Epidemiology and antibiotic resistance in community-acquired lower urinary tract infections in the Milan area

Urinary tract infections (UTIs) are among the most common bacterial infectious diseases occurring in the community and healthcare setting. Most community-acquired urinary tract infections are usually treated empirically. The knowledge of antibiotic resistance patterns of the microorganisms causing UTI is essential for defining the empirical treatment. The aim of the present study is to investigate the prevalence and the resistance patterns of bacterial species isolated from lower urinary tract infections, in a large population of Milan area. A retrospective analysis of the isolates obtained from urine samples received at the microbiology laboratory of Centro Diagnostico Italiano of Milan was performed from January 2019 to December 2019. Urine samples were plated on differential medium by automated inoculation system. Identification and antibiotic susceptibility testing were performed using the Phoenix 100™ system. All results were interpreted according to the European Committee on Antimicrobial Susceptibility Testing breakpoints. During a 12-month period a total of the 51,980 urine samples have been processed and 21,4% (11.148) were found to be positive (bacterial count ≥10⁵CFU/mL). Overall Escherichia coli was the most common Gram-negative bacteria of all isolates (72%), followed by Klebsiella pneumoniae (10.8%) and Proteus mirabilis (3.3%). Susceptibility of E. coli to oral antimicrobial agents was demonstrated to be as follows: fosfomycin (97%), trimethoprim/sulfamethoxazole (76%), ciprofloxacin (89%), ampicillin (51%) and amoxicillin/clavulanate (77%). The present study point-out the common antibiotic resistance trend of uropathogens in this area. Our results will help in the formulation of antibiotic policy and determination of empirical treatment of urinary tract infection.