EVALUATION OF POLYMERASE CHAIN-REACTION FOR DIAGNOSIS OF PNEUMOCOCCALPNEUMONIA

To test the ability of the polymerase chain reaction (PCR) to detect S treptococcus pneumoniae in blood, we generated two sets of nested prim ers. The first defined 559-bp and 649-bp regions of the pneumolysin ge ne, and the second defined 445-bp and 553-bp regions of the autolysin gene. These nucleotide segments were detected in DNAs from isolates of all 20 pneumococcal serotypes tested, but they were not detected when used to test DNAs from 41 isolates of nonpneumococcal bacteria and fu ngi. The sensitivity was evaluated by using purified pneumococcal DNA. We were able to detect 10 fg of S. pneumoniae DNA, or 4.3 genome equi valents. Blood samples were obtained from 16 patients with culture-pro ven pneumococcal bacteremia and were subjected to PCR analysis. Of eig ht buffy coat fractions tested, six showed reactivity in the PCR with the pneumolysin primers, and five of the eight produced the expected p roducts when tested with the autolysin primers (sensitivities, 75 and 63%, respectively). Of the eight whole-blood specimens tested, only th ree produced the expected products with either set of primers. Additio nally, we tested 14 samples from patients with bacteremia that were cu lture positive for nonpneumococcal bacterial species, and 13 were nega tive (specificity, 93%). This combination of sensitivity and specifici ty may make detection of S. pneumoniae in blood by PCR in comparison w ith that by blood culture a very promising alternative for a means of definitive diagnosis.