ANAEROBES - NEED FOR BETA-LACTAMASE INHIBITORS - IN-VITRO COMPARATIVE ACTIVITIES OF BETA-LACTAMASE INHIBITORS - BETA-LACTAMS COMBINATIONS

Beta-lactamase inhibitors (BLI) are able to overcome the increase of both antibiotic resistance and number of beta-lactamase- producing anaerobic species, to restore the previous activity of combined penicillins. Beta-lactamases of (i) nearly all Bacteroides fragilis group strains, (ii) at least 27 % and 42 % of Fusobacterium and Prevotella strains respectively (iii) some clostridia (with exception of C. clostridioforme) are susceptible to BLI. Their intrinsic antibiotic activities lead to a synergistic mechanism observed with non beta-lactamase producing anaerobes (Peptostreptococcus and Clostridium). The bactericidal effects of IBL- penicillins combinations are more frequent comparatively to penicillins used alone. Furthermore, IBL widen the spectra of IBL- penicillins combinations against aerobes that are associated to anaerobes during mixed infections. Three combinations (amoxycillin - clavulanic acid, ticarcillin - clavulanic acid and piperacillin - tazobactam) are highly effective against anaerobes. Further in vitro studies are needed to investigate other combinations, especially those with third generation cephalosporins.