OBJECTIVES: Candida albicans is a common cause of nosocomial urinary tract infections (UTIs) and is responsible for increased morbidity and healthcare costs. Moreover, the US Centers for Medicare & Medicaid Services no longer reimburse for hospital-acquired catheter-associated UTIs. Thus, development of specific approaches for the prevention of Candida urinary infections is needed. Cranberry juice-derived proanthocyanidins (PACs) have efficacy in the prevention of bacterial UTIs, partially due to anti-adherence properties, but there are limited data on their use for the prevention and/or treatment of Candida UTIs. Therefore, we sought to systematically assess the in vitro effect of cranberry-derived PACs on C. albicans biofilm formation in artificial urine.

METHODS: C. albicans biofilms in artificial urine were coincubated with cranberry PACs at serially increasing concentrations and biofilm metabolic activity was assessed using the XTT assay in static microplate and silicone disc models.

RESULTS: Cranberry PAC concentrations of >16 mg/L significantly reduced biofilm formation in all C. albicans strains tested, with a paradoxical effect observed at high concentrations in two clinical isolates. Further, cranberry PACs were additive in combination with traditional antifungals. Cranberry PACs reduced C. albicans adherence to both polystyrene and silicone. Supplementation of the medium with iron reduced the efficacy of cranberry PACs against biofilms.

CONCLUSIONS: These findings indicate that cranberry PACs have excellent in vitro activity against C. albicans biofilm formation in artificial urine. We present preliminary evidence that cranberry PAC activity against C. albicans biofilm formation is due to anti-adherence properties and/or iron chelation.

Despite cranberry being associated with the prevention of bacterial infections for over a century, our understanding of the bioavailability and mechanisms by which cranberry prevents infection is limited. This study investigates the interactions between cranberry proanthocyanidins (CPAC) and human serum proteins (albumin, alpha-1-acid glycoprotein, and fibrinogen) that may be encountered during CPAC metabolism following ingestion. To better understand how CPAC might interfere with bacterial infection, we also examined the interactions between CPAC and selected bacterial virulence factors; namely, lipopolysaccharide (LPS) and rhamnolipid. The binding of CPAC to the serum proteins, rhamnolipids and LPS from Escherichia coli O111:B4 can be described by Langmuir-type isotherms, allowing the determination of the apparent adsorption affinity constants, with CPAC interacting most strongly with fibrinogen with a binding constant of 2.2 x 10(8) M(-1). These binding interactions will limit the bioavailability of the CPAC at the site of action, an important consideration in designing further clinical trials. Furthermore, CPAC interacts with Pseudomonas aeruginosa 10 LPS, E. coli O111:B4 LPS, and P. aeruginosa rhamnolipids in fundamentally different manners, supporting the theory that cranberry prevents bacterial infections via multiple mechanisms.

Gut colonization by extra-intestinal pathogenic Escherichia coli (ExPEC) increases the risk of subsequent infections, including urinary tract infection and septicemia. Previous work suggests that cranberry proanthocyanidins (PAC) interact with bacterial surface factors, altering bacterial interaction with host cells. Methods were developed to determine if ratios of "A-type" to "B-type" interflavan bonds in PAC affect ExPEC agglutination and invasion of enterocytes. In cranberries, 94.5% of PAC contain one or more "A-type" bonds, whereas in apples, 88.3% of PAC contain exclusively "B-type" bonds. Results show that cranberry "A-type" PAC have greater bioactivity than apple "B-type" PAC for increasing ExPEC agglutination and decreasing ExPEC epithelial cell invasion.

Proteus mirabilis is an etiological agent of complicated urinary tract infections. North American cranberries (Vaccinium macrocarpon) have long been considered to have protective properties against urinary tract infections. This work reports the effects of cranberry powder (CP) on the motility of P. mirabilis HI4320 and its expression of flaA, flhD, and ureD. Our results show that swimming and swarming motilities and swarmer-cell differentiation were inhibited by CP. Additionally, transcription of the flagellin gene flaA and of flhD, the first gene of the flagellar master operon flhDC, decreased during exposure of P. mirabilis to various concentrations of CP. Moreover, using ureD-gfp, a fusion of the urease accessory gene ureD with gfp, we show that CP inhibits urease expression. Because we demonstrate that CP does not inhibit the growth of P. mirabilis, the observed effects are not attributable to toxicity. Taken together, our results demonstrate that CP hinders motility of P. mirabilis and reduces the expression of important virulence factors.

The motility of bacteria plays a key role in their colonization of surfaces during infection. Derivatives of cranberry fruit have been shown to interfere with bacterial motility. Herein, we report on the incorporation of cranberry derived materials (CDMs) into silicone substrates with the aim of impairing bacterial pathogen motility and spreading on the substrate surface. The release of CDMs from the silicone substrates when soaking in an aqueous medium was quantified for a period of 24h. Next, we showed that CDMs released from two silicone substrates remain bioactive as they downregulate the expression of the flagellin gene of two key uropathogens - Escherichia coli CFT073 and Proteus mirabilis HI4320. Furthermore, we demonstrate that CDM-modified silicone inhibits the swarming motility of P. mirabilis, an aggressive swarmer. The bioactive, CDM-modified substrates can find broad applications in the medical device and food industries where the impairment of bacterial colonization of surfaces is of paramount importance.

The antimicrobial properties of the American cranberry were studied against Escherichia coli O157:H7, Listeria monocytogenes, and Lactobacillus rhamnosus to determine the effects on growth inhibition, membrane permeability, and injury. Cranberry powder was separated using a C-18 Sep-Pak cartridge into sugars plus organic acids (F1), monomeric phenolics (F2), and anthocyanins plus proanthocyanidins (F3). Fraction 3 was further separated into anthocyanins (F4) and proanthocyanidins (F5) using an LH-20 Sephadex column. Each fraction was diluted in the brain heart infusion (BHI) broth to determine the minimum inhibitory/bactericidal concentrations (MIC/MBC). L. monocytogenes was the most susceptible to cranberry fraction treatment with the lowest MIC/MBC for each treatment, followed by E. coli O157:H7 and L. rhamnosus. Membrane permeability and potential was studied using LIVE/DEAD viability assay and using Bis (1, 3-dibutylbarbituric acid) trimethine oxonol (DiBAC4), respectively. L. rhamnosus demonstrated the highest permeability followed by E. coli O157:H7, and L. monocytogenes. L. rhamnosus demonstrated the highest recovery followed by E. coli O157:H7, and L. monocytogenes. Each cranberry fraction demonstrated membrane hyperpolarization at their native pH, while F2, F3, and F5 demonstrated membrane depolarization at neutral pH. With this knowledge cranberry compounds may be used to prevent maladies and potentially substitute for synthetic preservatives and antibiotics.

Cranberry A-type proanthocyanidins (PACs) have been recognized for their inhibitory activity against bacterial adhesion and biofilm-derived infections. However, the precise identification of the specific classes of degree-of-polymerization (DP) conferring PACs bioactivity remains a major challenge owing to the complex chemistry of these flavonoids. In this study, chemically characterized cranberries were used in a multistep separation and structure-determination technique to isolate A-type PAC oligomers of defined DP. The influences of PACs on the 3D architecture of biofilms and Streptococcus mutans-transcriptome responses within biofilms were investigated. Treatment regimens that simulated topical exposures experienced clinically (twice-daily, 60s each) were used over a saliva-coated hydroxyapatite biofilm model. Biofilm accumulation was impaired, while specific genes involved in the adhesion of bacteria, acid stress tolerance, and glycolysis were affected by the topical treatments (vs the vehicle-control). Genes (rmpC, mepA, sdcBB, and gbpC) associated with sucrose-dependent binding of bacteria were repressed by PACs. PACs of DP 4 and particularly DP 8 to 13 were the most effective in disrupting bacterial adhesion to glucan-coated apatitic surface (>85% inhibition vs vehicle control), and gene expression (eg rmpC). This study identified putative molecular targets of A-type cranberry PACs in S. mutans while demonstrating that PAC oligomers with a specific DP may be effective in disrupting the assembly of cariogenic biofilms.

Lactobacillus plantarum IFPL935 was incubated with individual monomeric flavan-3-ols and dimeric A- and B-type procyanidins to identify new metabolites and to determine the effect of compound structural features on bacterial growth and catabolism. Complex extracts rich in A-type proanthocyanidins and phenolic acids from cranberry were also tested. The results showed that L. plantarum IFPL935 exhibited higher resistance to nongalloylated monomeric flavan-3-ols, A-type dimeric procyanidins, and cranberry extract than to (−)-epicatechin-3-O-gallate and B-type dimeric procyanidins. Despite these findings, the strain was capable of rapidly degrading (−)-epicatechin-3-O-gallate, but not A- or B-type dimeric procyanidins. However, it
was able to produce large changes in the phenolic profile of the cranberry extract mainly due to the catabolism of
hydroxycinnamic and hydroxybenzoic acids. Of most relevance was the fact that L. plantarum IFPL935 cleaved the heterocyclic ring of monomeric flavan-3-ols, giving rise to 1-(3′,4′-dihydroxyphenyl)-3-(2″,4″,6″-trihydroxyphenyl)propan-2-ol, activity exhibited by only a few human intestinal bacteria.

The effects of 13 food extracts and juices, including shellfish, fruits, and vegetables, on the binding ability of human norovirus (NoV) were examined, using P particles of human NoV GII.4 as a research surrogate. The enhancements (positive values) or reductions (negative values) of NoV P particle detection (changes in optical density at 450 nm) in the presence of different
food extracts and juices as compared with P particles diluted in phosphate-buffered saline were tested by saliva-binding, enzymelinked immunosorbent assay in triplicate. In the presence of different food extracts and juices at different concentrations, an increase or decrease of the receptor-binding ability of the NoV P particles was observed. Due to a higher specific binding and thus a higher
accumulation of the viral particles, oysters may be contaminated with human NoV more often than other shellfish species (mussel, hard clams, and razor clams). Cranberry and pomegranate juices were shown to reduce the specific binding ability of human NoV P particles. No such binding inhibition effects were observed for the other tested extracts of fresh produce (strawberry, blackberry,
blueberry, cherry tomato, spinach, romaine lettuce) or, notably, for raspberry, which has been associated with human NoV outbreaks.

Surface-associated swarming motility is implicated in enhanced bacterial spreading and virulence, hence it follows
that anti-swarming effectors could have clinical benefits. When investigating potential applications of anti-swarming
materials it is important to consider whether the lack of swarming corresponds with an enhanced sessile biofilm
lifestyle and resistance to antibiotics. In this study, well-defined tannins present in multiple plant materials (tannic
acid (TA) and epigallocathecin gallate (EGCG)) and undefined cranberry powder (CP) were found to block swarming motility and enhance biofilm formation and resistance to tobramycin in Pseudomonas aeruginosa. In contrast, gallic acid (GA) did not completely block swarming motility and did not affect biofilm formation or tobramycin resistance. These data support the theory that nutritional conditions can elicit an inverse relationship between swarming motility and biofilm formation capacities. Although anti-swarmers exhibit the potential to yield clinical benefits, it is important to be aware of possible implications regarding biofilm formation and antibiotic resistance.