Journal Article

Use of Real-Time Quantitative Polymerase Chain Reaction to Monitor the Evolution of <i>Brucella melitensis</i> DNA Load During Therapy and Post-Therapy Follow-Up in Patients with Brucellosis

Elena Navarro, Juan Carlos Segura, María Jesús Castaño and Javier Solera

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 42, issue 9, pages 1266-1273
Published in print May 2006 | ISSN: 1058-4838
Published online May 2006 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/503035
Use of Real-Time Quantitative Polymerase Chain Reaction to Monitor the Evolution of Brucella melitensis DNA Load During Therapy and Post-Therapy Follow-Up in Patients with Brucellosis

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Background. We performed quantitative real-time polymerase chain reaction (Q-PCR) to monitor the evolution of Brucella melitensis DNA load from initial diagnosis through post-therapy follow-up in patients with brucellosis.

Methods. On the basis of real-time fluorometric quantification of PCR products, we used the ultra-rapid LightCycler system (Roche Diagnostics). We collected 180 peripheral blood samples from 18 patients with brucellosis. Analysis of bacterial DNA loads was performed for 2 groups: 11 patients who did not experience relapse and 7 patients who experienced relapse in the follow-up phase.

Results. Q-PCR was 100% specific for B. melitensis and showed an analytical sensitivity of 15 fg. Sensitivity of Q-PCR for both initial infections and relapses was 100%. There were no statistically significant differences between groups with respect to bacterial DNA load from initial diagnosis to the end of post-treatment follow-up (P > .05). Evolution of the bacterial DNA load throughout the treatment phase was similar among patients who relapsed and did not relapse. Despite positive response to treatment and a sharp decrease in bacterial DNA load after initiating therapy, the results of Q-PCR on finalizing treatment for 50% of the patients (7 from the relapse group and 2 from the nonrelapse group) were low-level positive. At the conclusion of follow-up, almost 40% of the patients (4 from the relapse group and 3 from the nonrelapse group), most of them asymptomatic, still maintained low bacterial DNA loads.

Conclusions. Using Q-PCR techniques, we consistently detected B. melitensis DNA in the blood samples of patients with brucellosis throughout treatment and follow-up, despite apparent recovery from infection. These findings may have diagnostic, pathogenic, and therapeutic implications.

Journal Article.  4260 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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