Interlaboratory agreement of pulsed-field gel electrophoresis identification of Leptospira serovars

Leptospirosis may be caused by > 250 Leptospira serovars. Serovar classification is a complex task that most laboratories cannot perform. We assessed the interlaboratory reproducibility of a pulsed-field gel electrophoresis (PFGE) identification technique developed by the Centers for Disease Control and Prevention (CDC). Blinded exchange of 93 Leptospiraceae strains occurred between San Antonio Military Medical Center (SAMMC) and the CDC. PFGE was performed and gel images were analyzed and compared with patterns present in each laboratory's database (CDC database: > 800 strain patterns; SAMMC database: > 300 strain patterns). Overall, 93.7% (74 of 79) of strains present in each receiving laboratory's database were correctly identified. Five isolates were misidentified, and two isolates did not match serovar PFGE patterns in the receiving laboratory's database. Patterns for these seven isolates were identical between laboratories; four serovars represented misidentified reference strains. The PFGE methodology studied showed excellent interlaboratory reproducibility, enabling standardization and data sharing between laboratories.