PSEUDOMONAS-AERUGINOSA - ANTIBIOTIC SUSCE PTIBILITY PATTERNS

Bacteria belonging to the former genus Pseudomonas was recently modifi ed with the creation of several genus including Pseudomonas, Stenotrop homonas, Burkholderia, Ralstonia, Comamonas... The complexity of these novel genus is in fact masked by the predominance of a single bacteri al species, P. aeruginosa. Several French and foreign multicentric sur veys focused on the importance of Gram-negative and non fermenters bac illi in infections. In the last decade, acquired resistance has been c haracterized by the emergence of new enzymatic mechanisms, formerly un suspected, in several countries (among which Turkey and Japan): PER-1 (class A), OXA-11, OXA-14, and OXA-18 (class D), or IMP-1 (class B). T hese novel beta-lactamases mediate broad resistance to beta-lactams as third generation cephalosporins including ceftazidime, and even carba penems (IMP-1). Nevertheless, the expression level of resistance may b e unsuspected because highly variable. Unfortunately this bacterial sp ecies can cumulate other resistance mechanisms to aminoglycosides and fluoroquinolones (single mutation for the corresponding DNA gyrase gen e or gyrA or/and topo-isomerase IV gene named parC). Such acquired mul tiresistance was mainly related to hospital environment, to hospitaliz ation unit, and finally according to the patient's underlying diseases . This is related to selective pressure of antibiotics. In conclusion, choosing the adequate treatment is related to the identification of r esistance mechanisms, at least for some antibiotics such as beta-lacta ms, it is also related to complementary laboratory tests such as killi ng curves of antibiotic combination.