[Microbiological approach to antibiotic therapy against multidrug-resistant bacteria].

Many severe infections that occur after gastrointestinal surgery are caused by multidrug-resistant bacteria such as methicillin-resistant staphylococcus aureus and Pseudomonas aeruginosa. (P. aeruginosa,) which has been isolated from such cases, is resistant to many beta-lactamantibiotics, including imipenem (IPM). IPM-resistant P. aeruginosa lacks the outer membrane proteins (Opr) D, OprD2, OprC, and OprE1, which together normally form an opening in the outer membrane. Therefore IPM cannot pass through the outer membrane. But it is also known that meropenem, caftazidime, and ciprofloxacin are not restricted by this effect and that they can easily pass through the outer membrane. Therefore if we can identify these genes by using the polymerase chain reaction, appropriate antibiotics can be swiftly administered without waiting for the results of drug sensitivity tests.