TABLE 2.

Neutralization of culture supernatants of S. aureus isolates selected according to the presence of lukM/lukF′-PV genes and species of origin^a

Genotype of isolate and origin	No. of supernatants tested	No. completely inhibitedb
lukM positive
Cow	6	5
Goat	6	6
Ewe	6	5
lukM negative
Cow	12	11
Goat	6	6

^aSupernatants were adjusted by dilution with RPMI-GH to yield 2 TLCs, mixed with 2 or 4 NLCs of affinity-purified Ab (anti-LukM + anti-LukF), and incubated for 1 h before addition of bovine PMN. Spreading of PMN was visually (with an inverted microscope) assessed after 20 min at 37°C. Complete inhibition means that <2% PMN had flattened (not different from control PMN incubated with RPMI-GH without culture supernatant). The leukotoxic activity of all supernates (2 TLCs) was completely inhibited with 4 NLCs of affinity-purified Ab.

^bNLC = 2.