Multiplex PCR to diagnose bloodstream infections in patients admitted from the emergency department with sepsis

Abstract

Sepsis is caused by a heterogeneous group of infectious etiologies. Early diagnosis and the provision of appropriate antimicrobial therapy correlate with positive clinical outcomes. Current microbiological techniques are limited in their diagnostic capacities and timeliness. Multiplex PCR has the potential to rapidly identify bloodstream infections and fill this diagnostic gap. We identified patients from two large academic hospital emergency departments with suspected sepsis. The results of a multiplex PCR that could detect 25 bacterial and fungal pathogens were compared to those of blood culture. The results were analyzed with respect to the likelihood of infection, sepsis severity, the site of infection, and the effect of prior antibiotic therapy. We enrolled 306 subjects with suspected sepsis. Of these, 43 were later determined not to have infectious etiologies. Of the remaining 263 subjects, 70% had sepsis, 16% had severe sepsis, and 14% had septic shock. The majority had a definite infection (41.5%) or a probable infection (30.7%). Blood culture and PCR performed similarly with samples from patients with clinically defined infections (areas under the receiver operating characteristic curves, 0.64 and 0.60, respectively). However, blood culture identified more cases of septicemia than PCR among patients with an identified infectious etiology (66 and 46, respectively; P = 0.0004). The two tests performed similarly when the results were stratified by sepsis severity or infection site. Blood culture tended to detect infections more frequently among patients who had previously received antibiotics (P = 0.06). Conversely, PCR identified an additional 24 organisms that blood culture failed to detect. Real-time multiplex PCR has the potential to serve as an adjunct to conventional blood culture, adding diagnostic yield and shortening the time to pathogen identification.

Trial registration: ClinicalTrials.gov NCT00258869.

FIG. 1.

Positive and negative agreement of PCR and blood culture (BC) results. (A) “Patient concordance” defines concordant positive as a single subject with a positive blood culture result and a positive PCR result but not necessarily for the same organism or number of organisms. “Isolate concordance” defines concordant positive as a single instance in which the same organism was isolated by blood culture and PCR, which might occur more than once in a subject with a polymicrobial infection. Subjects with polymicrobial infections are counted only once under patient concordance, but each isolate is counted independently under isolate concordance, resulting in more isolates than the total number of subjects. (B) Results of blood culture and PCR reconciled with other available culture data. “Concordant non-blood culture” represents instances in which some other microbiological investigation (e.g., urine culture or antigen testing) identified the same infectious etiology that PCR or blood culture did.