New N-substituted 7-aminocephalosporanic acid derivatives as potential agents against Streptococcus pneumoniae. Synthesis and in vitro activity

Synthesis and antimicrobial activity of new 7β-(benzo[a]dihydrocarbazolyloxyacetyl)-substituted cephalosporins

Selected 7beta-(benzo[a]dihydrocarbazolyloxyacetyl)-substituted cephalosporins (1a-e) were synthesised and tested for their antimicrobial activity against Gram-positive and Gram-negative clinical pathogens. All compounds synthesised (1a-e) showed an in vitro antimicrobial activity similar to that of ceftriaxone and cefpirome against the Gram-positive bacteria, and superior to that of penicillin and cefaclor against pen-R Staphylococcus aureus species. Like all beta-lactam agents, compounds 1a-e were in an inactive Minimum Inhibitory Concentration (MIC > 32 microg/ml) against methicillin-resistant S. aureus species. Furthermore, as expected, no cross-resistance was observed against the erythromycin-resistant Staphylococcus pyogenes strain. Finally, it is worth underlining that compounds 1a and 1e showed a similar activity to that of ceftriaxone and superior to cefaclor against penicillin-resistant Streptococcus pneumoniae isolates, a key respiratory tract infection (RTI) causing pathogen difficult to treat with currently marketed antibiotics.