ABSTRACT
This chapter examines the evidence for, and against, the use of combination therapy in comparison with monotherapy for the treatment of infections caused by Gram-negative bacilli. Infections with resistant strains of Gram-negative bacilli are associated with prolonged hospitalization, higher costs, and increased mortality compared with infection by an antimicrobial-susceptible organism. Many species of Gram-negative bacilli that cause serious infections associated with high mortality in the healthcare setting are intrinsically resistant and/or easily acquire resistance to antimicrobials. Enterobacter species possess, as do many other Gram-negative bacilli, the chromosomal gene AmpC that encodes for the ampC beta-lactamase that hydrolyzes penicillins and cephalosporins. Pseudomonas infection is clinically indistinguishable from other forms of Gram-negative bacterial infection. Randomized controlled trials of Gram-negative infections have too few cases of P. aeruginosa to allow a statistically robust analysis of the relative value of combination versus monotherapy.
