Dataset Information

Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of Aedes aegypti by a Photodynamic Process.

ABSTRACT: Aedes aegypti (Ae. aegypti) is a competent vector for transmitting important viral diseases such as yellow fever, dengue, chikungunya, and Zika. Several strategies have been applied to avoid Ae. aegypti proliferation by using environmental management, biological, and chemical approaches. However, the development of new methods for effective control of the insect vector population is still needed. Photodynamic control is an alternative way to control the vector population by using a physical approach based on the larval phototoxicity of a photosensitizer. In this context, the present study evaluated the use of eosin-methylene blue (EMB) as a new photosensitizer for photodynamic control of Ae. aegypti larval populations. The photodynamic assays were performed submitting Ae. aegypti third-instar larvae to different EMB concentrations (0.0, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 µg mL-1) in combination of three different light doses (24.3, 48.6, and 97.2 J cm-2) under either white-light radiation from RGB LEDs or sunlight. The results demonstrated that EMB presented a rapid internalization into the larvae and was phototoxic. The photodynamic action induced 100% of larval mortality after about 40 min of sunlight irradiation even using low EMB concentration (0.5 µg mL-1). The findings reveal EMB as an effective photoactive compound to control larval populations of Ae. aegypti by photodynamic process induced by either sunlight or white-light from RGB LEDs.

SUBMITTER: Lima AR

PROVIDER: S-EPMC6163889 | biostudies-other | 2018 Aug

REPOSITORIES: biostudies-other

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Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of Aedes aegypti by a Photodynamic Process.

Lima Alessandra R AR Silva Cicera M CM Caires Cynthia S A CSA Prado Esmael D ED Rocha Luciana R P LRP Cabrini Isaias I Arruda Eduardo J EJ Oliveira Samuel L SL Caires Anderson R L ARL

Insects 20180830 3

Aedes aegypti (Ae. aegypti) is a competent vector for transmitting important viral diseases such as yellow fever, dengue, chikungunya, and Zika. Several strategies have been applied to avoid Ae. aegypti proliferation by using environmental management, biological, and chemical approaches. However, the development of new methods for effective control of the insect vector population is still needed. Photodynamic control is an alternative way to control the vector population by ...[more]

PMID: 30200177

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Project description:A promising alternative to antibiotics for treatment of Staphylococcus aureus infections is photodynamic inactivation (PDI), which employs a photosensitizer (PS) that produces cytotoxic reactive oxygen species (ROS) when exposed to molecular oxygen and antimicrobial blue light in the spectrum of 400-470 nm. Although the precise mechanistic basis of PDI has not been defined, the formation of ROS and free radicals that oxidize a number of cellular targets, including membrane lipids, damage to proteins and nucleic acids result in inactivation of essential cellular functions and subsequent cell death. Because PDI is non-selective and affects multiple cellular targets, development of resistance or tolerance to PDI has been considered to be unlikely and attempts to induce S. aureus resistance or tolerance upon repeated sub-lethal doses of PDI have not succeeded. However, multiple aspects of PDI suggest that development of tolerance is highly probable, in particular when PDI is used for treatment of infections where the environment at the infection site prevents penetration of PDI at a level sufficient to cause death of all bacteria and with tolerant phenotypes emerging from the surviving bacteria. In this study, we sought to identify the mechanisms that contribute to PDI tolerance in S. aureus. S. aureus HG003 and the isogenic HG003DmutSL strain with defects in DNA mismatch repair were used to evaluate the response of S. aureus and the roles of DNA mismatch repair and gene regulatory networks to repeated sublethal doses of PDI. Global transcriptome and genome analyses were used in an agnostic approach to identify the underlying transcriptional responses and genetic adaptations that occur as a result of repeated PDI and contribute to PDI tolerance. Our results reveal multiple metabolic, transport and cell wall biogenesis pathways that contribute to PDI tolerance, and a S. aureus regulatory gene likely responsible for the adaptive transcriptional response to PDI.

Project description:BackgroundCurrent Aedes aegypti larval control methods are often insufficient for preventing dengue epidemics. To improve control efficiency and cost-effectiveness, some advocate eliminating or treating only highly productive containers. The population-level outcome of this strategy, however, will depend on details of Ae. aegypti oviposition behavior.Methodology/principal findingsWe simultaneously monitored female oviposition and juvenile development in 80 experimental containers located across 20 houses in Iquitos, Peru, to test the hypothesis that Ae. aegypti oviposit preferentially in sites with the greatest potential for maximizing offspring fitness. Females consistently laid more eggs in large vs. small containers (??=?9.18, p<0.001), and in unmanaged vs. manually filled containers (??=?5.33, p<0.001). Using microsatellites to track the development of immature Ae. aegypti, we found a negative correlation between oviposition preference and pupation probability (??=?-3.37, p<0.001). Body size of emerging adults was also negatively associated with the preferred oviposition site characteristics of large size (females: ??=?-0.19, p<0.001; males: ??=?-0.11, p?=?0.002) and non-management (females: ??=?-0.17, p<0.001; males: ??=?-0.11, p<0.001). Inside a semi-field enclosure, we simulated a container elimination campaign targeting the most productive oviposition sites. Compared to the two post-intervention trials, egg batches were more clumped during the first pre-intervention trial (??=?-0.17, P<0.001), but not the second (??=?0.01, p?=?0.900). Overall, when preferred containers were unavailable, the probability that any given container received eggs increased (??=?1.36, p<0.001).Conclusions/significanceAe. aegypti oviposition site choice can contribute to population regulation by limiting the production and size of adults. Targeted larval control strategies may unintentionally lead to dispersion of eggs among suitable, but previously unoccupied or under-utilized containers. We recommend integrating targeted larval control measures with other strategies that leverage selective oviposition behavior, such as luring ovipositing females to gravid traps or egg sinks.

Project description:BackgroundA five-year citywide control program based on regular application of temephos significantly reduced Aedes aegypti larval indices but failed to maintain them below target levels in Clorinda, northern Argentina. Incomplete surveillance coverage and reduced residuality of temephos were held as the main putative causes limiting effectiveness of control actions.MethodologyThe duration of temephos residual effects in household-owned water-holding tanks (the most productive container type and main target for control) was estimated prospectively in two trials. Temephos was applied using spoons or inside perforated small zip-lock bags. Water samples from the study tanks (including positive and negative controls) were collected weekly and subjected to larval mortality bioassays. Water turnover was estimated quantitatively by adding sodium chloride to the study tanks and measuring its dilution 48 hs later.Principal findingsThe median duration of residual effects of temephos applied using spoons (2.4 weeks) was significantly lower than with zip-lock bags (3.4 weeks), and widely heterogeneous between tanks. Generalized estimating equations models showed that bioassay larval mortality was strongly affected by water type and type of temephos application depending on water type. Water type and water turnover were highly significantly associated. Tanks filled with piped water had high turnover rates and short-lasting residual effects, whereas tanks filled with rain water showed the opposite pattern. On average, larval infestations reappeared nine weeks post-treatment and seven weeks after estimated loss of residuality.ConclusionsTemephos residuality in the field was much shorter and more variable than expected. The main factor limiting temephos residuality was fast water turnover, caused by householders' practice of refilling tanks overnight to counteract the intermittence of the local water supply. Limited field residuality of temephos accounts in part for the inability of the larval control program to further reduce infestation levels with a treatment cycle period of 3 or 4 months.

Dataset Information

Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of Aedes aegypti by a Photodynamic Process.

Publications

Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of <i>Aedes aegypti</i> by a Photodynamic Process.

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