Characterization of Bacillus Species Isolated from the Soil of Triveni Plant Assembly and Their Larvicidal Activity against Aedes aegypti

The Aedes aegypti mosquito is the primary vector of Dengue, Chikungunya and Zika causing major problems for public health, which requires new strategies for its control, like the use of entomopathogenic microorganisms. In this study, bacteria from various Amazonian environments were isolated and tested for their pathogenicity to A. aegypti larvae. Following thermal shock to select sporulated Bacillus spp., 77 bacterial strains were isolated. Molecular identification per 16S RNA sequences revealed that the assembled strains contained several species of the genus Bacillus and one species each of Brevibacillus, Klebsiella, Serratia, Achromobacter and Brevundimonas. Among the isolated Bacillus sp. strains, 19 showed larvicidal activity against A. aegypti. Two strains of Brevibacillus halotolerans also displayed larvicidal activity. For the first time, larvicidal activity against A. aegypti was identified for a strain of Brevibacillus halotolerans. Supernatant and pellet fractions of bacterial cultures were tested separately for larvicidal activities. Eight strains contained isolated fractions resulting in at least 50% mortality when tested at a concentration of 5 mg/mL. Further studies are needed to characterize the active larvicidal metabolites produced by these microorganisms and define their mechanisms of action.

Stinkvine ( Paederia foetida L.) is known as a plant that has many properties that are empirically used in traditional medicine. However, information of utilization of Stinkvine leaf outside as a traditional medicine has not been discovered yet. This research aims to determine the potential larvicidal extracts and fractions of stinkvine leaf. The ethanol extract of stinkvine leaf fractionated using column chromatography with n-hexane, ethyl acetate, and methanol. Larvicidal activity test against Aedes aegypti and Anopheles III instar was done using 25 larvae for each treatment extracts and fractions in 5 series of concentration, and left exposed for 24 hours. Total mortality of larvae is calculated and analyzed using a modified Finney probit to determine the LC50 and LC90 values. The results showed larvicidal activity on larvae of Aedes aegypti mosquitoes with LC50 and LC90 value of n-hexane, ethyl acetate, and methanol fraction respectively 67,89 ; 10,92 ; 30,98 µg/mL and 114,11 ; 18,80 ; 54, 12 µg/mL. Larvicidal activity on larvae of Anopheles mosquitoes with LC50 and LC90 value of n-hexane, ethyl acetate, and methanol fraction respectively 50,76 ; 14,96 ; 60,82 µg/mL and 87,23 ; 25,65 ; 90,92 µg/mL. Ethyl acetate fraction of ethanol extract of stinkvine leaf ( Paederia foetida L.) shows to have highest larvicidal activity against the mosquito larvae of Aedes aegypti and Anopheles. The results of GC-MS analysis of the ethyl acetate fraction showed there are 15 compounds, a constituent component consisting of lupeol (20,32 %), gamma-sitosterol (12,22 %), cyclohexanecarboxamide (11,82 %), campesterol (11,45 %), 3-butenol, 4- (2,6,6-trimethyl-1-sikloheksenil) (7,98 %), siklolanos-24-en-3-ol (7,87%), and there are 9 other components with a percentage amount of 0,18 to 5,86 %.

Aim and objectives: Mosquitoes are the transmitters of serious human diseases that cause millions of deaths every year. The use of synthetic insecticides causes harmful side effects to the environment and human health. So a natural alternative way is needed to solve this problem. Extracts from the various parts of plants like leaves, seeds, barks and roots can be used to control mosquitoes. This study aims to evaluate the larvicidal activity of ethanolic seed and leaf extracts of a traditionally used medicinal plant Croton tiglium, against Aedes aegypti, the vector of dengue fever. Material and methods: In this study, extracts from the dried leaf and seed powder of the Croton tiglium plant were extracted using ethanol in a soxhlet apparatus. Different concentrations were prepared from the extracts. Third instar larvae of Aedes aegypti were collected from the mosquito culture laboratory of the Life Sciences Department of Dibrugarh University. Prepared concentrations of the extracts were tested against the larvae of Aedes aegypti to evaluate the larvicidal activity by calculating percent mortality. Result: The ethanolic leaf and seed extracts of the selected plant were found effective against the larvae of Aedes aegypti. The 250 ppm concentration of both leaf and seed extracts showed the highest mortality of mosquito larva. The seed extract of this plant was found more effective in killing mosquito larva. Conclusion: From the study, it can be concluded that the ethanolic leaf and seed extracts of Croton tiglium possess larvicidal activity against Aedes aegypti. Hence, it could be useful in controlling mosquitoes without any harmful effects. However, further study and investigation will be needed to isolate and characterize bioactive components from this plant with larvicidal activity and the development of drugs for dengue from the components

BackgroundAedes aegypti is a potential vector of West Nile, Japanese encephalitis, chikungunya, dengue and Zika viruses. Alternative control measurements of the vector are needed to overcome the problems of environmental contamination and chemical resistance. Xenorhabdus and Photorhabdus are symbionts in the intestine of entomopathogenic nematodes (EPNs) Steinernema spp. and Heterorhabditis spp. These bacteria are able to produce a broad range of bioactive compounds including antimicrobial, antiparasitic, cytotoxic and insecticidal compounds. The objectives of this study were to identify Xenorhabdus and Photorhabdus isolated from EPNs in upper northern Thailand and to study their larvicidal activity against Ae. aegypti larvae.ResultsA total of 60 isolates of symbiotic bacteria isolated from EPNs consisted of Xenorhabdus (32 isolates) and Photorhabdus (28 isolates). Based on recA gene sequencing, BLASTN and phylogenetic analysis, 27 isolates of Xenorhabdus were identical and closely related to X. stockiae, 4 isolates were identical to X. miraniensis, and one isolate was identical to X. ehlersii. Twenty-seven isolates of Photorhabdus were closely related to P. luminescens akhurstii and P. luminescens hainanensis, and only one isolate was identical and closely related to P. luminescens laumondii. Xenorhabdus and Photorhabdus were lethal to Ae aegypti larvae. Xenorhabdus ehlersii bMH9.2_TH showed 100% efficiency for killing larvae of both fed and unfed conditions, the highest for control of Ae. aegypti larvae and X. stockiae (bLPA18.4_TH) was likely to be effective in killing Ae. aegypti larvae given the mortality rates above 60% at 72 h and 96 h.ConclusionsThe common species in the study area are X. stockiae, P. luminescens akhurstii, and P. luminescens hainanensis. Three symbiotic associations identified included P. luminescens akhurstii-H. gerrardi, P. luminescens hainanensis-H. gerrardi and X. ehlersii-S. Scarabaei which are new observations of importance to our knowledge of the biodiversity of, and relationships between, EPNs and their symbiotic bacteria. Based on the biological assay, X. ehlersii bMH9.2_TH begins to kill Ae. aegypti larvae within 48 h and has the most potential as a pathogen to the larvae. These data indicate that X. ehlersii may be an alternative biological control agent for Ae. aegypti and other mosquitoes.

Fatty acid-rich volatile oil from Syagrus coronata seeds has larvicidal and oviposition-deterrent activities against Aedes aegypti

Tetradenia riparia (Hochst.) Codd (Lamiaceae) is a shrub, commonly known as ginger bush or false myrrh, and several studies have shown that T. riparia exhibits a variety of biological properties. This study aimed to determine the chemical composition of T. riparia essential oil and its fractions, investigate their anticholinesterase activity, and assess their larvicidal activity against the cattle tick Rhipicephalus microplus and the mosquito Aedes aegypti. Eleven essential oil fractions were obtained by fractionation and analyzed by gas chromatography/mass spectrometry. Larvicidal activity against R. microplus and third-instar A. aegypti was assessed using a larval packet test and a larval immersion test, respectively. Anticholinesterase activity was determined by a bioautographic method. Forty-nine compounds were identified in the essential oil, of which the major classes were oxygenated sesquiterpenes (45.95%) and sesquiterpene hydrocarbons (35.20%) and the major components were isospathulenol (17.40%), β-caryophyllene (15.61%), 14-hydroxy-9-epi-caryophyllene (10.07%), 14-hydroxy-α-muurolene (8.32%), and 9β,13β-epoxy-7-abietene (5.53%). Bioassays showed that T. riparia essential oil (LC50 = 1.56 µg/mL) and FR3 (LC50 = 0.30 µg/mL) were the most active against R. microplus and A. aegypti larvae, respectively. The essential oil and FR1, FR2, and FR3 exhibited acetylcholinesterase inhibitory activity. These results indicate that T. riparia essential oil and its fractions hold promise in the development of novel, environmentally safe agents for the control of R. microplus and A. aegypti larvae.

Aedes aegypti is a vector of dengue fever and yellow fever, and is the cause of high rates of human morbidity and mortality worldwide. There is a tremendous need for new efficacious compounds to protect humans from mosquito bites. Natural repellents from essential oils have the advantage of potential low mammalian and environmental toxicity. Umbellularia californica Nutt. was well known from the first European settlers as a spice and antibacterial, but also for its insecticide properties. Also known as “California bay laurel”, it is a strong aromatic shrub belonging to the monotypic genus Umbellularia. The insecticidal activity of the essential oil against Ae. Aegypti was investigated by bio-guided assays. The essential oil of U. californica leaves was obtained by steam distillation and its chemical profile was determined using GC-FID and GC-MS. Umbellulone was isolated as one of the major constituents in very high yield (36.7%). Mosquito deterrent and larvicidal activities against Aedes aegypti L were evaluated. The oil showed higher activity against Ae. aegypti larvae than deterrent activity. Therefore, bioassay-guided isolation studies were performed on U. californica oil using larvicidal activity.

Larvicidal and ovicidal activities of phenyl acetic acid isolated from Streptomyces collinus against Culex quinquefasciatus Say and Aedes aegypti L. (Diptera: Culicidae)

Aedes aegypti is a mosquito and vector of dengue, chikungunya and Zika virus making it a serious global health problem. We aimed to evaluate the chemical composition of the essential oil (EO) of Laurus nobilis leaves obtained at different seasons and its A. aegypti larvicidal activity. The EO was obtained from fresh leaves by hydrodistillation. Larvicidal activity was determined by the larval immersion test. It was identified 37 EO chemical compounds and the major ones were 1,8-cineole and linalool. Seasonal variations affected EO larvicidal activity: spring LC50 was 0.41 mg/mL and LC99 0.77 mg/mL, autumn LC50 was 0.60 mg/mL and LC99 1.37 mg/mL, winter LC50 was 0.66 mg/mL and LC99 3.19 mg/mL and summer LC50 was 0.91 mg/mL and LC99 2.50 mg/mL. The EO extracted during spring showed the highest larvicidal activity on A. aegypti larvae. Our results present a new perspective of L. nobilis EO use as a larvicidal agent.

The purpose of this study was to determine the larvicidal effect of aqueous extracts of different parts of the Plumbago zeylanica plant on the dengue vector, Aedes aegypti. This research assessed P. zeylanica for its larvicide activity against A. aegypti larvae. Five different concentrations of hot and cold aqueous extracts of root, leaf, and stem powders of P. zeylanica were separately prepared. The larvicidal effect of these extracts was assessed against early 1st, 3rd, and 4th instar larvae of Aedes aegypti. Mosquito larvae were sampled, larval populations were monitored before and after application of aqueous extracts, and larval mortality was monitored after 12, 24, and 48 hours. Three trials were carried out under the same conditions. The percentage mortality of larvae in the sample was calculated, and the mean mortality was obtained for the 3 trials. Then the LC50 value was calculated according to the mean mortality with the SPSS package. The lowest LC50 values were obtained for the hot aqueous extracts on 1st instar larvae: root 122.74 mg/l, leaf 274.95 mg/l and stem 275.92 mg/l, 3rd instar larvae: root 129.37 mg/l, leaf 205.74 mg/l and stem 286.21 mg/l, 4th instar larvae: root 165.52 mg/l, leaf 216.89 mg/l and stem 329.94 mg/l and the root was found to have the highest larvicide activity. Finally, it was identified that by using 165.52 mg/l all three larval instar stages could be killed up to 50% and 90% with 280.921 mg/l. The present study reports that Plumbago zeylanica could serve as a potential larvicidal agent.

Objective: Aim of this work was to study the larvicidal activity of Artemisia nilagirica (Clarke) Pamp. and Ocimum sanctum Linn. against dengue, malaria, and filariasis transmitting mosquito larvae. Methods: The larvicidal activity of essential oil, chloroform, petroleum ether, and methanolic extracts of A. nilagirica and O. sanctum were tested against three different mosquito larvae viz., Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus . Late third instar or early fourth instar larvae were selected for the screening. These extracts and essential oil were used for determining the larvicidal activity by using WHO method for evaluation of new larvicidal agent. Results: The result suggests larvicidal activity by essential oil, petroleum ether and chloroform extract of both the plants against all three selected mosquito species, while methanolic extract was found to be inactive up to 300 ppm. Among the essential oil and extracts of A. nilagirica and O. sanctum , essential oil of O. sanctum was found to be the most potent larvicide against C. quinquefasciatus and A. aegypti larvae, while A. nilagirica essential oil was more potent larvicide against A. stephensi larvae. Conclusion: The results suggest the use of the plants in insect control as an alternative method for minimizing the noxious effects of some pesticide compounds on the environment. Thus the essential oil of O. sanctum and A. nilagirica may deliver promising, more selective and biodegradable larvicidal agents.

Aedes aegypti (L.) is the main vector of tropical diseases such as dengue, chikungunya and Zika. Due to the overuse of insecticides, Ae. aegypti resistant populations have increased. Biological control with Lysinibacillus sphaericus (Ahmed) has been used against Culex sp. and Anopheles sp. Although Ae. aegypti is refractory to the binary toxin of L. sphaericus spores, vegetative cells have been shown to be effective against Ae. aegypti larvae. In this work, the effect of L. sphaericus vegetative cells on Ae. aegypti temephos-resistant larvae was assessed under lab and simulated field conditions. L. sphaericus caused about 90% mortality of insecticide-resistant Ae. aegypti larvae under simulated field conditions. Likewise, Ae. aegypti larvae were more sensitive to mixed cultures of L. sphaericus than to individual strains; then, the most effective mixed culture exhibited an LC50 of 1.21 × 105 CFU/mL with Rockefeller larvae and 8.04 × 104 CFU/mL with field-collected larvae. Additionally, we found that mixed cultures composed of two L. sphaericus strains were more effective than a culture formed by the three strains. Our results suggest that mixed cultures comprising L. sphaericus vegetative cells could be useful for controlling temephos-resistant populations of Ae. aegypti, as evidenced by the effectiveness demonstrated under laboratory and simulated field conditions.

Bacillus spp. metabolites are effective in eradicating Aedes aegypti (Diptera: Culicidae) larvae with low toxicity to non-target species

Mosquito larvicidal activity of Aloe vera (Family: Liliaceae) leaf extract and Bacillus sphaericus, against Chikungunya vector, Aedes aegypti

BackgroundThe use of plant-based formulations is an easy and economical method to control insect pests. The objectives of the present study were to evaluate ovicidal and larvicidal potential of ethanolic leaf extracts of four plants, Cyathocline purpurea, Blumea lacera, Neanotis lancifolia, and Neanotis montholonii, and their effects on gut histology of Aedes aegypti (Diptera: Culicidae) larvae. We identified the phytochemicals present in the ethanolic extracts of these plants by LC-MS analysis. The eggs and larvae of A. aegypti were exposed to four concentrations (0.05, 0.1, 0.2, and 0.3 mg/mL) of crude ethanol extracts for different time durations. We observed egg hatching for 48 h, mortality, and gut histology of the 3rd instar larvae after 24, 48, and 72 h of treatments.ResultsLC-MS analysis revealed the presence of various active compounds such as alkaloids, tannins, saponins, and flavonoids in the ethanol extracts of all these plants. The extracts of all plants showed ovicidal activity. The extracts of C. purpurea showed the highest larvicidal activity (LC50 at 72 h = 0.088 mg/mL) followed by B. lacera (LC50 at 72 h = 0.758 mg/mL) while N. lancifolia and N. montholonii extracts did not show significant larvicidal activity. All plant extracts affected gut morphology in concentration and treatment duration-dependent manner. The plant extracts used in the present study have ovicidal properties and affected the gut histology of A. aegypti larvae.ConclusionThese results suggest that C. purpurea has the highest larvicidal activity against A. aegypti larvae and can be further evaluated for application purposes.