Background: Growing resistance to antibiotics among both community-acquired and hospital pathogens is making the treatment of most infections increasingly diffi cult. Therefore, the aim of our multi-center study was to determine the antimicrobial susceptibility of the most frequent aerobic microorganisms isolated from children with intraabdominal infections.
Material/Methods: Bacterial pathogens were isolated from 256 consecutive patients treated in fi ve large specialized hospitals in Poland from January 2001 to February 2002. Minimal inhibitory concentrations (MICs) of piperacillin, piperacillin-tazobactam, cefotaxime, ceftazidime and cefepime were determined by Etests. The production of extended spectrum b-lactamases (ESBL) was detected by a double-disk test.
Results: Piperacillin-tazobactam was the most active agent against Enterobacteriaceae and Pseudomonas aeruginosa,inhibiting 92% and 78% of isolates respectively. Susceptibility of Enterobacteriaceae to cefotaxime,ceftazidime and cefepime was 73%, 73% and 87% respectively, and susceptibility of P. aeruginosa to both ceftazidime and cefepime was 76%. Extended-spectrum b-lactamases were detected in 56% Klebsiella sp. and 11.5% E. coli, but the vast majority of these isolates remained susceptible to piperacillin-tazobactam (MIC90=12 mg/L and MIC90=1 mg/L, respectively).
Conclusions: Piperacillin/tazobactam remains a valuable therapeutic option in Polish pediatric patients with intraabdominal infections, due to its good activity against ESbL-producing organisms and P.aeruginosa.

Keywords: beta-Lactamases - analysis, Pseudomonas aeruginosa - isolation & purification, Poland, Piperacillin - pharmacology, Penicillanic Acid - pharmacology, Microbial Sensitivity Tests, Klebsiella - isolation & purification, Infant, Newborn, Abdomen, Escherichia coli - isolation & purification, Enterobacteriaceae - isolation & purification, Drug Resistance, Bacterial, Child, Preschool, Child, Bacterial Infections - microbiology, Bacteria, Aerobic - isolation & purification, Adolescent