Last data update: Jun 03, 2024. (Total: 46935 publications since 2009)
Records 1-4 (of 4 Records) |
Query Trace: Liebman KA [original query] |
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Borrelia miyamotoi infection in immunocompromised man, California, USA, 2021
Rubio LA , Kjemtrup AM , Marx GE , Cronan S , Kilonzo C , Saunders MEM , Choat JL , Dietrich EA , Liebman KA , Park SY . Emerg Infect Dis 2023 29 (5) 1011-1014 Infection with Borrelia miyamotoi in California, USA, has been suggested by serologic studies. We diagnosed B. miyamotoi infection in an immunocompromised man in California. Diagnosis was aided by plasma microbial cell-free DNA sequencing. We conclude that the infection was acquired in California. |
Susceptibility to insecticides and resistance mechanisms in three populations of Aedes aegypti from Peru.
Pinto J , Palomino M , Mendoza-Uribe L , Sinti C , Liebman KA , Lenhart A . Parasit Vectors 2019 12 (1) 494 BACKGROUND: Epidemics of dengue, chikungunya and Zika are a growing threat to areas where Aedes aegypti are present. The efficacy of chemical control of Ae. aegypti is threatened by the increasing frequency of insecticide resistance. The objective of this study was to determine the susceptibility status as well as the biochemical and molecular mechanisms underlying insecticide resistance in three populations of Ae. aegypti in high risk areas of dengue, chikungunya, and Zika in Peru. METHODS: Bioassays were conducted on adult Ae. aegypti to evaluate their susceptibility to insecticides used currently or historically for mosquito control in Peru, including six pyrethroids, three organophosphates and one organochlorine, in populations of Ae. aegypti from the districts of Chosica (Department of Lima), Punchana (Department of Loreto) and Piura (Department of Piura). Resistance mechanisms were determined by biochemical assays to assess activity levels of key detoxification enzyme groups (nonspecific esterases, multi-function oxidases, glutathione S-transferases and insensitive acetylcholinesterase). Real-time PCR assays were used to detect two kdr mutations (V1016I and F1534C) on the voltage-gated sodium channel gene. RESULTS: Resistance to DDT was detected in all three populations, and resistance to pyrethroids was detected in all populations except the population from Chosica, which still exhibited susceptibility to deltamethrin. Resistance to organophosphates was also detected, with the exception of populations from Punchana and Piura, which still demonstrated susceptibility to malathion. In general, no increase or alteration of activity of any enzyme group was detected. Both 1016I and 1534C alleles were detected in Punchana and Piura, while only the 1534C allele was detected in Chosica. CONCLUSIONS: The results suggest that resistance to multiple classes of insecticides exist in areas important to Ae. aegypti-borne disease transmission in Peru. The F1534C mutation was present in all 3 populations and the V1016I mutation was present in 2 populations. To our knowledge, this is the first report of the presence of 1016I and 1534C in Ae. aegypti in Peru. The absence of highly elevated enzymatic activity suggests that target site resistance is a key mechanism underlying insecticide resistance in these populations, although further research is needed to fully understand the role of metabolic resistance mechanisms in these populations. |
Novel mutations on the ace-1 gene of the malaria vector Anopheles albimanus provide evidence for balancing selection in an area of high insecticide resistance in Peru.
Liebman KA , Pinto J , Valle J , Palomino M , Vizcaino L , Brogdon W , Lenhart A . Malar J 2015 14 74 BACKGROUND: Resistance to multiple classes of insecticides has been detected in the malaria vector Anopheles albimanus in northwest Peru. Acetylcholinesterase (AChE) insensitivity has previously been associated with resistance to organophosphate (OP) and carbamate (CA) insecticides in arthropods. A single point mutation on the ace-1 gene (G119S) associated with resistance to OPs and CAs has been described previously in four anopheline species, but not in field-collected An. albimanus. The present study aimed to characterize the role of ace-1 in conferring resistance to both OPs and CAs in the An. albimanus population in Tumbes, Peru. METHODS: The frequency and intensity of resistance to OPs and CAs was quantified through bioassays of female An. albimanus collected between 2012 and 2014, and the presence of insensitive AChE was confirmed using biochemical assays. A portion of the ace-1 gene flanking codon 119 was amplified and sequenced from individuals used in the bioassays and biochemical assays, as well as from historical samples collected in 2008. Statistical analyses were conducted to determine: (1) associations between genotype and AChE insensitivity; and, (2) associations between genotype and resistance phenotype. RESULTS: After confirming high levels of resistance to fenitrothion, malathion, and bendiocarb through bioassays, two novel polymorphisms were identified at the first and second loci of codon 119, with all individuals from the 2012-2014 collections being heterozygous at the first base (G/T) and either heterozygous (G/C) or homozygous mutants (C/C) at the second base. Based on sequence data from historical samples, these mutations arose prior to 2008, but became fixed in the population between 2008 and 2012. Homozygotes at the second locus had significantly higher levels of AChE insensitivity than heterozygotes (p <0.05). Individuals phenotypically susceptible to OPs and CAs were more likely to be heterozygous at the second locus (p <0.01). Cloning identified four individuals each containing three distinct genotypes, suggesting that a duplication of the ace-1 gene may have occurred. CONCLUSIONS: The occurrence of heterozygotes at two loci and the presence of three genotypes in four individuals suggest that balancing selection could be maintaining OP and CA resistance in this population, while minimizing associated fitness costs. |
Molecular evidence for historical presence of knock-down resistance in Anopheles albimanus, a key malaria vector in Latin America
Lol JC , Castellanos ME , Liebman KA , Lenhart A , Pennington PM , Padilla NR . Parasit Vectors 2013 6 268 BACKGROUND: Anopheles albimanus is a key malaria vector in the northern neotropics. Current vector control measures in the region are based on mass distributions of long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) with pyrethroids. Resistance to pyrethroid insecticides can be mediated by increased esterase and/or multi-function oxidase activity and/or mutations in the voltage-gated sodium channel gene. The aim of this work was to characterize the homologous kdr region of the voltage-gated sodium channel gene in An. albimanus and to conduct a preliminary retrospective analysis of field samples collected in the 1990's, coinciding with a time of intense pyrethroid application related to agricultural and public health insect control in the region. METHODS: Degenerate primers were designed to amplify the homologous kdr region in a pyrethroid-susceptible laboratory strain (Sanarate) of An. albimanus. Subsequently, a more specific primer pair was used to amplify and sequence the region that contains the 1014 codon associated with pyrethroid resistance in other Anopheles spp. (L1014F, L1014S or L1014C). RESULTS: Direct sequencing of the PCR products confirmed the presence of the susceptible kdr allele in the Sanarate strain (L1014) and the presence of homozygous-resistant kdr alleles in field-collected individuals from Mexico (L1014F), Nicaragua (L1014C) and Costa Rica (L1014C). CONCLUSIONS: For the first time, the kdr region in An. albimanus is described. Furthermore, molecular evidence suggests the presence of kdr-type resistance in field-collected An. albimanus in Mesoamerica in the 1990s. Further research is needed to conclusively determine an association between the genotypes and resistant phenotypes, and to what extent they may compromise current vector control efforts. |
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