In the present study the antimicrobial potential of various extracts from 12 medicinal plants has been investigated in vitro on multiple antibiotic resistant pathogens and some selected protozoa isolated from poultry. The initial examination was performed on E. coli (n = 10) using disc and agar well diffusion assays. Only two plants, Peganum harmala (seeds) and Eucalyptus globulus (leaves) showed positive responses. The active extracts were also investigated against an additional 19 bacteria and the clonal cultures of three protozoa (Histomonas meleagridis, Tetratrichomonas gallinarum and Blastocystis sp.). Only Peganum harmala was found to inhibit the growth of all bacteria and protozoa at 0.38-1.55 mg/mL and 0.63-1.65 mg/mL, respectively. To investigate the potential role of alkaloids in crude extracts of Peganum harmala, four known beta-carbolin alkaloids were quantified and their antimicrobial activity was compared using a microdilution assay. Harmaline was found to be in the highest concentration followed by harmine and harmalol, whereas harmane could not be detected. The activity of the pure alkaloids was in the order harmane > harmaline > harmalol > or = harmine for all bacteria, while for protozoa, it was different depending on the microorganism. It is concluded that Peganum harmala or its alkaloids could probably be used for the control of antibiotic resistant isolates of bacteria as well as protozoa.

The in vitro antibacterial activities of 29 traditional medicinal plants used in respiratory ailments were assessed on multidrug resistant Gram-positive and Gram-negative bacteria isolated from the sore throat patients and two reference strains. The methanolic, n-hexane, and aqueous extracts were screened by the agar well diffusion assay. Bioactive fractions of effective extracts were identified on TLC coupled with bioautography, while their toxicity was determined using haemolytic assay against human erythrocytes. Qualitative and quantitative phytochemical analysis of effective extracts was also performed. Methanolic extract of 18 plants showed antimicrobial activity against test strains. Adhatoda vasica (ZI = 17–21 mm, MIC: 7.12–62.5 μg/mL), Althaea officinalis (ZI = 16–20 mm, MIC: 15.62–31.25 μg/mL), Cordia latifolia (ZI = 16–20 mm, MIC: 12.62–62.5 μg/mL), Origanum vulgare (ZI = 20–22 mm, MIC: 3–15.62 μg/mL), Thymus vulgaris (ZI = 21–25 mm, MIC: 7.81–31.25 μg/mL), and Ziziphus jujuba (ZI = 14–20 mm, MIC: 7.81–31.25 μg/mL) showed significant antibacterial activity. Alkaloid fractions of Adhatoda vasica, Cordia latifolia, and Origanum vulgare and flavonoid fraction of the Althaea officinalis, Origanum vulgare, Thymus Vulgaris, and Ziziphus jujuba exhibited antimicrobial activity. Effective plant extracts show 0.93–0.7% erythrocyte haemolysis. The results obtained from this study provide a scientific rationale for the traditional use of these herbs and laid the basis for future studies to explore novel antimicrobial compounds.

Peganum harmala seed extracts have been frequently reported to possess antibacterial potential through in vitro studies, but in vivo studies have acquired less attention. The present study was therefore designed to investigate its efficacy on the course of colibacillosis and effects of long-term feeding on selected parameters of general health in chickens. Two experiments were conducted in this regard. Experiment 1 (a pilot study) was performed to determine the dose of a field strain of Escherichia coli (O1:K1) required to induce clinical symptoms in 4- and 15-d-old specific-pathogen-free chickens. A successful induction of colibacillosis, in terms of clinical signs, mortality, and pathological lesions in addition to reisolation of the pathogen was observed by inoculating 4- and 15-d-old chicks with 4.3 log(10) and 6.4 log(10) cfu of E. coli, respectively, by intraperitoneal injection. Using these doses experiment 2 (main study) consisting of a single experiment with 3 parts was performed. Parts A and B generated the information regarding efficacy of the extract against infection in 4- and 15-d-old chickens applying different treatment schemes, whereas the effects of continuous feeding of the extract were assessed in part C. Whereas no protective effect of the extract could be recorded in young chickens, significant differences (P < 0.05) with regard to BW, clinical score, gross lesion score, and total granulocyte counts were observed in 15-d-old birds. Bacterial recovery per gram of tissue and reisolation frequency were lower in treated birds. The continuous feeding of the extract for 6 wk resulted in an augmentation in relative liver weight and depletion in alkaline phosphatase, protein, albumin, and globulin. It can be concluded that the crude extract of Peganum harmala possesses limited antimicrobial activity against E. coli in vivo and long-term continuous feeding may induce undesired effects. Furthermore, the study underlines the value of in vivo experiments and the diverse picture that herbal products, in this case Peganum harmala, may deliver by testing them against specific pathogens.