Role of Urinary Cathelicidin LL-37 and Human β-Defensin 1 in Uncomplicated Escherichia coli Urinary Tract Infections
ABSTRACTCathelicidin (LL-37) and human β-defensin 1 (hBD-1) are important components of the innate defense in the urinary tract. The aim of this study was to characterize whether these peptides are important for developing uncomplicatedEscherichia coliurinary tract infections (UTIs). This was investigated by comparing urinary peptide levels of UTI patients during and after infection to those of controls, as well as characterizing the fecal flora of participants with respect to susceptibility to LL-37 andin vivovirulence. Forty-seven UTI patients and 50 controls who had never had a UTI were included. Participants were otherwise healthy, premenopausal, adult women. LL-37 MIC levels were compared for fecalE. coliclones from patients and controls and were also compared based on phylotypes (A, B1, B2, and D).In vivovirulence was investigated in the murine UTI model by use of selected fecal isolates from patients and controls. On average, UTI patients had significantly more LL-37 in urine during infection than postinfection, and patient LL-37 levels postinfection were significantly lower than those of controls. hBD-1 showed similar urine levels for UTI patients and controls. FecalE. coliisolates from controls had higher LL-37 susceptibility than fecal and UTIE. coliisolates from UTI patients.In vivostudies showed a high level of virulence of fecalE. coliisolates from both patients and controls and showed no difference in virulence correlated with the LL-37 MIC level. The results indicate that the concentration of LL-37 in the urinary tract and low susceptibility to LL-37 may increase the likelihood of UTI in a complex interplay between host and pathogen attributes.