Effect of nutrient depletion on sensitivity of Pseudomonas cepacia to phagocytosis and serum bactericidal activity at different temperatures

Abstract

Pseudomonas cepacia grown under different specific nutrient depletions in batch culture showed varying degrees of sensitivity to engulfment and killing by human polymorphonuclear leukocytes (PMN) and to killing by human serum. Resistance to killing by the combined action of PMN and serum in while blood was found to increase in the following order of depletions: glucose less than iron less than sulphate less than phosphate or ammonium less than magnesium. There was also an increase in resistance to killing by whole blood with decrease in temperature, except that carbon-depleted cells remained very sensitive irrespective of temperature. Cells in the exponential phase of growth also showed a consistent increase in resistance as the temperature was decreased. Similar, but smaller effects were observed with oxygen-depleted cells. The increase in killing by whole blood as the phagocytic temperature was raised correlated with an increase in the number of bacteria ingested per PMN. A pattern of serum sensitivity was observed with cells grown under different nutrient depletions similar to that for whole blood. But in all cases whole blood was 6 to 10 times more effective than serum alone in killing the cells at 37 degrees C.