In vitro antibacterial activity of several plant extracts and oils against some gram-negative bacteria

Background: Medicinal plants are considered new resources for producing agents that could act as alternatives to antibiotics in the treatment of antibiotic-resistant bacteria. The aim of this study was to evaluate the antibacterial activity of 28 plant extracts and oils against four Gram-negative bacterial species

Methods: Experimental, in vitro, evaluation of the activities of 28 plant extracts and oils as well as some antibiotics against E. coli O157:H7, Yersinia enterocolitica O9, Proteus spp., and Klebsiella pneumoniae was performed. The activity against 15 isolates of each bacterium was determined by disc diffusion method at a concentration of 5%. Microdilution susceptibility assay was used in order to determine the minimal inhibitory concentrations [MICs] of the plant extracts, oils, and antibiotics

Results: Among the evaluated herbs, only Origanum syriacum L., Thymus syriacus Boiss., Syzygium aromaticum L., Juniperus foetidissima Wild, Allium sativum L., Myristica fragrans Houtt, and Cinnamomum zeylanicum L. essential oils and Laurus nobilis L. plant extract showed anti-bacterial activity. The MIC[50] values of these products against the Gram-negative organisms varied from 1.5 [Proteus spp. and K. pneumoniae[and 6.25 micro l/ ml [Yersinia enterocolitica O9] to 12.5 micro l/ml [E. coli O:157]

Conclusion: Among the studied essential oils, O. syriacum L., T. syriacus Boiss., C. zeylanicum L., and S. aromaticum L. essential oils were the most effective. Moreover, Cephalosporin and Ciprofloxacin were the most effective antibiotics against almost all the studied bacteria. Therefore, O. syriacum L., T. syriacus Boiss., C. zeylanicum L., and S. aromaticum L. could act as bactericidal agents against Gram-negative bacteria

Expression and purification of brucella-specific nanobodies

Brucellosis is still considered as one of the major zoonosis afflicting Syrian health and economy. This disease is caused by members of the genus Brucella which are gram-negative bacteria living facultatively within mammalian cells during infection. In this paper, a strategy was developed to introduce a new generation of binders called Nanobodies [Nbs] in our combat against Brucella. Nbs are genetically engineered camelid-derived single-domain antibody fragments that are very stable and highly soluble, making them promising tools in numerous biotechnological and medical applications. In our previous work, three Nb-displaying phages [Nb-phage], referred to as NbBruc01, 02 and 03, were retrieved by a phage display panning of a Nb library constructed from Brucella- immunized camel. In this work, soluble Nbs were produced after recloning their genes in protein expression plasmid followed by purification with affinity chromatography. Interestingly, two of these soluble Nbs [NbBruc02 and 03] were able to detect Brucella antigens from two main Brucella species [B. abortus and B. melitensis] and distinguish them from those of Yersinia. This is remarkable as the camel IgG failed in such antigen discriminations. High similarity, mainly in the structure of lipopolysaccharides [LPS] of these different types of bacteria, causes regular serum cross reactivity and thus lack of specificity urging the need for more accurate diagnostic techniques, e.g. a multiplex PCR. Furthermore, NbBruc02 and 03 targets may represent Brucella immunodominant proteins as shown by immunoblotting. In addition to their own importance, identifying these antigenic targets will open new perspectives for diagnosis, vaccines and treatment of Brucellosis.

antibacterial activity of selected labiatae [Lamiaceae] essential oils against Brucella melitensis

Background: Brucellosis, a zoonosis caused by four species of brucella, has a high morbidity. The major cause of brucellosis worldwide is brucella melitensis. Medicinal plants are considered as new antibacterial sources that could replace conventional antibiotics in the treatment of antibiotic-resistant bacteria. The aim of this study was to evaluate the efficacy of some native plants, alone and in combination with some antibiotics, in the treatment of brucellosis

Methods: The present experimental in vitro study was carried out to evaluate the anti-brucella activities of essential oils of Rosmarinus officinalis L., Origanum syriacum, Thymus syriacus, Salvia palaestina Benth, Mentha piperia, and Lavandula stoechas L., alone and in combination with some antibiotics. The activity against 16 tetracycline-resistant B. melitensis isolates was determined by disc diffusion method incorporating a concentration of 5%. Antibiotic discs were also used as a control. Microdilution brucella broth susceptibility assay was used in order to determine the MICs of essential oils and five antibiotics

Results: Among all the herbs evaluated, only the essential oils of O. syriacum and T. syriacus plants demonstrated most effective anti-brucella activity, and were then chosen for MIC study. The minimal inhibitory concentrations [MIC[50]] of essential oils of O. syriacum and T. syriacus against tetracycline-resistant B. melitensis were 3.125 micro l/ml and 6.25 micro l/ml, respectively

Conclusion: Among the essential oils studied, those of O. syriacum and T. syriacus were most effective. Since a combination of levofloxacin and Thymus syriacus essential oil increased the efficacy of this antibiotic, O. syriacum and T. syriacus are recommended to be used as bactericidal agents against B. melitensis

Effect of medium pH on antibiotic activity against Syrian Brucella spp. isolates

Background: Brucellosis is an endemic zoonosis in Syria, affecting large numbers of animals. There are an increasing number of cases in humans. Brucella is a facultative intracellular pathogen, a small, non-motile, Gram-negative coccobacillus, which causes abortion in domestic animals and a febrile illness in humans

Methods: One hundred isolates collected from different Syrian regions were confirmed to be Brucella melitensis by biochemical tests. The minimum inhibitory concentration [MIC] of 6 antibiotics, alone and in combination, was determined at pH 7.0 and pH 5.0

Results: Ciprofloxacin and sparfloxacin were the most effective antibiotics tested at either pH value. In contrast, rifampicin had low activity and streptomycin was ineffective at either pH value. A combination of rifampicin-doxycycline revealed the highest synergistic activity at both test pH values [against 19/24 and 17/24 isolates, respectively] in vitro. Antagonistic activities were observed using a ciprofloxacin-streptomycin combination [against 9/24 and 13/24 isolates, respectively] as well as a ciprofloxacintetracycline combination [against 6/24 and 9/24 isolates, respectively]. No differences were observed at both test pH values, when combining a Quinolone with rifampicin or doxycycline

Conclusion: Combination of a Quinolone with doxycycline demonstrated good in vitro activity against B. melitensis. Further in vivo studies are necessary to support this suggestion

Inactivation of gram-negative bacteria by low- pressure RF remote plasma excited in N[2]-O[2] mixture and SF[6] gases

The role of low-pressure RF plasma in the inactivation of Escherichia coli O157, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter sakazakii using N[2]-O[2] and SF[6] gases was assessed. 1×10[9] colony-forming units [CFUs] of each bacterial isolate were placed on three polymer foils. The effects of pressure, power, distance from the source, and exposure time to plasma gases were optimized. The best conditions to inactivate the four bacteria were a 91%N[2]-9%O[2] mixture and a 30-minute exposure time. SF[6] gas was more efficient for all the tested isolates in as much as the treatment time was reduced to only three minutes. Therefore, low-pressure plasma could be used to sterilize heat and/or moisture-sensitive medical instruments

Antibacterial activity of thymus syriacus boiss essential oil and Its components against some syrian gram-negative bacteria isolates

Background: Despite the medical discoveries of different medicines and advanced ways of treatment, statistics have shown that the number of patients is increasing. This may be due to chemical drugs used in healthcare, agriculture, and diets. This soaring demand in medicines urges us to look for natural sources such as aromatic plants and essential oils, which are rich in efficient compounds

Methods: Extraction of essential oils was performed using a Clevenger-type apparatus. Identification was achieved using the GC-FID technique. Confirmation was made using the GC-MS technique, and isolation was done using a preparative HPLC, equipped with an aliquots collector. The microdilution broth susceptibility assay was utilized to determine minimum inhibitory concentrations [MICs]

Results: Our in vitro study demonstrated the antibacterial activity of the Thymus syriacus Boiss essential oil and its components against the tested isolates at levels between 0.375 and 50 ƒÊl/ ml. The main components of the T. syriacus essential oil were carvacrol, ƒÁ-terpinene, and s.caryophyllene. MIC90 values for the T. syriacus essential oil against the gram-negative organisms varied between 3.125 and 12.5 ƒÊl/ml. The most effective components against the gram-negative bacteria were thymol, carvacrol, dihydro-carvon, and linalool respectively

Conclusions: The T. syriacus essential oil and some of its components exhibited very good inhibitory effects against Syrian gram-negative isolates

In vitro antibacterial effects of five volatile oil extracts against intramacrophage Brucella abortus 544

Brucella abortus is a gram-negative facultative intracellular bacterium that can cause a highly contagious disease in sheep, goats, cattle and one-humped camels. It is responsible for one of the most important zoonosis in human. The aim of this study was to evaluate the role of Mentha piperita, Origanum majorana, Citrus lemon, Cinnamomum verum and Myristica fragrans essential volatile oil extracts on human macrophages infected by B. abortus 544. Essential volatile oil extracts from M. piperita, O. majorana, C. lemon, C. verum and M. fragrans were extracted. Human macrophages were cultured at a density of 2_10[5] cells per well in sterile 96-well microtiter plates, and infected with B. abortus 544 at a ratio of 1:100 bacteria/cell. Then essential volatile oil extracts were added at a concentration of 1%. At specified times; cells were washed, lysed with 0.1% Triton, and plated on 2YT agar to determine the number of intracellular bacteria. Cinnamomum verum volatile oil at a concentration of 1% had the highest antibacterial activity against B. abortus 544 inside human macrophages. Its inhibitory effect observed from 24 h and continued till 144 h after the infection. Moreover, C. verum [0.1%] in combination with 1% concentration of M. piperita, O. majorana, C. lemon or M. fragrans volatile oil extracts produced a synergistic inhibitory effect against B. abortus 544. The results indicate that, among the five selected oil extracts, C. verum volatile oil applied either separately or in combination with other oil extracts had the most effective antimicrobial activity against Brucella