الفهرس 
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Abstract
Two hundred and eighty eight Gram negative clinical isolates, 64 of E coli, 80 of Klebsiella pneumonia, 64 of Proteus mirabilis and 80 of Pseudomonas aeruginosa with known identity and purity were tested for the ability to form biofilms by three in vitro screening procedures. The spectrophotometric procedure was the most sensitive procedure. The sensitivity of thirty two planktonic isolates (8 isolates of each group of organisms) to the tested fluoroquinolones and aminoglycosides antimicrobials, anti-inflammatory drugs and mucolytic agents revealed that all the isolates were resistant to gatifloxacin, gemifloxacin and ciprofloxacin and mostly resistant to gentamicin and levofloxacin while they varied in their resistance to amikacin and moxifloxacin. All isolates used were able to grow in the presence of all anti-inflammatory drugs used at concentrations below (300 ug/ml) and all tested mucolytics at concentrations below (1 mg/ml). The MICs of diclofenac and piroxicam for all the tested isolates were (500- 1200 fig/mi), ibuprofen (1000- 1200 ug/ml), indomethacin and ketorolac (800-1500 ug/ml) and salicylate (300- 1000 ug/ml). The MICs of ambroxol and N- acetylcysteine for all the tested isolates were (4 and 8 mg/ml), bromohexine (1-8 mg/ml) and that of carboxymethyl cysteine (8 and 16 mg/ml). Carboxymethyl cysteine has lowest effect on the growth of the tested isolates. The four isolates E. coli, E29; K. pneumonia, K53; Pr. mirabilis, Pr59 and Ps. aeruginosa, Ps22 were selected on the basis of high biofilm formation and high antibiotics resistance. The effect of different five selected antimicrobial agents (ciprofloxacin, gatifloxacin, levofloxacin, amikacin and gentamicin), anti- inflammatory drugs and mucolytics on the biofilm formation and eradication of the
four tested isolates were evaluated. Generally the eradicating effect of these agents on pre-formed biofilms is lower than the inhibitory effect. Supra inhibitory concentrations above 2MIC of all the five selected antimicrobials completely inhibited biofilm formation and eradicated the pre-formed biofilms by 66-100%.