Bacterial spectrum and antibiotic resistance of urinary tract infections in patients treated for upper urinary tract calculi: a multicenter analysis

The purpose of this study is to collect information on the bacterial resistance to antibiotics of bacteria isolated from urine cultures of patients treated for upper urinary tract calculi. Data of patients with urinary tract infection and urolithiasis were retrospectively reviewed to collect information on age, gender, stone size, location, hydronephrosis, procedure of stone removal and antibiotic treatment, identification and susceptibility of pathogens, symptoms, and infectious complications. A total of 912 patients from 11 centers in 7 countries (Bulgaria, Greece, Italy, North Macedonia, Spain, and Turkey) were studied. Mean age was 54 ± 16 years and M/F ratio 322/590. Out of 946 microbial isolates, the most common were E. coli, Gram-positive, KES group (Klebsiella, Enterobacter, Serratia), Proteus spp., and P. aeruginosa. Carbapenems, piperacillin/tazobactam and amikacin showed low resistance rates to E. coli (2.5%, 7%, and 3.6%) and Proteus spp. (7.7%, 16%, and 7.4%), but higher rates were observed with Klebsiella spp., P. aeruginosa, and Gram-positive. Fosfomycin had resistance rates less than 10% to E. coli, 23% to KES group, and 19% to Gram-positive. Amoxicillin/clavulanate, cephalosporins, quinolones, and TMP/SMX showed high resistance rates to most bacterial strains. High rates of antibiotic resistance were observed in patients candidate to stone treatment from South-Eastern Europe. The empirical use of antibiotics with low resistance rates should be reserved to the most serious cases to avoid the increase of multidrug resistant bacteria. Basing on our results, carbapenems, piperacillin/tazobactam, and amikacin may be a possible option for empiric treatment of urinary stone patients showing systemic symptoms.