First Evaluation of Field Evolved Resistance to Commonly Used Insecticides in House Fly Populations from Saudi Arabian Dairy Farms

The house fly, Musca domestica L. (Diptera: Muscidae), is one of the major vectors of several pathogens that affect humans and animals. We evaluated the toxicity of eight insecticides commonly used for house fly control using five field populations collected from dairies in Riyadh, Saudi Arabia. Among the five tested pyrethroids, non to moderate resistance was found in adults of both sexes compared to a susceptible strain. Resistance ratios ranged from 0.5- to 7-fold for alpha-cypermethrin, 2- to 21-fold for deltamethrin, 4- to 19-fold for bifenthrin, 1- to 9-fold for cyfluthrin, and 1- to 8-fold for cypermethrin. Among the three tested organophosphates, low to moderate resistance was found among adult flies compared to the susceptible strain, and the resistance ratios ranged from 4- to 27-fold for fenitrothion, 2- to 14-fold for chlorpyrifos, and 3- to 12-fold for malathion. The median lethal times for the tested insecticides were 3–33 h for alpha-cypermethrin, 3–24 h for deltamethrin, 5–59 h for bifenthrin, 1–7 h for cypermethrin, 0.3–7 h for cyfluthrin, 6–36 h for fenitrothion, 2–21 h for chlorpyrifos, and 3–34 h for malathion. This study presents baseline data pertaining to registered public health insecticides, and the results will assist future studies monitoring insecticide resistance, and the planning of effective integrated vector management programs.

SENSIBILIDAD DE LA GARRAPATA COMÚN DEL BOVINO Rhipicephalus (Boophilus) microplus A IVERMECTINA ESTIMADA CON EL MODELO SIGMOIDEO DE RESPUESTA MÁXIMA O DE HILL

The aim of this study was to obtain pharmacodynamics parameters to detect resistance or susceptibility of R. microplus strains to ivermectin (IVM). Two larvae samples; a susceptible strain (S) and field isolation (T) were treated with increasing concentrations of IVM using the larvae immersion technique the efficacy values measured at 24 hours were analysed with the sigmoidal maximum response so called Hill model as statistical analysis. The results obtained showed that the IVM have an all or nothing response represented by the Hill coefficient value >1 in both samples. Additionally, a low concentration effect was observed as E0 de 12.83% (S) and 9.91% (T). The field isolation larvae were susceptible to IVM in comparison with the susceptible strain by the resistance ratio (RR) which in one case was not significantly greater that one (RR50= 0.756 and RR90=1.009).

QTL mapping of a Brazilian bioethanol strain links the cell wall protein-encoding gene GAS1 to low pH tolerance in S. cerevisiae

Background Saccharomyces cerevisiae is largely applied in many biotechnological processes, from traditional food and beverage industries to modern biofuel and biochemicals factories. During the fermentation process, yeast cells are usually challenged in different harsh conditions, which often impact productivity. Regarding bioethanol production, cell exposure to acidic environments is related to productivity loss on both first- and second-generation ethanol. In this scenario, indigenous strains traditionally used in fermentation stand out as a source of complex genetic architecture, mainly due to their highly robust background—including low pH tolerance. Results In this work, we pioneer the use of QTL mapping to uncover the genetic basis that confers to the industrial strain Pedra-2 (PE-2) acidic tolerance during growth at low pH. First, we developed a fluorescence-based high-throughput approach to collect a large number of haploid cells using flow cytometry. Then, we were able to apply a bulk segregant analysis to solve the genetic basis of low pH resistance in PE-2, which uncovered a region in chromosome X as the major QTL associated with the evaluated phenotype. A reciprocal hemizygosity analysis revealed the allele GAS1, encoding a β-1,3-glucanosyltransferase, as the casual variant in this region. The GAS1 sequence alignment of distinct S. cerevisiae strains pointed out a non-synonymous mutation (A631G) prevalence in wild-type isolates, which is absent in laboratory strains. We further showcase that GAS1 allele swap between PE-2 and a low pH-susceptible strain can improve cell viability on the latter of up to 12% after a sulfuric acid wash process. Conclusion This work revealed GAS1 as one of the main causative genes associated with tolerance to growth at low pH in PE-2. We also showcase how GAS1PE-2 can improve acid resistance of a susceptible strain, suggesting that these findings can be a powerful foundation for the development of more robust and acid-tolerant strains. Our results collectively show the importance of tailored industrial isolated strains in discovering the genetic architecture of relevant traits and its implications over productivity.

QTL Mapping of a Brazilian Bioethanol Strain Unravels the Cell Wall Protein-Encoding Gene GAS1 as a Major Contributor to Low Ph Tolerance in S. Cerevisiae

BACKGROUNDSaccharomyces cerevisiae is largely applied in many biotechnological processes, from traditional food and beverage industries to modern biofuel and biochemicals factories. During the fermentation process, yeast cells are usually challenged in different harsh conditions, which often impact productivity. Regarding bioethanol production, cell exposure to acidic environments is related to productivity loss on both first and second generation ethanol. In this scenario, indigenous strains traditionally used in fermentation stand out as a source of complex genetic architecture, mainly due to their highly robust background - including low pH tolerance. RESULTSIn this work, we pioneer the use of QTL mapping to uncover the genetic basis that endow industrial strain Pedra-2 (PE-2) with outstanding acid resistance. First, we developed a fluorescence-based high-throughput approach to collect a large number of haploid cells using flow cytometry. Then, we were able to apply a bulk segregant analysis to solve the genetic basis of low pH resistance in PE-2, which uncovered a region in chromosome XIII as the major QTL associated with the evaluated phenotype. A reciprocal hemizygosity analysis revealed allele GAS1, encoding a β-1,3-glucanosyltransferase, as the major contributor to this phenotype. The GAS1 sequence alignment of 48 S. cerevisiae strains pointed out a non-synonymous mutation (T211A) prevalence in wild type isolates, which is absent in laboratory strains. We further showcase that GAS1 allele swap between PE-2 and a low pH-susceptible strain can improve cell viability on the latter of up to 12% after a sulfuric acid wash process.CONCLUSIONThis work revealed GAS1 as the major causative gene associated with low pH resistance in PE-2, harboring a non-synonymous mutation persistent in industrial strains. We also showcase how GAS1PE-2 can improve acid resistance of a susceptible strain, suggesting that these findings can be a powerful foundation for the development of more robust and acid-tolerant strains for the industrial production of economically-relevant goods. Our results collectively show the importance of tailored industrial isolated strains in the discovery of the genetic architecture of relevant traits and its implications over productivity.

Evaluation of Developmental and Reproductive Fitness of Laboratory Selected Thiamethoxam Resistance in Black Legume Aphid Aphis craccivora Koch.

Thiamethoxam is a neonicotinoid group of insecticide which are selective agonists of the insect nicotinic acetylcholine receptor (nAChR), a pentameric cys-loop ligand-gated ion channel located in the central nervous system of insects. They provide farmers with invaluable, highly effective tools against some of the world’s most destructive crop pests. Black legume aphids, Aphis craccivora is one of the devastating polyphagous pests in agroecosystem and to manage their population, farmers are still relying on application of synthetic insecticides like Thiamethoxam. To evaluate the risk of resistance development, selection of A. craccivora was done to characterize Thiamethoxam resistance along with evaluation of developmental and reproductive fitness cost of the resistance. About 86.19 folds of resistance were developed after selecting for 24 generations. In the first twelve generations steady development of resistance was noticed followed by development become stiffer till 16th generation and more or less stable till 24th generations. Relative fitness of the selected resistant strain of aphids was decreased with longer nymphal duration and adult longevity. The mean nymphal duration was increased from 4.35±1.02 days (in F0) to 7.9±0.57 days (in F24). The fecundity rate was significantly less in resistant population (16.0±5.34) as compared to the susceptible strain (54.71±7.63) whereas, oviposition periods were significantly longer (12.49±1.44 days) in resistant population as compare to susceptible strain (9.50±1.22 days).

Structure and Properties of the di- ((2S) -2-amino-3- (1H-indol-3-yl)propionate)-dihydro-tetraiodide

New organic iodine complex in the amino acid - alkali metal salt - iodine - water systemwas synthesized. The physico-chemical properties of complexdi- ((2S) -2-amino-3- (1H-indol-3-yl) propionate)-dihydro-tetraiodide were studied. Microscopic analysis shows that particles of complex have elongated needle-like linear stick-like shapes with average size 2.50-4.00 µm. The cytotoxicity test on MDCK cell culture, antimicrobial activity on S. aureus ATCC 6538-Р (museum susceptible strain); S. aureus ATCC-BAA-39 (museum multiresistant strain); E. coli ATCC 8739 (museum susceptible strain); E. coli ATCC-BAA-196 (museum multiresistant strain); P. aeruginosa ATCC 9027 (museum susceptible strain); P. aeruginosa TA2were observed. Complex has low cytotoxicity, direct antiviral effect, and antimicrobial activity against antibiotic-resistant strains of microorganisms. Di- ((2S) -2-amino-3- (1H-indol-3-yl) propionate)-dihydro-tetraiodide does not cause any mutagenic effect on mammalian cells of the L5178Y line, both in the presence and in the absence of metabolic activation.

Impact of deltamethrin-resistance in Aedes albopictus on its fitness cost and vector competence

Background Aedes albopictus is one of the most invasive species in the world as well as the important vector for mosquito-borne diseases such as dengue fever, chikungunya fever and zika virus disease. Chemical control of mosquitoes is an effective method to control mosquito-borne diseases, however, the wide and improper application of insecticides for vector control has led to serious resistance problems. At present, there have been many reports on the resistance to pyrethroid insecticides in vector mosquitoes including deltamethrin to Aedes albopictus. However, the fitness cost and vector competence of deltamethrin resistant Aedes albopictus remain unknown. To understand the impact of insecticide resistant mosquito is of great significance for the prevention and control mosquitoes and mosquito-borne diseases. Methodology/Principal findings A laboratory resistant strain (Lab-R) of Aedes albopictus was established by deltamethrin insecticide selecting from the laboratory susceptible strain (Lab-S). The life table between the two strains were comparatively analyzed. The average development time of Lab-R and Lab-S in larvae was 9.7 days and 8.2 days (P < 0.005), and in pupae was 2.0 days and 1.8 days respectively (P > 0.05), indicating that deltamethrin resistance prolongs the larval development time of resistant mosquitoes. The average survival time of resistant adults was significantly shorter than that of susceptible adults, while the body weight of resistant female adults was significantly higher than that of the susceptible females. We also compared the vector competence for dengue virus type-2 (DENV-2) between the two strains via RT-qPCR. Considering the results of infection rate (IR) and virus load, there was no difference between the two strains during the early period of infection (4, 7, 10 day post infection (dpi)). However, in the later period of infection (14 dpi), IR and virus load in heads, salivary glands and ovaries of the resistant mosquitoes were significantly lower than those of the susceptible strain (IR of heads, salivary glands and ovaries: P < 0.005; virus load in heads and salivary glands: P < 0.05; virus load in ovaries: P < 0.001). And then, fourteen days after the DENV-2-infectious blood meal, females of the susceptible and resistant strains were allow to bite 5-day-old suckling mice. Both stains of mosquito can transmit DENV-2 to mice, but the onset of viremia was later in the mice biting by resistant group as well as lower virus copies in serum and brains, suggesting that the horizontal transmission of the resistant strain is lower than the susceptible strain. Meanwhile, we also detected IR of egg pools of the two strains on 14 dpi and found that the resistant strain were less capable of vertical transmission than susceptible mosquitoes. In addition, the average survival time of the resistant females infected with DENV-2 was 16 days, which was the shortest among the four groups of female mosquitoes, suggesting that deltamethrin resistance would shorten the life span of female Aedes albopictus infected with DENV-2. Conclusions/Significance As Aedes albopictus developing high resistance to deltamethrin, the resistance prolonged the growth and development of larvae, shorten the life span of adults, as well as reduced the vector competence of resistant Aedes albopictus for DENV-2. It can be concluded that the resistance to deltamethrin in Aedes albopictus is a double-edged sword, which not only endow the mosquito survive under the pressure of insecticide, but also increase the fitness cost and decrease its vector competence. However, Aedes albopictus resistant to deltamethrin can still complete the external incubation period and transmit dengue virus, which remains a potential vector for dengue virus transmission and becomes a threat to public health. Therefore, we should pay high attention for the problem of insecticide resistance so that to better prevent and control mosquito-borne diseases.

UDP-Glycosyltransferases from the UGT344 Family Are Involved in Sulfoxaflor Resistance in Aphis gossypii Glover

UDP-glycosyltransferases (UGTs) are major phase II detoxification enzymes that catalyze the transfer of glycosyl residues from activated nucleotide sugars to acceptor hydrophobic molecules and play very important roles in the biotransformation of various endogenous and exogenous compounds. Our previous studies demonstrated that UGTs participated in the detoxification of insecticides in Aphis gossypii. However, the potential roles of UGTs in A. gossypii resistance to sulfoxaflor are still unclear. In this study, two inhibitors of UGT enzymes, sulfinpyrazone and 5-nitrouracil, significantly increased the toxicity of sulfoxaflor to a resistant strain of A. gossypii, whereas there were no synergistic effects in the susceptible strain. Based on the transcriptome sequencing results, the expression levels of 15 UGTs were analyzed by quantitative real-time PCR, and we found that seven UGT genes were highly over-expressed in a sulfoxaflor-resistant strain compared to the susceptible strain, including UGT344B4, UGT344C5, UGT344A11, UGT344A14, and UGT344L2. Further suppressing the expression of UGT344B4, UGT344C5, and UGT344A11 by RNA interference significantly increased the sensitivity of resistant aphids to sulfoxaflor, indicating that the overexpression of UGT genes is potentially associated with sulfoxaflor resistance. These results could provide valuable information for further understanding the mechanisms of insecticide resistance.

Comparative proteomics reveals mechanisms that underlie insecticide resistance in Culex pipiens pallens Coquillett

Mosquito control based on chemical insecticides is considered as an important element of the current global strategies for the control of mosquito-borne diseases. Unfortunately, the development of insecticide resistance of important vector mosquito species jeopardizes the effectiveness of insecticide-based mosquito control. In contrast to target site resistance, other mechanisms are far from being fully understood. Global protein profiles among cypermethrin-resistant, propoxur-resistant, dimethyl-dichloro-vinyl-phosphate-resistant and susceptible strain of Culex pipiens pallens were obtained and proteomic differences were evaluated by using isobaric tags for relative and absolute quantification labeling coupled with liquid chromatography/tandem mass spectrometric analysis. A susceptible strain of Culex pipiens pallens showed elevated resistance levels after 25 generations of insecticide selection, through iTRAQ data analysis detected 2,502 proteins, of which 1,513 were differentially expressed in insecticide-selected strains compared to the susceptible strain. Finally, midgut differential protein expression profiles were analyzed, and 62 proteins were selected for verification of differential expression using iTRAQ and parallel reaction monitoring strategy, respectively. iTRAQ profiles of adaptation selection to three insecticide strains combined with midgut profiles revealed that multiple insecticide resistance mechanisms operate simultaneously in resistant insects of Culex pipiens pallens. Significant molecular resources were developed for Culex pipiens pallens, potential candidates were involved in metabolic resistance and reducing penetration or sequestering insecticide. Future research that is targeted towards RNA interference of the identified metabolic targets, such as cuticular proteins, cytochrome P450s, glutathione S-transferases and ribosomal proteins proteins and biological pathways (drug metabolism—cytochrome P450, metabolism of xenobiotics by cytochrome P450, oxidative phosphorylation, ribosome) could lay the foundation for a better understanding of the genetic basis of insecticide resistance in Culex pipiens pallens.

Insecticide resistance status of malaria vectors Anopheles gambiae (s.l.) of southwest Burkina Faso and residual efficacy of indoor residual spraying with microencapsulated pirimiphos-methyl insecticide

Background The rapid spread of insecticide resistance in malaria vectors and the rebound in malaria cases observed recently in some endemic areas underscore the urgent need to evaluate and deploy new effective control interventions. A randomized control trial (RCT) was conducted with the aim to investigate the benefit of deploying complementary strategies, including indoor residual spraying (IRS) with pirimiphos-methyl in addition to long-lasting insecticidal nets (LLINs) in Diébougou, southwest Burkina Faso. Methods We measured the susceptibility of the Anopheles gambiae (s.l.) population from Diébougou to conventional insecticides. We further monitored the efficacy and residual activity of pirimiphos-methyl on both cement and mud walls using a laboratory susceptible strain (Kisumu) and the local An. gambiae (s.l.) population. Results An. gambiae (s.l.) from Diébougou was resistant to DDT, pyrethroids (deltamethrin, permethrin and alphacypermethrin) and bendiocarb but showed susceptibility to organophosphates (pirimiphos-methyl and chlorpyrimiphos-methyl). A mixed-effect generalized linear model predicted that pirimiphos-methyl applied on cement or mud walls was effective for 210 days against the laboratory susceptible strain and 247 days against the local population. The residual efficacy of pirimiphos-methyl against the local population on walls made of mud was similar to that of cement (OR = 0.792, [0.55–1.12], Tukey’s test p-value = 0.19). Conclusions If data on malaria transmission and malaria cases (as measured trough the RCT) are consistent with data on residual activity of pirimiphos-methyl regardless of the type of wall, one round of IRS with pirimiphos-methyl would have the potential to control malaria in a context of multi-resistant An. gambiae (s.l.) for at least 7 months.