Brucella melitensis DNA persistence in patients with chronic brucellosis

Abstract number: P1862

Castaño Aroca M.J., Navarro E., Segura J.C., Alfaro-Martínez E., Muñoz M.D., Martínez A.I., Lorente S., Solera J.

Objective: The aim of this study was to evaluate the evolution of bacterial load (B. melitensis DNA copies/ml sample) at baseline, during therapy and post-therapy follow-up in patients with chronic brucellosis.

Methods: For that purpose, we applied the Real-Time Quantitative Polymerase Chain reaction technique (QPCR) described by our team in a previous study [1]. We analysed 125 whole-blood and 122 serum samples from 10 patients using QPCR. Blood culture and serological tests (rose bengal stain, serum agglutination test (SAT) and Coombs test) were performed for each sample.

Results: The mean bacterial load (± SD) at baseline was 634±1403 copies/ml and 1738±4813 copies/ml for whole-blood and serum samples, respectively. Eight patients received therapy, doxycycline alone or in combination with rifampin or cotrimoxazol. The duration of therapy ranged from 90 to 430 days (mean 140 days). Therapy improved symptoms in all patients. During the first month of the treatment period the bacterial load declined to 19±39 copies/ml and 26±102 copies/ml for whole-blood and serum samples, respectively. Thereafter, there was an increase in load until the end of the therapy (1507±3787 copies/ml blood and 2669±7790 copies/ml serum).

In the first 3 months of the post-therapy follow-up, the bacterial load decreased again to 29±126 copies/ml and 222±882 copies/ml for whole-blood and serum samples, respectively. Only six patients were followed for more than 12 months. At the end of the follow-up period, the bacterial load amounted to 2917 ±11354 and 2549±8691 copies/ml in whole-blood and serum samples respectively for 33% (2/6) patients.

In 4 patients, although presenting clinical features of brucellosis, the samples collected were negative for all the classical serological procedures. However B. melitensis DNA was still detectable by QPCR.

Conclusion: In conclusion, we detect fluctuating B. melitensis DNA levels in patients with chronic brucellosis during the course of the disease despite positive clinical response to therapy. We found a subgroup of brucellosis patients showing negative serology but presenting detectable levels of B. melitensis DNA assed by QPCR.


1. Navarro et al, Clin Infect Dis 2006 May 1; 42(9):1266–73.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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