In vitro and in vivo antibacterial activities of cranberry press cake extracts alone or in combination with β-lactams against Staphylococcus aureus

Abstract

BackgroundCranberry fruits possess many biological activities partly due to their various phenolic compounds; however the underlying modes of action are poorly understood. We studied the effect of cranberry fruit extracts on the gene expression of Staphylococcus aureus to identify specific cellular processes involved in the antibacterial action.MethodsTranscriptional profiles of four S. aureus strains grown in broth supplemented or not with 2 mg/ml of a commercial cranberry preparation (Nutricran®90) were compared using DNA arrays to reveal gene modulations serving as markers for biological activity. Ethanol extracted pressed cakes from fresh fruits also produced various fractions and their effects on marker genes were demonstrated by qPCR. Minimal inhibitory concentrations (MICs) of the most effective cranberry fraction (FC111) were determined against multiple S. aureus strains and drug interactions with β-lactam antibiotics were also evaluated. Incorporation assays with [3H]-radiolabeled precursors were performed to evaluate the effect of FC111 on DNA, RNA, peptidoglycan (PG) and protein biosynthesis.ResultsTreatment of S. aureus with Nutricran®90 or FC111 revealed a transcriptional signature typical of PG-acting antibiotics (up-regulation of genes vraR/S, murZ, lytM, pbp2, sgtB, fmt). The effect of FC111 on PG was confirmed by the marked inhibition of incorporation of D-[3H]alanine. The combination of β-lactams and FC111 in checkerboard assays revealed a synergistic activity against S. aureus including strain MRSA COL, which showed a 512-fold drop of amoxicillin MIC in the presence of FC111 at MIC/8. Finally, a therapeutic proof of concept was established in a mouse mastitis model of infection. S. aureus-infected mammary glands were treated with amoxicillin, FC111 or a combination of both; only the combination significantly reduced bacterial counts from infected glands (P<0.05) compared to the untreated mice.ConclusionsThe cranberry fraction FC111 affects PG synthesis of S. aureus and acts in synergy with β-lactam antibiotics. Such a fraction easily obtained from poorly exploited press-cake residues, may find interesting applications in the agri-food sector and help reduce antibiotic usage in animal food production.

Antibiotics in Canadian poultry productions and anticipated alternatives

“…Ethanol extraction of pomaces (pressed cakes) from fresh fruits also produced a cranberry fraction (FC111) modulating the same marker genes as demonstrated by qPCR. S. aureus cell surface disruption by cranberry is also supported by work from Wu et al (2008) and by cell wall biosynthesis assays (Diarra et al, 2013). Besides, it was noted that NC90 and FC111 also modulated the expression of some S. aureus genes (like lytM , Figure 1) that respond to membrane depolarization, as provoked by carbonyl cyanide m -chlorophenylhydrazone (CCCP) and daptomycin (Muthaiyan et al, 2008).…”

“…Based on our own experience, commercially available cranberry products like Nutricran®90 (NC90) and some of our own cranberry extracts yielded stronger growth inhibition effects against Gram positive pathogens such as Staphylococcus aureus (Diarra et al, 2013), Listeria monocytogenes (Block et al, 2012), and Clostridium perfringens (Delaquis et al, 2010), although the minimal inhibitory concentrations of the cranberry products were several times higher than that of conventional antibiotics such as penicillin. Similarly to work done with E. coli , transcriptional analyses by microarrays allowed determining the modes of action of the cranberry product NC90 against S. aureus (Diarra et al, 2013).…”

“…Similarly to work done with E. coli , transcriptional analyses by microarrays allowed determining the modes of action of the cranberry product NC90 against S. aureus (Diarra et al, 2013). The effect of cranberry on the S. aureus transcriptome yielded the identification of several bacterial genes known to be up-regulated by the presence of cell-wall acting antibiotics, such as oxacillin, vancomycin, and daptomycin (Singh et al, 2001; Utaida et al, 2003; Muthaiyan et al, 2008), as represented in Figure 1.…”

“…Genes up- and down-regulated are represented by up and down arrows, respectively. Genes affected by cranberry also include those involved in capsular polysaccharide biosynthesis (Diarra et al, 2013), which correlates with the presence of a thinner capsule at the surface of S. aureus (lower right panel compared to the untreated control, top right panel). The capsule material (indicated by arrows) was labeled using polycationic ferritin as described before (Diarra et al, 2002).…”

Intramammary Propolis Formulation for Subclinical Mastitis Prevention and Treatment in Dairy Cows

“…The greatest risk lays in development of antibiotic resistant bacteria, but it also presents an obstacle for organic milk production. Many subclinical mastitis treatment studies [1,2] proposed alternatives to conventional antimicrobial treatment solutions. Propolis is a resinous mixture that honeybees collect from trees and various plants.…”