tetracycline and carvacrol

Dental caries remains the most prevalent oral infectious disease worldwide. In this study, the antibacterial and the antibiofilm activities of five essential oils (EO's): eugenol (EUG), carvacrol (CAR), thymol (TYH), p-cymene (CYM) and γ-terpinene (TER) were tested (alone or in combinaison with tetracycline) against oral bacteria. In addition, their potential roles to enhance the accumulation of ethidium bromide (EtBr) in bacterial cells were tested. Our results indicated that EO's induced a selective antimicrobial activity. A synergistic effect of EO's and tetracycline (TET) was noticed with a reduction rate ranged from 2 to 8-fold. In addition, the efflux of EtBr was inhibited with a decrease in loss of EtBr from the bacteria. On the other hand a significant anti-biofilm activities of EO's (alone or combined with antibiotics) was noticed. In conclusion the tested EO's may be considered as a potential natural source with a resistance-modifying activity and may be applied to eradicate bacterial biofilm.

Topics: Anti-Bacterial Agents; Bacteria; Biofilms; Cyclohexane Monoterpenes; Cymenes; Dental Caries; Dental Enamel; Drug Resistance, Bacterial; Drug Synergism; Ethidium; Eugenol; Microbial Sensitivity Tests; Microbiota; Microscopy, Electron, Scanning; Monoterpenes; Mouth; Oils, Volatile; Staphylococcus aureus; Tetracycline; Thymol

In this study thymol (THY) and carvacrol (CAR), two monoterpenic phenol produced by various aromatic plants, was tested for their antibacterial and efflux pump inhibitors potencies against a panel of clinical and foodborne pathogenes. Our results demonstrated a substantial susceptibility of the tested bacteria toward THY and CAR. Especially, THY displayed a strong inhibitory activity (MIC's values ranged from 32 to 64 μg/mL) against the majority of the tested strains compared to CAR. Moreover, a significant reduction in MIC's of TET and benzalkonium chloride (QAC) were noticed when tested in combinations with THY and CAR. Their synergic effect was more significant in the case of THY which resulted a reduction of MIC's values of TET (2-8 fold) and QAC (2-8 fold). We noted also that THY and CAR inhibited the ethidium bromide (EtBr) cell efflux in a concentration-dependent manner. The rate of EtBr accumulation in food-borne pathogen was enhanced with THY and CAR (0, 250 and 500 μg/mL). The lowest concentration causing 50% of EtBr efflux inhibition (IC 50) was noticed in Salmonella enteritidis (1129) at 150 μg/mL of THY and 190 μg/mL of CAR respectively. These findings indicate that THY and CAR may serve as potential sources of efflux pump inhibitor in food-borne pathogens.

Topics: Anti-Infective Agents; Bacteria; Benzalkonium Compounds; Biological Transport, Active; Cymenes; Drug Synergism; Ethidium; Foodborne Diseases; Inhibitory Concentration 50; Microbial Sensitivity Tests; Monoterpenes; Phytochemicals; Tetracycline; Thymol

In an ongoing project to evaluate essential oils as modulators of antibiotic resistance, the essential oil from Origanum vulgare L. (OVEO), as well as its individual constituents carvacrol (CAR) and thymol (THY), were investigated using Staphylococcus aureus strains possessing efflux mechanisms of resistance to norfloxacin, erythromycin and tetracycline.. The minimum inhibitory concentration (MIC) values of the antibiotics were determined by agar dilution method, in the absence and in the presence of subinhibitory concentrations of OVEO, CAR or THY.. Along with relevant antistaphylococcal activity, OVEO, CAR and THY modulated the activity of tetracycline, i.e. in combination with antibiotics a reduction in the MIC was observed (up to fourfold).. The results presented here represent, as far as we know, the first report of OVEO, CAR and THY as putative efflux pump inhibitors. Broadly, these findings indicate that essential oils could serve as potential sources of compounds capable of modulating drug resistance.

Topics: Anti-Bacterial Agents; Cymenes; Humans; Microbial Sensitivity Tests; Monoterpenes; Oils, Volatile; Origanum; Staphylococcus aureus; Tetracycline; Thymol

This study investigated the efficacy of plant-derived antimicrobials, namely, trans-cinnamaldehyde, β-resorcylic acid, carvacrol, thymol, and eugenol or their combination, in increasing the sensitivity of Salmonella Typhimurium DT104 to five antibiotics. The subinhibitory concentrations of each antimicrobial or their combination containing concentrations lower than the individual subinhibitory concentrations were added to tryptic soy broth supplemented with antibiotics at their respective break points for resistance. Salmonella Typhimurium DT104 was inoculated into tryptic soy broth at ~6 log CFU/mL, and growth (optical density at 600 nm) was determined before and after incubation at 37° C for 24 hours. Appropriate controls were included. Duplicate samples were assayed and the experiment was replicated three times. Trans-cinnamaldehyde increased the sensitivity of Salmonella Typhimurium DT104 (p<0.05) toward all five antibiotics, namely, ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline, thereby making the pathogen susceptible to drugs. Thymol made the pathogen susceptible to all four antibiotics except ampicillin, whereas carvacrol increased the sensitivity to two antibiotics (chloramphenicol and sulfamethoxazole for strain H3380, and streptomycin and sulfamethoxazole for strain 43). The combination of five molecules was more effective than individual ones (p<0.05) in rendering the pathogen susceptible to the antibiotics. Results indicate that these natural molecules individually and synergistically increased the sensitivity of Salmonella Typhimurium DT104 to all the five antibiotics, and justify future studies to control antibiotic resistance of the pathogen in food animals using these plant molecules.

Topics: Acrolein; Ampicillin; Anti-Bacterial Agents; Anti-Infective Agents; Chloramphenicol; Cymenes; Drug Resistance, Bacterial; Drug Resistance, Multiple; Eugenol; Hydroxybenzoates; Microbial Sensitivity Tests; Monoterpenes; Plants; Salmonella typhimurium; Streptomycin; Sulfamethoxazole; Tetracycline; Thymol