Effects of Extracellular Slime Produced by Staphylococcus epidermidis on Oxidative Responses of Rabbit Alveolar Macrophages

Abstract

Bacterial slime produced in muss cultures of the RP 12 strain of Staphylococcus epidermidis was extracted with 4 M guanidine-HCl plus 0.05 M sodium acetate and 0.55% CHAPS, concentrated, dialyzed, und subjected to separation on DEAE sephacel columns. Three fractions, I-2A, I-2B, und I-4, were eluted with linear gradients of NaCl. Fractions I-2A and I-2B were alcian blue positive, whereas I-4 was alcian blue negative but the most electronegative The crude polysaccharide fraction and the three purified fraction were incubated individually for 2.5 or 20 h with normal rabbit alveolar macrophages (AM) to determine their effect on a subsequent PMA-induced oxidative burst. The crude fraction (50–200 µg/mL) und I-2B (50–200 µg/mL) primed the AM to give approximately a threefold increase in the PMA-induced burst after 2.5 h incubation. In contrast, a 20-h incubation resulted in a 30–40% incubation of the PMA-induced burst Mith AM incubated with the same concentrations of the crude, I-2A, or I-2B fractions. Fraction I-4 had no detectable effect. The fractions also were tested to determine if they could elicit an oxidative burst in BCG-immune AM. None of the fractions (up to 500 µg/mL) elicited a significant oxidative burst even though BCG-immune. AM yielded a PMA-induced burst 100 times that observed with normal resident AM. These data suggest that slime from S. epidermidis can impair the PMA-induced oxidative burst of normal AM during a 20-h incubation period and could explain in part why host defenses are compromised by slime-producing S. epidermidis

Key Words:

• Staphylococcus epidermidis
• alveolar macrophages
• capsular slime
• oxidative response
• PMA
• zymosan