Comparison of results generated by serotyping, pulsed-field restriction analysis, ribotyping, and repetitive-sequence PCR used to characterize penicillin-resistant pneumococci from the United States.

One hundred forty-seven isolates of Streptococcus pneumoniae with high-level penicillin resistance collected during a national surveillance program in the United States were characterized by serotyping, pulsed-field restriction analysis, ribotyping, and repetitive-sequence (BOX element) PCR. The results generated by each method were compared by frequency of association to examine whether relationships existed between the various typing methods and statistically to determine association with the geographic source of the isolate or the age of the patient from whom the isolate was obtained. When the data were examined by pairwise analysis of individual strain classifications produced by each typing method, no statistically significant relationships between strain type, geographic location, or patient age were identified, suggesting that distinct clones of penicillin-resistant S. pneumoniae have been widely distributed throughout the United States. However, we did observed shared expression of two or three typing markers at a high frequency (>50%) among clusters of strains, indicating a certain level of concordance between the various typing methods used to classify penicillin-resistant S. pneumoniae.