Piperine, a trans-trans isomer of 1-piperoyl-piperidine, in combination with ciprofloxacin markedly reduced the MICs and mutation prevention concentration of ciprofloxacin for Staphylococcus aureus, including methicillin-resistant S. aureus. The enhanced accumulation and decreased efflux of ethidium bromide in the wild-type and mutant (CIP r -1) strains in the presence of piperine suggest its involvement in the inhibition of bacterial efflux pumps.Ciprofloxacin, the most frequently used fluoroquinolone, is less effective against gram-positive bacteria, including Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecalis (8). Fluoroquinolones inhibit DNA synthesis by inhibiting the closely related enzymes gyrase and topoisomerase IV. The resistance to this class of antibiotics is caused by changes in the genes coding for DNA gyrase (gyrA or gyrB) or for topoisomerase IV (parC or parE) (11). The regions in which these mutations occur are termed quinolone resistance-determining regions (16,17). However multidrug efflux transporters also play a major role in contributing to the resistance of gram-positive organisms to fluoroquinolones by actively extruding fluoroquinolones and multiple other drugs from cells (4, 12, 21).Piperine, the major plant alkaloid present in black pepper (Piper nigrum) and long pepper (Piper longum), is reported to have bioavailability-enhancing activity for some nutritional substances and for some drugs (1, 3). Piperine has previously been shown to inhibit several cytochrome P450-mediated pathways and phase II reactions in animal models (2,19). It has also been proven to be an inhibitor of human P-glycoprotein (5). In this report, we describe for the first time the potentiating effect of piperine with ciprofloxacin in in vitro combination studies against S. aureus and its suggestive role as an efflux pump inhibitor.S. aureus ATCC 29213 was obtained from the American Type Culture Collection (Manassas, Va.). Methicillin-resistant S. aureus (MRSA) 33, MRSA 450, and MRSA 15187 were obtained as a kind gift from Ranbaxy Research Laboratories (New Delhi, India). Ciprofloxacin powder was obtained from Cadila Pharmaceuticals, Gujarat, India. Piperine of 99% purity was provided by the Pharmacology Division, Regional Research Laboratory, Jammu Tawi, India. Reserpine was obtained from Sigma Aldrich, St. Louis, Mo. Mueller-Hinton broth (Becton Dickinson, Cockeysville, Md.) supplemented with calcium (25 mg/liter) and magnesium (12.5 mg/liter) was used for all susceptibility and killing curve experiments. MuellerHinton agar (Becton Dickinson) was used for mutation studies. Trypticase soy agar (Becton Dickinson) was used for colony counts.In vitro combination studies. Combination studies were performed by a broth checkerboard method (9). The final concentrations ranged from 0.03 g/ml to 64 g/ml for ciprofloxacin and from 0.8 g/ml to 50 g/ml for piperine. The final bacterial inoculum in each well was 5 ϫ 10 5 CFU/ml. The plates were incubated at 37°C for 24 h. Piperine did not show any antiba...

Hydroxychavicol isolated from the chloroform extraction of aqueous extract of Piper betle leaves showed inhibitory activity against oral cavity pathogens. It exhibited an inhibitory effect on all of the oral cavity pathogens tested (MICs of 62.5 to 500 g/ml) with a minimal bactericidal concentration that was twofold greater than the inhibitory concentration. Hydroxychavicol exhibited concentration-dependent killing of Streptococcus mutans ATCC 25175 up to 4؋ MIC and also prevented the formation of water-insoluble glucan. Interestingly, hydroxychavicol exhibited an extended postantibiotic effect of 6 to 7 h and prevented the emergence of mutants of S. mutans ATCC 25175 and Actinomyces viscosus ATCC 15987 at 2؋ MIC. Furthermore, it also inhibited the growth of biofilms generated by S. mutans and A. viscosus and reduced the preformed biofilms by these bacteria. Increased uptake of propidium iodide by hydroxychavicol-treated cells of S. mutans and A. viscosus indicated that hydroxychavicol probably works through the disruption of the permeability barrier of microbial membrane structures. Hydroxychavicol also exhibited potent antioxidant and anti-inflammatory activities. This was evident from its concentration-dependent inhibition of lipid peroxidation and significant suppression of tumor necrosis factor alpha expression in human neutrophils. Its efficacy against adherent cells of S. mutans in water-insoluble glucan in the presence of sucrose suggests that hydroxychavicol would be a useful compound for the development of antibacterial agents against oral pathogens and that it has great potential for use in mouthwash for preventing and treating oral infections.Diverse microorganisms inhabit the human oral cavity, and there is always a risk of infection with bacterial pathogens associated with the oral cavity. Streptococcus constitutes 60 to 90% of the remaining bacteria that colonize the teeth within the first 4 h after professional cleaning (17). Other early colonizers include Actinomyces spp., Eikenella spp., Haemophilus spp., Prevotella spp., Propionibacterium spp., and Veillonella spp. Many of the physical interactions that occur between the organisms of this community are known. Streptococcus is the only genus of oral cavity bacteria that demonstrates extensive and intergenic coaggregation (12, 13). The ability of this genus to bind to other early colonizers and to host oral matrices may confer an opportunity to viridians streptococci in establishing early dental plaque (17). Streptococcus mutans can colonize the tooth surface and initiate plaque formation by its ability to synthesize extracellular polysaccharides, mainly water-insoluble glucan from sucrose, using its glucosyltransferase (11).The current research targeting microbial biofilm inhibition has attracted a great deal of attention, and the search for effective antimicrobial agents against these oral pathogens could lead to identification of new agents for the prevention of dental caries and periodontal diseases arising out of dental plaque formation (23...

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A newly identified class of compounds derived from a natural amide, piperine, is more potent than the parent molecule in potentiating the activity of ciprofloxacin through the inhibition of the NorA efflux pump. These molecules may prove useful in augmenting the antibacterial activities of fluoroquinolones in a clinical setting.

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