Characterization of Panton-Valentine leukocidin (PVL)–positive Staphylococcus aureus strains in the Bronx, New York. A, Pulsed-field gel electrophoresis patterns of PVL-positive methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains. Patterns I, III, and V represent USA300 and USA400 and constitute the majority of patterns found (>90%), whereas 10 different patterns were detected in PVL-positive MSSA strains. B, Varying levels of PVL toxin production by 5 MRSA clones and 10 MSSA clones. C, spa and multilocus sequence typing (MLST) of 5 MRSA and 10 MSSA clones. Only the high-PVL-producing MRSA clone (strain 2) has different spa and MLST types, but 8 different spa types were found in MSSA clones.