1131 The Effect of Pseudomonas aeruginosa Mucopolysacsharide on Neutrophil Function

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Pseudomonas aeruginosa is a bacterial species frequently isolated from the lungs of cystic fibrosis (CF) patients. We used a recently described ‘phagocytosis assay to examine the interaction between P. aerug and human neutrophils (PMN). Staphyloeoccus aureus, also frequently isolated from the CF lung, was used as a control. A variety of assays were used to examine the effect on PMN of a mucopolysaccharide (slime) produced by P. aerug. A “surface phagocytosis” assay was used to determine the uptake of 3H-labeled S. aureus and P. aerug by PMN. The bacteria were washed vigorously or left untreated after 18 hr. growth so that the effect of slime could be determined when PMN were added. The overall phagocytosis of P. aerug was significantly less than S. aureus. Opsonization (10% pooled (human sera) effected a 25% increase in the uptake of S. aureus at 15 and 60 min. The uptake of opsonized P. aerug was increased by 150% at 15 min. but was reduced to the level of increase seen in S. aureus at 60 min. Only A moderate decrease in chemotaxis was observed when PMN were treated with crude or purified slime. No difference was seen in chemiluminescence, degranulation, O2− production, or LDH release when treated PMN were compared to untreated PMN. These data together with electron and light microscopy suggest that slime and the absence of opsonin in the aveoli may be detrimental to PMN interaction with P. aerug. The effect of slime on PMN function appears to be minor.