A 36-year-old woman recently treated for leukemia is admitted to hospital with malaise, chills and high fever. Gram stain of blood reveals the presence of gramnegative bacilli. The initial diagnosis is bacteremia and parenteral antibiotics are indicated. The records of the patient reveal that she had a severe uriticarial risk, hypotension, and respiratory difficulty following oral penicillin V about 6 months ago. The most appropriate drug regimen for empiric treatment is (a) Ampicillin plus sulbactam (b) Aztreonam (c) Cefazolin (d) Imipenem plus cilastatin (e) Ticarcillin plus clavulanic acid