Current concepts on antibiotic resistance and therapeutic problems raised by Pseudomonas aeruginosa

Resistance: Pseudomonas aeruginosa is characterized by its low intrinsic su sceptibility to many antibiotics and its capacity to acquire additional res istance mechanisms to usually active drugs. Some beta-lactam resistance mec hanisms are well known (penicillinase production, cephalosporinase overprod uction) and others have been recently identified, such as active efflux sys tems, which confer coresistance to quinolones, and new beta-lactamases whic h are limited to a few countries (extended-spectrum beta-lactamases, imipen emase). Ceftazidime remains the most active beta-lactam agent. Active drugs: Among aminoglycosides, amikacin and isepamicin are the most f requently active drugs. The use of fluoroquinolones is limited by a high in cidence of acquired resistance. The percentage of resistant strains is high ly variable according to countries, hospitals and wards. Clinical practice: Therapy, usually based on a beta-lactam-aminoglycoside c ombination, will be empirical at first, according to local epidemiological factors, site of infection and previously administered antibiotics, then re -evaluated according to susceptibility results.