FIG. 6.

Nasal carriers of S. aureus are deficient in antimicrobial components that are restored by the addition of noncarrier secretions. (A) S. aureus, isolated from donor 24, was used as the target bacterium in a CFU microassay of nasal fluid from two noncarriers (donors 4 and 11) and two carriers (donors 20 and 24, gamma-irradiated fluid). While the noncarriers’ fluids were bacteriostatic or bactericidal, the carriers’ fluids did not inhibit bacterial growth. (B) The 1:1 mix of nasal secretions from an S. aureus carrier (donor 24) with fluid from a noncarrier (donor 4) is bactericidal to indigenous flora, while the mix of nasal secretions from an S. aureus carrier with heat-inactivated (boiling for 10 min) secretions from a noncarrier promoted the growth of indigenous bacteria.