Mean Minimum Bactericidal Concentration Research Articles

Antimicrobial activity of Southern African medicinal plants on Helicobacter pylori and Lactobacillus species

Ethnopharmacological relevanceNumerous medicinal plants have been used traditionally in South Africa for gastric ulcer treatment. Helicobacter pylori is known for causing inflammation and the onset of gastric ulcers. While several studies explored medicinal plants against H. pylori, investigation of medicinal plants used for gastric ulcers has been neglected, as well as the effects these plants would have on bacteria occurring naturally in the gut microbiome. Aim of the studyThis study aimed to investigate Southern African medicinal plants used traditionally for treating gastric ulcers against H. pylori , as well as the effects that these plants have when combined with Lactobacillus species and tested against H. pylori. MethodologyBased on evidence from the ethnobotanical literature, 21 plants were collected. Their antimicrobial activity was assessed against five clinical H. pylori strains, and in combination with each of three Lactobacillus species, using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) broth microdilution assays. Toxicity was assessed using the brine shrimp lethality assay. ResultsNoteworthy activity was observed against at least one H. pylori strain for 12 plant species. The lowest mean MICs were from organic extracts of Carissa edulis Vahl (0.18 mg/mL) and Chironia baccifera L. (0.20 mg/mL), and aqueous extracts of Sansevieria hyacinthoides (L.) Druce (0.26 mg/mL) and Dodonaea viscosa Jacq. (0.30 mg/mL). Aqueous extracts of the investigated plants were combined with Lactobacillus species, and the majority of combinations showed increased antimicrobial activity compared with the extracts alone. Combinations of Lactobacillus rhamnosus with 18 of the 21 aqueous plant extracts showed at least a two-fold decrease in the mean MBC against all H. pylori strains tested. Lactobacillus acidophilus combined with either Protea repens L., Carpobrotus edulis (L.) L. Bolus or Warburgia salutaris (Bertol.f.) Chiov. aqueous extracts had the best anti-H. pylori activity (mean MBCs of 0.10 mg/mL for each combination). Only four organic and one aqueous extract(s) were considered toxic. ConclusionThese results highlight the potential of medicinal plants to inhibit H. pylori growth and their role in traditional treatments for the management of ulcers. The results also indicate that aqueous extracts of these plants do not hinder the growth of bacteria that occur naturally in the gut microbiome and play a role in maintaining gut health, as well as show the potential benefit of including Lactobacillus species as potentiators of H. pylori activity.

Antibacterial activity of <i>Citrullus lanatus</i> seed extract against clinical isolates of <i>Klebsiella pneumoniae</i> and <i>Staphylococcus aureus</i>

As a result of increased emergence of bacterial resistance to the conventionally used antibiotics, it is necessary to search for alternatives from other sources like plant materials. This study was aimed at evaluating the in vitro antibacterial activity of Citrullus lanatus seed extract against isolates of Klebsiella pneumoniae from urine and Staphylococcus aureus from wound. The seeds were extracted using distilled water and methanol via cold maceration and then analysed for the presence of phytochemicals using standard methods. Tannins, steroids, cardiac glycosides and carbohydrates were present in both extracts. Only the aqueous extract contained alkaloids. The antibacterial activity of the two extracts was determined by agar well diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using broth dilution method. The aqueous extract had better activity than the methanol extract, having inhibition zones of 20 mm and 23 mm at 200 mg/mL and, 10 mm and 11 mm at 25 mg/mL against Klebsiella pneumoniae isolates respectively, and mean zone of inhibition between 27.50 mm to 29.33 mm at 200 mg/mL and, 16.50 mm to 17.33 mm at 25 mg/mL against Staphylococcus aureus isolates with MIC and MBC values of 0.195 mg/mL and 0.39 mg/mL against Klebsiella pneumoniae and, mean MIC and MBC values ranging from 0.30 mg/mL to 0.39 mg/mL and 0.78 mg/mL to 2.73 mg/mL against Staphylococcus aureus isolates. The results obtained reveal the potential use of Citrullus lanatus seeds in the development of standard antibiotics.

Antibacterial activity of Chrysophyllum albidium seed oil extract on pathogenic Staphylococcus aureus

Antimicrobial resistance in Staphylococcus aureus has continued to rise and has become a general medical problem. Thus, the objective of this study was to use the Chrysophyllum albidum seed extract as an antibiotic against pathogenic Staphylococcus aureus. The antimicrobial impact of Chrysophyllum albidum seed oil on pathogenic Staphylococcus aureus from various sources were explored utilizing agar well dissemination strategy. The oil was separated utilizing the Soxhlet extraction strategy with n-hexane as the solvent. The oil extract was then prepared in various concentrations (62.5–500 mg/mL) and tested against three different pathogenic isolates of Staphylococcus aureus. At the highest concentration (500 mg/mL), the oil extract yielded 22–24.6 mm inhibition zones. Meanwhile, at the lowest concentration (62.5 mg/mL), the inhibition zones achieved were 14.6–16 mm. The minimum inhibitory concentration was 125 mg/mL, while the mean minimum bactericidal concentration was 250 mg/mL. In conclusion, our data suggested that the oil from seeds of Chrysophyllum albidum has antibacterial activities against Staphylococcus aureus and this needs to be further studied.

In vitro antimicrobial activity of crude propolis extracts and fractions.

The search for antimicrobials in propolis presents a new dimension for addressing the problem of antimicrobial drug resistance. The aim of this study was to determine the antimicrobial activity of extracts of crude propolis collected from different regions in Ghana and their active fractions. The antimicrobial activity of the extracts, as well as that of the chloroform, ethyl acetate, and petroleum ether fractions of the active samples were determined using the agar well diffusion method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the most active fractions were determined. The various crude propolis extracts frequently produced zones of inhibition against Staphylococcus aureus (17/20) than Pseudomonas aeruginosa (16/20), and Escherichia coli (1/20) test isolates. Chloroform and ethyl acetate solvents produced fractions possessing greater antimicrobial activity than the petroleum ether fraction. The mean MIC range of the most active fractions was greatest for S. aureus (76.0 ± 34.8-48.0 ± 33.0mg/ml) than for P. aeruginosa (40.8 ± 33.3-30.4 ± 6.7mg/ml) and E. coli, as was the mean MBC. Propolis has antimicrobial potential, and hence should be exploited as an alternative for the treatment of bacterial infections.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity

Background & Objective: The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques.Methods: Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results: Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively).Conclusion: BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

The Effect of Pimpinella Anisum and Origanum Vulgare Extracts Against Streptococcus Sanguinis, Streptococcus Mutans, and Streptococcus Salivarius.

Statement of the Problem: There are global efforts for introducing a new herbal antimicrobial agent with minimal side effects. There are some reports about the antimicrobial properties of Pimpinella anisum and Oregano Vulgare.Purpose: In this study, the antimicrobial properties of Pimpinella anisum and Oregano Vulgare have been assessed.Material and Method: In this experimental in vitro study, the dental plaque samples were collected from children aged 3 to 5 years old who were referred to a private dental office with diagnosis of dental caries. After determination of the bacterial colonies of Streptococcus sanguinis, Streptococcus mutans and Streptococcus salivarius, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ethanolic and methanolic extracts of Pimpinella anisum and Oregano vulgare were measured by macrodilution and microdilution methods.Results: The mean MIC and MBC of Pimpinella anisum extract and Oregano vulgare extract and their combination against Streptococcus mutans, Streptococcus sanguinis, and Streptococcus salivarius were statistically different (p< 0.001). The combination of these extracts showed the lowest MIC and MBC.Conclusion: Hydroalcoholic extracts of the Pimpinella anisum and Oregano Vulgare were effective antibacterial agent against Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguinis so the combination of these two extracts showed the highest antibacterial properties on all the bacteria evaluated.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity.

Background & Objective:The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques. Methods:Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results:Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively). Conclusion:BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

Comparative Assessment of the Antimicrobial Efficacy of Triclosan, Amoxicillin and Eugenol against Enterococcus faecalis.

AimsElimination of microorganisms and prevention of recurrence of infection from the complex root canal system of primary teeth requires an obturating material with broad antimicrobial activity. Hence, the purpose of the study is to assess and compare the antimicrobial efficacy of Triclosan, Amoxicillin and Eugenol individually and in combinations against a resistant microorganism viz., Enterococcus faecalis.Materials and methodsA two-fold serial dilution method was used to check the minimum inhibitory concentration (MIC) of triclosan, amoxicillin and eugenol against thirty E. faecalis (isolated from oral lesions). The resistant strains were subjected to different combinations of three agents by modified checkerboard method. MIC was determined after incubation for 24 hours at 370°C. Then the three dilutions from MIC were inoculated on BHI agar plates and incubated overnight to determine minimum bactericidal concentration (MBC).ResultsThe mean MIC and MBC of triclosan was 3.43 μg/mL and 3.75 μg/mL respectively. Whereas for amoxicillin, it was 3.43 μg/mL and 3.85 μg/mL. Eugenol did not show any inhibition up to a concentration of 3200 μg/mL. In combination, eugenol showed good synergistic effect with both triclosan and amoxicillin. In combination with triclosan, eugenol showed much promising result as compared with amoxicillin. But triclosan and amoxicillin combination showed inhibition at higher concentrations.ConclusionTriclosan and eugenol combination showed better effectiveness against E. faecalis in comparison to amoxicillin and eugenol. Triclosan and amoxicillin showed antagonism when used in combination against E. faecalis.How to cite this articleGowda J, Tavarageri A, Kulkarni R, et al. Comparative Assessment of the Antimicrobial Efficacy of Triclosan, Amoxicillin and Eugenol against Enterococcus faecalis. Int J Clin Pediatr Dent 2021;14(1):59–62.

Evaluation of antimicrobial efficacy of Trachyspermum ammi (Ajwain) oil and chlorhexidine against oral bacteria: An in vitro study.

Plaque removal is of utmost importance for control of dental caries and other associated diseases of oral cavity. However, various natural agents have proven their efficacy over chemotherapeutic agents in terms of antibacterial activity against various microorganisms. The effect is mainly due to polyphenol as its major constituent. In this in vitro study, we aimed to determine the antibacterial efficacy of Trachyspermum ammi oil at different concentrations against five oral bacteria. Herbal compound, T. ammi oil is effective in reducing five oral plaque-forming bacteria. We determined the antimicrobial activity of T. ammi oil (test material) against chlorhexidine (gold standard). Pure cultures of Streptococcus mutans MTCC No 497, Streptococcus oralis MTCC No. 2696, Lactobacillus acidophilus MTCC No. 10307, Lactobacillus fermentum MTCC No. 903, and Candida albicans MTCC No. 183 were obtained and grown in selective culture media. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of both materials were evaluated by serial dilution and disc diffusion method, respectively. Our results revealed that T. ammi oil moderately inhibits bacterial growth with mean MIC of 250, 125, 250, 125, and 250 μg/ml, respectively. Mean MBC for T. ammi oil obtained was 18.60 ± 0.65, 11.60 ± 1.14, 14.10 ± 0.55, 11.50 ± 0.61, and 15.10 ± 0.74 mm. The MIC and MBC values were higher as compared to chlorhexidine gluconate and it was statistically significant. T. ammi (ajwain) can serve as a potential, natural, nontoxic, and economical therapeutic antiplaque agent.

Evaluation of antibacterial activity of honey against multidrug resistant bacteria in Ayder Referral and Teaching Hospital, Northern Ethiopia.

BackgroundMultidrug resistance is a global health issue. Hence integration of traditional medicine like honey and modern medicine could be a best option in the treatment of patients infected with drug resistant bacteria. Despite the multi floral and huge honey production in the region, there are no studies that evaluate the antibacterial activity of honey against multidrug resistant bacteria.ObjectiveTo evaluate the antibacterial activity of honey against multidrug resistant human pathogenic bacterial isolates of wound and ear infections.MethodsRed and white honeys were obtained from three districts Eastern Zone of Tigray namely Temben, Atsbi and Samre. The antibacterial potential of these honeys was determined against multidrug resistant isolates of clinical isolates of bacterial species of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Coagulase negative Staphylococcus, Streptococcus pyogenes and Klebsiella pneumonia, and five controls bacterial using tube dilutions methods. Undiluted and twofold serial dilutions of honeys were tested to determine minimum inhibitory concentration (MIC) using broth tube dilution methods through visual inspection and minimum bactericidal concentration (MBC) was determined by sub-culturing tubes showing no visible sign of growth/turbidity in MIC.ResultsThe mean MIC of red honeys for control and test bacteria was 7.7–8.9 and 12.6–17.9 % (v/v) respectively. Whilst the MIC of white honey was 12.2–12.5 % (v/v) for control and 16.1–27.7 % (v/v) for test bacteria. Mean MBC of red honeys for control and test isolates was from 25–40 to 30.4–62.5 % (v/v) respectively, and 40–55 and 60.7–75 % (v/v) for white honeys. Honey collected from Samre area has shown better antibacterial activity than other sites. Similarly red honeys from all areas were found to have better antibacterial activity against the multidrug bacteria than the white honey. Over all the MIC and MBC of all isolates was between 6.25–50 and 12.5–100 % (v/v) respectively.ConclusionRed honey from all sites showed better antibacterial activity than the white honey. Likewise, honey from Samre area showed better antibacterial activity than Temben and Atsbi districts. All collected honeys showed varied bacteriostatic and bactericidal activities, and none of the isolates was resistant to tested honeys.

High-level antimicrobial efficacy of representative Mediterranean natural plant extracts against oral microorganisms.

Nature is an unexplored reservoir of novel phytopharmaceuticals. Since biofilm-related oral diseases often correlate with antibiotic resistance, plant-derived antimicrobial agents could enhance existing treatment options. Therefore, the rationale of the present report was to examine the antimicrobial impact of Mediterranean natural extracts on oral microorganisms. Five different extracts from Olea europaea, mastic gum, and Inula viscosa were tested against ten bacteria and one Candida albicans strain. The extraction protocols were conducted according to established experimental procedures. Two antimicrobial assays—the minimum inhibitory concentration (MIC) assay and the minimum bactericidal concentration (MBC) assay—were applied. The screened extracts were found to be active against each of the tested microorganisms. O. europaea presented MIC and MBC ranges of 0.07–10.00 mg mL−1 and 0.60–10.00 mg mL−1, respectively. The mean MBC values for mastic gum and I. viscosa were 0.07–10.00 mg mL−1 and 0.15–10.00 mg mL−1, respectively. Extracts were less effective against C. albicans and exerted bactericidal effects at a concentration range of 0.07–5.00 mg mL−1 on strict anaerobic bacteria (Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Parvimonas micra). Ethyl acetate I. viscosa extract and total mastic extract showed considerable antimicrobial activity against oral microorganisms and could therefore be considered as alternative natural anti-infectious agents.

Comparitive phytochemical Analysis and Resilience Pattern Exhibited by thyme and tea tree oil against Selected Poultry Isolates

The volatile oils of Melaleuca alternifolia (tea tree) and Thymus vulgaris (thyme), of the family Myrtaceae and Lamiaceae respectively, were asessed for antibacterial activity against different avian pathogens isolated from infected chickens which involved Escherichia coli, Staphylococcus aureus, S.epidermidis, S. carnosus and Salmonella gallinarum. The antimicrobial activity of both the oils was assessed by using disc diffusion, minimum inhibitory concentration (MIC) as well as minimum bactericidal concentration (MBC) method. Thyme oil exhibited higher activity than tea tree oil against all the pathogens. Mean inhibition zones, MIC and MBC values of bacterial strains varied from 19 and 34 mm, 0.03%- 0.15% to 0.07 - 0.3% respectively. GC-MS analysis of essential oil of thyme showed the presence of 13 components. The major components were carvacrol, thymol, terpinene-4-ol, α- Terpinene, carvacrol methyl ether. Tea tree oil showed the presence of 16 components upon GC-MS analysis. The major compounds were Limonene, γ -Terpinene, α- Terpinene, Cineol and α- Terpinolene. Since aromatic and medicinal plants produce a wide variety of volatile terpenes, hydrocarbons (aliphatic and cyclic) and their corresponding oxygenated isoprenoid derivatives and analogues, the bactericidal effect observed in this study may be attributed to these components. Therefore, these oils could be a source of pharmaceutical materials required for the preparation of new therapeutic and antimicrobial agents.

The Antibacterial Effect of Ethanol Extract of Polish Propolis on Mutans Streptococci and Lactobacilli Isolated from Saliva

Dental caries occurrence is caused by the colonization of oral microorganisms and accumulation of extracellular polysaccharides synthesized by Streptococcus mutans with the synergistic influence of Lactobacillus spp. bacteria. The aim of this study was to determine ex vivo the antibacterial properties of ethanol extract of propolis (EEP), collected in Poland, against the main cariogenic bacteria: salivary mutans streptococci and lactobacilli. The isolation of mutans streptococci group bacteria (MS) and Lactobacillus spp. (LB) from stimulated saliva was performed by in-office CRT bacteria dip slide test. The broth diffusion method and AlamarBlue assay were used to evaluate the antimicrobial activity of EEP, with the estimation of its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The biochemical composition of propolis components was assessed. The mean MIC and MBC values of EEP, in concentrations ranging from 25 mg/mL to 0.025 mg/mL, for the MS and LB were found to be 1.10 mg/mL versus 0.7 mg/mL and 9.01 mg/mL versus 5.91 mg/mL, respectively. The exposure to an extract of Polish propolis affected mutans streptococci and Lactobacillus spp. viability, exhibiting an antibacterial efficacy on mutans streptococci group bacteria and lactobacilli saliva residents, while lactobacilli were more susceptible to EEP. Antibacterial measures containing propolis could be the local agents acting against cariogenic bacteria.

Antimicrobial potentials of silver colloidal (nanorods) on clinical isolates in Bayelsa state, Nigeria

Antimicrobial resistance in developing countries has long been an issue of major concern. Nanotechnology has become an eye opener for the intervention on multiple drug resistance organisms. In this study we investigated the antimicrobial potentials of Silver Nitrate (nanorods) solution used in managing infectious diseases, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the product against microbial isolates were determined using standard microbiological techniques. The mean MIC and MBC of silver nitrate solution on fungi (0.16 µg/ml and 0.29 µg/ml respectively) was significantly lower than that of Gram positive organisms (2.35µg/ml and 2.62µg/ml) and Gram negative organisms (2.05 µg/ml and 2.10 µg/ml). Of all the Gram positive organisms, Staphylococcus spp recorded the lowest mean MIC and MBC while in the Gram negative organisms group, E. coli isolates showed the lowest mean MIC and MBC of the silver nitrate solution, though not significantly different from the other isolates. In conclusion, results from this study revealed that Silver Nitrate(nanorods) may have be broad spectrum in activity, but with higher antifungal potentials.

Antibacterial Activity ofMyristica fragransagainst Oral Pathogens

Myristica fragrans Houtt is mostly cultivated for spices in Penang Island, Malaysia. The ethyl acetate and ethanol extracts of flesh, mace and seed of Myristica fragrans was evaluated the bactericidal potential against three Gram-positive cariogenic bacteria (Streptococcus mutans ATCC 25175, Streptococcus mitis ATCC 6249, and Streptococcus salivarius ATCC 13419) and three Gram-negative periodontopathic bacteria (Aggregatibacter actinomycetemcomitans ATCC 29522, Porphyromonas gingivalis ATCC 33277, and Fusobacterium nucleatum ATCC 25586). Antibacterial activities of the extracts was determined by twofold serial microdilution, with minimum inhibitory concentrations (MIC) ranging from 1.25 to 640 mg/mL and 0.075 to 40 mg/mL. The minimum bactericidal concentration (MBC) was obtained by subculturing method. Among all extracts tested, ethyl acetate extract of flesh has the highest significant inhibitory effects against Gram-positive and Gram-negative bacteria with mean MIC value ranging from 0.625 to 1.25 ± 0.00 (SD) mg/mL; P = 0.017) and highest bactericidal effects at mean MBC value ranging from 0.625 mg/mL to 20 ± 0.00 (SD) mg/mL. While for seed and mace of Myristica fragrans, their ethanol extracts exhibited good antibacterial activity against both groups of test pathogens compared to its ethyl acetate extracts. All of the extracts of Myristica fragrans did not show any antibacterial activities against Fusobacterium nucleatum ATCC 25586. Thus, our study showed the potential effect of ethyl acetate and ethanol extracts from flesh, seed and mace of Myristica fragrans to be new natural agent that can be incorporated in oral care products.

Increased Susceptibility to Resveratrol of Helicobacter pylori Strains Isolated from Patients with Gastric Carcinoma

The increasing therapeutic failures against Helicobacter pylori infection has determined the need to develop new drugs. The susceptibility to resveratrol (1) of twenty-six H. pylori strains representing nine CagA+ strains from patients with gastric carcinoma and eight CagA- and nine CagA+ strains from patients with chronic gastritis only was evaluated. Compound 1 was dissolved in DMSO and double diluted in Brucella broth with 10% BFS; ca. 10(6) organisms were added to each dilution. After incubation, subcultures were performed using Columbia-blood agar plates. The lowest concentration in broth at which all the organisms were killed was considered the minimum bactericidal concentration (MBC). Tests were performed in triplicate. The mean MBC of 1 for CagA positive GC strains was significantly lower than those for both CagA positive and CagA negative CG strains. An F1 ATPase of H. pylori showed a significant linear homology with a human ATPase considered a possible target of 1. It was hypothesized that strains infecting patients with gastric carcinoma have a reduced expression of F-type ATPases, which normally protect the bacteria from low pH levels by maintaining a proton gradient across membranes. Such behavior can be considered as an adaptive response to decreased gastric acidity. Since the targets of resveratrol (1) are also the bacterial ATPases, their putative reduced expression could increase the susceptibility to this compound, so that it saturates its targets more quickly and efficiently.

Antibacterial Activity Against FoodborneStaphylococcus aureusand Antioxidant Capacity of Various Pure Phenolic Compounds

Six pure phenolic compounds (hydroquinone, thymol, carvacrol, butylated hydroxyanisole, gallic acid, and octyl gallate) were tested for their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against several strains of Staphylococcus aureus isolated from dairy and meat products. In addition, S. aureus reference strains (American Type Culture Collection) for antimicrobial studies and/or isolated from human infections and outbreaks of food poisoning were included in the study. Of the compounds tested, octyl gallate and hydroquinone were the most effective against S. aureus (mean MIC values of 20.89 and 103.05 μg/mL, respectively) and carvacrol and thymol the least (mean MIC values of about 413 μg/mL). The mean MBC values were 40.84, 194.37, 417.46, and 581.90 μg/mL for octyl gallate, hydroquinone, carvacrol, and thymol, respectively. Meat isolates were more resistant than those of dairy origin to hydroquinone, gallic acid, and octyl gallate, as well as to penicillin G (used as a control of the methodology used); gallic acid and penicillin G showed the highest differences in MIC values between the groups of strains (about 10 and 200 times, respectively). On the other hand, when we tested the isolates included in each group of strains (dairy, meat, and other/mixed sources) we only detected significant differences (p < 0.05) among dairy and isolates from other/mixed sources for hydroquinone and thymol, respectively. However, strains of meat origin exhibited significant differences among each other (p < 0.05) to most of the phenolic compounds tested (hydroquinone, carvacrol, gallic acid, and octyl gallate). The relationship between MICs and MBCs for each of the phenolic compounds tested suggested a bactericidal mechanism of action against S. aureus. Gallic acid and octyl gallate exhibited the highest antioxidant capacity and thymol and carvacrol the lowest. So, octyl gallate is an agent with both antimicrobial and antioxidant properties, which would be of interest to use in the food industry.