Inappropriate and uncontrolled use of antibiotics in humans and animals leads to the emergence of multi-resistant bacteria. Before the discovery of antibiotics, plant extracts and essential oils were used for therapeutic purposes. Today, due to increasing antibiotic resistance, many studies are frequently carried out on the antimicrobial activities of natural active substances that can be a source for new drug candidates. The aim of this study was to investigate the antibacterial activity of components such as α-pinene (α-PN), p-cymene (p-CYM), carvacrol (CAR), thymol (TY) and eugenol (EG) found in the essential oils of many plants and their synergistic interaction with antibiotics. In this study, the antibacterial activity of these essential oil components and antibiotics in clinical use such as gentamicin (GEN), tetracycline (TET), tigecycline (TGC) and linezolid (LZD), against Staphylococcus aureus [methicillin resistant S.aureus (MRSA), and methicillin sensitive S.aureus (MSSA)], Escherichia coli and Pseudomonas aeruginosa strains were determined by disc diffusion and microdilution method. In addition, the interaction between the essential oil components and antibiotics was also determined by the checkerboard method. While CAR, TY and EG components showed strong antibacterial activity, the antibacterial activity of αPN and p-CYM was found to be weak. Combinations of α-pinene, carvacrol, thymol and eugenol with gentamicin and tetracycline mostly showed synergistic interactions against all bacteria. In αPN, CAR, TY and EG with GEN and TET, synergistic/partial synergistic interaction was observed against S.aureus strains, while indifferent interaction was detected in E.coli and P.aeruginosa strains. The combination of αPN and p-CYM with TGC showed synergistic interaction against E.coli and P.aeruginosa strains, and additive and indifferent interaction against S.aureus strains. On the other hand, synergistic interaction was observed against all bacterial strains in combinations of TGC and CAR, TY and EG components. Antagonistic interaction was not detected in any of the tested component-antibiotic combinations against the bacteria used in our study. A synergistic interaction between natural bioactive components and commonly used antibiotics may contribute to the effectiveness of antibiotics and components at lower doses, minimizing their potential toxic side effects and reducing treatment costs. However, more research is needed in terms of their pharmacokinetic and toxic properties to evaluate the therapeutic application potential of phytochemicals.

In this study, it was aimed to investigate the antimalarial activity of cinnamaldehyde (CIN) and cannabidiol (CBD) which have shown various biological activities such as potent antimicrobial activity and eravacycline (ERA), a new generation tetracycline derivative, in an in vivo malaria model. The cytotoxic activities of the active substances were determined by the MTT method against L929 mouse fibroblasts and their antimalarial activity were determined by the four-day test in an in vivo mouse model. In this study, five groups were formed: the CIN group, the CBD group, the ERA group, the chloroquine group (CQ) and the untreated group (TAG). 2.5 x 107 parasites/mL of P.berghei-infected erythrocyte suspension was administered IP to all mice. The determined doses of active substances were given to the mice by oral gavage in accordance with the four-day test and the parasitemia status in the mice was controlled for 21 days with smear preparations made from the blood taken from the tail end of the mice. The IC50 values, which express the cytotoxic activity values of the active substances were determined as 27.55 μg/mL, 16.40 μM and 48.82 μg/mL for CIN, CBD and ERA, respectively. The mean parasitemia rate in untreated mice was 33% on day nine and all mice died on day 11. On the ninth day, when compared with the TAG group, no parasites were observed in the CIN group, while the average parasitemia was 0.08% in the CBD group and 17.8% in the ERA group. Compared to the mice in the TAG group, the life expectancy of the other groups was prolonged by eight days in the CIN group, 12 days in the CBD group and eight days in the ERA group. It has been determined that all three active subtances tested in this study suppressed the development of Plasmodium parasites in an in vivo mouse model and prolonged the life span of the mice. It is thought that the strong antimalarial activity of CIN and CBD shown in the study and the possible positive effect of ERA on the clinical course can be improved by combining them with the existing and potential antimalarial molecules.

In recent years, isolation of resistant Leishmania species to drugs in use has made it necessary to search alternative molecules that may be drug candidates. In this study, it was aimed to investigate the cytotoxic and in vitro antileishmanial activity of hybrid silver nanoparticle (AgNP) complexes. In this study, three types of nanoparticles (NPs), oxidized amylose-silver (OA-Ag) NPs, oxidized amylose-curcumin (OA-Cur) NPs and oxidized amylose-curcumin-silver (OA-CurAgNP) nanoparticles were synthesized. The cytotoxic activity of the synthesized nanoparticles was determined against L929 mouse fibroblasts and the in vitro antileishmanial activity was determined against Leishmania tropica, Leishmania infantum and Leishmania donovani isolates by the broth microdilution method. It was observed that the hybrid OA-CurAgNP complex obtained by combining curcumin and silver nanoparticles showed cytotoxic effects against L929 mouse fibroblasts at concentrations of 1074 µg/mL and above. IC50 values expressing the antileishmanial activity of the hybrid OA-CurAgNP complex against L.tropica, L.infantum and L.donovani isolates, were found to vary between 95-121 µg/mL, 202-330 µg/mL and 210-254 µg/mL, respectively. Resistance development has emerged as a major challenge in the treatment of leishmaniasis in recent times. Metallic nanoparticles are considered excellent candidates for medical applications due to their chemical and physical properties, as well as their prolonged circulation in the body. The current drugs used for leishmaniasis treatment are highly toxic, while nanoparticles offer advantages such as low toxicity and easy cellular uptake due to their nanoscale dimensions. The identification of strong efficacy in these particles may contribute scientific evidence for their potential use in leishmaniasis treatment. Therefore, the therapeutical value of OA-CurAgNP complex alone in combination with existing drugs should be examined.

Human African trypanosomiasis, also known as sleeping sickness, is a parasitic disease in which Glossina is transmitted by human intervention and Trypanosoma b. rhodosiense and Trypanosoma b. gambiense are the causative agents Production of parasites in axenic cultures provides great advantage in parasite biochemistry, immunological, physiological and molecular studies. In this study, it is aimed to determine the medium which will produce in vigorous amount of Trypanosoma b. rhodosiense and Trypanasoma cruzi and to establish a new medium. In this study, Trypanosoma b. rhodosiense and Trypanasoma cruzi strains stored in Manisa Celal Bayar University Parasite Bank will be removed from liquid nitrogen tank under suitable conditions, planted in Medium I, Medium II, Medium III and newly developed medium. Reproductive densities of the media will be statistically analyzed on Thoma lamina depending on the time, using the Sidak’s multiplequality test. As a result of this study, it has been concluded that the best medium, to produce abundantly Trypanosoma b. rhodosiense and Trypanasoma cruzi strains, to be used in diagnosis and active substance screenings, molecular studies, metabolic analyzes and drug studies is the medium IV. This study is one of the first studies related to the production of Trypanosoma species in Turkey and planned to provide a basis for the studies of African sleeping disease, Chagas disease and their agents.

Trichomonas vaginalis is a protozoan parasite with unicellular, flagellate, and anaerobic metabolism. It is the second most prevalent pathogen among sexually transmitted agents after viruses. Microscopic examination, culture, and molecular methods are used in the laboratory diagnosis of T. vaginalis. However, in most routine microbiology laboratories, microscopy is preferred instead of culture and molecular methods for T. vaginalis diagnosis because microscopy is cheaper than other methods. This study aimed to produce T. vaginalis in media that can be detected frequently in microbiology laboratories. In this study, four media, namely, thioglucholate medium (THIO), brain heart infusion medium (BHI), tryptic soy broth medium (TSB), and Brucella broth medium (BRB) were modified and tested. Trypticase-yeast extract-maltose (TYM) medium was used as a reference medium. Each medium tested was enriched with three different serum additives. T. vaginalis trophozoite at a density of 10⁴ parasites/mL was inoculated into each medium and incubated at 37 °C for 10 days. We determined the number of trophozoites using a hemocytometer, and the viability rates were determined using trypan blue. Trichomonas vaginalis grew extremely well on THIO, BHI, and TSB media but not on BRB media. The time and number of parasites peaked were determined as 100×10⁴ parasites/mL on THIO-ATS and THIO-FCS media on days five and four, respectively, 100×10⁴ parasites/mL on BHI-ATS on day three, 98×10⁴ parasite/mL on BHI-FCS media on day five, 100×10⁴ parasites/mL on TSB-ATS on day four, and 82×10⁴ parasite/mL on TSB-FCS media on day seven. Compared with the reference medium, TYM, T. vaginalis trophozoites survived significantly longer in THIO, BHI, and TSB media. The rich content of THIO, TSB, and BHI media, which are widely available in routine microbiology laboratories, may allow T. vaginalis growth.

Microbes are increasingly being explored as tools to control leishmaniasis and sandfly populations. This study investigated the interactions between sandflies, Leishmania, and their microbiota. The in vitro and in vivo survival and development of Leishmania major in the presence of seven bacterial species were assessed. In vitro experiments included Leishmania co-cultures with bacteria applied at different concentrations (10²-10⁸ CFU/ml), monitoring parasite survival/development at early (30-120 min) and late (12-240 h) time points. In vivo experiments in Phlebotomus papatasi examined Leishmania infection rate and intensity on days 2, 6, and 8 post co-infection with the same bacterial species (10⁸ CFU/ml). All bacteria demonstrated negative effects on Leishmania survival and development. Under in vitro conditions, the speed of Leishmania ablation (48-216 h) depended on the bacterial species and concentration, impacting Leishmania motility and viability, and halting the development of metacyclic forms. In vivo studies demonstrated that bacterial overgrowth negatively impacted the intensity of Leishmania infection and percentage of stomodeal valve colonization (27.58-82.14%). The observed effect of bacteria on Leishmania under in vitro and in vivo conditions points out toward the potentially greater role of microbes in Leishmania survival in vectors, highlighting the need for deeper investigations of sandfly-Leishmania-microbiota interactions.