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Human infectious diseases once treatable with antibiotics are now becoming a serious life-threatening problem due to the emergence of multidrug resistant (MDR) micro-organisms. For this, essential oils (EOs) could constitute a viable source of bioactive compounds capable of inhibiting the mechanisms of this antimicrobial resistance. In this context, our goals were to determine for the first time the chemical composition of EO extracted from aerial parts of Rhus albida, its antibacterial and synergistic interactions with fluoroquinolones and finally to evaluate its ability to inhibit the Staphylococcus aureus NorA efflux pump. The chemical profile and antibacterial activity of R. albida EO were determined using Gas Chromatography coupled to Mass Spectrometry and microdilution assays, respectively. While its NorA efflux-pump-inhibiting activity was assessed using a fluorescent real-time efflux method (based on ethidium bromide (EtBr)) against two S. aureus strains: a NorA overproducing strain (SA1199B) and a wild type strain (SA1199). Results showed that the EO, which is characterized by the abundance sesquiterpenes (δ-cadinene (15.6%), α-copaene (6.3%) and caryophyllene (6.2%)), displayed moderate antimicrobial activities against both SA1199 and SA1199B (MIC = 2048 µg/mL). Nevertheless, its combination with fluoroquinolones contributed to the reduction of their intrinsic MICs only against SA1199B by 4- to 8-fold. Furthermore, the EO at 1/32 MIC, contributed to a large accumulation of EtBr and inhibition of its efflux in SA1199B. Our findings demonstrated the ability of R. albida EO to inhibit the NorA efflux pump. Thus, further studies should be performed in order to make the combination of this natural product with approved antimicrobials a viable option for future administrations in infections with S. aureus strains overproducing NorA EPs.

The aim of this study was to determine the chemical profile of the essential oils (EOs) of three Moroccan lavender species (Lavandula pedunculata, LP; Lavandula angustifolia, LA; and Lavandula maroccana, LM) and to investigate, for the first time, the synergistic effect of the optimal mixture of the EOs with conventional antibiotic ciprofloxacin against three pathogenic foodborne bacteria. Gas chromatography/mass spectrometry analysis showed that eucalyptol (39.05%), camphor (24.21%) and borneol (8.29%) were the dominant compounds of LA-EO. LP-EO was characterized by the abundance of camphor (74.51%) and fenchone (27.06%), whereas carvacrol (42.08%), camphor (17.95%) and fenchone (12.05%) were the main constituents of LM-EO. EOs alone or combined showed a remarkable antimicrobial activity against the tested bacteria with minimum inhibitory concentrations (MICs) ranging from 3.53 mg/mL to 15.96 mg/mL. The optimal mixture, calculated using a mixture design, corresponded to 19% LA, 38% LP and 43% LM. All combination of the EOs and the best EO mixture with ciprofloxacin exhibited a total synergism with fractional inhibitory concentration index (FICI) values ranging from 0.27 to 0.37. The best EO mixture showed the highest gain of 128 fold, especially against Salmonella spp., more than that found testing the EOs separately. These findings should be taken into consideration for a possible application in the pharmaceutical and food industries.

The present work was conducted to study the antioxidant activity and to determine for the first time the antimicrobial potential of Moroccan Cannabis sativa essential oil (EO) singly or in combination with two conventional antibiotics (fluconazol and ciprofloxacin) against some resistant and pathogenic microorganisms. The chemical composition analyzed by means of GC/MS showed that C. sativa EO was characterized by the dominance of (E)-caryophyllene (35.0%), α-humulene (12.8%) and caryophyllene oxide (10.6%). Results from antioxidant tests showed that C. sativa EO exhibit a moderate potency (IC50 = 1.6 ± 0.1 mg/m L for 2,2- diphenyl-1-picrylhydrazyl (DPPH) assay, IC50 = 1.8 ± 0.2 mg/mL for β-carotene/linoleic acid assay, and IC50 = 0.9 ± 0.1 mg/m L for ferric reducing power assay). Regarding antimicrobial assays, the results demonstrated that C. sativa EO displayed interesting antimicrobial activities with minimum inhibitory concentration (MIC) values in the range from (1.2 to 37.8) mg/m L for tested microorganisms. The combination of the studied EO with fluconazol and ciprofloxacin showed a significant decrease in their individual MICs. In fact, at sub-inhibitory concentrations, C. sativa EO contributed to the decrease of ciprofloxacin MICs of bacterial strains by 2- to 64-fold and by16-fold regarding fluconazol MICs against Candida spp. These findings suggest that C. sativa EO can be considered as a potential source of natural antioxidant and antimicrobials, and constitute in combinational treatments a promising strategy to overcome the intense use of antibiotics against some infectious diseases.

Ficus carica is one of the oldest and earliest cultivated fruits in the world. To our knowledge, little information is available on the antimicrobial and antioxidant activities of F. carica...

The aims of the present study were to evaluate for the first time the chemical composition and in vitro antimicrobial potential of essential oil (EO) obtained from endemic Lavandula maroccana (Murb.) singly or in combination with some conventional antimicrobials (ciprofloxacin, vancomycin, fluconazol, and amphotericin B) against a panel of pathogenic microorganisms. The gas chromatography/mass spectrometry (GC/MS) analysis of EO led to the identification of 20 components, representing 98.8% of the total oil. The main constituent was the phenolic monoterpene carvacrol (78.2%), followed by 2-Methoxy-4-vinylphenol (2.5%), and Spathulenol (2.2%). The results of the antimicrobial assays demonstrated that L. maroccana EO displayed moderate activity, with minimal inhibitory concentration (MIC) values of 4.604 mg/mL for yeasts and ranged from 2.302 to 18.416 mg/mL for bacteria. According to FIC index values, the combination between L. maroccana EO and conventional antimicrobials elicited very promising synergistic effects against all tested strains. In fact, at sub-inhibitory concentrations L. maroccana EO contributed to the decrease of fluconazol and amphotericin B MICs of Candida strains by 64- to 128-fold and by 2- to 4-fold, respectively. Regarding bacterial strains, L. maroccana EO has reduced the ciprofloxacin and vancomycin MICs by 4- to 33-fold and by 2- to 4-fold, respectively. From these results, it can be concluded that L. maroccana EO can be considered as a promising source of natural antimicrobials, and constitute a potential candidate to be used in combination antibiotic therapy in order to reduce the overuse of antibiotics, and to combat some human infectious diseases.

Over the past years, the emergence of multidrug-resistant pathogens has become a pressing public health problem. It is an important cause of morbidity and mortality worldwide and puts a considerably financial burden on the health care system. The development of new antimicrobials is becoming increasingly difficult, time-consuming and expensive. Hence, new approaches are urgently needed to replenish our arsenal of antimicrobial agents. Plant tissues contain a wild variety of antimicrobial constituents discovered and used to reverse drugs resistance and restore their efficiency. For this, essential oil (EO) extracted from aerial parts of Senecio anteuphorbium (L) Haw, a Moroccan endemic plant, was studied for the first time for its: (i) Qualitative and quantitative chemical profile, (ii) antimicrobial activities, (iii) and synergistic interactions with two conventional antifungals and ciprofloxacin. The data of the chemical composition showed that S. anteuphorbium EO was characterized by the abundance of γ-selinene (27.2%), cyperene (21.7%), γ-cadinene (11.4%) and α-cyperone (8.1%). Regarding antimicrobial assays, results demonstrated that S. anteuphorbium EO displayed moderate antimicrobial activities with MIC values in the range of 0.51 mg/mL and 1.02 mg/mL for yeasts and between 2.3 mg/mL and 4.6 mg/mL for bacteria. However, the combination of the studied EO with fluconazole and ciprofloxacin showed a significant decrease in their individual MICs. In fact, at sub-inhibitory concentrations S. anteuophorbium EO contributed to the decrease of fluconazole MICs of Candida strains by 4- to 64- fold and by 2- to 16- fold regarding ciprofloxacin MICs. The overall data suggest that the topical or systemic use of S. anteuphorbium EO in combinational treatments may be a promising strategy to combat infectious diseases and further studies should be performed in order to well determine the main mechanism of these synergistic associations.

Inhibition of bacterial efflux mechanisms has been investigated as a promising target to combat the bacterial resistance to antibiotics. The present work investigated the ability of Artemisia herba-alba and Cymbopogon citratus essential oils (EOs) to inhibit efflux pumps of some selected antibiotic-resistant Gram-negative bacteria. The chemical profiles of tested EOs were evaluated by GC–MS. The major constituents of the oils were chrysanthenone (47.0%), camphor (24.0%), and verbenone (7.2%) in A. herba-alba EO and geranial (46.3%), neral (35.2%), and geraniol (5.4%) in C. citratus EO. Antibacterial tests showed that these EOs had high antibacterial activity. This activity was significantly enhanced in the presence of an efflux pump inhibitor, phenylalanine arginyl s-naphthylamide (PAsN). When combined with PAsN, the MIC values against EA27 and AG102 (strains overexpressing efflux pumps) were decreased 32-fold and >32-fold, respectively, for A. herba-alba , and 512-fold and 1024-fold, respectively, for C. citratus EO. The involvement of a lipopolysaccharide (LPS) structure in the resistance to the active compounds of the studied EOs was also demonstrated in Salmonella LPS deep-rough mutants. Moreover, the combination of A. herba-alba and C. citratus EOs, at a low concentration, reduced significantly chloramphenicol MIC 2–4-fold, 4-fold and 8–16-fold, respectively, for EAEP294 (deleted of AcrAB), EA27 and AG102. For Salmonella strains, all tested combinations recorded a gain greater than or equal to 64-fold. It was concluded that these EOs can alter efflux pump activity and may be good candidates for the development of new chemosensitizer drugs able to restore antibiotic activity of some drug-resistant Gram-negative bacteria.

The in vitro antibacterial activity of Thymus riatarum essential oil was evaluated in the present study using different assays toward human pathogenic isolates collected during serious infections. The phytochemical analysis of T. riatarum essential oil (EO) indicated the presence of 20 components, including mainly borneol (41.67%), terpinen-4-ol (8.65%), and trans -caryophyllene (7.59%). Determination of antibacterial activity showed that the EO possesses a noticeable potential of inhibiting the growth of tested strains with Minimum Inhibitory Concentrations (MICs) ranging from 3.57 mL/L to 7.5 mL/L. However, Pseudomonas aeruginosa showed the least sensitivity and was only inhibited with high concentrations (MIC > 7.5 mL/L). The release of cytoplasmic material absorbing at 260 nm, measured in the presence of T. riatarum EO, increased in response to oil concentration. The ability of T. riatarum EO to block efflux pumps systems of resistant Gram-negative bacteria was also studied. The results indicated that the EO activity was significantly enhanced in the presence of an efflux pump inhibitor such as phenylalanine arginyl s-naphthylamide (PAsN). In addition, the tested EO, used at MIC/4, was able to increase chloramphenicol susceptibility of several resistant isolates. These results demonstrated that T. riatarum EO could permeabilize bacterial membrane impairing efflux pump activity and may be used in combination with conventional antibiotics against multidrug-resistant bacteria. To our knowledge, this is the first report about the antibacterial activity and the mode of action of T. riatarum EO.

The aim of this study was to evaluate the antibacterial effect of the association between conventional antibiotics and essential oils (EOs) of endemic Moroccan thyme species, Thymus maroccanus and T. broussonetii, on antibiotic-resistant bacteria involved in nosocomial infections. Synergistic interactions between antibiotics (ciprofloxacin, gentamicin, pristinamycin, and cefixime) and EOs, and between T. maroccanus and T. Broussonetii EOs were determined by the checkerboard test. Serial dilutions of two antimicrobial agents were mixed together so that each row (and column) contained a fixed amount of the first agent and increasing amounts of the second one. The results indicate that the oils had a high inhibitory activity against tested bacteria, except for Pseudomonas aeruginosa. In parallel with the increase of cellular killing, the release of 260nm-absorbing materials from bacterial cells, treated with EOs, increased in response to oil concentration. Out of 80 combinations tested between EOs and antibiotics, 71% showed total synergism, 20% had partial synergistic interaction and 9% showed no effect. Combination with carvacrol, the major constituent of T. maroccanus and T. broussonetii, showed also an interesting synergistic effect in combination with ciprofloxacin. The effect on Gram-positive bacteria was more important than on Gram-negative bacteria. These findings are very promising since the use of these combinations for nosocomial infections treatment is likely to reduce the minimum effective dose of the antibiotics, thus minimizing their possible toxic side effects and treatment cost. However, further investigations are needed to assess the potential for therapeutic application.

Bacterial drug resistance is a worrying public health problem. Antibiotic efflux is a major non-specific resistance mechanism used by bacteria, and efflux pumps are involved in the low-level susceptibility of various important Gram-negative pathogens. Use of molecules that can block bacterial pumps is an attractive strategy, but several studies report only partial efficacy owing to limits of these molecules (stability, selectivity, bioavailability, toxicity, etc.). The objective of this study was to search for natural sources of molecules able to inhibit efflux pump systems of resistant Gram-negative bacteria (Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Salmonella enterica serotype Typhimurium and Pseudomonas aeruginosa). The results indicate that the studied essential oils exhibit interesting activity against the tested bacteria. This activity was significantly enhanced in the presence of an efflux pump inhibitor such as phenylalanine arginyl β-naphthylamide (PAβN). The role of lipopolysaccharide (LPS) structure in the effect of essential oils was also reported in Salmonella LPS deep-rough mutants. In addition, essential oils of Thymus maroccanus and Thymus broussonetii, used at a low concentration (a fraction of the minimum inhibitory concentration), are able to significantly increase chloramphenicol susceptibility of several resistant isolates. These results demonstrate that these essential oils can alter efflux pump activity and may be attractive candidates to develop new drugs for chemosensitising multidrug-resistant strains to clinically used antibiotics.

The dynamic, hemolytic and hemagglutination activities and the antibiotic resistance of non-O1 Vibrio cholerae , Pseudomonas aeruginosa , faecal coliforms (FC) and faecal streptococci (FS), isolated by standard membrane filtration methods from suburban and rural groundwater supplies, were carried out. Detectable non-O1 V. cholerae and P. aeruginosa was present in 81% and 88% of samples. The total occurrence of FC and FS during the period of study was 94%. The annual average densities of non-O1 V. cholerae were 4,903 MPN/100 mL. While, they were 206, 1,891 and 1,246 cfu/100 mL for P. aeruginosa , FC and FS respectively. Non-O1 V. cholerae strains had the highest percentage of hemolytic activities (α + β) (71.29%), whereas 20.71% of FS, 16.88% of FC and 9.13% of P. aeruginosa strains produced hemolysin. Bacterial strains isolated were found to be adhesive, with percentages of 63.09%, 65.09%, 84.06% and 87.98% respectively for non-O1 V. cholerae , FS, FC and P. aeruginosa . As for antibiotic resistance, the overall resistance of non-O1 V. cholerae strains was 79%, whereas it was 100% for the other bacteria. Non-O1 V. cholerae resistance was expressed towards sulfamethoxazole (75%), streptomycin (62%) and cephalothin (60%). Obtained results indicated correlation between bacteriological pollution and their public health implications.

The activated sludge process is one of the biological treatment methods used in many countries to reduce the high levels of organic and mineral pollutants and pathogenic micro-organisms present in wastewater. The present work was undertaken to study the dynamic and antibiotic-resistance of faecal coliforms (FC) in the activated sludge system of Beni Mellal. This work has also as objective the study of the survival of FC, protozoan cysts, helminth eggs and FC antibiotic resistance in the sludge dehydrated in drying beds in order to know if the agricultural usage of sludge presents any problems to public health. The activated sludge treatment of Beni Mellal resulted in an average reduction of FC and faecal streptococci of 90.75 and 91.06%, respectively. The overall resistance (resistance to at least one antibiotic) of 111 FC strains isolated from the system was 72.07%. This treatment system did not increase the incidence of FC antibiotic resistance in treated wastewaters. The antibiotic resistance of FC was found to be similar in both raw (71.05%) and treated sewage (77.77%). High levels of antibiotic resistance were towards streptomycin (54.05%), ampicillin (42.34%), amoxicillin (42.34%) and amoxicillin–clavulanic acid (31.53%). The treatment of sludge in drying beds appeared to be efficient in eliminating pathogenic micro-organisms: FC, protozoan cysts and helminth eggs. Moreover, the FC antibiotic resistance did not change over time in sludge-drying bed. According to the standard norms, agricultural utilization of this sludge cannot be excluded. However, it is important to study in the receptor environment the survival and the behaviour of antibiotic-resistant FC present in sludge and water.

In waste stabilisation pond systems the interactions between algae and bacteria have an important ecological effect and appeared to play a key role in the self-purification process. The aim of the present study is to evaluate the interactions between two axenic cyanobacteria: Synechocystis sp. and Pseudanabaena sp. with heterotrophic bacteria and some pathogenic bacteria: E. coli, Salmonella sp. and non-O1 V. cholerae. The results obtained showed that Synechocystis sp. (planktonic cyanobacterium) and Pseudanabaena sp. (benthic cyanobacterium) stimulated the growth and the survival of heterotrophic bacteria and non-O1 V. cholerae and reduced the survival of E. coli and Salmonella. Blooms of these cyanobacteria during hot periods which are a particularity in stabilisation ponds of Marrakech, could explain the dynamics of bacteria studied in this sewage treatment process. The presence of heterotrophic bacteria, showing relative high densities during hot periods, could be considered as an important bioticfactor which led to the cyanobacteria blooms in the Marrakech ponds which function under an arid Mediterranean climate.

The abundance and antibiotic resistance of non-O1 Vibrio cholerae strains were studied in wastewater before and after treatment in stabilization ponds in an arid Mediterranean climate. The seasonal abundance of non-O1 Vibrio cholerae was the inverse of those of fecal coliforms, with high densities in hot periods and low densities in cold periods. Although the stabilization pond presents a good efficiency in removing fecal coliforms (97.97%), this treatment system did not produce any significant reduction in non-O1 V. cholerae abundances between the inflow and outflow stations. Among the 240 non-O1 V. cholerae strains isolated before and after treatment in the stabilization ponds, 89 (37.1%) isolates were resistant to at least one of 14 tested antibiotics. The levels of antibiotic resistance at the inflow and outflow points of the system were respectively 40 and 34%. High ampicillin, amoxicillin and mezlocillin resistance was observed at all sampling points, followed by resistance to cefalexin, cefoperazone and amikacin. Antibiotic resistance can be transferred from non-O1 V. cholerae to other members of the Enterobacteriaceae family such as Escherichia coli K12. Transfer frequencies in nutrient broth and filtered wastewater were 3 × 10−5 and 2 × 10−8, respectively.