In vitro antimicrobial activity of piperacillin/tazobactam in comparison with other broad-spectrum ß-Lactams

ABSTRACT

Combinig tazobactam, a ß-lactamase inhibitor, with the ureidopenicillin, piperacillin, successfully restores the activity of piperacillin against ß-lactamase producing bacteria. Thus, piperacillin/tazobactam is highly active against most clinically important species of Gram-negative and Gram-positive bacteria, including anaerobes. We evaluated the in vitro activity of piperacillin/tazobactam against clinical isolates from a tertiary university hospital located in Säo Paulo, Brazil. Its activity was compared to the ticarcillin/ clavulanic acid, ampicillin/sulbactam, ceftazidimeceftriaxone, cefotaxime, cefoxitin, aztreonam and imipenem against 820 isolates (608 Gram-negative and 212 Gram-positive) collected from hospitalized patients in 1999. The most frequent species tested were Pseudomonas aeruginosa (168/20 por cento), Escherichia coli (139/17 por cento), Acinetobacter spp (131/16 porcento), and Staphylococcus aureus (76/9 por cento). Of the isolates studied, 30 por cento were from the blodstream, 16 porcento from the lower respiratory tract, and 11 por cento from surgical wounds or soft tissue. The isolates were susceptibility tested by the broth microdilution method according to NCCLS procedures. The isolates tested were highly resistant to most antimicrobial agents evaluated. Imipenem resistance was not verified among Enterobacteriaceae, and piperacillin/tazobactam was the second most active ß-lactam against this group of bacteria (80.0 por cento susceptibility). Extended-spectrum ß-lactamase production was very high among E. coli (approximately 20 por cento) and KLebsiella pneumoniae (approximately 40 por cento). Imipenem was uniformly active against these species (100 por cento susceptibility) and piperacillin/tazobactam was the second most active compound inhibiting 84.4 por cento of isolates. Pseudomonas aeruginosa was highly resistant to all ß-lactams evaluated and piperacillin/tazobactam was the most active compound against this species. Our results demonstrate an extremely high level of antimicrobial resistance in the hospital evaluated, especially among non-enteric Gram-negative bacilli. Due to this high level of resistence, piperacillin/tazobactam represents an important ciontribution to the treatment of nosocomial infections...