Objective The etiology of urinary tract infection (UTI) is dominated by gram negative bacilli. Antibiotic susceptibility of the implicated germs can change in time, with different factors being involved in this process. Establishing antibiotic susceptibility for gram negative bacteria; emphasizing their place in the etiology of UTI; monitoring the susceptibility to obtain useful information for the antibacterial therapy.

Methods 917 cases of uncomplicated UTI admitted in our clinic between 2000–2007: 720 – E coli, 95 – Proteus, 70 – Klebsiella, 19 – Enterobacter, 13 – Pseudomonas. The antibiotic susceptibility was tested by common diffusion method. We have tested the susceptibility for Ampicillin, Amoxicillin + Clavulanic Acid (Au), Cephalosporins, Gentamicin, Trimethoprim-Sulfamethoxazole (Bi), Nalidixic Acid (Nx)—the most used drugs in children’s UTI.

Results The testing performed for antibiotic susceptibility showed the following: E coli proved a high sensitivity (>80%) to Cephalosporins, Nx, Gentamicin, Bi, and significant resistance (>60%) to Ampicillin, Au; Proteus: high sensitivity (>90%) to Bi, Nx, and significant resistance (>70%) to Ampicillin, Au, Gentamicin; Klebsiella: significant resistance (>70%) to Au, Cephalosporins, Gentamicin, Bi; Enterobacter and Pseudomonas (inconstant tested): 100% sensitivity to Nx, respectively Cephalosporins, Gentamicin.

Conclusions The susceptibility remained constant for the majority of antibiotics, but we have noticed a significant increase of sensitivity for all tested germs in the case of Bi (25% up to 90%), and a significant decrease for Au (80% down to 30%).