Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), a bicyclic naphthoquinone naturally distributed among Plumbago species, has been reported to have antimicrobial activity against a wide range of microorganisms. In this study, plumbagin was examined for its combinatory antimicrobial effect with tetracycline or oxacillin against nine strains of Staphylococcus aureus, including its methicillin- and multidrug-resistant strains. Minimum inhibitory concentrations were determined through the broth microdilution method, whereas the combinatory effect was evaluated according to the sum of fractional inhibitory concentration (ΣFIC) indices. Additive interactions were obtained for both combinations against most of the strains tested. Synergy was obtained for combination with oxacillin against two out of seven strains (ΣFIC range 0.273-0.281), both were methicillin resistant. Our results proved plumbagin as a compound suitable for anti-Staphylococcal combinatory testing. Moreover, to the best of our knowledge, this is the first report of plumbagin synergy with oxacillin against S. aureus strains, including its resistant forms.

• Klíčová slova
• 2-methyl-juglone, anti-Staphylococcal, microdilution, plumbagone, resistance, synergy,
• MeSH
• antibakteriální látky farmakologie   MeSH
• mikrobiální testy citlivosti MeSH
• mnohočetná bakteriální léková rezistence MeSH
• naftochinony farmakologie   MeSH
• oxacilin farmakologie   MeSH
• Staphylococcus aureus klasifikace   účinky léků   MeSH
• synergismus léků MeSH
• tetracyklin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• naftochinony MeSH
• oxacilin MeSH
• plumbagin MeSH Prohlížeč
• tetracyklin MeSH

AIMS: The objective of the study was to evaluate the antimicrobial interactions between two volatile agents, Cinnamomum cassia essential oil (CCEO) and 8-hydroxyquinoline (8-HQ) against Staphylococcus aureus strains in liquid and vapour phases. METHODS AND RESULTS: In vitro antimicrobial effect of CCEO in combination with 8-HQ was evaluated against 12 strains of S. aureus by broth volatilization chequerboard method. Results show additive effects against all S. aureus strains for both phases. In several cases, sums of fractional inhibitory concentration values of our test combinations were lower than 0·6, which can be considered as a strong additive interaction. Moreover, composition of CCEO was analysed by gas chromatography-mass spectrometry analysis. In the CCEO, 26 compounds in total were identified, where (E)-cinnamaldehyde was the predominant compound, followed by cinnamyl acetate, α-copaene, bornyl acetate and caryophyllene. CONCLUSIONS: Results showed additive in vitro growth-inhibitory effect of CCEO and 8-HQ combination against various standard strains and clinical isolates of S. aureus. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on antibacterial effect of 8-HQ and CCEO combination in liquid and vapour phases. Results of the study suggest these agents as potential candidates for development of new anti-staphylococcal applications that can be used in the inhalation therapy against respiratory infections.

• Klíčová slova
• GC-MS, antimicrobial interactions, broth volatilization chequerboard method, chemical composition, fractional inhibitory concentration, volatile compound,
• MeSH
• akrolein analogy a deriváty   chemie   MeSH
• antibakteriální látky farmakologie   MeSH
• mikrobiální testy citlivosti MeSH
• oleje prchavé farmakologie   MeSH
• oxychinolin farmakologie   MeSH
• plynová chromatografie s hmotnostně spektrometrickou detekcí MeSH
• skořicovník čínský chemie   MeSH
• Staphylococcus aureus účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• akrolein MeSH
• antibakteriální látky MeSH
• cinnamaldehyde MeSH Prohlížeč
• oleje prchavé MeSH
• oxychinolin MeSH

Combinatory action of antimicrobial agents such as essential oils (EOs) show to be an effective strategy to overcome the problem with increasing antibiotic resistance of microorganisms, including Staphylococcus aureus. The objective of this study was to evaluate in vitro antimicrobial interactions between Origanum vulgare and Thymus vulgaris EOs against various S.aureus strains in both liquid and vapor phases using the broth volatilization checkerboard method. Fractional inhibitory concentrations (FICs) were determined for both liquid and vapor phases, and the composition of EOs was analyzed by gas chromatography-mass spectrometry using dual-column/dual-detector gas chromatograph. Results of oregano and thyme EOs combination showed additive effects against all S. aureus strains in both phases. In several cases, sums of FICs were lower than 0.6, which can be considered a strong additive interaction. The lowest FICs obtained were 0.53 in the liquid phase and 0.59 in the gaseous phase. Chemical analysis showed that both EOs were composed of many compounds, including carvacrol, thymol, γ-terpinene, and p-cymene. This is the first report on oregano and thyme EOs interactions against S. aureus in the vapor phase. It also confirms the accuracy of the broth volatilization checkerboard method for the evaluation of combinatory antimicrobial effects of EOs in the vapor phase.

• Klíčová slova
• GC/MS, antimicrobial interactions, broth volatilization chequerboard method, chemical composition, fractional inhibitory concentration, gaseous phase, oregano, thyme, volatile compound,
• Publikační typ
• časopisecké články MeSH

Carvacrol and thymol, both plant-derived volatile compounds, have extensively been studied individually as well as in combination with other agents for their antimicrobial activity in liquid phase. However, in contrast to well-established assays for testing of antimicrobial combinatory effects in liquid media, there are no standardized methods for evaluation of interactions between volatile compounds in vapour phase. The objective of this study was to verify new broth volatilization chequerboard method by testing the combination of carvacrol and thymol and to determine in vitro inhibitory effect of these compounds in liquid and vapour phase against twelve Staphylococcus aureus strains. The new method, based on combination of standard microdilution chequerboard and new broth volatilization tests allowing calculation of fractional inhibitory concentrations (FICs), was used. Combination of carvacrol and thymol produced the additive antimicrobial effect against all strains tested. In several cases, they reached ΣFIC values lower than 0.6, which can be considered as a strong additive interaction. The best result was found in vapour phase against one standard strain at combination of 128 μg/mL of carvacrol and 16-256 μg/mL of thymol (ΣFIC = 0.51) and in liquid phase against one clinical isolate at combination of 256 μg/mL of carvacrol and 256 μg/mL of thymol (ΣFIC = 0.53). The study verified that the new technique is suitable for simple and rapid high-throughput combinatory antimicrobial screening of volatile compounds simultaneously in vapour and liquid phase and that it allows determination and comparison of MIC and FIC values in both, liquid and solid media.

• Klíčová slova
• Combinatory antimicrobial effect, Essential oil, Fractional inhibitory concentration, Vapour phase, Volatile compound,
• MeSH
• cymeny MeSH
• mikrobiální testy citlivosti metody   MeSH
• monoterpeny farmakologie   MeSH
• rychlé screeningové testy MeSH
• Staphylococcus aureus účinky léků   MeSH
• thymol farmakologie   MeSH
• volatilizace MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• carvacrol MeSH Prohlížeč
• cymeny MeSH
• monoterpeny MeSH
• thymol MeSH

Antibiotic resistance in diarrhea-causing bacteria and its disruption of gut microbiota composition are health problems worldwide. The development of combinatory agents that increase the selective inhibitory effect (synergism) against diarrheagenic pathogens and, simultaneously, have a lowered impact (antagonism) or no negative action on the gut microbiota is therefore proposed as a new strategy efficient for chemotherapy against diarrheal conditions. In this study, the in vitro selective combinatory effect of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione, representing various classes of alkaloid-related compounds (nitroquinolines, benzylisoquinolines and metal-pyridine derivative complexes) against selected standard diarrhea-causing (Bacillus cereus, Enterococcus faecalis, Listeria monocytogenes, Shigella flexneri, and Vibrio parahaemolyticus) and gut-beneficial (Bifidobacterium adolescentis, Bifidobacterium animalis subsp. lactis, Bifidobacterium breve, Lactobacillus casei, and Lactobacillus rhamnosus) bacteria, was evaluated according to the sum of fractional inhibitory concentration indices (FICIs) obtained by the checkerboard method. The results showed that the individual combination of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione produced a synergistic effect against the pathogenic bacteria, with FICI values ranging from 0.071 to 0.5, whereas their antagonistic interaction toward the Bifidobacterium strains (with FICI values ranging from 4.012 to 8.023) was observed. Ciprofloxacin-zinc pyrithione produced significant synergistic action against S. flexneri, whereas a strong antagonistic interaction was observed toward B. breve for the ciprofloxacin-nitroxoline combination. These findings suggest that certain combinations of agents tested in this study can be used for the development of antidiarrheal therapeutic agents with reduced harmful action on the gastrointestinal microbiome. However, further studies focused on their pharmacological efficacy and safety are needed before they are considered for clinical trials. IMPORTANCE Diarrheal infections, which are commonly treated by antibiotics, are still responsible for over 4 to 5 million cases of human deaths annually. Moreover, the rising incidence of antibiotic resistance and its negative effect on beneficial bacteria (e.g., Bifidobacteria) of the gut microbial community are another problem. Thus, the development of selective agents able to inhibit diarrheal bacteria and, simultaneously, that have no negative impact on the gut microbiota, is important. Our results showed that individual combinations of ciprofloxacin with nitroxoline, sanguinarine, and zinc pyrithione produced synergism against the pathogenic bacteria, whereas their antagonistic interaction toward the beneficial strains was observed. The antagonism can be considered a positive effect contributing to the safety of the therapeutic agents, whereas their synergism against diarrheal bacteria significantly potentiates total antimicrobial efficacy. The certain combinations tested in this study can be used for the development of antidiarrheal agents with reduced harmful action on the gastrointestinal microbiome.

• Klíčová slova
• antagonism, antimicrobial agents, diarrhea, gut microbiota, selectivity, synergism,
• MeSH
• antibakteriální látky farmakologie   MeSH
• Bacteria MeSH
• benzylisochinoliny * MeSH
• Bifidobacterium MeSH
• ciprofloxacin farmakologie   MeSH
• lidé MeSH
• nitrochinoliny * MeSH
• obstipancia MeSH
• průjem farmakoterapie   MeSH
• pyridiny farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antibakteriální látky MeSH
• benzylisochinoliny * MeSH
• ciprofloxacin MeSH
• nitrochinoliny * MeSH
• nitroxoline MeSH Prohlížeč
• obstipancia MeSH
• pyridiny MeSH
• pyrithione zinc MeSH Prohlížeč
• sanguinarine MeSH Prohlížeč

Musculoskeletal infections (MIs) are among the most difficult-to-treat staphylococcal diseases due to antibiotic resistance. This has encouraged the development of innovative strategies, such as combination therapy, to combat MI. The aim of this study was to investigate the in vitro antistaphylococcal activity of anti-inflammatory drugs and the combined antimicrobial effect of celecoxib and oxacillin. The minimum inhibitory concentrations (MICs) of 17 anti-inflammatory drugs against standard strains and clinical isolates of S. aureus, including methicillin-resistant strains (MRSAs), were determined using the broth microdilution method. The fractional inhibitory concentration indices (FICIs) were evaluated using checkerboard assays. Celecoxib produced the most potent antistaphylococcal effect against all tested strains (MICs ranging from 32 to 64 mg/L), followed by that of diacerein against MRSA3 and MRSA ATCC 33592 (MIC 64 mg/L). Several synergistic effects were observed against the tested S. aureus strains, including MRSA (FICI ranging from 0.087 to 0.471). The strongest synergistic interaction (FICI 0.087) was against MRSA ATCC 33592 at a celecoxib concentration of 2 mg/L, with a 19-fold oxacillin MIC reduction (from 512 to 26.888 mg/L). This is the first report on the combined antistaphylococcal effect of celecoxib and oxacillin. These findings suggest celecoxib and its combination with oxacillin as perspective agents for research focused on the development of novel therapies for MI caused by S. aureus. This study further indicates that celecoxib could resensitize certain MRSA strains, in some cases, to be susceptible to β-lactams (e.g., oxacillin) that were not previously tested. It is essential to mention that the in vitro concentrations of anti-inflammatory drugs are higher than those typically obtained in patients. Therefore, an alternative option for its administration could be the use of a drug delivery system for the controlled slow release from an implant at the infection site.

• Klíčová slova
• antibacterial activity, antistaphylococcal synergistic effect, methicillin-resistant S. aureus, musculoskeletal infections, non-steroidal anti-inflammatory drugs,
• MeSH
• antibakteriální látky * farmakologie   MeSH
• antiflogistika * farmakologie   MeSH
• celekoxib * farmakologie   MeSH
• lidé MeSH
• methicilin rezistentní Staphylococcus aureus * účinky léků   MeSH
• mikrobiální testy citlivosti * MeSH
• oxacilin * farmakologie   MeSH
• stafylokokové infekce farmakoterapie   mikrobiologie   MeSH
• Staphylococcus aureus * účinky léků   MeSH
• synergismus léků * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antibakteriální látky * MeSH
• antiflogistika * MeSH
• celekoxib * MeSH
• oxacilin * MeSH

Staphylococcal infections are often hard to treat due to increasing resistance, especially to β-lactams. Previous studies described the synergy between common antibiotics and isoflavonoids; however, little is yet known about the combinatory effects of antibiotics with products of human isoflavone metabolism. In this study, demethyltexasin (DT), a human body metabolite of soybean isoflavones, was evaluated for its possible antistaphylococcal combinatory effect with amoxicillin and oxacillin. For comparison, common therapeutically used combination of amoxicillin/clavulanic acid was tested. DT showed strong synergistic interactions against most of Staphylococcus aureus strains when combined with amoxicillin (sum of fractional inhibitory concentrations [ΣFIC] 0.257-0.461) and oxacillin (ΣFIC 0.109-0.484). When oxacillin was combined with DT, resistance to this antibiotic was overcome in many cases. Moreover, antibiotic/DT combinations were effective mainly against methicillin-resistant S. aureus (MRSA); however, the commonly used drug amoxicillin/clavulanic acid was effective only against sensitive strains. Our results indicated DT as a compound able to act synergistically with β-lactams. In addition, some combinations are effective against MRSA and decrease staphylococcal resistance. To the best of our knowledge this is the first report of the antimicrobial synergistic effects of isoflavone human body metabolite with common antibiotics. DT seems to be a possible candidate for further research focused on antistaphylococcal drug development, especially against antibiotic-resistant strains.

• Klíčová slova
• antibiotic resistance, antimicrobial combinatory effect, checkerboard method, β-lactam antibiotics,
• MeSH
• amoxicilin farmakologie   MeSH
• antibakteriální látky farmakologie   MeSH
• fixní kombinace léků MeSH
• isoflavony farmakologie   MeSH
• kombinace amoxicilinu a kyseliny klavulanové farmakologie   MeSH
• lidé MeSH
• methicilin rezistentní Staphylococcus aureus účinky léků   růst a vývoj   MeSH
• mikrobiální testy citlivosti MeSH
• oxacilin farmakologie   MeSH
• rezistence na methicilin účinky léků   MeSH
• Staphylococcus aureus účinky léků   růst a vývoj   MeSH
• synergismus léků MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 6,7,4'-trihydroxyisoflavone MeSH Prohlížeč
• amoxicilin MeSH
• antibakteriální látky MeSH
• fixní kombinace léků MeSH
• isoflavony MeSH
• kombinace amoxicilinu a kyseliny klavulanové MeSH
• oxacilin MeSH

The emergence of biofilm-induced drug tolerance poses a critical challenge to public healthcare management. Pseudomonas aeruginosa, a gram-negative opportunistic bacterium, is involved in various biofilm-associated infections in human hosts. Towards this direction, in the present study, a combinatorial approach has been explored as it is a demonstrably effective strategy for managing microbial infections. Thus, P. aeruginosa has been treated with cuminaldehyde (a naturally occurring phytochemical) and gentamicin (an aminoglycoside antibiotic) in connection to the effective management of the biofilm challenges. It was also observed that the test molecules could show increased antimicrobial activity against P. aeruginosa. A fractional inhibitory concentration index (FICI) of 0.65 suggested an additive interaction between cuminaldehyde and gentamicin. Besides, a series of experiments such as crystal violet assay, estimation of extracellular polymeric substance (EPS), and microscopic images indicated that an enhanced antibiofilm activity was obtained when the selected compounds were applied together on P. aeruginosa. Furthermore, the combination of the selected compounds was found to reduce the secretion of virulence factors from P. aeruginosa. Taken together, this study suggested that the combinatorial application of cuminaldehyde and gentamicin could be considered an effective approach towards the control of biofilm-linked infections caused by P. aeruginosa.

• Klíčová slova
• Pseudomonas aeruginosa, Antibiofilm, Antimicrobial, Cuminaldehyde, Gentamicin,
• MeSH
• antibakteriální látky * farmakologie   MeSH
• benzaldehydy * farmakologie   MeSH
• biofilmy * účinky léků   MeSH
• cymeny farmakologie   MeSH
• faktory virulence MeSH
• gentamiciny * farmakologie   MeSH
• lidé MeSH
• mikrobiální testy citlivosti * MeSH
• Pseudomonas aeruginosa * účinky léků   fyziologie   MeSH
• synergismus léků MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antibakteriální látky * MeSH
• benzaldehydy * MeSH
• cuminaldehyde MeSH Prohlížeč
• cymeny MeSH
• faktory virulence MeSH
• gentamiciny * MeSH

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), the major active constituent of Plumbago indica L., has been shown to be effective against a wide range of infectious microbes. In this study, plumbagin has been evaluated in vitro for its antifungal combinatory effect with amphotericin B against Candida albicans (C. albicans) clinical isolates and anti-hepatitis C virus (HCV) activity. Antifungal activity was determined by broth microdilution method, and combinatory effect was evaluated by checkerboard assay according to ΣFIC indices, while cytotoxicity was determined by MTT assay. Anti-HCV activity was determined in infected Huh7.5 cells using quantitative real-time reverse transcription PCR, and cytotoxicity was evaluated by MTT assay. Plumbagin exerted inhibitory effect against all C. albicans strains with minimum inhibitory concentration values ranging from 7.41 to 11.24 µg/mL. The additive effect of plumbagin when combined with amphotericin B at concentrations of (0.12, 0.13 and 0.19, 1.81 µg/mL, respectively) was obtained against five of seven strains tested with ΣFIC ranging from 0.62 to 0.91. In addition, plumbagin was found to be used safely for topical application when combined with amphotericin B at concentrations corresponding to the additive effect. Plumbagin exerted anti-HCV activity compared with that of telaprevir with IC50 values of 0.57 and 0.01 μM/L, respectively, and selectivity indices SI = 53.7 and SI = 2127, respectively. Our results present plumbagin as a potential therapeutic agent in the treatment of C. albicans and HCV infections. Copyright © 2016 John Wiley & Sons, Ltd.

• Klíčová slova
• HCV infection, antimicrobial agents, fungal infection, natural products, plumbagin,
• MeSH
• amfotericin B farmakologie   terapeutické užití   MeSH
• antifungální látky farmakologie   terapeutické užití   MeSH
• Candida albicans účinky léků   MeSH
• Hepacivirus účinky léků   MeSH
• lidé MeSH
• naftochinony aplikace a dávkování   terapeutické užití   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• amfotericin B MeSH
• antifungální látky MeSH
• naftochinony MeSH
• plumbagin MeSH Prohlížeč

Context The increasing problem of drug-resistant strains has led to the failure of current treatment regimens of Helicobacter pylori (HP) infection. Recently, a new treatment strategy has been developed to overcome the problem by using natural products in combination with antibiotics to enhance the treatment efficacy. Objective The antimicrobial combinatory effect of the aqueous extract of Hibiscus sabdariffa L. (Malvaceae) (AEHS) with antibiotics (clarithromycin, CLA; amoxicillin, AMX; metronidazole, MTZ) has been evaluated in vitro against HP strains. Materials and methods Hibiscus calyces (35 g) were brewed in 250 mL of boiled water for 30 min, and minimum inhibitory concentrations (MICs) were determined by agar dilution method. The checkerboard assay was used to evaluate the antimicrobial combinatory effect according to the sum of fractional inhibitory concentration (∑FIC) indices. Results In this study, AEHS exerted remarkable bacteriostatic effect against all HP strains tested with MICs values ranging from 9.18 to 16.68 μg/mL. Synergy effect of AEHS with CLA or MTZ was obtained against four of seven HP strains tested with ∑FIC ranging from 0.21 to 0.39. The additive effect of AEHS with AMX was obtained against five of seven HP strains tested with ∑FIC ranging from 0.61 to 0.91. Conclusion This study presents AEHS as a potent therapeutic candidate alone, or in combination with antibiotics for the treatment of HP infection.

• Klíčová slova
• Antimicrobial agents, H. pylori infection, combinatory effect, drug-resistant strains, natural products,
• MeSH
• amoxicilin farmakologie   MeSH
• antibakteriální látky izolace a purifikace   farmakologie   MeSH
• fytoterapie MeSH
• Helicobacter pylori účinky léků   růst a vývoj   izolace a purifikace   MeSH
• Hibiscus chemie   MeSH
• infekce vyvolané Helicobacter pylori farmakoterapie   mikrobiologie   MeSH
• klarithromycin farmakologie   MeSH
• kombinovaná farmakoterapie MeSH
• květy MeSH
• léčivé rostliny MeSH
• lidé MeSH
• metronidazol farmakologie   MeSH
• mikrobiální testy citlivosti MeSH
• rostlinné extrakty izolace a purifikace   farmakologie   MeSH
• synergismus léků MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• amoxicilin MeSH
• antibakteriální látky MeSH
• klarithromycin MeSH
• metronidazol MeSH
• rostlinné extrakty MeSH