Effect of oral cranberry extract (standardized proanthocyanidin-A) in patients with recurrent UTI by pathogenic E. coli: a randomized placebo-controlled clinical research study



To evaluate the effect of cranberry extract (PAC-A ~ proanthocyanidin-A) on the in vitro bacterial properties of uropathogenic (E. coli) and its efficacy/tolerability in patients with subclinical or uncomplicated recurrent UTI (r-UTI).

Materials and methods

After obtaining clearance from the ethics committee and administering a written informed consent, 72 patients with r-UTI were enrolled as per protocol (November 2011 to March 2013) in this prospective study, to randomly receive (PAC-A: group I, 36) or (placebo: group II, 36), for 12 weeks. Any change/reduction in the incidence of r-UTI at 12 weeks was construed to be the primary endpoint of this study.


After 12 weeks, bacterial adhesion scoring decreased (0.28)/(2.14) in group I/II (p < 0.001); 32/36 (88.8 %) and 2/36 (5.5 %) in groups I and II, respectively, turned MRHA negative (p < 0.001); biofilm (p < 0.01) and bacterial growth (p < 0.001) decreased in group I; microscopic pyuria score was 0.36/2.0 in group I/II (p < 0.001); r-UTI decreased to 33.33 versus 88.89 % in group I/II (p < 0.001); mean subjective dysuria score was 0.19 versus 1.47 in group I/II (p < 0.001), while mean urine pH was 5.88 versus 6.30 in group I/II (p < 0.001). No in vitro antibacterial activity of cranberry could be demonstrated, and no adverse events were noted.


The overall efficacy and tolerability of standardized cranberry extract containing (PAC-A) as a food supplement were superior to placebo in terms of reduced bacterial adhesion; bacterial MRHA negativity; urine pH reduction; and in preventing r-UTI (dysuria, bacteriuria and pyuria). Larger randomized controlled trials are needed to elucidate the precise role, exact dose and optimal duration of PAC-A therapy in patients at risk of r-UTI.

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Fig. 1





Recurrent urinary tract infection


Mannose sensitive


Mannose resistant


Mannose-resistant hemagglutination assay


Microscopic pyuria score


Mean bacterial adhesion


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The authors certify that the above study was conducted entirely from within regular running expenditure available to the government institution and no extra institutional financial grant or funding was availed of in any manner whatsoever.

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Corresponding author

Correspondence to Iqbal Singh.

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The authors further declare that they have nothing to disclose and have no direct or indirect commercial and/or financial incentive associated with this research.

Ethical statement

The authors declare that the above manuscript is in compliance with ethical standards for research in human participants and the authors have no potential sources of conflict of interest associated with its publication.

Informed consent

The authors also certify that informed consent was obtained from all the human participants in this study as per its protocol registered with the Clinical Trials Registry of India.

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Singh, I., Gautam, L.K. & Kaur, I.R. Effect of oral cranberry extract (standardized proanthocyanidin-A) in patients with recurrent UTI by pathogenic E. coli: a randomized placebo-controlled clinical research study. Int Urol Nephrol 48, 1379–1386 (2016). https://doi.org/10.1007/s11255-016-1342-8

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  • Cranberry
  • Vaccinium macrocarpon
  • Proanthocyanidin-A
  • Lactobacillus
  • Urinary tract infection
  • Escherichia coli
  • Non-antibiotic strategies