Accuracy of a polymerase chain reaction-based assay for detection of pneumococcal bacteremia in children.

OBJECTIVE: To evaluate the utility of a polymerase chain reaction (PCR)-based assay for identifying pneumococcal DNA in the blood of pediatric patients with suspected bacteremia.
METHODS: Children evaluated at the Children's Hospital of Pittsburgh who were having blood drawn for culture had an additional 2 to 3 mL of blood (from the same sampling) obtained and placed in a sodium citrate tube for PCR processing (study group). The control group for this study consisted of children having blood drawn for biochemical analysis who were afebrile, well-appearing, and had no recent illnesses. Specimens were frozen at -70 degrees C and then batch-processed for PCR-based analyses with the JM201/202-204 primer/probe set. Amplified products were detected after liquid hybridization format wherein a 32P end-labeled probe was annealed to the amplified DNA and visualized by autoradiographic analysis after gel retardation.
RESULTS: Four hundred eighty study group patients and 103 controls had specimens tested by both PCR and blood culture. Twenty-six (5%) patients had a positive blood culture for a pathogenic organism (21 of which were Streptococcus pneumoniae). Twelve (57%) of the 21 patients with blood cultures positive for S pneumoniae also were positive by PCR. In addition, 206 study group patients and 16 controls with negative blood cultures had positive PCR results. A greater proportion of study group patients were PCR-positive/culture-negative than were controls (206/459 vs 16/103).
CONCLUSION: Although this assay currently lacks adequate sensitivity and specificity for clinical use, the high frequency of PCR-positive cases in patients with suspected bacteremia may indicate a greater role for S pneumoniae than had previously been appreciated. Further refinement of this assay as well as the development of a rapid PCR-based assay appears warranted.