Agarose gel electrophoresis of PCR products amplified from reference strains of Leptospira serovars pomona, pyrogenes, icterohaemorrhagiae, tarassovi, wolffi, canicola and patoc using primers S3a and S3b (A) or S4a and S4b (B). Positive control: recombinant E. coli carrying the leptospiral fragment antigenically related to equine cornea (E. coli 3.12). Negative control: distilled water (without sample DNA). Lane MW contains DNA molecular size marker (100 bp DNA Ladder, Promega, Madison, Wl). Arrows indicate PCR products.