ALTERATIONS IN PSEUDOMONAS-AERUGINOSA EXOPRODUCTS BY SUB-MICS OF SOMEANTIBIOTICS

Aminoglycoside antibiotics, most effective at the level of 1/4 of the MIC, suppressed all the tested activities of P. aeruginosa, except cyt otoxicity. Proteinase activity was decreased to 60 % (gentamicin) and 63 % (streptomycin), permeability was reduced to 61 % (gentamicin) and 73 % (streptomycin), phospholipase C to 13 % (gentamicin) and 51 % (s treptomycin) of the control values. Subinhibitory concentrations of be ta-lactams inhibited only phospholipase C activity to 89 % (ticarcilli n) and 64 % (cefotaxim) of the control values. These antibiotics did n ot suppress the cytotoxic activity and increased protease activity up to 155 % (ticarcillin) and 192 % (cefotaxim) as well as permeability u p to 121 % (ticarcillin) and 154 % (cefotaxim) of the control values.