INVITRO STUDY OF SUSCEPTIBILITY TO ANTIBI OTICS 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 a cid (TCC), cefsulodine (CFS), ceftazidime (CAZ), imipenem (IMP) gentam icin (G), tobramycin (TOB), amikacin (AN), ofloxacin (OFX), norfloxaci n (NOR) and ciprofloxacin (CIP). Antibiotic susceptibility testing was performed by disk agar diffusion test and by measuring minimum inhibi tory 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 imip enem and amikacin were the most active antibiotics. From 1989 et 1990, the increase number of strains resistant to imipenem, amikacin and fl uoroquinolones could be explained by massive use of those antibiotics. Besides their heigh level of resistance, strains isolated in intensiv e care unit ere characterized by their multiresistance : 24 strains we re resistant to 8 of 11 antibiotics tested ; four of them showed resis tance to all antibiotics the multiresistance of those strains suggest strongly that decreased permeability could be the cause.