In vitro activity of piperacillin/tazobactam versus other broad-spectrum antibiotics against nosocomial gram-negative pathogens isolated from burn patients.

Burn patients are at high risk for nosocomial infections due to multiresistant bacteria, a large proportion of which are gram-negative. Tazobactam, a potent inhibitor of beta-lactamases, extends the spectrum of piperacillin to include many beta-lactamase producing bacteria. Consequently, it was decided to evaluate the activity of piperacillin/tazobactam in comparison with that of eight other antibiotics that are usually used for therapy against gram-negative bacterial infections in our burn unit. All consecutive gram-negative isolates from wounds, blood, respiratory tract, urine etc. from burn patients considered to be clinically significant were tested for their susceptibility to piperacillin/tazobactam, piperacillin, ceftazidime, cefotaxime, ceftriaxone, ciprofloxacin, gentamicin, amikacin and imipenem, determined by disk diffusion test. The zone inhibition was interpreted according to NCCLS recommendations. A total of 948 strains, isolated during the period of July, 1994 to September, 1995, made up of Pseudomonas spp (326), Acinetobacter spp (268) and Enterobacteriaceae (354), were tested. Overall piperacillin/tazobactam showed superior activity over the other antibiotics except for imipenem. Of the 948 isolates, 87% were susceptible to the combination, 56% to the three third generation cephalosporins, 69% to ciprofloxacin, 59% to the aminoglycosides and 97% to imipenem. Piperacillin/tazobactam showed strikingly superior activity over piperacillin alone against Acinetobacter spp followed by Enterobacteriaceae and the least against Pseudomonas. The emergence of Acinetobacter spp as a dominant gram-negative pathogen in burn patients and its high level of resistance against most of the antibiotics tested except piperacillin/tazobactam (87%) and imipenem (100%) were significant in light of the epidemiology of burn infections and treatment. This study suggests that piperacillin/tazobactam holds good promise against gram-negative infections in burn patients.