a large Canadian city and the susceptibilities of these strains to penicillin, five quinolones and three other antibiotics commonly used to treat infections caused by this pathogen.(DBO)