During recent years development of resistance in bacterial species as
Enterobacter cloacae or Pseudomonas aeruginosa after therapy with newe
r beta-lactams or fluoroquinolones has been well documented. A murine
model of peritonitis has been developed to study this emergence of res
istance due to the selection of resistant variants under various antib
iotic regimens and to confirm the prophylactic role of antibiotic comb
inations to prevent therapeutic failure,