Cranberry Juice Inhibit Bacterial Pathogens Associated To Urinary Tract Infection

Aims: To evaluate in vitro antimicrobial potential of 35% reconstituted juice (RJCr) against bacterial pathogen related to urinary tract infections (UTIs).

Place and Duration of Study: Food and Biotechnology Laboratory, Brazil.

Study Design: Cranberry juice for in vitro evaluation by agar well diffusion assay and direct in vitro assay.

Methodology: Cranberry fruits were used to produce RJCr pH 3. Five bacterial pathogens were tested: Escherichia coli ATCC 35218, Klebsiella pneumoniae ATCC 700603, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 27853 and Proteus mirabilis, an isolate of clinical origin. Two methods were used to assess antimicrobial activity. In the agar well diffusion (AWD) assay, each pathogen was inoculated on agar plates and the juice was added in wells drilled on this agar by incubation at 35°C/24hours. Then, the diameter of the inhibition zone was measured (mm). Based on dilutions methods, a direct in vitro assay (DA) was also performed. In test tubes 4.5 ml of RJCr was added an inoculum of each pathogen for a final concentration of >106 and <107 CFU.mL-1.The performance was evaluated based on CFU.mL-1 resulting on agar plates (35°C / 24 hours).

Results: By using AWD the RJCr inhibited E. coli and the average size of the diameter of inhibition halo reached 23.3 mm, that is, greater when compared to the group with Chloramphenicol (11.6 mm). However, for the other strains the RJCr was not inhibiting with this method. But, by using DA, the action of RJCr was inhibitory for all strains here tested, with an average of 5.1 Log cycles of reduction in relation to initial concentration. For E. coli and P. mirabilis the reduction reached six Log cycles.

Conclusion: The inhibitory effect of RJCr was evident to E. coli by both types of inhibitory methods, a relevant result since it is the most recurrent microorganism in UTIs. Cranberry juice was stronger in inhibiting E. coli than antibiotic chloramphenicol as observed by AWD. Thus, the study reinforces the importance of Cranberry, even in the form of juice, in inhibiting E. coli.