Accuracy of a Polymerase Chain Reaction-based Assay for Detection of Pneumococcal Bacteremia in Children

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Abstract
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 Children9s 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°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.