Biofilm formation and virulence of uropathogenic Escherichia coli in urine after consumption of cranberry-lingonberry juice.

Cranberry-lingonberry juice (CLJ) was effective in preventing urinary tract infections (UTIs) in our earlier randomized clinical trial. We aimed to test whether consumption of CLJ at a similar dose to earlier reduces the biofilm formation and virulence of uropathogenic Escherichia coli in urine. Twenty healthy women drank 100 ml of CLJ daily for two weeks. Urine samples were obtained 2-4 hours after the last dose. Control samples were taken after a one-week period without berry consumption. Biofilm formation of 20 E. coli strains was measured at 72 hours by the polystyrene microtitre plate method. Quantitative real-time PCR analyses were performed for selected genes. Four of the 20 clinical strains produced more biofilm in urine after CLJ consumption (P < 0.05) and one produced less. Expression levels of the pga, cpxA, fimA and papF genes did not differ between bacteria grown in control urine and urine obtained after CLJ consumption, except for pga gene expression, which was reduced in one strain after CLJ (P = 0.04). It appears that the effect of CLJ in preventing UTIs is not explained by mechanisms that reduce biofilm formation or the expression of selected virulence genes of Escherichia coli in urine.

Biofilm formation by Escherichia coli isolated from patients with urinary tract infections.

AIMS: The significance of biofilm formation for the clinical picture of urinary tract infections (UTI) is largely unknown. We wanted to find out whether Escherichia coli (E. coli) strains isolated from UTI patients differ in their ability to form biofilms and whether this ability is associated with the clinical presentation of UTI. MATERIAL AND METHODS: 70 E. coli strains were isolated from patients with cystitis (43 strains), pyelonephritis (11 strains) and urosepsis (16 strains) and biofilm formation was assessed on polystyrene microtiter plates by measuring the optical density (OD) of the attached material after 72 h of incubation and crystal violet staining of the bacteria. The formation of organized biofilm structures and the viability of the attached bacteria were verified by scanning electron microscopy and confocal scanning laser microscopy in a subsample of 22 strains. RESULTS: 31% of the E. coli strains formed a biofilm. The strains isolated from patients with pyelonephritis had higher ODs than those from patients with cystitis (difference of the means 0.19, 95% confidence limits (CL) 0.06 - 0.32, p = 0.02). The E. coli strains susceptible to antibiotics had higher ODs than the resistant strains (difference of the means 0.21, 95% CL 0.03 - 0.27, p = 0.016). CONCLUSIONS: The ability of bacteria to persist and grow in a biofilm seems to be one of the important factors in both the resistance to antibiotics and the severity of urinary tract inflammation.