Multiplex PCR allows rapid and accurate diagnosis of bloodstream infections in newborns and children with suspected sepsis

Abstract

Sepsis is a major health problem in newborns and children. Early detection of pathogens allows initiation of appropriate antimicrobial therapy that strongly correlates with positive outcomes. Multiplex PCR has the potential to rapidly identify bloodstream infections, compensating for the loss of blood culture sensitivity. In an Italian pediatric hospital, multiplex PCR (the LightCycler SeptiFast test) was compared to routine blood culture with 1,673 samples obtained from 803 children with suspected sepsis; clinical and laboratory information was used to determine the patient infection status. Excluding results attributable to contaminants, SeptiFast showed a sensitivity of 85.0% (95% confidence interval [CI] = 78.7 to 89.7%) and a specificity of 93.5% (95% CI = 92.1 to 94.7%) compared to blood culture. The rate of positive results was significantly higher with SeptiFast (14.6%) than blood culture (10.3%) (P < 0.0001), and the overall positivity rate was 16.1% when the results of both tests were combined. Staphylococcus aureus (11.6%), coagulase-negative staphylococci (CoNS) (29.6%), Pseudomonas aeruginosa (16.5%), and Klebsiella spp. (10.1%) were the most frequently detected. SeptiFast identified 97 additional isolates that blood culture failed to detect (24.7% P. aeruginosa, 23.7% CoNS, 14.4% Klebsiella spp., 14.4% Candida spp.). Among specimens taken from patients receiving antibiotic therapy, we also observed a significantly higher rate of positivity of SeptiFast than blood culture (14.1% versus 6.5%, respectively; P < 0.0001). On the contrary, contaminants were significantly more frequent among blood cultures than SeptiFast (n = 97 [5.8%] versus n = 26 [1.6%]), respectively; P < 0.0001). SeptiFast served as a highly valuable adjunct to conventional blood culture in children, adding diagnostic value and shortening the time to result (TTR) to 6 h.

Fig. 1.

Algorithms for interpretation of blood culture and SeptiFast results (A and B, respectively). *, in case of polymicrobial infections and/or detection of different microorganisms, the same criteria reported above were applied for the assessment of each microorganism as a pathogen or probable contaminant; 1, clinical, laboratory, and microbiological information; 2, TTP, time to positivity; 3, positive result reported by the SeptiFast software.

Fig. 2.

Concordance of results of blood culture and SeptiFast test related to clinical wards (NP, SeptiFast negative/blood culture positive; PN, SeptiFast positive/blood culture negative; PP, SeptiFast plus blood culture positive). NF Gram−, nonfermentative Gram-negative organisms. Numbers on the y axis refer to the number of isolates.