202060 Evaluation of variable number tandem repeat genotyping of Leptospira as a tool for epidemiological investigations of leptospirosis

Monday, November 9, 2009: 9:15 AM

Barbara Szonyi, DVM , Population Medicine and Diagnostic Sciences, Cornell University, College of Veterinary Medicine, Ithaca, NY
Adriano Queiroz Silva , Fundação Oswaldo Cruz (Fiocruz), Centro de Pesquisas Gonçalo Moniz, Salvador, Brazil
Rudy A. Hartskeerl , Royal Tropical Institute, Amsterdam, WHO/FAO/OIE and National Collaborating Centre for Reference and Research on Leptospirosis, Amsterdam, Netherlands
Mitermayer G. Reis, MD , Fundação Oswaldo Cruz (Fiocruz), Centro de Pesquisas Gonçalo Moniz, Salvador, Brazil
Alan J. A. McBride , Fundação Oswaldo Cruz (Fiocruz), Centro de Pesquisas Gonçalo Moniz, Salvador, Brazil
Mathieu Picardeau, PhD , Laboratoire des Spirochetes, Institut Pasteur, Paris, France
Albert I. Ko, MD , Division of International Medicine and Infectious Diseases, Weill Medical College of Cornell University, New York, NY
Introduction: Leptospirosis is a zoonosis maintained by chronic renal infection of animals. The basic taxon is the serovar, however serotyping is limited to few reference laboratories. Our objective was to evaluate two genotyping methods based on Variable Number Tandem Repeat (VNTR) sequences, as tools for quality control in reference laboratories, and for identifying serovars in epidemiologic investigations.

Methods: We used two VNTR protocols (VNTR1 and VNTR2) to genotype 24 L. interrogans strains representing 20 serovars from a WHO reference collection, and 25 isolates from surveillance in Brazil and Columbia (11 human and 10 rat serovar Copenhageni isolates; 2 dog and 1 human serogroup Canicola isolates; 1 human serogroup Djasiman isolate). Sensitivity analysis was performed at the serovar level based on UPGMA trees.

Results: Overall discriminatory power of VNTR1 and VNTR2 was 62% and 92%. We found discrepancies between our and published results for 2 strains. Sensitivity analysis found that for the 95% similarity threshold, VNTR1 had a higher sensitivity than VNTR2 (98% vs. 90%) but a lower specificity (97% vs. 100%). No associations were found between genotypes and temporal or spatial clustering of cases and disease severity.

Discussion: This was the first study to evaluate two VNTR methods on the same set of reference and field strains. We recommend that either method should be implemented as a quality control measure for reference strains used in serologic testing. Although VNTR may be used to identify serovar for L. interrogans isolates, it lacks sufficient discriminatory power for molecular epidemiology applications.

Learning Objectives:
Describe the utility of VNTR in a leptospirosis outbreak Explain why reference strain collections are essential for understanding the epidemiology of leptospirosis Evaluate the use of VNTR in quality control of Leptospira reference collections Compare the performance of the two VNTR methods in Leptospira serovar typing

Keywords: International Public Health, Epidemiology

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: DVM, PhD candidate; Fogarty International Clinical Research Scholar
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.