INVITRO STUDY OF SUSCEPTIBILITY TO ANTIBIOTICS OF 213 PSEUDOMONAS-AERUGINOSA STRAINS ISOLATED IN AN INTENSIVE-CARE UNIT OF SFAX HOSPITAL (TUNISIA)

Susceptibility of 213 strains of Pseudomonas aeruginosa isolated in a general intensive care un t during two years 1989 and 1990 was tested againts 11 antibiotics : ticarcillin (TIC), ticarcillin + clavulanic acid (TCC), cefsulodine (CFS), ceftazidime (CAZ), imipenem (IMP) gentamicin (G), tobramycin (TOB), amikacin (AN), ofloxacin (OFX), norfloxacin (NOR) and ciprofloxacin (CIP). Antibiotic susceptibility testing was performed by disk agar diffusion test and by measuring minimum inhibitory concentrations (MIC(S) using test agar dilution. 65 % of strains were isolated from respiratory tract infections. Resistance frequency of this antibiotics was: TIC : 41,3 %, TCC 33,8 %. CFS : 26,5 %, CAZ : 23,2 %, IMP 11,6 %, G : 72,5 %, TOB : 46,5 %, AN : 12,6 %, OFX : 29,3 %, NOR : 21,3 %, CIP : 17,6 %. We observed by measuring CMI that imipenem and amikacin were the most active antibiotics. From 1989 et 1990, the increase number of strains resistant to imipenem, amikacin and fluoroquinolones could be explained by massive use of those antibiotics. Besides their heigh level of resistance, strains isolated in intensive care unit ere characterized by their multiresistance : 24 strains were resistant to 8 of 11 antibiotics tested ; four of them showed resistance to all antibiotics the multiresistance of those strains suggest strongly that decreased permeability could be the cause.