Revival of older antibiotics for the therapy of urinary tract infections: old, but gold Part 1: Antimicrobial susceptibility of extended-spectrum β-lactamase-producing and AmpC β-lactamase-producing Escherichia coli isolates

The most prevalent causative agent of urinary tract infections (UTIs) is uropathogenic Escherichia coli, corresponding to 50–90% of uncomplicated, around 30–70% of nosocomial UTIs. There has been renewed interest toward the clinical value of older, nonβ-lactam antibiotics (including fosfomycin, nitrofurantoin, trimethoprim/sulfamethoxazole) used for the therapy UTIs caused by drug resistant bacteria, including AmpC-producing or an extended-spectrum β-lactamases (ESBL)-producing Gram-negative strains. The aim of our study was to determine the resistance levels of AmpC-producing or ESBL-producing E. coli strains, against the relevant ancillary antibiotics that may be used in the treatment of UTIs. Isolates were collected from the time period between 1 January 2013 and 31 December 2017 from patients with uncomplicated and complicated UTIs treated at the Albert Szent-Györgyi Clinical Center (Szeged, Hungary). Antibiotic susceptibility testing was carried out using the Kirby-Bauer method. Out of the 10 837 isolates, n = 2010 (18.5%; 402 ± 43 isolates/year) E. coli isolates were either AmpC-producers or ESBL-producers, whereas n = 1398 (12.8%; 280 ± 12 isolates/year) produced the two groups of β-lactamases simultaneously. The highest levels of coresistance overall was seen for ciprofloxacin (68.2%), followed by trimethoprim-sulfamethoxazole (58.6%), whereas resistance levels were lower in regards to gentamicin (39.0%), fosfomycin (20.3%) and considerably lower for nitrofurantoin (11.1%). Our analysis of urine-specific AmpC-producing or ESBL-producing E. coli isolates is a useful addition to the literature, as clinicians may rely on this data for empiric antibiotic selection for UTI.