Penicillin resistance of pneumococci in Israel: In vitro studies and clinical correlates

Antibiotic resistance of Streptococcus pneumoniae is increasing worldwide, creating a major problem in treating pediatric infections. The aims of the present study were to determine current resistance rates of S. pneumoniae in central Israel, to evaluate the various methods of determining resistance, and to define factors associated with resistance. Noninvasive (n=165) and invasive (n=93) isolates over 1995 to 1996 were studied. Disk diffusion (1 mcg oxacillin disk) showed overall resistance of 43%, with the noninvasive strains being mildly more resistant than the invasive ones (45% vs 41%). When compared to data since 1988, a steady increase in the rate of resistance was found. Minimal inhibitory concentration values determined by E-test(TM) showed an overall resistance of 42% mostly intermediate; high resistance was found in only 7%. As compared to the E-test(TM), disk diffusion had a sensitivity and specificity of 98% and 97%, respectively. A good correlation (r=0.78) was found between the E-test(TM) and tube dilutions. The clinical factors associated with penicillin resistance of S. pneumoniae were previous antibiotic use, young age and presence of a central IV line. In conclusion: S. pneumoniae has a high rate of antibiotic resistance. Factors associated with increased resistance should be considered when starting empiric therapy.