Baseline Susceptibility to Bacterial Insecticides in Populations of &lt;I&gt;Culex pipiens&lt;/I&gt; Complex (Diptera: Culicidae) from California and from the Mediterranean Island of Cyprus

Wirth, Margaret C.; Ferrari, James A.; Georghiou, George P.

doi:10.1603/0022-0493-94.4.920

Cited by 22 publications

(16 citation statements)

References 19 publications

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“…Susceptibility to B. sphaericus in two nontreated populations of IPO and JAB showed that RR values at the LC 90 were similar to that of the reference colony, and the slight variations in RRs found at the LC 50 are comparable to previous RRs reported for other nontreated mosquito populations, which have demonstrated the existence of natural variations in their B. sphaericus susceptibilities (4,20,34,36,37). The status of two other nontreated populations of ROD and AZE could not be analyzed; nevertheless, they were expected to be susceptible since B. sphaericus had not been used in these areas and they were also geographically isolated from the only two exposed areas in RMA at the time the samples were collected (28,31).…”

Section: Discussionsupporting

confidence: 72%

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Chalegre

Romão

Tavares

et al. 2012

Appl Environ Microbiol

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Bin toxin from Bacillus sphaericus acts on Culex quinquefasciatus larvae by binding to Cqm1 midgut-bound receptors, and disruption of the cqm1 gene is the major cause of resistance. The goal of this work was to screen for a laboratory-selected resistance cqm1 REC allele in field populations in the city of Recife, Brazil, and to describe other resistance-associated polymorphisms in the cqm1 gene. The cqm1 REC allele was detected in the four nontreated populations surveyed at frequencies from 0.001 to 0.017, and sequence analysis from these samples revealed a novel resistant allele (cqm1 REC-D16 ) displaying a 16-nucletotide (nt) deletion which is distinct from the 19-nt deletion associated with cqm1 REC . Yet a third resistant allele (cqm1 REC-D25 ), displaying a 25-nt deletion, was identified in samples from a treated area exposed to B. sphaericus. A comparison of the three deletion events revealed that all are located within the same 208-nt region amplified during the screening procedure. They also introduce equivalent frameshifts in the sequence and generate the same premature stop codon, leading to putative transcripts encoding truncated proteins which are unable to locate to the midgut epithelium. The populations analyzed in this study contained a variety of alleles with mutations disrupting the function of the corresponding Bin toxin receptor. Their locations reveal a hot spot that can be exploited to assess the resistance risk through DNA screening.T he utilization of biolarvicides based on Bacillus sphaericus requires monitoring strategies which can predict or prevent potential resistance selection among exposed mosquito populations. The binary (Bin) crystal toxin, which is the major active insecticidal factor found in commercial B. sphaericus strains, acts on mosquito larvae after ingestion, processing and binding to specific receptors located on the midgut epithelium (5, 24). Bin toxin displays high activity against larvae of the Culex pipiens complex and B. sphaericus has an excellent persistence under field conditions, which make this an effective biolarvicide for controlling these species in urban areas (17). However, the mode of action of Bin toxin relies entirely on its binding to a single class of midgut receptors which are glycosylphosphatidylinositol (GPI)-anchored ␣-glucosidases named Cpm1 and Cqm1 for Culex pipiens and Culex quinquefasciatus, respectively (7,29,30). Failure of toxins to bind to their midgut receptors has been described, in a wide range of target insects, as the primary resistance mechanism to insecticidal proteins from entomopathogenic bacteria (11,16,25). In the case of B. sphaericus, this is a critical aspect since resistance cases have also been reported after laboratory selection or field exposure (2,25,27,36,38,44).Investigation of the B. sphaericus resistance mechanisms has confirmed the essential role for the binding of Bin toxin to its receptors, since mutations within the cpm1/cqm1 genes, which are recessively inherited, are the major causes leading to the absence of ...

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Section: Discussionsupporting

confidence: 72%

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Chalegre

Romão

Tavares

et al. 2012

Appl Environ Microbiol

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“…These RRs are likely due to natural variations in toxicity ratios rather than to resistance selection, as observed in the studies described below. For instance, surveys carried out on around fifty Culex pipiens populations with no history of Bti exposure showed that variation in the susceptibility to Bti ranged from RRs of 2 to 12.5 [49,50], while populations from three Bti-treated areas displayed RRs < 1 [51]. In China, five populations of Anopheles sinensis that were exposed to chemical and microbial larvicides showed RRs to Bti between 1.7 and 5.9, although pre-treatment data were not available and it was not possible to estimate pre existing variation [52].…”

Section: Discussionmentioning

confidence: 99%

The susceptibility of Aedes aegypti populations displaying temephos resistance to Bacillus thuringiensis israelensis: a basis for management

et al. 2013

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BackgroundAedes aegypti is the vector of dengue virus, and its control is essential to prevent disease transmission. Among the agents available to control this species, biolarvicides based on Bacillus thuringiensis serovar israelensis (Bti) are an effective alternative to replace the organophosphate temephos for controlling populations that display resistance to this insecticide. The major goal of this study was to determine the baseline susceptibility of Brazilian Ae. aegypti populations to Bti, taking into account their background in terms of larvicide exposure, status of temephos resistance and the level of activity of detoxifying enzymes involved in metabolic resistance to insecticides.MethodsPopulation samples were established under insectarium conditions. Larval susceptibility to temephos and Bti was evaluated through bioassays and lethal concentrations of these compounds were determined. Biochemical assays were performed to determine the specific activity of five detoxifying enzymes in these samples.ResultsFourteen populations were characterized and, except for one case, all displayed resistance to temephos. Most populations were classified as highly resistant. The populations also showed increased activity of one or more detoxifying enzymes (glutathione-S-transferases, esterases and mixed function oxidases), regardless of their temephos resistance status. All populations analyzed were susceptible to Bti, and the lethal concentrations were similar to those detected in two laboratory susceptible colonies. The response to Bti showed little variation. A maximum resistance ratio of 2.1 was observed in two untreated populations, while in two Bti-treated populations, the maximum resistance ratio was 1.9. No positive correlation was found between temephos resistance, increased activity of detoxifying enzymes, and susceptibility to Bti.ConclusionsData from this study show that all populations were susceptible to Bti, including twelve untreated and two treated populations that had been exposed to this agent for more than ten years. The temephos resistance and increased activity of detoxifying enzymes observed in thirteen populations was not correlated with changes in susceptibility to Bti. Our data show a lack of cross-resistance between these two compounds; thus, Bti can be used in an integrated control program to fight Ae. aegypti and counteract the temephos resistance that was found among all populations analyzed.

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“…Wirth et al (2004) testaram combinações da toxina binária de Bacillus sphaericus, que apresenta duas proteínas (42 kDa e 51 kDa), com as toxinas de B. thuringiensis var. israelensis para larvas de C. quinquefasciatus resistentes e constataram que algumas dessas combinações foram tóxicas para as larvas, fato decorrente da maior complexidade das toxinas em ação.…”

Section: Resultsunclassified

Atividade tóxica de isolados de Bacillus Thuringiensis a larvas de Aedes Aegypti (l.) (diptera: culicidae)

Costa¹,

Rossi²,

Marucci³

et al. 2010

Neotrop. entomol.

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Baseline Susceptibility to Bacterial Insecticides in Populations of <I>Culex pipiens</I> Complex (Diptera: Culicidae) from California and from the Mediterranean Island of Cyprus

Cited by 22 publications

References 19 publications

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

Novel Mutations Associated with Resistance to Bacillus sphaericus in a Polymorphic Region of the Culex quinquefasciatus cqm1 Gene

The susceptibility of Aedes aegypti populations displaying temephos resistance to Bacillus thuringiensis israelensis: a basis for management

Atividade tóxica de isolados de Bacillus Thuringiensis a larvas de Aedes Aegypti (l.) (diptera: culicidae)

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