A significant increase of resistance in out-of-hospital and hospital pathogens to antimicrobials is being lately observed all over the world, including the Russian Federation. Within 2005-2007 clinical strains of potential producers of extended spectrum beta-lactamases were isolated in diverse medical centres. The isolates suspected to produce extended spectrum beta-lactamases by the criteria of CLSI (Clinical and Laboratory Standards Institute, USA) were included into the test with the polymerase chain reaction and sequence for detecting the genes of beta-lactamases TEM, SHV, CTX, OXA and MBL by the original primers. The total of 99 isolates of gramnegative bacteria suspected to produce extended spectrum beta-lactamases by the findings of the local laboratories were tested at the National Research Centre of Antibiotics: 44 strains of the family Enterobacteriaceae, 38 strains of P. aeruginosa and 17 strains of A. baumanii. The Enterobacteriaceae isolates were mainly multiple resistant (29.5%) carrying simultaneously the genes of 4 groups of beta-lactamases (TEM, SHV, CTX and OXA). The investigation revealed 1 strain of E. coli having the gene of metal-beta-lactamase VIM. The strains of A. baumanii mainly contained the genes of beta-lactamases OXA (23%). Group CTX-M1 prevailed (95%) among the detected genes CTX, 2 strains of group CTX-M9 were also isolated. The mechanisms of antibiotic resistance were not elucidated in 35 strains of P. aeruginosa (92%), gene TEM being detected only in 1 strain and gene MBL (metal-beta-lactamase) being detected in 2 strains. The prevalence of multiple resistant strains carrying the beta-lactamase genes OXA and TEM in the medical centres was shown. The most negative fact was isolation of the E. coli strain producing metal-beta-lactamase.